Co-reporter:Kaiqiang Yu;Shaohua Fang;Yide Jin;Jianzhi Song;Shin-ichi Hirano;Jianhao Zhang;Zhengxi Zhang
Industrial & Engineering Chemistry Research February 26, 2014 Volume 53(Issue 8) pp:2860-2871
Publication Date(Web):2017-2-22
DOI:10.1021/ie4022804
Twenty-four new functionalized ionic liquids (ILs) based on trialkylimidazolium cations with the alkoxymethyl group at the N-1 position were synthesized and characterized. Physicochemical properties of these ILs, such as melting point, thermal stability, density, viscosity, conductivity, and electrochemical stability, were studied systematically. Twenty-one ILs appeared in the liquid state at room temperature, and 14 ILs showed a melting point lower than −60 °C. Introduction of the alkoxymethyl group at the N-1 position of trialkylimidazolium cations could not be more beneficial than that of the alkoxyethyl group for reducing viscosity. Li/LiFePO4 cells employing three trialkylimidazolium ILs with methoxymethyl-group-based electrolytes showed good discharge capacity and cycle stability at a current rate of 0.1 C. This is the first report of ILs with the alkoxymethyl group used as electrolytes without an additive for a lithium ion battery.
Co-reporter:Dong Luo, Shaohua Fang, Li Yang, Shin-ichi Hirano
Journal of Alloys and Compounds 2017 Volume 723(Volume 723) pp:
Publication Date(Web):5 November 2017
DOI:10.1016/j.jallcom.2017.06.259
•A molten-salt method using KCl and NaCl as complex flux is designed.•Li1.18Mn0.56Ni0.13Co0.13O2 cathodes possess excellent rate and cycling properties.•The outstanding properties are due to the uniform distribution of TM-elements.•The uniformity of TM elements can be improved by molten-salt method.Li-rich layered oxides, one of the most promising cathodes for high energy Li-ion batteries, commonly undergo some issues such as poor rate performance, low Coulombic efficiency, voltage degradation and so on. In this work, Li1.18Mn0.56Ni0.13Co0.13O2 cathodes with excellent rate capability and cycling stability are prepared by a new molten-salt method using KCl and NaCl as complex flux. The electrochemical tests show that these cathodes can deliver an initial discharge specific capacity of 224.3 mA h g−1 at 300 mA g−1. Meanwhile, the capacity retention ratio remains 92.1% after 100 cycles. The outstanding electrochemical performance is mainly attributed to the uniform distribution of TM-elements in Li1.18Mn0.56Ni0.13Co0.13O2 cathodes, which can promote the electrochemical activation of Li2MnO3-like component. Especially, it is found that the uniformity of TM elements in Li-rich cathodes can be improved by choosing molten-salt method as the synthetic strategy.
Co-reporter:Qinghua Tian, Peng Chen, Zhengxi Zhang, Li Yang
Carbon 2017 Volume 118(Volume 118) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.carbon.2017.03.098
The current research priorities about tin dioxide-based anodes mainly focus on improvement of structure stability and rate performance due to the intrinsic issues of huge volume change and poor conductivity of tin dioxide materials. Herein, it is demonstrated that a one-dimensional quasi-hollow nanostructure of tin dioxide@carbon (SnO2@C) composite with improved electrochemical performance can be prepared by an elaborately simplified approach. It is worthy of noting that a proposed hydrothermal treatment plays an indispensable role in formation of this SnO2@C composite. As a promising anode for lithium-ion batteries, this as-prepared versatile nanostructure of SnO2@C composite combining advantages of one-dimension, hollow-confine and carbon coating able to exhibit high capacities of 749.3 and 549.8 mAh g−1 after 100 cycles respectively at 200 and even 1000 mA g−1, as well as superior rate properties. The well-designed versatile nanostructure should be responsible for thus outstanding performance.A versatile one-dimensional SnO2@C composite was prepared by an elaborately simplified route and exhibited an outstanding lithium storage performance as a promising anode for lithium-ion batteries.Download high-res image (331KB)Download full-size image
Co-reporter:Dong Luo;Pei Shi;Shaohua Fang;Wenbin Guo;Shin-ichi Hirano
Inorganic Chemistry Frontiers 2017 vol. 4(Issue 4) pp:650-658
Publication Date(Web):2017/04/11
DOI:10.1039/C6QI00571C
Assembled microspherical cathodes have attracted great attention thanks to their high tap density, good rate capability and cycling stability. However, for layered Li-rich transition-metal oxides (LROs), the preparation of uniformly assembled microspheres still faces many challenges due to harsh synthetic conditions and the nature of multiple metal elements. In this work, Li1.17Mn0.50Ni0.16Co0.17O2 assembled microspheres have been prepared by a new route tactfully combining a solvothermal process and a molten-salt method. The use of a solvothermal process is helpful for the preparation of precursors with assembled microspherical morphology, and the addition of complex salts (NaCl and KCl), can increase the uniformity of cation distribution. The product obtained at 800 °C delivers the best electrochemical performances among all samples. At a current density of 300 mA g−1, its initial discharge capacity is larger than 228 mA h g−1, corresponding to a capacity retention ratio of 86.8% after 200 cycles. Even if the current density increases to 2000 mA g−1, its discharge capacity is still as large as 156 mA h g−1. What's more, we discover the moving rate of Li-ions during the sintering process will affect the uniformity of Li2MnO3-like and LiMO2 components in LRO assembled microspheres. This discovery is helpful for the preparation of LRO assembled microspheres with excellent electrochemical performances.
Co-reporter:Xiaowei Li;Zhengxi Zhang;Sijian Li;Kaihua Yang
Journal of Materials Chemistry A 2017 vol. 5(Issue 40) pp:21362-21369
Publication Date(Web):2017/10/17
DOI:10.1039/C7TA04204C
In developing all-solid-state polymer electrolytes for wide operating temperature range lithium metal batteries, an exciting organic ionic plastic crystal, N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (P12FSI), has been introduced into the pyrrolidinium-based polymeric ionic liquid (PIL)/LiTFSI solid system to obtain a novel class of PIL–P12FSI–LiTFSI solid polymer electrolytes (SPEs). Such SPEs reveal flexible mechanical characters, attractive room temperature ionic conductivity above 10−4 S cm−1, and high thermal and electrochemical stability as well as potential to suppress the lithium dendrite growth. Particularly, Li/LiFePO4 cells assembled with the as-obtained SPE exhibit high discharge capacity and excellent cycle life over a broad operating temperature range (25–80 °C) and good rate performance. This significant finding indicates that the SPE system obtained in our work has great potential for use in wide operating temperature range lithium metal batteries.
Co-reporter:Jun Huang;Kaihua Yang;Zhengxi Zhang;Shin-ichi Hirano
Chemical Communications 2017 vol. 53(Issue 55) pp:7800-7803
Publication Date(Web):2017/07/06
DOI:10.1039/C7CC03933F
∼1 V lithium intercalation materials are promising anodes for lithium-ion batteries, because such materials give consideration to both the tolerance of lithium plating (e.g., graphite with ∼0.1 V versus Li+/Li easily results in lithium plating due to a too low potential) and the energy density of the batteries (e.g., Li4Ti5O12 with ∼1.55 V decreases the battery voltage, and thus reduces the energy density). Herein, the layered perovskite compound LiEuTiO4 with a 0.8 V lithium intercalation/deintercalation potential plateau was successfully synthesized by the ion-exchange reaction with NaEuTiO4 prepared via a sol–gel method. LiEuTiO4 can deliver a high capacity of 219.2 mA h g−1 (2nd discharge) at a rate of 100 mA g−1. Even after 500 cycles, the discharge capacity remains at ∼217 mA h g−1 and the Coulombic efficiency is 99.2%. To our knowledge, the cycle stability of LiEuTiO4 exceeds all previous ∼1 V electrodes. Different from the common lithium intercalation Ti-based electrodes (such as Li4Ti5O12) based on the reduction of the Ti4+ to Ti3+, electrochemical lithium intercalation into LiEuTiO4 leads to the reduction of the Eu3+ to Eu2+.
Co-reporter:Pei Shi;Shaohua Fang;Jun Huang;Dong Luo;Shin-ichi Hirano
Journal of Materials Chemistry A 2017 vol. 5(Issue 37) pp:19982-19990
Publication Date(Web):2017/09/26
DOI:10.1039/C7TA05743A
In this work, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (F-EPE), a kind of non-flammable hydrofluoroether, was initially mixed with lithium bis(oxalato)borate (LiBOB) and gamma-butyrolactone (GBL) to formulate a safe electrolyte for lithium-ion batteries. It was found that the addition of F-EPE endowed this novel electrolyte with a high safety level, low surface tension and good wettability to the separator and electrodes. More importantly, this safe electrolyte supported the graphite/LiCo1/3Mn1/3Ni1/3O2 full cell in achieving excellent electrochemical performances. During the prolonged cycle test at room temperature, its capacity retention after 500 cycles could reach 80.6%, which was comparable to that of a commercial electrolyte. Its rate performance at room temperature and cycle performance at elevated temperature (60 °C) surpassed those of the commercial electrolyte. In particular, its low-temperature performance was remarkable, and the cell could deliver a capacity as high as 74.2 mA h g−1 at −40 °C. In view of these results, such a safe electrolyte showed tremendous potential for practical application.
Co-reporter:Qinghua Tian, Peng Chen, Zhengxi Zhang, Li Yang
Journal of Power Sources 2017 Volume 350(Volume 350) pp:
Publication Date(Web):15 May 2017
DOI:10.1016/j.jpowsour.2017.03.065
•A hierarchical structure of Li4Ti5O12 assembled by ultrafine nanowires was prepared.•This structure offered Li4Ti5O12 improved diffusion dynamics of lithium-ions.•The Li4Ti5O12 exhibited excellent lithium storage performance and ultra-long life.Spinel lithium titanate (Li4Ti5O12) has attracted extensive attention by virtue of its inherent features of zero strain and high operating potential, which results in outstanding structural stability and remarkable safety as anode materials for lithium-ion batteries. But, there are two issues of low specific capacity and poor electrical conductivity yet need to be satisfactorily solved before the practical application of Li4Ti5O12 anode can be well achieved in lithium-ion batteries. Herein, a novel hierarchical structure of clew-like microparticles constructed by ultrafine Li4Ti5O12 nanowires has been successfully prepared via a facile approach. The combination effect of ultrafine nanowire unites and non-compact clew-like architecture provides the as-prepared Li4Ti5O12 with excellent electrochemical performance. A high reversible specific capacity of 184.1 mAh g−1 can be obtained at 20 mA g−1 after 400 cycles. What is more, a capacity of 177.8 and 152.2 mAh g−1 can be gained even after 2500 cycles respectively at 200 and 4000 mA g−1, exhibiting high capacity, superior rate property and outstanding cycling stability. This work may open up a broader vision into developing nanostructure Li4Ti5O12 anode materials for advanced lithium-ion batteries.The combination effect of ultrafine nanowires and non-compact clew-like architecture provides the Li4Ti5O12 anode with excellent lithium storage performance.Download high-res image (276KB)Download full-size image
Co-reporter:Qinghua Tian, Peng Chen, Zhengxi Zhang, Li Yang
Materials Chemistry and Physics 2017 Volume 201(Volume 201) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.matchemphys.2017.08.001
•A synergistic effect supported Li4Ti5O12 was proposed.•The synergistic effect greatly improved electrochemical dynamics of Li4Ti5O12.•The Li4Ti5O12 exhibited excellent lithium storage performance.•A strategy for facilely preparing advanced performance Li4Ti5O12 was demonstrated.Low specific capacity and poor electrical conductivity are the two intrinsic problems of spinel lithium titanate (Li4Ti5O12), which limit the practical use of Li4Ti5O12 anode in lithium-ion batteries. Herein, we demonstrate that the capacity and rate performance of Li4Ti5O12 anodes can be greatly improved by the synergistic effect of facile hierarchical structure design and in-situ decoration of tiny TiO2. The as-prepared ultrafine nanowire assembled and TiO2 in-situ decorated clew-like Li4Ti5O12 anode is able to deliver a ultrahigh reversible specific capacity of 195.2 mAh g−1 at 20 mA g−1 and 125 mAh g−1 at 5000 mA g−1 even after 5000 cycles, exhibiting excellent lithium storage performance and cycling stability. Thus obtained outstanding electrochemical performance largely surpasses that of reportedly state-of-the-art LTO-based anode materials. This work may pave the way to facilely prepare advanced Li4Ti5O12-based anode materials for lithium-ion batteries.The as-prepared T-LTO NWs exhibits ultrahigh lithium storage due to the synergistic effect between nanostructure engineering and second phase decoration.Download high-res image (342KB)Download full-size image
Co-reporter:Dong Luo, Pei shi, Shaohua Fang, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2017 Volume 364(Volume 364) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.jpowsour.2017.07.078
•Two nanoplates with exposed (101) or (001) facets are prepared.•Effect of exposed facets on voltage decay and capacity fading of LLOs is unraveled.•Large area of active surface will accelerate electrochemical corrosion of LLOs.•Phase transformation of LLOs can be mitigated by increasing the area of inactive surface.•We discover Co and Ni are easier to react with electrolyte than Mn.In this work, the effect of exposed facets on voltage decay and capacity fading of Li-rich layered oxides (LLOs) is unraveled via two nanoplates which are prepared by very similar co-precipitated-precursor method. The top-bottom surface of one nanoplate is (101) facet (S101 sample, active plane) and the other is exposed (001) facet (S001 sample, inactive plane). Although S101 sample delivers an excellent rate capability (149 mA h g−1 at 2000 mA g−1), both its voltage and capacity decrease faster than S001 sample. TEM, HRTEM, XPS and XRD of cycled samples demonstrate: (1) Large area of active surface will accelerate electrochemical corrosion and phase transformation of LLOs and (2) electrochemical corrosion and phase transformation of LLOs with large area of inactive surface can be mitigated, leading to slow voltage decay and capacity fading. In addition, we discover Co and Ni are easier to react with electrolyte than Mn. Therefore, suitable facets and compositions may be more useful for improving the electrochemical performance of LLOs.Voltage decay and capacity fading of Li-rich layered oxides can be mitigated by large area of exposed inactive surface.Download high-res image (198KB)Download full-size image
Co-reporter:Xueqin Tao, Qinghua Tian, Li Yang, Yixin Xiang
Materials Letters 2017 Volume 202(Volume 202) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.matlet.2017.05.055
•A uniquely quasi-coral-like SnOx@C composite was prepared by a very facile method.•This composite had a durable structure.•This composite exhibited outstanding lithium storage performance.Herein, a quasi-coral-like nanostructure of SnO2/SnO@C composite (SnOx@C) has been prepared by a facile one-pot hydrothermal and subsequent carbonization strategy. This interesting architecture of ultrasmall SnOx nanoparticles embedded into quasi-coral-like carbon matrix can not only accommodate the volume change of SnO2, but also improve the conductivity of whole SnOx@C electrode. In consequence, the SnOx@C exhibits outstanding lithium storage.
Co-reporter:Xiaowei Li, Zhengxi Zhang, Sijian Li, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2016 Volume 307() pp:678-683
Publication Date(Web):1 March 2016
DOI:10.1016/j.jpowsour.2016.01.032
•Polymeric ionic liquid-plastic crystal composite electrolytes are obtained.•The composite electrolytes show high ionic conductivity.•The composite electrolytes present favorable mechanical properties.•The composite electrolytes reveal impressive battery performance.In this work, composite polymer electrolytes (CPEs), that is, 80%[(1−x)PIL–(x)SN]–20%LiTFSI, are successfully prepared by using a pyrrolidinium-based polymeric ionic liquid (P(DADMA)TFSI) as a polymer host, succinonitrile (SN) as a plastic crystal, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a lithium salt. XRD and DSC measurements confirm that the as-obtained CPEs have amorphous structures. The 80%[50%PIL–50%SN]–20%LiTFSI (50% SN) electrolyte reveals a high room temperature ionic conductivity of 5.74 × 10−4 S cm−1, a wide electrochemical window of 5.5 V, as well as good mechanical strength with a Young's modulus of 4.9 MPa. Li/LiFePO4 cells assembled with the 50% SN electrolyte at 0.1C rate can deliver a discharge capacity of about 150 mAh g−1 at 25 °C, with excellent capacity retention. Furthermore, such cells are able to achieve stable discharge capacities of 131.8 and 121.2 mAh g−1 at 0.5C and 1.0C rate, respectively. The impressive findings demonstrate that the electrolyte system prepared in this work has great potential for application in lithium ion batteries.
Co-reporter:Long Qu, Dong Luo, Shaohua Fang, Yi Liu, Li Yang, Shin-ichi Hirano, Chun-Chen Yang
Journal of Power Sources 2016 Volume 307() pp:69-76
Publication Date(Web):1 March 2016
DOI:10.1016/j.jpowsour.2015.12.137
•Mg-doped Li2FeSiO4/C is synthesized by sol-gel method with Fe2O3 nanoparticle.•Rietveld refinement confirms that Mg is doped in Fe site in Li2FeSiO4 lattice.•Mg-doped product shows high capacity retention of 96% after 100 cycles at 0.1 C.•Doping Mg can effectively improve the electrochemical performance of Li2FeSiO4/C.Mg-doped Li2FeSiO4/C is synthesized by using Fe2O3 nanoparticle as iron source. Through Rietveld refinement of X-ray diffraction data, it is confirmed that Mg-doped Li2FeSiO4 owns monoclinic P21/n structure and Mg occupies in Fe site in the lattice. Through energy dispersive X-ray measurement, it is detected that Mg element is distributed homogenously in the resulting product. The results of transmission electron microscopy measurement reveal that the effect of Mg-doping on Li2FeSiO4 crystallite size is not obvious. As a cathode material for lithium-ion battery, this Mg-doped Li2FeSiO4/C delivers high discharge capacity of 190 mAh g−1 (the capacity was with respect to the mass of Li2FeSiO4) at 0.1C and its capacity retention of 100 charge-discharge cycles reaches 96% at 0.1C. By the analysis of electrochemical impedance spectroscopy, it is concluded that Mg-doping can help to decrease the charge-transfer resistance and increase the Li+ diffusion capability.
Co-reporter:Qinghua Tian, Dong Luo, Xiaowei Li, Zhengxi Zhang, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2016 Volume 313() pp:189-197
Publication Date(Web):1 May 2016
DOI:10.1016/j.jpowsour.2016.02.082
•Four hierarchical structures of TiO2 were prepared by facile routes.•The unique architecture endowed the TiO2 superior physical and chemical properties.•The as-prepared TiO2 exhibited impressive cycling performance and rate capability.Titanium dioxide (TiO2) has been considered to be a promisingly alternative anode material for lithium-ion batteries and thus attracted wide research interest. But, its practical application in lithium-ion batteries is seriously impeded by low capacity and poor rate capability. In the present work, the electrochemical performance of TiO2 is significantly improved by elaborately fabricating hierarchical structures. These as-prepared four hierarchical structure TiO2 assembled by different building blocks (TO2-2 h, TO2-6 h, TO2-18 h and TO2-24 h) all exhibit impressed performance. More importantly, the TO2-6 h constructed by curved nanosheets exhibits the best performance, delivering a capacity of 231.6 mAh g−1 at 0.2C after 200 cycles, and capacities of 187.1 and 129.3 mAh g−1 at 1 and 10C after even 1200 cycles, respectively. The results indicated that design and fabrication of hierarchical structure is an effective strategy for significantly improving the electrochemical performance of TiO2 electrodes, and the electrochemical performance of hierarchical structure TiO2 is heavily dependent on its building blocks. It is suggested that thus excellent electrochemical performance may make TiO2-6 h a promising anode material for advanced lithium-ion batteries with high capacity, good rate capability and long life.
Co-reporter:Dong Luo, Guojun Wang, Shaohua Fang, Li Yang, Shin-ichi Hirano
Electrochimica Acta 2016 Volume 219() pp:516-523
Publication Date(Web):20 November 2016
DOI:10.1016/j.electacta.2016.10.033
In this work, Li1.15Mn0.49Ni0.18Co0.18O2 nanoplates with exposed (012) facet are prepared for the first time by co-precipitation method under the assistance of cetyltrimethyl ammonium bromide. As cathode materials of lithium-ion batteries, the Li1.15Mn0.49Ni0.18Co0.18O2 nanoplates can deliver the initial discharge capacities of 219.8 and 192 mA h g−1 at 300 and 700 mA g−1, respectively. It suggests the Li1.15Mn0.49Ni0.18Co0.18O2 nanoplates possess an excellent rate capability. After 200 cycles, the capacity retention ratio at 700 mA g−1 is still as large as 82.6%. The superior rate capability can be attributed to the shorter transport distance of lithium ions in these nanoplates with exposed (012) facet. The above results also indicate that the electrochemical performances of Li-rich layered oxides can be improved by allocating proper facets.
Co-reporter:Guojun Wang, Shaohua Fang, Dong Luo, Li Yang, Shin-ichi Hirano
Electrochemistry Communications 2016 Volume 72() pp:148-152
Publication Date(Web):November 2016
DOI:10.1016/j.elecom.2016.09.023
•New FSI-based imidazolium ILs are proposed as electrolytes for lithium-ion batteries.•Neat IL electrolytes are evaluated by full cells with commercial electrodes.•Ether functionalization brings the prominent improvement of performance.•MCMB/LiFePO4 full cells can show excellent cycling performance.Neat ionic liquid electrolytes based on functionalized 1,3-dialkylimidazolium cation and bis(fluorosulfonyl)imide anion were investigated in MCMB/LiFePO4 full cells with commercial electrodes for the first time. Ether functionalization could bring the prominent improvement of initial efficiency and the comparable cycle performance to a conventional carbonate-based electrolyte. In view of full cells, it was inferred that the further oxidation on cathode of the reduction products on anode during the charge process might result in the serious capacity loss of initial cycle.
Co-reporter:Qinghua Tian, Yang Tian, Zhengxi Zhang, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2016 306() pp: 213-218
Publication Date(Web):29 February 2016
DOI:10.1016/j.jpowsour.2015.12.027
Co-reporter:Dong Luo, Shaohua Fang, Qinghua Tian, Long Qu, Li Yang, Shin-ichi Hirano
Nano Energy 2016 Volume 21() pp:198-208
Publication Date(Web):March 2016
DOI:10.1016/j.nanoen.2016.01.014
•Li1.14Mn0.48Ni0.19Co0.19O2 nanoplate exposed (001) is prepared.•A surface protective layer (SPL) is discovered at the outer edge of nanoplate.•The direction and order of TM ions migration during cycling have been demonstrated.•Capacity and voltage degradation of Li-rich layered cathodes is countered.Capacity and voltage degradation is a crucial factor that restricts the commercialization of Li-rich layered cathode materials. Recently, it has been demonstrated that the degradation results from the structural evolution from layered to spinel-like phase, caused by the migration of transition metal (TM) ions. However, the direction and order of TM ions migration is hard to identify. In this study, a surface protective layer (SPL) is discovered for the first time at the outer edge of Li1.14Mn0.48Ni0.19Co0.19O2 nanoplate by the research on the surface condition of nanoplates after charge–discharge cycles. More importantly, by the detailed analysis for the SPL, we further reveal that the formation of SPL is active facet dependent, TM ions migrate toward the active facets, and Ni and Co ions hop more preferentially than Mn ions during the cycling. These discoveries can help to understand the fading mechanism of Li-rich layered cathode materials. In addition, electrochemical test indicates that the SPL greatly delays the corrosion of active surfaces in electrolyte and improves the cycling stability of Li-rich layered cathode materials. This insight provides a new thought for preparing long-life cathodes of high energy Li-ion batteries.Figure optionsDownload full-size imageDownload as PowerPoint slide
Co-reporter:Kun Yin, Zhengxi Zhang, Xiaowei Li, Li Yang, Kazuhiro Tachibana and Shin-ichi Hirano
Journal of Materials Chemistry A 2015 vol. 3(Issue 1) pp:170-178
Publication Date(Web):05 Nov 2014
DOI:10.1039/C4TA05106H
Polymeric ionic liquids (PILs) have stirred up great interest for their potential applications as electrolyte hosts in lithium metal batteries (LMBs) because of their desirable performance. In this work, PIL-based gel polymer electrolytes applied in lithium metal batteries (LMBs) at low–medium temperatures (25 °C, 30 °C and 40 °C) are first reported. A novel imidazolium-tetraalkylammonium-based dicationic polymeric ionic liquid, poly(N,N,N-trimethyl-N-(1-vinlyimidazolium-3-ethyl)-ammonium bis(trifluoromethanesulfonyl)imide) is successfully synthesized, and its structure and purity are confirmed by 1H NMR, FTIR and elemental analysis. Subsequently, the ternary gel polymer electrolytes are prepared by blending the as-synthesized dicationic PIL as the polymer host with 1,2-dimethyl-3-ethoxyethyl imidazolium bis(trifluoromethanesulfonyl)imide (IM(2o2)11TFSI) ionic liquid and LiTFSI salt in different weight ratios. The PIL-LiTFSI-IM(2o2)11TFSI electrolytes reveal low glass transition temperatures around −54 °C and high thermal stability to about 330 °C. Moreover, the ternary gel polymer electrolytes show good ion conductivity around 10−4 S cm−1 at low–medium temperatures, high electrochemical stability and good interfacial stability with lithium metal. Particularly, the Li/LiFePO4 cells assembled with polymer electrolytes at a rate of 0.1 C are able to deliver discharge capacities of about 160 mA h g−1, 140 mA h g−1 and 120 mA h g−1 at 40 °C, 30 °C and 25 °C, respectively, with excellent capacity retention, as well as exhibiting acceptable rate capability. These findings reveal that dicationic PIL-based electrolytes have great potential for use as safe electrolytes in LMBs.
Co-reporter:Xiaowei Li, Zhengxi Zhang, Li Yang, Kazuhiro Tachibana, Shin-ichi Hirano
Journal of Power Sources 2015 Volume 293() pp:831-834
Publication Date(Web):20 October 2015
DOI:10.1016/j.jpowsour.2015.06.033
•TiO2-based ionogel electrolytes are prepared by a one-pot sol–gel processing.•TiO2-based ionogel electrolytes have good electrochemical properties.•TiO2-based ionogel electrolytes reveal impressive battery performance.In this work, TiO2-based ionogel electrolytes (TIEs), TiO2/ionic liquid/LiTFSI, are prepared by a one-pot sol–gel processing. The electrochemical performance and potential application in lithium metal batteries (LMBs) of TIEs are evaluated for the first time. It is found that the as-prepared TIE system reveals liquid-like high ionic conductivity, good electrochemical stability and ability to promote uniform lithium electrodeposition. Specifically, LMBs containing the TIE show high discharge capacity and good capacity retention at 25 °C under the 0.1C rate. Also, acceptable rate performance and low-temperature discharge ability can be obtained.
Co-reporter:Qinghua Tian, Yang Tian, Zhengxi Zhang, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2015 Volume 291() pp:173-180
Publication Date(Web):30 September 2015
DOI:10.1016/j.jpowsour.2015.04.171
•The CNT@void@SnO2@C nanostructure was prepared by a novel and facile route.•This peculiar architecture endowed the composite superior physical buffer and electric conductivity ability.•This composite exhibited excellent electrochemical performances.Tin dioxide/carbon composites is an important class of promising candidates for anode materials with superior electrochemical performance and thus have attracted extensive attention. Herein, a tube-in-tube nanostructure, denoted as CNT@void@SnO2@C, has been fabricated by a facile and novel strategy. The possible formation mechanism is also discussed and determined by TEM, XRD and XPS characterizations. As a promising anode material for lithium-ion batteries, the CNT@void@SnO2@C exhibits superior lithium storage properties, delivering a reversible capacity of 702.5 mAh g−1 at 200 mA g−1 even after 350 cycles. The excellent performances should be benefited from the peculiar tube-in-tube nanostructure, in which SnO2 located between CNT and outermost carbon coating layers can sure the structural integrity and high conductivity during long-term cycling, and one-dimensional void space formed between the inner CNT and outer SnO2@C nanotubes, in particular, can provide larger free space for alleviating the huge volume variation of SnO2 and accommodating the stress formed during repeated discharge/charge process.
Co-reporter:Qinghua Tian, Zhengxi Zhang, Li Yang, Shin-ichi Hirano
Carbon 2015 Volume 93() pp:887-895
Publication Date(Web):November 2015
DOI:10.1016/j.carbon.2015.06.010
Design and fabrication of tin dioxide/carbon composites with peculiar nanostructures have been proven to be an effective strategy for improving the electrochemical performance of tin dioxide-based anode for lithium-ion batteries, and thus have attracted extensive attention. Herein, we have successfully prepared a uniquely three-dimensional and interweaved wire-in-tube nanostructure of nitrogen-doped carbon nanowires encapsulated into tin dioxide@carbon nanotubes, denoted as NCNW@void@SnO2@C, via a facile and novel approach for the first time. Interestingly, one-dimension void space located between nitrogen-doped carbon nanowires and innermost wall of tin dioxide@carbon tubes is also formed. The possible formation mechanism of wire-in-tube nanostructure is also discussed and determined by transmission electron microscopy, X-ray diffraction measurement, laser Raman spectroscopy and X-ray photoelectron spectroscopy characterizations. This unique NCNW@void@SnO2@C fully combines all the advantages of using a three-dimensional architecture, hollow structure, carbon coating, and a mechanically robust carbon nanowires support, thus exhibiting an excellent electrochemical performance as promising anode materials for lithium-ion batteries. A high reversible capacity of 721.3 mAh g−1 can be remained even after 500 cycles at a current density of 200 mA g−1, as well as a capacity of 456.7 mAh g−1 is obtained even at 3000 mA g−1.
Co-reporter:Long Qu, Yi Liu, Shaohua Fang, Li Yang, Shin-ichi Hirano
Electrochimica Acta 2015 Volume 163() pp:123-131
Publication Date(Web):1 May 2015
DOI:10.1016/j.electacta.2015.02.102
Low-cost sorbitanlaurat is used as new carbon source to synthesize Li2FeSiO4/C by sol–gel method. Four Li2FeSiO4/C products with different carbon contents are pursued as the cathode material of lithium-ion battery. The structures and morphologies of these products are characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope. The particle size of these Li2FeSiO4 products is about 10–20 nm. The product with 8.4 wt% carbon delivers an initial discharge capacity of 187 mA h g−1 at 0.1 C. This product also exhibits good rate and cycle performances. By Raman spectroscopy, cyclic voltammogram and impedance spectroscopy, the factor which can affect the rate performance of these Li2FeSiO4/C products is analyzed.
Co-reporter:Qinghua Tian, Zhengxi Zhang, Li Yang and Shin-ichi Hirano
RSC Advances 2015 vol. 5(Issue 50) pp:40303-40309
Publication Date(Web):20 Apr 2015
DOI:10.1039/C5RA04629G
In spite of high-profile theoretical capacity, the practical application of SnO2 or Sn anode materials for lithium-ion batteries is severely impeded by poor electric conductivity and structural instability. Herein, a hybrid structure of SnO2/Sn sandwiched between TiO2 and carbon with rich porosity, good electric conductivity and stable structure, denoted as TiO2@SnOx@C, is fabricated based on the complementary merits of SnO2, TiO2 and carbon anode materials. The TiO2@SnOx@C exhibits a good electrochemical performance when used as anode material for lithium-ion battery, delivering a capacity of 629 mA h g−1 at 200 mA g−1 after 300 cycles. Moreover, a reversible capacity of 490.3 mA h g−1 is obtained at 1000 mA g−1 even after 1000 cycles and is much higher than theoretical capacity of graphite (372 mA h g−1). The effectively complementary and synergic effect among structural stability of TiO2, high theoretical capacity of SnOx, and good conductive and flexible ability of carbon should be responsible for the superior electrochemical performance of TiO2@SnOx@C.
Co-reporter:Qinghua Tian, Jianzhi Song, Zhengxi Zhang, Li Yang, Shin-ichi Hirano
Materials Chemistry and Physics 2015 Volume 151() pp:66-71
Publication Date(Web):1 February 2015
DOI:10.1016/j.matchemphys.2014.11.036
•3-dimensional interweaved TiO2 hollow nanowires were fabricated by a facile strategy.•This structure can buffer the volume change and facilitate Li+ and e− diffusion.•This TiO2 anode presented effective physical buffer ability and conductivity.•It delivered a capacity of 180.8, 153.3 mAh g−1 at 0.2 C and 2 C, respectively.•It exhibited a desirable rate capability.To overcome the issue of inferior practical capacity and electronic conductivity for titanium dioxide (TiO2) anode materials in lithium-ion batteries, an effective strategy is explored to fabricate a nanostructured TiO2 with large specific surface area and confined dimension, considering the nanostructure to achieve increased contact interface between the active materials and the electrolyte, restricted agglomeration of TiO2, enhanced structure stability, shortened diffusion distance of lithium-ion and electron, contributing to desirable electrochemical properties. Herein, we have prepared an intriguing nanostructure of 3-dimensional interweaved anatase TiO2 hollow nanowires (denoted as HNW TiO2) by a facile strategy. When tested as potential anode materials for lithium-ion batteries, this nanostructured HNW TiO2 delivers a reversible capacity of 180.8, 153.3 mAh g−1 at current rate of 0.2 C and 2 C, respectively, indicating good lithium storage performance, which should be benefited from its unique architecture.
Co-reporter:Yang Tian, Qinghua Tian, Zhengxi Zhang, Li Yang, Shin-ichi Hirano
Materials Letters 2015 Volume 155() pp:142-145
Publication Date(Web):15 September 2015
DOI:10.1016/j.matlet.2015.03.082
Co-reporter:Qinghua Tian, Zhengxi Zhang, Li Yang and Shin-ichi Hirano
Journal of Materials Chemistry A 2014 vol. 2(Issue 32) pp:12881-12887
Publication Date(Web):11 Jun 2014
DOI:10.1039/C4TA02059F
In this work, a peculiar nanostructure of SnO2/Sn@carbon nanospheres dispersed in the interspaces of a three-dimensional SnO2/Sn@carbon nanowires network composite (denoted as SnO2/Sn@C) has been successfully fabricated by a facile strategy and confirmed by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, laser Raman spectroscopy, Brunauer–Emmett–Teller method, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy characterization, illustrating the combination of the nanospheres and the 3-dimensional nanowires network. This architecture effectively withstands the volume change and restricts the agglomeration of SnO2/Sn during the cycling process. Moreover, the SnO2/Sn distributed in carbon matrix and the SnO2/Sn@carbon nanospheres dispersed in interspaces of three-dimensional SnO2/Sn@carbon nanowires network facilitate electron and ion transport throughout the electrode. As a result, this composite exhibits excellent performance as a potential anode material for lithium ion batteries and delivers a reversible capacity of 678.6 mA h g−1 at 800 mA g−1, even after 500 cycles.
Co-reporter:Yide Jin, Jianhao Zhang, Jianzhi Song, Zhengxi Zhang, Shaohua Fang, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2014 Volume 254() pp:137-147
Publication Date(Web):15 May 2014
DOI:10.1016/j.jpowsour.2013.12.048
•New functionalized quaternary ammonium ILs with two ether groups are reported.•They have low viscosity and good electrochemical stability.•Li/LiFePO4 cells using these IL electrolytes have good electrochemical performance.New functionalized ILs based on quaternary ammonium cations with two ether groups and bis(trifluoromethanesulfonyl)imide (TFSA−) anion are synthesized and characterized. Physical and electrochemical properties, including melting point, thermal stability, viscosity, conductivity and electrochemical stability are investigated for these ILs. All these ILs are liquids at room temperature except N,N-diethyl-N,N-bis(2-ethoxyethyl)ammonium TFSA (N22(2o2)(2o2)-TFSA, Tm = 29.7 °C), and the viscosities of N-methyl-N-ethyl-N-(2-methoxyethyl)-N-(2-ethoxyethyl)ammonium TFSA (N12(2o1)(2o2)-TFSA) and N-methyl-N-ethyl-N,N-bis(2-ethoxyethyl)ammonium TFSA (N12(2o2)(2o2)-TFSA) are 68.0 cP and 63.0 cP at 25 °C, respectively. N-Methyl-N,N-diethyl-N-(2-methoxyethyl)ammonium TFSA (DEME–TFSA) and five ILs with lower viscosity are chosen to dissolve 0.6 mol kg−1 of LiTFSA as IL electrolytes without additive for lithium battery. Lithium plating and striping on Ni electrode can be observed in these IL electrolytes, and cycle performances of lithium symmetrical cells are also investigated for these IL electrolytes. Li/LiFePO4 cells using these IL electrolytes without additives have good cycle property at the current rate of 0.1 C, and the N-methyl-N-ethyl-N,N-bis(2-methoxyethyl)ammonium TFSA (N12(2o1)(2o1)-TFSA) and N12(2o2)(2o2)-TFSA electrolytes own better rate property than DEME–TFSA electrolyte.
Co-reporter:Qinghua Tian, Zhengxi Zhang, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2014 Volume 253() pp:9-16
Publication Date(Web):1 May 2014
DOI:10.1016/j.jpowsour.2013.12.049
•We fabricated a new morphological nanostructure of composite: encapsulation of SnO2 nanoparticles into hollow TiO2 nanowires.•The composite realized the integration of the high capacity SnO2 and structural stability TiO2.•This nanostructure made the composite to have sufficient physical buffer ability.•The composite exhibited good lithium storage performance and excellent cyclability.In this work, a new nanostructure of SnO2 nanoparticles (NPs) encapsulated into hollow TiO2 nanowires (SnO2@TiO2) has been successfully fabricated. This unique architecture intrinsically possess void space in between the TiO2 shell and SnO2 nanoparticle cores, as confirmed by XRD, XPS, SEM, TEM and HRTEM characterizations. The TiO2 shell of the composite can not only alleviate the pulverization and drastic volume change of the SnO2 NPs and maintain the structural integrity, but also contribute to the total capacity of the composite. Moreover, the void space can also accommodate the volume expansion of SnO2 and provide highly efficient channels for the fast transport of both electrons and lithium ion during discharge/charge cycling process. When tested as potential anode materials for lithium ion batteries, the as-prepared hollow TiO2 nanowires shell encapsulating SnO2 NPs architecture exhibits good lithium storage performance and excellent cyclability (which delivers a higher reversible capacity of 445 mAh g−1 at 800 mA g−1 after 500 cycles). The unique architecture should be responsible for the superior electrochemical performance.
Co-reporter:Kun Yin, Zhengxi Zhang, Li Yang, Shin-Ichi Hirano
Journal of Power Sources 2014 Volume 258() pp:150-154
Publication Date(Web):15 July 2014
DOI:10.1016/j.jpowsour.2014.02.057
•An imidazolium-based PIL is successfully obtained via new synthetic strategy.•Based on the PIL host, flexible polymer electrolyte membranes are prepared.•The polymer electrolytes show excellent electrochemical performance.An imidazolium-based polymerized ionic liquid (PIL), poly(1-ethyl-3-vinylimidazolium bis(trifluoromethanesulfonylimide)) is successfully synthesized via a new three-step process comprising the direct radical polymerization of the 1-vinylimidazole monomer, and subsequent quaternization reaction followed by an anion exchange procedure. Furthermore, polymer electrolytes are prepared by blending as-obtained PIL as the polymer host with an ionic liquid and LiTFSI salt. Electrochemical measurements demonstrate that compared with polymer electrolytes containing the PIL host synthesized by the conventional route, polymer electrolytes containing the PIL host obtained by new synthetic process exhibit significantly improved capacity and cycling performance, which is due to higher ionic liquid content.
Co-reporter:Qinghua Tian, Zhengxi Zhang, Jizhang Chen, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2014 Volume 246() pp:587-595
Publication Date(Web):15 January 2014
DOI:10.1016/j.jpowsour.2013.08.009
•We prepared a new morphological nanostructure of composite: CNWs@ultrathin SnO2 NSs@C composite.•The coaxial nanocable-like structure made the composite to have sufficient physical buffer ability.•The composite exhibited good results in performance of capacity and cycling.In this work, a new morphological nanostructure of the CNWs@ultrathin SnO2 NSs@C composite has been successfully fabricated, realizing the integration of two-dimensional ultrathin SnO2 NSs and one-dimensional CNWs. The nanosized ultrathin SnO2 NSs (thickness of ca. 1–3 nm) are uniformly distributed between one dimension CNWs core and C shell, as confirmed by XRD, SEM, TEM and HRTEM characterizations. When tested as potential anode materials for LIBs, the as-prepared coaxial nanocable-like CNWs@ultrathin SnO2 NSs@C composite exhibits outstanding reversible capacity for lithium storage (695 mAh g−1 after 40 cycles at 160 mA g−1, 651 and 618 mAh g−1 after 80 cycles at 400 and 800 mA g−1, respectively). This intriguing architecture, which integrates both electronic conductivity and buffering matrix design strategies, contributing to enhanced lithium storage performance.
Co-reporter:Qinghua Tian, Yang Tian, Zhengxi Zhang, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2014 Volume 269() pp:479-485
Publication Date(Web):10 December 2014
DOI:10.1016/j.jpowsour.2014.07.019
•A composite of ultrasmall SnO2 embedded in carbon was prepared by a facile strategy.•The peculiar structure brought the composite sufficient physical buffer ability.•This composite (SnO2/C-59) exhibited an excellent electrochemical performance.Tin oxide (SnO2) has received great attention as promising anode for lithium ion batteries because it offers a high theoretical capacity (ca. 782 mAh g−1 for Li4.4Sn) and a safe discharge potential versus Li/Li+ in comparison to commercialized graphite anodes, whereas it also suffer from the drawbacks of the huge volume change and low electronic conductivity during lithiation/delithiation processes. Herein, we have prepared a SnO2/C composite of ultrasmall SnO2 nanoparticles (∼6 nm and ∼59.4% by weight) embedded in carbon matrix (denoted as SnO2/C-59) by a facile hydrothermal and subsequent carbonization approach. In this peculiar architecture, uniform distribution of SnO2, and electronic conductivity of carbon matrix, which can effectively solve the problems of pulverization, loss of electrical contact and particle aggregation during cycling, therefore contributing to excellent lithium storage and cycling stability. A reversible capacity of 839.1 mAh g−1 is obtained at 200 mA g−1 after 217 cycles. More importantly, 712.8 mAh g−1 can be obtained at 800 mA g−1 even after 378 cycles.
Co-reporter:Long Qu, Shaohua Fang, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2014 Volume 252() pp:169-175
Publication Date(Web):15 April 2014
DOI:10.1016/j.jpowsour.2013.11.076
•Pure-phased Li2MnSiO4/C is prepared by sol–gel method with Mn3O4 nanoparticle.•It owns nano-sized active material particle with 20–30 nm.•It delivers an initial discharge capacity of 240 mAh g−1 at room temperature.•Irreversible distortion might mainly effect on the cycle performance of Li2MnSiO4/C.Li2MnSiO4/C composite is prepared by sol–gel method with Mn3O4 nanoparticle, and its carbon content, structure, and morphology are characterized. The results show that Li2MnSiO4/C exhibits pure phase with orthorhombic structure and the size of Li2MnSiO4 (20–30 nm) is smaller than Mn3O4 nanoparticle. As the cathode material of lithium-ion battery, Li2MnSiO4/C delivers an initial discharge capacity of about 240 mAh g−1 at the current density of 8 mA g−1, corresponding to 1.44 mol of Li+ per formula unit. The cycle performance of Li2MnSiO4/C at different current densities from 8 mA g−1–320 mA g−1 is studied, and it is found that the capacity retention is improved with the increasing of current density. Basing on the results of ex-situ X-ray diffraction measurement, it is inferred that low degree of irreversible distortion for Li2MnSiO4 may result in the improved capacity retention at high current density.
Co-reporter:Jizhang Chen, Li Yang, Shaohua Fang, Zhengxi Zhang, Aniruddha Deb, Shin-ichi Hirano
Electrochimica Acta 2014 Volume 127() pp:390-396
Publication Date(Web):1 May 2014
DOI:10.1016/j.electacta.2014.02.066
•Sn-contained N-rich carbon nanowires are obtained via a facile procedure.•Our product is abundant in nitrogen.•Our product possesses the morphology of nanowires.•The encapsulation of Sn contributes to a higher capacity upon long cycles.•Our product delivers excellent cycling stability and high reversible capacity.We report here for the first time Sn-contained N-rich carbon nanowires, which are prepared via a facile and scalable procedure using poly-pyrrole as the carbon source. As-obtained nanowires with a diameter of about 50 nm crosslink with each other with enough void space, beneficial to accommodating lithiation-induced volumetric change and mechanical stress. In particular, this product contains abundant nitrogen (9.8 wt.%), favorable for Li+ diffusion and storage. It therefore exhibits excellent cycling stability of 682.6 and 760.1 mAhg−1 at 500 mAg−1 after 200 and 600 cycles, respectively. It also delivers great high rate performance even at 10 Ag−1.
Co-reporter:Senlin Wang, Zhengxi Zhang, Aniruddha Deb, Chunchen Yang, Li Yang, Shin-ichi Hirano
Electrochimica Acta 2014 Volume 143() pp:297-304
Publication Date(Web):10 October 2014
DOI:10.1016/j.electacta.2014.07.139
Nanostructured Li3V2(PO4)3/C composite has been synthesized by a facile microemulsion method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results confirm that the as-prepared Li3V2(PO4)3/C sample shows the pure monoclinic structure and nanosphere morphology. Li3V2(PO4)3/C has a particle size of about 100 nm, and these nanoparticles are connected each other by the conductive carbon network. Electrochemical measurements demonstratethat the Li3V2(PO4)3/C nanoparticles can deliver discharge capacities of 129.8, 126.1, 118.0, 116.1 and 110.1 mAh g−1 between 3.0 and 4.3 V, and 171.4, 163.1, 153.2, 144.0 and 133.4 mAh g−1 between 3.0 and 4.8 V at 1, 2, 5, 10 and 20 C, respectively. Even at 20 C rate, it still can present a reversible discharge capacity of 101.8 mAh g−1 with 92.5% capacity retention after 1400 cycles and 96.4 mAh g−1 with 72.3% capacity retention after 1000 cycles in the potential ranges of 3.0-4.3 V and 3.0-4.8 V, respectively. The excellent rate capability and long-term cycle performance demonstrate that the Li3V2(PO4)3/C nanoparticles prepared in this work has great potential for application as cathode materials in high-power lithium ion batteries.Spheric Li3V2(PO4)3/C nanoparticles, which are fabricated by a facile microemulsion method, exhibit excellent rate capability and long cycle life over an extended 1000 cycles when evaluated as a cathode material for lithium ion batteries. These results are due to the nanoscale Li3V2(PO4)3 particles and conductive carbon network.
Co-reporter:Qinghua Tian, Zhengxi Zhang, Li Yang, Shin-ichi Hirano
Electrochimica Acta 2014 Volume 138() pp:155-162
Publication Date(Web):20 August 2014
DOI:10.1016/j.electacta.2014.06.047
Titanium dioxide (TiO2) has received increasing attention as promising anode for lithium ion batteries because it offers a distinct safety advantage in comparison to commercialized graphite anodes, whereas it also suffer from the drawbacks of low practical capacity and relatively low electronic conductivity. Herein, one-dimensional mesoporous anatase TiO2 composed of nanocrystals prepared by a facile procedure is reported for the first time. Such peculiar architecture and intrinsical mesoporous can effectively improve pseudocapacitance charge storage, increase contact interface between the active materials and electrolyte, and enhance the structure stability during cycling, therefore contributing to good lithium storage and excellent cycling stability. A reversible capacity of 202.9 mAhg−1is obtained at 30 mAg−1 after 70 cycles. More importantly, 151 mAhg−1 can be obtained at 200 mAg−1 even after 500 cycles.
Co-reporter:Senlin Wang, Zhengxi Zhang, Aniruddha Deb, Li Yang, and Shin-ichi Hirano
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 50) pp:19525-19532
Publication Date(Web):November 24, 2014
DOI:10.1021/ie502917b
A series of Ce3+-doped ordered macroporous Li3V2–xCex(PO4)3/C (x = 0, 0.01, 0.03, 0.05) samples have been fabricated via a colloidal crystal template method. The X-ray powder diffraction and scanning electron microscopy analysis demonstrate that the Ce element doping does not affect the original monoclinic structure and macroporous morphology of the pristine Li3V2(PO4)3/C sample. Electrochemical measurement results prove that the Li3V1.97Ce0.03(PO4)3/C sample presents the best electrochemical performance as the cathode material for lithium ion batteries among the as-prepared samples in the potential ranges of both 3–4.3 V and 3–4.8 V. The substitution of V3+ with an appropriate amount of Ce3+ increases the Li+ diffusion coefficient based on the electrochemical impedance spectroscopy results, which is mainly responsible for the excellent electrochemical performance.
Co-reporter:Jianhao Zhang, Shaohua Fang, Long Qu, Yide Jin, Li Yang, and Shin-ichi Hirano
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 43) pp:16633-16643
Publication Date(Web):2017-2-22
DOI:10.1021/ie502716p
A family of new ether-functionalized ionic liquids based on 1,3-dialkylimidazolium cation with alkoxymethyl or alkoxyethyl group and TFSA anion were synthesized and characterized. The properties of these ionic liquids, including melting point, thermal stability, density, viscosity, conductivity, and electrochemical window, were determined and compared with those of 3 typical 1,3-dialkylimidazolium ionic liquids without ether group. The effect of ether group on the properties was systematically investigated. All these ionic liquids were liquid at room temperature, and their melting points were lower than −60 °C. It was demonstrated that alkoxyethyl group was favorable to decreasing viscosity of 1,3-dialkylimidazolium ionic liquids, and alkoxymethyl group was not helpful for decreasing viscosity. At room temperature, 6 new ionic liquids had the viscosities lower than 45 cP, and the viscosity of IM2o2-2-TFSA was only 31.3 cP.
Co-reporter:Jizhang Chen, Li Yang, Saibihai Rousidan, Shaohua Fang, Zhengxi Zhang and Shin-ichi Hirano
Nanoscale 2013 vol. 5(Issue 21) pp:10623-10628
Publication Date(Web):30 Aug 2013
DOI:10.1039/C3NR03955B
Si has the second highest theoretical capacity among all the known anode materials for lithium ion batteries, whereas it is vulnerable to pulverization and crumbling upon lithiation/delithiation. Herein, Si mesoporous nanowires prepared by a scalable and cost-effective procedure are reported for the first time. Such nanowire morphology and mesoporous structure can effectively buffer the huge lithiation-induced volume expansion of Si, therefore contributing to excellent cycling stability and high-rate capability. Reversible capacities of 1826.8 and 737.4 mA h g−1 can be obtained at 500 mA g−1 and a very high current density of 10 A g−1, respectively. After 1000 cycles at 2500 mA g−1, this product still maintains a high capacity of 643.5 mA h g−1.
Co-reporter:Jizhang Chen, Li Yang, Zhengxi Zhang, Shaohua Fang and Shin-ichi Hirano
Chemical Communications 2013 vol. 49(Issue 27) pp:2792-2794
Publication Date(Web):18 Feb 2013
DOI:10.1039/C3CC40671G
Using amorphous TiO2 microspheres as precursors, we obtain mesoporous TiO2–Sn@C core–shell microspheres. Sn is encapsulated into a TiO2 matrix, and carbon is coated outside. This intriguing architecture can effectively buffer volume change and structural stress, thus contributing to excellent long-term cycling stability and superior high-rate cyclability.
Co-reporter:Yide Jin, Shaohua Fang, Ming Chai, Li Yang, Kazuhiro Tachibana, Shin-ichi Hirano
Journal of Power Sources 2013 Volume 226() pp:210-218
Publication Date(Web):15 March 2013
DOI:10.1016/j.jpowsour.2012.10.076
Six low-viscosity ionic liquids based on trialkylimidazolium cation with one or two ether groups and TFSA− anion are used as new electrolytes for lithium battery, and compared with three typical trialkylimidazolium ILs without ether group. It is found that ether group in trialkylimidazolium cation can have an obvious effect on properties of electrolyte and performances of lithium battery. Introducing of ether group into trialkylimidazolium cation can be benefit for lithium redox behavior on Ni electrode, and affect passivation layer between IL electrolyte and lithium metal. Li/LiFePO4 cells using these ether-functionalized IL electrolytes without additive have good battery performance, and IM(2o1)1(2o2)-TFSA electrolyte owns better rate property.Highlights► New trialkylimidazolium ILs are used as electrolytes for lithium battery. ► Ether group in IL cation can have effect on properties of IL electrolyte. ► Li/LiFePO4 cells using these IL electrolytes have good electrochemical performance.
Co-reporter:Jizhang Chen, Li Yang, Shaohua Fang, Zhengxi Zhang, Shin-ichi Hirano
Electrochimica Acta 2013 Volume 105() pp:629-634
Publication Date(Web):30 August 2013
DOI:10.1016/j.electacta.2013.05.052
•Graphene/Cu6Sn5 nanocomposite is prepared via a facile one-pot method.•The buffer effects of copper, graphene, and hollow structure are combined.•This composite delivers excellent long-term (∼1700 cycles) cycling stability.•High rate (merely 80 s for discharge or charge) capability is obtained.Graphene/Cu6Sn5 nanocomposite is successfully prepared via a facile one-pot method. Cu6Sn5 nanoparticles with the average size below 10 nm are homogeneously encapsulated into graphene nanosheets. Inactive Cu can release the volume expansion of Sn, prevent Sn from aggregation, and accommodate structural stress. Graphene can enhance mechanical properties, prevent the aggregation between Cu6Sn5 nanoparticles, and provide enough void space to buffer volume change of Cu6Sn5. Part of Cu6Sn5 nanoparticles possesses hollow structure, which is also favorable for volume buffer and stress accommodation. Due to such intriguing structure, it delivers great long term cycling stability and excellent high rate performance. Up to 411.4 mAh g−1 is obtained after 1600 cycles at a high current density of 500 mA g−1. The reversible capacity is as large as 220 mAh g−1 at 10,000 mA g−1 (merely 80 s for discharge or charge).
Co-reporter:Senlin Wang, Zhengxi Zhang, Shaohua Fang, Li Yang, Chunchen Yang, Shin-ichi Hirano
Electrochimica Acta 2013 Volume 111() pp:685-690
Publication Date(Web):30 November 2013
DOI:10.1016/j.electacta.2013.08.086
A series of ordered macroporous Li3V2(PO4)3 (LVP) cathode materials with three different pore sizes (65 nm, 120 nm and 210 nm) are prepared via a templating method using poly(methyl methacrylate) (PMMA) colloidal crystals as templates. The structure, morphology and electrochemical properties of the as-prepared LVP samples are characterized by SEM, TEM, XRD, BET, galvanostatic charge–discharge tests, cyclic voltammograms and electrochemical impedance spectroscopy measurements. The three LVP samples all show pure monoclinic structure and ordered macroporous morphology. The LVP sample with pore size of 210 nm shows the best electrochemical performance. In the potential range of 3.0–4.8 V, it delivers a high initial discharge capacity of 189.4 mAh g−1 at 0.1 C, which is close to the theoretical capacity (197 mAh g−1). Moreover, at 0.5 C, 1 C and 5 C, it exhibits initial discharge capacities of 170.5, 166.0 and 145.9 mAh g−1, and can still retain 77.3%, 71.2% and 77.1% of the initial discharge capacity after 100 cycles, respectively.
Co-reporter:Yide Jin, Shaohua Fang, Zhengxi Zhang, Jianhao Zhang, Li Yang, and Shin-ichi Hirano
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 22) pp:7297-7306
Publication Date(Web):May 9, 2013
DOI:10.1021/ie400371q
A new family of C-2 functionalized trialkylimidazolium ionic liquids with alkoxymethyl groups were synthesized and characterized. Their physicochemical properties including melting point, thermal stability, viscosity, conductivity, and electrochemical windows were systematically investigated. All of these functionalized trialkylimidazolium ionic liquids were liquids at room temperature, and most of them had melting points lower than −60 °C. At room temperature, 24 ionic liquids had viscosities lower than 90 cP, and the viscosities of IM2(1o2)2TFSA and IM1(1o2)2TFSA were 50.3 and 53.3 cP.
Co-reporter:Long Qu, Shaohua Fang, Zhengxi Zhang, Li Yang, Shin-ichi Hirano
Materials Letters 2013 Volume 108() pp:1-4
Publication Date(Web):1 October 2013
DOI:10.1016/j.matlet.2013.06.072
•Pure-phased Li2FeSiO4/C is prepared by the sol–gel method with Fe2O3 nanoparticle.•The particle size of Li2FeSiO4 is close to Fe2O3 nanoparticle.•It owns stable cycle performance at 0.1C to 5C rate.•It has good rate performance.Li2FeSiO4/C has been prepared by the ultrasonic-assisted sol–gel method with about 50 nm Fe2O3 particle as Fe source. The structures, morphologies, and carbon content of the product are characterized. Li2FeSiO4/C owns pure phase and the particle size of Li2FeSiO4 is close to Fe2O3 nanoparticle. As the cathode material of Li-ion battery, the product shows stable cycle performance at the wide range of rate and good rate performance. The discharge capacities of the 100th cycle are 140 mAh g−1, 125 mAh g−1, 120 mAh g−1, 110 mAh g−1, and 90 mAh g−1 at 0.1C, 0.5C, 1C, 2C, and 5C rate, respectively.
Co-reporter:Jizhang Chen, Li Yang, Shaohua Fang, Shin-ichi Hirano
Journal of Power Sources 2012 Volume 209() pp:204-208
Publication Date(Web):1 July 2012
DOI:10.1016/j.jpowsour.2012.02.111
Mesoporous Sn–Cu composite consisting of Cu6Sn5 (active), Cu3Sn (inactive), and Sn is prepared by using silica SBA-15 as the hard template. As-prepared composite has a large BET surface area of 197.8 m2 g−1 and a large pore volume of 0.517 cm3 g−1. As the anode material for lithium ion batteries, no obvious capacity decay can be observed from 2nd to 20th cycles when the current density is 500 mA g−1. It delivers much better cycling performance than bulk Sn–Cu composite without porous structure. The mesoporous structure can provide sufficient contact of the active material with the electrolyte, and can buffer volume changes of Sn in the electrochemical process. Charge transfer process is also found to be favored by using EIS measurements.Highlights► Mesoporous Sn–Cu composite is obtained via a nanocasting process. ► Our product has a large BET surface area and a huge pore volume. ► Our product delivers superb cycling performance at a high current density.
Co-reporter:Jizhang Chen, Li Yang, Shaohua Fang, Shin-ichi Hirano, Kazuhiro Tachibana
Journal of Power Sources 2012 Volume 199() pp:341-345
Publication Date(Web):1 February 2012
DOI:10.1016/j.jpowsour.2011.10.043
Core–shell Cu@Cu6Sn5 nanowires with three-dimensional structure have been successfully synthesized via an electrodeposition process, using Cu(OH)2 nanorods prepared by anodization as the substrate. Different temperatures have been employed to heat-treat Sn–Cu composites. After heat-treated at 80 °C, strong adherence of the active material Cu6Sn5 to the current collector is achieved, and the crystal structure becomes more stable, thus delivering best cycling performance of 0.162 mAh cm−2 after 200 cycles at 1 C. Furthermore, superior rate capability (as high as 20 C) is also obtained.Graphical abstractHighlights► We obtain Cu(OH)2 nanorods substrate by anodization. ► We obtain three-dimensional core–shell Cu@Cu6Sn5 nanowires after electrodeposition. ► We obtain great cycling performance and rate capability. ► The morphology and structure can be maintained after cycles.
Co-reporter:Ming Chai, Yide Jin, Shaohua Fang, Li Yang, Shin-ichi Hirano, Kazuhiro Tachibana
Journal of Power Sources 2012 Volume 216() pp:323-329
Publication Date(Web):15 October 2012
DOI:10.1016/j.jpowsour.2012.05.082
Four new functionalized ILs based on pyrazolium cations and bis(trifluoromethylsulfonyl)imide anions (TFSI−) are synthesized and characterized. These ILs show low-melting point and low-viscosity characteristics, and the viscosity of OEPZ–TFSI is 41.2 mPa s at 25 °C. These IL electrolytes with 0.4 mol kg−1 LiTFSI have good chemical stability against lithium metal. Li/LiFeO4 cells using these IL electrolytes without additives own good electrochemical performance, and the cells using OMPZ–TFSI and OEPZ–TFSI electrolytes own better rate property.Highlights► New ether-functionalized pyrazolium ILs are reported. ► They have low-viscosity and low-melting point characteristics. ► Li/LiFePO4 cells using these IL electrolytes have good electrochemical performance.
Co-reporter:Long Qu, Shaohua Fang, Li Yang, Shin-ichi Hirano
Journal of Power Sources 2012 Volume 217() pp:243-247
Publication Date(Web):1 November 2012
DOI:10.1016/j.jpowsour.2012.05.093
Fe2O3 microsphere is used as iron source and template to prepare Li2FeSiO4/C nanocomposite by a sol–gel method. The carbon content, structure, and morphology of the sample are characterized by carbon–sulfur inferred analysis (CSI), X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM) techniques. The results show that the Li2FeSiO4/C owns pure phase and sphere-like morphology as a result of an agglomeration of nanoparticles with an average particle size of about 50 nm. The Li2FeSiO4/C exhibits stable cycle performance at different rates from 0.1 C to 2 C, and its capacity at 0.1 C rate can reach 160 mAh g−1.Highlights► Li2FeSiO4/C nanocomposite is prepared by sol–gel method with Fe2O3 microsphere. ► It exhibits sphere-like morphology. ► It owns stable cycle performance at 0.1 C–2 C rate.
Co-reporter:Ming Chai, Yide Jin, Shaohua Fang, Li Yang, Shin-ichi Hirano, Kazuhiro Tachibana
Electrochimica Acta 2012 Volume 66() pp:67-74
Publication Date(Web):1 April 2012
DOI:10.1016/j.electacta.2012.01.059
Two new functionalized ILs based on pyrazolium cations and bis(trifluoromethylsulfonyl)imide anions (TFSI−) were synthesized and characterized. Their physicochemical and electrochemical properties, including melting point, thermal stability, density, viscosity, conductivity, and electrochemical window were investigated. The two ILs had low melting points and wide electrochemical windows. Behaviors of lithium redox, chemical stability against lithium metal, and charge–discharge cycle performance of lithium battery were also examined for the two IL electrolytes with 0.4 mol kg−1 LiTFSI. The IL electrolytes showed good chemical stability against lithium metal, and Li/LiFeO4 cells using the two IL electrolytes without additives owned good capacity and cycle property at the current rate of 0.1 C.Highlights► New ether-functionalized pyrazolium ILs are reported. ► They have low melting point and good electrochemical stability. ► Li/LiFePO4 cells using the IL electrolytes have good capacity and cycle property.
Co-reporter:Yide Jin, Shaohua Fang, Ming Chai, Li Yang, and Shin-ichi Hirano
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 34) pp:11011-11020
Publication Date(Web):August 7, 2012
DOI:10.1021/ie300849u
A family of new ether-functionalized ILs based on trialkylimidazolium cations with one or two ether groups and TFSA– anion was synthesized and characterized. Their properties including melting point, thermal stability, viscosity, conductivity, and electrochemical windows were determined and compared to those of the trialkylimidazolium ILs without ether group. The relationship between the cations structure and IL physicochemical properties was systematically studied. Most of these ether-functionalized ILs were liquids at room temperature, and the melting points of 21 ILs were lower than −60 °C. At room temperature, 26 ILs owned the viscosities lower than 100 mPa s, and the viscosities of IM(2o1)12TFSA and IM(2o2)12TFSA were 57.4 and 54.4 mPa s.
Co-reporter:J.S. Huang, L. Yang, K.Y. Liu
Materials Letters 2012 Volume 66(Issue 1) pp:196-198
Publication Date(Web):1 January 2012
DOI:10.1016/j.matlet.2011.08.097
Li3V2(PO4)3/C is synthesized by an improved rheological phase method using Hydroxy Ethylidene-1,1-Diphosphonic Acid (HEDP) as organic phosphoric sources. The phosphoric sources with carbon chains can inhibit the grain growth of Li3V2(PO4)3 particles. X-ray powder diffraction pattern shows that the obtained Li3V2(PO4)3/C sample is monoclinic phase. Transmission electron microscope results show that the thickness of carbon layer is about 10 nm. The form of residual carbon is confirmed by Raman spectroscopy. The Li3V2(PO4)3/C sample prepared by 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (HEDP) displays the initial discharge capacity of 158 mAh g− 1 and keeps 130 mAh g− 1 after 100 cycles at 1 C rate. The improved rheological phase reaction method can be used for synthesis of Li3V2(PO4)3 cathode material and other polyanion materials.Research highlights►Li3V2(PO4)3/C was prepared by improved rheological phase reaction (RPR) method. ►Organic phosphoric sources can inhibit Li3V2(PO4)3 grains growth. ►Li3V2(PO4)3/C with enhanced electrochemical performance for lithium ion battery. ►The strategy can be applied to prepare polyanion cathode materials.
Co-reporter:Mingtao Li;Siming Dong;Shaohua Fang
Journal of Applied Electrochemistry 2012 Volume 42( Issue 10) pp:851-856
Publication Date(Web):2012 October
DOI:10.1007/s10800-012-0450-0
A new kind of polymeric ionic liquid (PIL) membrane based on guanidinium ionic liquid (IL) with ester and alkyl groups was synthesized. On addition of guanidinium IL, lithium salt, and nano silica in the PIL, a gel PIL electrolyte was prepared. The chemical structure of the PIL and the properties of gel electrolytes were characterized. The ionic conductivity of the gel electrolyte was 5.07 × 10−6 and 1.92 × 10−4 S cm−1 at 30 and 80 °C, respectively. The gel electrolyte had a low glass transition temperature (Tg) under −60 °C and a high decomposition temperature of 310 °C. When the gel polymer electrolyte was used in the Li/LiFePO4 cell, the cell delivered 142 mAh g−1 after 40 cycles at the current rates of 0.1 C and 80 °C.
Co-reporter:Yide Jin, Shaohua Fang, Li Yang, Shin-ichi Hirano, Kazuhiro Tachibana
Journal of Power Sources 2011 Volume 196(Issue 24) pp:10658-10666
Publication Date(Web):15 December 2011
DOI:10.1016/j.jpowsour.2011.08.008
Two new functionalized ionic liquids (ILs) based on guanidinium cation with two ether groups and TFSA− anion are synthesized and characterized. Their physicochemical and electrochemical properties, including melting point, thermal stability, density, viscosity, conductivity, and electrochemical window are determined. Both the ILs are liquids at room temperature, and the viscosities are about 60 mPa s at 25 °C. Behavior of lithium redox, chemical stability against lithium metal and charge–discharge characteristics of lithium battery, are also examined for the two ILs as electrolyte with 0.6 mol kg−1 LiTFSA. Though the cathodic limiting potentials of the two ILs are higher than 0 V versus Li/Li+, the lithium plating and stripping on Ni electrode can be observed in the two IL electrolytes, indicating their good chemical stability against lithium metal. Li/LiFePO4 cells using the two IL electrolytes without any additive showed good cycle property at the current rate of 0.2 C at 25 °C and 55 °C.Highlights► New functionalized guanidinium ILs with two ether groups are reported. ► They have low viscosity and good electrochemical stability. ► Li/LiFePO4 cells using these IL electrolytes have good capacity and cycle property.
Co-reporter:Shaohua Fang, Yufeng Tang, Xingyao Tai, Li Yang, Kazuhiro Tachibana, Kouichi Kamijima
Journal of Power Sources 2011 Volume 196(Issue 3) pp:1433-1441
Publication Date(Web):1 February 2011
DOI:10.1016/j.jpowsour.2010.08.012
One ether-functionalized guanidinium ionic liquid is used as new electrolytes for lithium battery. Viscosity, conductivity, behavior of lithium redox, chemical stability against lithium metal, and charge–discharge characteristics of lithium batteries, are investigated for the IL electrolytes with different concentrations of lithium salt. Though the cathodic limiting potential of the IL are 0.7 V vs. Li/Li+, the lithium plating and striping on Ni electrode can be observed in the IL electrolytes, and the IL electrolytes show good chemical stability against lithium metal. Li/LiCoO2 cells using the IL electrolytes without additives have good capacity and cycle property at the current rate of 0.2 C when the LiTFSI concentration is higher than 0.3 mol kg−1, and the cell using the IL electrolyte with 0.75 mol kg−1 LiTFSI owns good rate property. The activation energies of the LiCoO2 electrode for lithium intercalation are estimated, and help to analyze the factors determining the rate property.
Co-reporter:Mingtao Li, Li Yang, Shaohua Fang, Siming Dong, Shin-ichi Hirano, Kazuhiro Tachibana
Journal of Power Sources 2011 Volume 196(Issue 20) pp:8662-8668
Publication Date(Web):15 October 2011
DOI:10.1016/j.jpowsour.2011.06.059
The electrochemical properties of solvent-free, quaternary polymer electrolytes based on a novel polymeric ionic liquid (PIL) as polymer host and incorporating 1g13TFSI ionic liquid, LiTFSI salt and nano-scale silica are reported. The PIL–LiTFSI–1g13TFSI–SiO2 electrolyte membranes are found to be chemically stable even at 80 °C in contact with lithium anode and thermally stable up to 320 °C. Particularly, the quaternary polymer electrolytes exhibit high lithium ion conductivity at high temperature, wide electrochemical stability window, time-stable interfacial resistance values and good lithium stripping/plating performance. Batteries assembled with the quaternary polymer electrolyte at 80 °C are capable to deliver 140 mAh g−1 at 0.1C rates with very good capacity retention.Highlights• We prepare quaternary polymer electrolytes based on novel polymeric ionic liquids. • The electrolytes are chemically stable even at 80 °C in contact with lithium anode. • Batteries discharge 140 mAh g−1 at 0.1C rates with good capacity retention.
Co-reporter:Mingtao Li, Li Yang, Shaohua Fang, Siming Dong
Journal of Membrane Science 2011 Volume 366(1–2) pp:245-250
Publication Date(Web):1 January 2011
DOI:10.1016/j.memsci.2010.10.004
A series of guanidinium polymeric ionic liquid (PIL) electrolyte membranes combining different anions, such as BF4−, PF6−, ClO4− and N(CF3SO2)2−, were synthesized through copolymerization and anion exchange reaction as new promising solid polymer electrolytes. The chemical structures of the PILs were characterized by 1H NMR and ATR–FT IR spectra, and their thermal properties, ionic conductivity and electrochemical stability were evaluated, respectively. The PILs present different decomposition temperature and glass transition temperature (Tg), and their thermal properties strongly depend on the sort of anions. The 1g2-MA-BF4 possesses the better thermal stability and it decomposes at 353 °C. The 1g2-MA-TFSI shows the lower Tg and it is below −60 °C. The ionic conductivity of the PIL electrolytes depends on the lithium salts used and its content. The best ionic conductivity of the PILs electrolyte 1g2-MA-BF4/LiBF4 (30 wt%) was 1.35 × 10−4 S cm−1 at 30 °C.Graphical abstractResearch highlights▶ A novel series of guanidinium PIL membranes with different anions ▶ The ionic conductivity of the PIL electrolyte reaches 1.35 × 10-4 S cm-1 at 30 °C. ▶ The PIL membranes have good thermal stability and wide electrochemical windows.
Co-reporter:Shaohua Fang, Zhengxi Zhang, Yide Jin, Li Yang, Shin-ichi Hirano, Kazuhiro Tachibana, Shingo Katayama
Journal of Power Sources 2011 Volume 196(Issue 13) pp:5637-5644
Publication Date(Web):1 July 2011
DOI:10.1016/j.jpowsour.2011.02.047
Four new functionalized ILs based on piperidinium and pyrrolidinium cations with two ether groups and TFSI− anion are synthesized and characterized. Physical and electrochemical properties of these ILs, including melting point, thermal stability, viscosity, conductivity and electrochemical stability, are investigated. All the ILs are liquids at room temperature, and the viscosities of P(2o1)2-TFSI and P(2o1)(2o2)-TFSI are 55 and 53 mPa s at 25 °C, respectively. Behavior of lithium redox, chemical stability against lithium metal and charge–discharge characteristics of lithium batteries, are also investigated for these IL electrolytes with 0.6 mol kg−1 LiTFSI. Though the cathodic limiting potentials of these ILs are 0.4 V versus Li/Li+, the lithium plating and striping on Ni electrode can be observed for these IL electrolytes, and these IL electrolytes show good chemical stability against lithium metal. Li/LiFePO4 cells using these IL electrolytes without additives have good capacity and cycle property at the current rate of 0.1 C, and the cell using the P(2o1)(2o2)-TFSI electrolyte owns good rate property.Highlights► Four functionalized ILs based on piperidinium and pyrrolidinium cations with two ether groups are reported for the first time. ► They have low viscosity and good electrochemical stability. ► Li/LiFeO4 cells using these IL electrolytes without additives have good capacity and cycle property at the rate of 0.1 C, and one electrolyte owns good rate property.
Co-reporter:Shaohua Fang, Yide Jin, Li Yang, Shin-ichi Hirano, Kazuhiro Tachibana, Shingo Katayama
Electrochimica Acta 2011 Volume 56(Issue 12) pp:4663-4671
Publication Date(Web):30 April 2011
DOI:10.1016/j.electacta.2011.02.107
New functionalized ILs based on quaternary ammonium cations with three or four ether groups and TFSI− anion were synthesized and characterized. Physical and electrochemical properties, including melting point, thermal stability, viscosity, conductivity and electrochemical stability were investigated for these ILs. Five ILs with lower viscosity in these ILs were applied in lithium battery as new electrolytes. Behavior of lithium redox and charge–discharge characteristics of lithium battery were investigated for these IL electrolytes with 0.6 mol kg−1 LiTFSI. Lithium plating and striping on Ni electrode could be observed in these IL electrolytes. Li/LiFePO4 cells using these IL electrolytes without additives had good capacity and cycle property at the current rate of 0.1 C, and the N(2o1)3(2o2)TFSI and N2(2o1)3TFSI electrolytes owned better rate property.Research highlights► Some new functionalized ILs with three or four ether groups are reported. ► They have good electrochemical stability. ► Li/LiFePO4 cells using five IL electrolytes have good capacity and cycle property.
Co-reporter:Jizhang Chen, Li Yang, Shaohua Fang, Shin-ichi Hirano
Electrochemistry Communications 2011 Volume 13(Issue 8) pp:848-851
Publication Date(Web):August 2011
DOI:10.1016/j.elecom.2011.05.019
A unique ordered mesoporous Sn–C composite with Sn nanoparticles confined in carbon nanorods was prepared using SBA-15 as the template. This composite was employed as the anode material of Li-ion batteries, delivering excellent electrochemical properties of high reversible lithium storage capacity (554 mAh g−1 after 200 cycles) and great rate capability (as high as 5000 mA g−1).Research highlights► Ordered mesoporous Sn–C composite is first reported. ► Nanocasting process and hydrothermal treatment are employed. ► Sn nanoparticles are confined in carbon nanorod arrays. ► Sn–C composite delivers excellent cycling and rate performances.
Co-reporter:J.S. Huang, L. Yang, K.Y. Liu
Materials Chemistry and Physics 2011 Volume 128(Issue 3) pp:470-474
Publication Date(Web):15 August 2011
DOI:10.1016/j.matchemphys.2011.03.036
Monoclinic Li3V2(PO4)3/C composite synthesized by ascorbic acid reduction method is examined as a cathode material for Li-ion batteries. Transmission electron microscopy (TEM) images show that the nano-size particles are obtained. The reversible capacity of Li3V2(PO4)3/C prepared with LiOH and H3PO4 is 141.2 mAh g−1 after 100 cycles at 1C discharge rate between 3 V and 4.8 V, and the retention rates of discharge capacity is 93.4%. Ascorbic acid plays not only as reduction reagent, but also as carbon sources. This strategy shortens the time of solid state reaction and facilitates the procedure of synthesis. Effects of different precursors materials on the performance of the Li3V2(PO4)3/C are investigated.Highlights► Ascorbic acid (C6H8O6) was used as reducing agent and organic carbon source. ► The strategy shortened the period of material preparation and lowered energy cost. ► Li3V2(PO4)3/C was obtained with enhanced electrochemical performance. ► Effects of reagents on electrochemical performance of Li3V2(PO4)3 were evaluated.
Co-reporter:XinYue Zhang;ShaoHua Fang;ZhengXi Zhang
Science Bulletin 2011 Volume 56( Issue 27) pp:
Publication Date(Web):2011 September
DOI:10.1007/s11434-011-4655-0
A new guanidinium-based ionic liquid (IL) was investigated as a novel electrolyte for a lithium rechargeable battery. The viscosity, conductivity, lithium redox behavior, and charge-discharge characteristics of the lithium rechargeable batteries were investigated for the IL electrolyte with 0.3 mol kg−1 lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. Li/LiFePO4 cells incorporating the IL electrolyte without additives showed good cycle properties at a charge-discharge current rate of 0.1 C, and exhibited good rate capabilities in the presence of a mass fraction of 10% vinylene carbonate or gamma-butyrolactone.
Co-reporter:J.S. Huang, L. Yang, K.Y. Liu, Y.F. Tang
Journal of Power Sources 2010 Volume 195(Issue 15) pp:5013-5018
Publication Date(Web):1 August 2010
DOI:10.1016/j.jpowsour.2010.02.009
Li3V(2 − 2x/3)Mgx(PO4)3/C (x = 0, 0.15, 0.30, 0.45) composites have been synthesized by the sol–gel assisted solid state method, using adipic acid C6H10O4 (hexanedioic acid) as carbon source. The particle size of the composites is ∼1 μm. During the pyrolysis process, Li3V(2 − 2x/3)Mgx(PO4)3/C network structure is formed. The effect of Mg2+ doped on the electrochemical properties of Li3V2(PO4)3/C positive materials has been studied. Li3V1.8Mg0.30(PO4)3/C as the cathode materials of Li-ion batteries, the retention rate of discharge capacity is 91.4% (1 C) after 100 cycles. Compared with Li3V2(PO4)3/C, Li3V(2 − 2x/3)Mgx(PO4)3/C composites have shown enhanced capacity and retention rate capability. The long-term cycles and ex situ XRD tests disclose that Li3V1.8Mg0.30(PO4)3 exhibits higher structural stability than the undoped system.
Co-reporter:Jizhang Chen, Li Yang, Yufeng Tang
Journal of Power Sources 2010 Volume 195(Issue 19) pp:6893-6896
Publication Date(Web):1 October 2010
DOI:10.1016/j.jpowsour.2010.04.005
TiO2 hollow microspheres with the shell consisting of nanotubes have been successfully synthesized via a template-free hydrothermal process and subsequent treatments. The electrochemical properties of the anatase sample have been investigated by cyclic voltammetry and galvanostatic method. The initial Li insertion/extraction capacity at a current density of 0.2 C reach 290 and 232 mAh g−1 respectively. Moreover, as-prepared TiO2 delivers a reversible capacity of ca. 150 mAh g−1 after 500 cycles at 1 C, and it also shows superior high rate performance (e.g., 90 mAh g−1 at 8 C) without any modification.
Co-reporter:Jizhang Chen, Li Yang, Shaohua Fang, Yufeng Tang
Electrochimica Acta 2010 Volume 55(Issue 22) pp:6596-6600
Publication Date(Web):1 September 2010
DOI:10.1016/j.electacta.2010.06.015
Hierarchical layered hydrous lithium titanate and Li4Ti5O12 microspheres assembled by nanosheets have been successfully synthesized via a hydrothermal process and subsequent thermal treatment. The electrochemical properties of the two samples have been investigated by galvanostatic methods. The former, with the obvious layered structure and a large surface area, delivers a reversible capacity of 180 mA h g−1 after 200 cycles at 200 mA g−1. As for Li4Ti5O12, with the intriguing and unique sawtooth-like morphology, it presents exceptional high rate performance and excellent cycling stability. Up to 132 mA h g−1 is obtained after 200 cycles at 10,000 mA g−1 (57 C), proving itself promising for high-rate applications.
Co-reporter:Li Yang, BingJia Yao and Tomonori Takahashi
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 9) pp:4377-4382
Publication Date(Web):March 26, 2010
DOI:10.1021/ie900624v
Hydrogen was purified by a series of Pd−Ag/ceramic composite membranes with different Pd−Ag alloy thickness ranging from 2.5 to 15 μm. During the process, methane (CH4) was found to be formed in the permeated gas, which was also reported in related studies. A comprehensive study was carried out to identify the source of CH4 by discussing the influence of membrane defect and feed composition with several gas mixtures as feed gas. It was found that CH4 content in the purified hydrogen increased with the defect degree, and for obtaining 99.9% permeated hydrogen, the helium leakage of the membrane should be less than 0.01 mL min−1 cm−2; whereas no helium flow should be detected, that is, the membranes should be completely defect-free, to achieve 99.999+% hydrogen. Meanwhile, different feed gases were used to discover the reason for production of CH4 during purification; the results revealed that only CO in the feed gas resulted in the formation of CH4 on the permeated side. Finally, on the basis of the above findings, a small amount of Au in the Pd−Ag alloy was added to examine the possibility of preventing CH4 formation, and the preliminary result was satisfactory.
Co-reporter:Zheng Qiu;Yufeng Tang;Shaohua Fang ;Jianshu Huang
Chinese Journal of Chemistry 2010 Volume 28( Issue 6) pp:911-915
Publication Date(Web):
DOI:10.1002/cjoc.201090170
Abstract
Li4Ti5O12 (LTO) nanoparticles were prepared by gel-hydrothermal process and subsequent calcination treatment. Calcination treatment led to structural water removal, decomposition of organics and primary formation of LTO. The formation temperature of spinel LTO nanoparticles was lower than that of bulk materials counterpart prepared by solid-state reaction or by sol-gel processing. Based on the thermal gravimetric analysis (TG) and differential thermal gravimetric (DTG), samples calcined at different temperatures (350, 500 and 700°C) were characterized by X-ray diffraction (XRD), field emitting scanning electron microscopy (FESEM), transmission electron microscopy (TEM), cyclic voltammogram and charge-discharge cycling tests. A phase transition during the calcination process was observed from the XRD patterns. And the sample calcined at 500°C had a distribution of diameters around 20 nm and exhibited large capacity and good high rate capability. The well reversible cyclic voltammetric results of both electrodes indicated enhanced electrochemical kinetics for lithium insertion. It was found that the Li4Ti5O12 anode material prepared through gel-hydrothermal process, when being cycled at 8 C, could preserve 76.6% of the capacity at 0.3 C. Meanwhile, the discharge capacity can reach up to 160.3 mAh·g−1 even after 100 cycles at 1 C, close to the theoretical capacity of 175 mAh·g−1. The gel-hydrothermal method seemed to be a promising method to synthesize LTO nanoparticles with good application in lithium ion batteries and electrochemical cells.
Co-reporter:Yufeng Tang, Li Yang, Jizhang Chen and Zheng Qiu
Langmuir 2010 Volume 26(Issue 12) pp:10111-10114
Publication Date(Web):April 29, 2010
DOI:10.1021/la1002379
Hierarchical hollow microspheres assembled by titanate nanotubes were fabricated via a hydrothermal process. During the entire process, the hydrous titanium oxide microspheres served as a template and source of titanate ions and H2O2 was used to facilitate the conversion of titanate sheets into nanotubes in low-concentration NaOH (0.1 M). Furthermore, this synthesis route is more friendly than the previous hydrothermal synthesis of TiO2-derived nanotubes in a highly alkaline (10−15 M) medium.
Co-reporter:Chengxin Peng;Shaohua Fang;Jixian Wang
Journal of Applied Electrochemistry 2010 Volume 40( Issue 3) pp:653-662
Publication Date(Web):2010 March
DOI:10.1007/s10800-009-0040-y
The electrochemical behaviors of copper current collector in 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide ionic liquid electrolytes were investigated and compared with that in ethylene carbonate/dimethyl carbonate solutions. Cyclic voltammetry results showed that large oxidation–reduction current of the copper foil appeared in ethylene carbonate/dimethyl carbonate solutions, while a much smaller current in the room temperature ionic liquid electrolytes decreased gradually, indicating that the copper foil was anodically stable. Further study by X-ray photoelectron spectroscopy analysis showed that an unstable product was composed mainly of the carbonate and carbonyl species on the surface of the copper foil after the electrochemical measurement in ethylene carbonate/dimethyl carbonate solutions, leading to the dissolution of the copper foil. While a better passivating film from the reduction of the anions in the room temperature ionic liquid electrolytes covered the surface of copper foil and protected the copper foil from being oxidized even in a higher potential. These results indicate that the use of room temperature ionic liquid electrolytes can improve the stability of copper current collector in the advanced lithium ion batteries.
Co-reporter:Yufeng Tang, Li Yang, Zheng Qiu and Jianshu Huang
Journal of Materials Chemistry A 2009 vol. 19(Issue 33) pp:5980-5984
Publication Date(Web):30 Jun 2009
DOI:10.1039/B907480E
Mesoporous spinel lithium titanate Li4Ti5O12 microspheres were prepared by template-free hydrothermal process in ethanol–water mixed solution and subsequent heat treatment. The role of ethanol helps the formation of a mesoporous structure during the hydrothermal process. A mechanism analogous to the Kirkendall effect was proposed to account for the template-free formation of these mesoporous nanostructures. As anode materials for high-rate lithium ion battery, the Li4Ti5O12 mesoporous spheres exhibited superior high-rate performance of 114 mA h g−1 at 30C and good capacity retention of 125 mA h g−1 after 200 cycles at 20C, which indicates promising application in high-rate lithium ion batteries.
Co-reporter:Shaohua Fang, Li Yang, Jixian Wang, Huanqi Zhang, Kazuhiro Tachibana, Kouichi Kamijima
Journal of Power Sources 2009 Volume 191(Issue 2) pp:619-622
Publication Date(Web):15 June 2009
DOI:10.1016/j.jpowsour.2009.02.062
Two ionic liquids based on guanidinium cations and TFSA− anion were prepared, and their electrochemical stabilities were investigated. The cathodic limiting potentials of the two ILs were 0.7 V versus Li/Li+, and their electrochemical windows were 4.2 V. However, the lithium plating and striping on Ni electrode could been observed in the two IL electrolytes containing 0.3 mol kg−1 of LiTFSA without additive. And Li/LiCoO2 cells using the two IL electrolytes without additive showed good capacity and cycle property at the current rate of 0.2 C.
Co-reporter:Yufeng Tang, Li Yang, Shaohua Fang, Zheng Qiu
Electrochimica Acta 2009 Volume 54(Issue 26) pp:6244-6249
Publication Date(Web):1 November 2009
DOI:10.1016/j.electacta.2009.05.092
In this paper, Li4Ti5O12 (LTO) hollow microspheres with the shell consisting of nanosheets have been synthesized via a hydrothermal route and following calcination. Because of the favorable transport properties of this hollow structure, it is the rate performance at high current densities which is exceptional. When the LTO hollow microspheres were used as the anode material in lithium ion battery, they exhibited superior rate performance and high capacity even at a very high rate (131 mAh g−1 at 50 C).
Co-reporter:Shaohua Fang, Li Yang, Jixian Wang, Mingtao Li, Kazuhiro Tachibana, Kouichi Kamijima
Electrochimica Acta 2009 Volume 54(Issue 17) pp:4269-4273
Publication Date(Web):1 July 2009
DOI:10.1016/j.electacta.2009.02.082
Eight new functionalized guanidinium ILs based on small cations containing ether group (methoxyethyl group) or ester group (methyl acetate group) and TFSI− anion were synthesized and characterized. Physical and electrochemical properties of these products, including melting point, thermal stability, viscosity, conductivity and electrochemical window, were investigated. All the products were liquids at room temperature, and they had low-melting points. The viscosities of cg1(2o1)TFSI and cg2(2o1)TFSI were 46 and 48 mPa s at 25 °C, respectively. Electrochemical and thermal stabilities of these functionalized guanidinum ILs permitted them to become potential electrolytes used in electrochemical devices.
Co-reporter:Shaohua Fang, Li Yang, Chao Wei, Chen Jiang, Kazuhiro Tachibana, Kouichi Kamijima
Electrochimica Acta 2009 Volume 54(Issue 6) pp:1752-1756
Publication Date(Web):15 February 2009
DOI:10.1016/j.electacta.2008.09.065
Sixteen new guanidinium salts based on small cations and TFSI− anion were prepared and characterized. Physical and electrochemical properties of these products, including melting point, thermal stability, viscosity, conductivity and electrochemical window were investigated. Reducing symmetry of cations can reduce the melting points, and 12 products are liquids at room temperature. The viscosities of cg22TFSI, cg12TFSI and cg13TFSI were 45, 46 and 52 mPa s at 25 °C, respectively. Electrochemical and thermal stabilities of these ILs permitted them to become promising electrolytes used in electrochemical devices.
Co-reporter:Jixian Wang;Chengxin Peng
Chinese Journal of Chemistry 2009 Volume 27( Issue 11) pp:2159-2165
Publication Date(Web):
DOI:10.1002/cjoc.200990361
Abstract
The anodic polarization behavior of Al, Ta and Nb foil was investigated in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid (BMI-BF4). Compared with that of Ta and Nb foil, it showed that a better passive film was formed on Al foil surface after the anodic polarization in BMI-BF4, which could resist the potential up to 94.58 V vs. Ag+/Ag. Besides, similar anodic behavior of Al foil was observed in N-methyl-N-butylpiperidinium tetrafluoroborate ionic liquid (PP14-BF4), which indicated that the anodic polarization behavior of Al foil was independent of the cations of RTIL. In addition, the investigation of anodic polarization behavior of Al foil was carried out in the mixture electrolytes composed of BMI-BF4·PC. Differently, two breakdown potential processes of Al foil were presented compared to pure BMI-BF4. Further research showed that the passive film on Al foil was mainly composed of AlF3 and Al2O3 after the first breakdown potential process, while the fluoride film increased with continual anodic polarization, which improved the anodic stability of Al foil and resisted higher breakdown potential. The high breakdown potential properties of Al foil in BMI-BF4, PP14-BF4 and the mixture of BMI-BF4·PC during the anodic polarization can be favored for R&D of the high performance electrochemical devices.
Co-reporter:HuanQi Zhang;ShaoHua Fang;ChengXin Peng;HongJun Luo
Science Bulletin 2009 Volume 54( Issue 8) pp:1322-1327
Publication Date(Web):2009 April
DOI:10.1007/s11434-009-0038-1
New ionic liquids based on S-alkylthiolanium cations with TFSI anions were synthesized and characterized. The physical and electrochemical properties, including melting point, thermal stability, solubility, viscosity, conductivity and electrochemical window, were reported. Relation between these properties and the structure of the cations was discussed. In this series, T4TFSI and T5TFSI have melting points below −60°C, and their conductivities are 2.10 mS/cm and 1.46 mS/cm; their electrochemical windows are 4.1 V and 4.5 V at room temperature. These cyclic alkylthiolanium-based ionic liquids are promising as novel electrolytes in various electrochemical devices, especially under low temperature condition.
Co-reporter:Chengxin Peng, Li Yang, Zhengxi Zhang, Kazuhiro Tachibana, Yong Yang, Shiyong Zhao
Electrochimica Acta 2008 Volume 53(Issue 14) pp:4764-4772
Publication Date(Web):30 May 2008
DOI:10.1016/j.electacta.2008.01.080
We have investigated the anodic behaviors of aluminum as a cathodic current collector for lithium ion batteries in several kinds of room temperature ionic liquids (RTILs) and EC + DMC solutions containing LiN(CF3SO2)2 by cyclic voltammetry (CV), chronoamperometry (CA), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry and chronoamperometry data showed that the current density for aluminum foil with the RTIL electrolytes was less than that of aluminum foil in the EC + DMC solutions. Besides, much corrosion pits appeared on the aluminum foil surface after the electrochemical measurement in the EC + DMC solutions, while they were not observed on the aluminum foil with the RTIL electrolytes, suggesting that aluminum current collector was stable in the RTIL electrolytes. Further research by EDX and XPS analysis revealed that a good passivating film composed mainly of the products from the oxidation between aluminum and the anions of the RTIL electrolytes on the aluminum foil surface after the anodic polarization which suppressed the aluminum corrosion.
Co-reporter:ZhengXi Zhang, HongYan Zhou, Li Yang, Kazuhiro Tachibana, Kouichi Kamijima, Jian Xu
Electrochimica Acta 2008 Volume 53(Issue 14) pp:4833-4838
Publication Date(Web):30 May 2008
DOI:10.1016/j.electacta.2008.02.008
Asymmetrical dicationic ionic liquids based on the combination of imidazolium and aliphatic ammonium cations with TFSI anion, MICnN111-TFSI2, have been synthesized for the first time, wherein MI represents imidazolium cation, N111 represents trimethylammonium cation, and Cn represents spacer length. The physical and electrochemical properties of this family of ionic liquids were studied. 1-(3-Methylimidazolium-1-yl)ethane-(trimethylammonium) bi[bis(trifluoromethane-sulfonyl) imide] (MIC2N111-TFSI2) shows solid–solid transition characteristics. 1-(3-Methylimidazolium-1-yl)pentane-(trimethylammonium) bi[bis(trifluoromethan-esulfonyl)imide] (MIC5N111-TFSI2) has one of the lowest solid–liquid transformation temperatures among analogues, and belongs to the greatest thermal stable ionic liquids. Additionally, it has an order of conductivity of 10−1 ms cm−1, and electrochemical window of about 3.7 V at room temperature. To evaluate the potential of MIC5N111-TFSI2 as an additive of electrolyte for lithium secondary batteries, cells composed of LiMn2O4 cathode/1 M LiPF6 in EC:DMC (1:1, v/v) electrolytic solution containing 5 wt% of MIC5N111-TFSI2/lithium metal anode have been prepared. The charge–discharge cycling test reveals that unlike the cases of Li/LiMn2O4 cells employing a conventional electrolyte with a monocationic ionic liquid, such as 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (EtMeImTFSI) as an additive, the performances of Li/LiMn2O4 cells do not drop with the addition of MIC5N111-TFSI2 at 1C rate, moreover, the cell exhibits better discharge capacity and cycle durability compared with the cell using the conventional electrolyte.
Co-reporter:Bingjia Yao, Li Yang
Journal of Colloid and Interface Science 2008 Volume 319(Issue 1) pp:316-321
Publication Date(Web):1 March 2008
DOI:10.1016/j.jcis.2007.11.033
In the cloud point extraction (CPE) process with PEG/PPG-18/18 dimethicone, the flexible chain structure of the silicone surfactant efficiently decreased the water content remaining in the surfactant-rich phase, compared with conventional nonionic surfactants, represented by Triton X-114. Meanwhile, the phase volume ratio of surfactant-rich phase to aqueous phase obtained in the silicone surfactant CPE system was found to be maintained at a low value with increasing surfactant concentration; whereas a rapid increase tendency was commonly observed in that of other nonionic surfactants. Based on these advantages, the equilibrium partition of three polycyclic aromatic hydrocarbons (PAHs), anthracene, phenanthrene and pyrene, was studied in the CPE process with PEG/PPG-18/18 dimethicone. Equilibrium parameters, including preconcentration factor, distribution coefficient and recovery, were determined, and the performance was compared with that of another related CPE research, where Tergitol 15-S-7 was used. Due to the low surfactant-rich phase volume, higher concentrations of the three PAHs in the surfactant-rich phase, and the resulting higher preconcentration factors and distribution coefficients were able to be achieved at the same time. Moreover, the great performance was able to be maintained even at a high surfactant concentration or PAHs initial concentration.PEG/PPG-18/18 dimethicone offered a much lower water content in the surfactant-rich phase and a sustained phase volume ratio in cloud point extractions of PAHs.
Co-reporter:Bingjia Yao and Li Yang
Industrial & Engineering Chemistry Research 2008 Volume 47(Issue 11) pp:3949
Publication Date(Web):April 17, 2008
DOI:10.1021/ie071618l
A novel cloud-point extraction (CPE) process, namely, stirring-assisted cloud-point extraction (S-CPE), was developed with a stirring rate over 380 rpm in a PEG/PPG-18-18 dimethicone aqueous solution at a temperature over its cloud point. Compared with a general CPE process with centrifugation (C-CPE), the stirring process successfully accelerated the phase separation, where the whole process was able to be finished in 15 min and a lower water content in the surfactant-rich phase was also obtained, e.g., the water content was as low as 52 wt % at a 2 wt % surfactant solution, indicating a higher resulting distribution coefficient. The phase separation of the process was studied with dynamic lighting scattering. Because of the increasing contact chances between micelles and extractable species, the stirring operation is also in favor to increase the extractability of the CPE process, where higher recoveries of polycyclic aromatic hydrocarbons (PAHs) were obtained even with a lower surfactant concentration, e.g., a 98.9% recovery of anthracene was obtained in a 1 wt % surfactant solution. What is more important is that the stirring operation is suitable for a scaling-up process, and the surfactant-rich phase floating upon the solution is more easily collected and removed. In addition, the extractant used in the S-CPE, PEG/PPG-18-18 dimethicone, has little UV absorbance, avoiding the disturbance to the signal of PAHs in UV or fluorescence detector, so it is convenient to determine PAHs concentration in every phase during S-CPE process by high-performance liquid chromatography (HPLC) directly. The stirring operation successfully avoids the low phase-separation efficiency like in the CPE process with heating and has no treatment capacity limitation like in C-CPE. Therefore, S-CPE offers an efficient possibility for scaling up a typical CPE process to be applied in the separation of PAHs in the water treatment.
Co-reporter:ShiChun Luo;ZhengXi Zhang
Science Bulletin 2008 Volume 53( Issue 9) pp:1337-1342
Publication Date(Web):2008 May
DOI:10.1007/s11434-007-0526-0
A new asymmetric sulfonium-based ionic liquid, 1-butyldimethylsulfonium bis(trifluoromethylsulfonyl) imide (S114TFSI), was developed as electrolyte material for lithium secondary battery. Its cathodic potential was a little more positive against the Li/Li+, so vinylene carbonate (VC) was added into the LiTFSI/S114TFSI ionic liquid electrolyte to ensure the formation of a solid electrolyte interface (SEI), which effectively prevented the decomposition of the electrolyte. The properties of the Li/LiMn2O4 cell containing S114TFSI-based electrolyte were studied and the cycle performances were compared to those with a conventional organic electrolyte (1 mol/L LiPF6/DMC:EC=1:1(w/w)) at room temperature. Electrochemical impedance spectroscopy (EIS) and X-ray diffraction (XRD) were conducted to analyze the mechanisms affecting the cell performances at different temperatures. The lithium secondary battery system, using the above ionic liquid electrolyte material, shows good cycle performances and good safety at room temperature, and is worthwhile to further investigate so as to find out the potential application.
Co-reporter:Chengxin Peng, Li Yang, Zhengxi Zhang, Kazuhiro Tachibana, Yong Yang
Journal of Power Sources 2007 Volume 173(Issue 1) pp:510-517
Publication Date(Web):8 November 2007
DOI:10.1016/j.jpowsour.2007.05.006
The anodic behaviors of aluminum current collector for lithium ion batteries were investigated in a series of 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide room temperature ionic liquids (RTILs) and EC + DMC electrolytes. It was found that the aluminum corrosion, which occurred in EC + DMC electrolytes containing LiTFSI, was not observed in the RTIL electrolytes. Further research showed that a passive film with amide compounds as main components formed firmly on aluminum surface during the anodic polarization in the RTIL electrolytes, which inhabited the aluminum corrosion. In addition, the additives generally used in the batteries, such as ethylene carbonate, ethylene sulfite and vinyl carbonate, as well as temperature did not obviously affect the aluminum passive film, the oxidation of the RTILs increased at the elevated temperature, which only resulted in the corrosion potential of aluminum in the RTIL electrolytes shifted to more negative potential, a passive film still firmly formed on the aluminum surface to surpassed the further oxidation of the aluminum current collector. Those results lead to a potential for the practical use of LiTFSI salt in the room temperature ionic liquid electrolytes for lithium ion batteries.
Co-reporter:Zhengxi Zhang, Li Yang, Shichun Luo, Miao Tian, Kazuhiro Tachibana, Kouichi Kamijima
Journal of Power Sources 2007 Volume 167(Issue 1) pp:217-222
Publication Date(Web):1 May 2007
DOI:10.1016/j.jpowsour.2007.01.033
Co-reporter:Shaohua Fang, Li Yang, Chao Wei, Chengxin Peng, Kazuhiro Tachibana, Kouichi Kamijima
Electrochemistry Communications 2007 Volume 9(Issue 11) pp:2696-2702
Publication Date(Web):November 2007
DOI:10.1016/j.elecom.2007.09.003
Nine new ionic liquids based on small asymmetric trialkylsulfonium cations with TFSI− anion were prepared and characterized. Physical and electrochemical properties of these ionic liquids, including melting point, thermal stability, viscosity, conductivity and electrochemical window were determined. Reducing symmetry of cations reduces the melting points of these ILs. Some of these hydrophobic ionic liquids showed low-viscosity and low-melting point characteristics. The viscosities of S223TFSI, S221TFSI and S123TFSI were 33, 36 and 39 mPa s at 25 °C, respectively. Electrochemical and thermal stabilities of these ILs permitted them to become promising electrolytes used in electrochemical devices.
Co-reporter:Li Yang, Zhengxi Zhang, Shaohua Fang, Xuhui Gao, Masamichi Obata
Solar Energy 2007 Volume 81(Issue 6) pp:717-722
Publication Date(Web):June 2007
DOI:10.1016/j.solener.2006.10.001
Solid-state dye-sensitized solar cells (DSSCs) were fabricated in which the thin p-CuI film acts as a hole collector. Influences of the different preparation methods, composition, aging time of the TiO2 pastes and sensitizing time on the performance of the cells were investigated. Different preparation routes for the TiO2 paste do not obviously affect the performance of the cells. The volume of water, acetic acid and 2-propanol contained in the TiO2 pastes and the amount of the TiO2 powder were determined. The efficiency of the cells remains nearly stable when the aging period of the TiO2 pastes is within one week. The favorable dying time is above 2 h. The cells having a favorable performance deliver a mean short-circuit photocurrent of ∼10.8 mA cm−2 and mean open-circuit voltage of 0.61 V at 100 mW cm−2 (1.5 AM). The mean fill factor and the mean efficiency of these cells are ∼0.55% and 3.7%, respectively. The short-circuit photocurrent rapidly decays after 3 h, and at the same time, the open-circuit voltage slowly decreases when the time increases, and then remains nearly stable after 24 h.
Co-reporter:Li Yang, ZhengXi Zhang, XuHui Gao, HuanQi Zhang, Kiyotaka Mashita
Journal of Power Sources 2006 Volume 162(Issue 1) pp:614-619
Publication Date(Web):8 November 2006
DOI:10.1016/j.jpowsour.2006.06.050
A novel series of molten salts based on asymmetric sulfonium cations ([R1R2RS]+, wherein R1, R2 = CH3, R = C2H5, n-C4H9, n-C6H13, n-C8H17, corresponding to S112+, S114+, S116+, S118+, respectively) with TFSI− or PF6− anion as novel electrolytes have been prepared and characterized. Some of the physical and electrochemical properties of the salts, including thermal property, density, solubility in common solvents, conductivity, and electrochemical stability have been investigated. Three types of phase transition behavior and two types of decomposition behavior have been observed for these molten salts on heating. In the case of [R1R2RS]+ PF6−, which have much higher solubility in water compared to those with imidazolium cation which have only alkyl groups. In addition, the Arrhenius equation approximately describes the relationship between conductivity and temperature for some of these sulfonium-based molten salts with TFSI− anion in the high temperature region studied. The electrochemical windows are approximately 4.1 V for S112TFSI and S114TFSI, which are liquid at room temperature (25 °C).
Co-reporter:Li Yang, Michio Takahashi, Baofeng Wang
Electrochimica Acta 2006 Volume 51(Issue 16) pp:3228-3234
Publication Date(Web):10 April 2006
DOI:10.1016/j.electacta.2005.09.014
The capacity fading mechanism of lithium-ion cell was studied by disassembling the charge–discharged cells and analyzing their electrodes using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), etc. Cu ion dissolved from current collector of anode and Mn ion dissolved from LiMn2O4 spinel (cathode) were all existing in solid electrolyte interface (SEI) layer on carbon anode as Cu2O and MnO or MnO2, respectively. These depositions of Cu and Mn oxides did not uniformly deposited on the anode side, and most of them were detected on the carbon surface nearby to the separator side. The SEI layer is hard and about 0.3 μm in thickness. Furthermore, the cycling performance of the cells can be improved by adding 1,2,3-benzotrazole (a corrosion inhibitor of Cu) before assembling the cell, it then coordinates strongly with Cu ions into the electrolyte. From the results, it is obvious that the existing of Cu oxide as well as Mn oxide in the SEI layer, which blocks the normal intercalation of the lithium ions, is one of the factors for the capacity fading of the cells.
Co-reporter:Li Yang, Zhengxi Zhang, Xuhui Gao, Yaju Guo, Baofeng Wang, Osamu Sakai, Hitoshi Sakai, Tomonori Takahashi
Journal of Membrane Science 2005 Volume 252(1–2) pp:145-154
Publication Date(Web):15 April 2005
DOI:10.1016/j.memsci.2004.12.006
Changes in hydrogen permeability and surface state of a Pd–Ag/ceramic membrane have been investigated as a function of thermal treatment. The surface state is determined by X-ray photoelectron spectroscopy (XPS). The XPS data show a significant enrichment of the Ag alloying element and an accumulation of impurity atoms (C, S, Na, Cl, O) in the surface layer of an as-prepared membrane. The thermal treatment, conducted at 400 °C in air for 1 h, results in a decrease of the Pd/Ag ratio in the surface (from 1:3.4 to 1:2.9), and an obvious chemical shift (ca. 1.4 eV) of Pd 3d core level but no change in the Ag 3d level, indicating the Pd2+ state of PdO is formed. The thermal treatment does not change the surface states of impurities of Na, Cl and O. On the other hand, XPS signal of the oxidized sulfur, SO42− species, is found. It is noted that the carbon concentration is decreased dramatically (from 67 to 32 at.%) by decomposition of carbon, a new XPS peak (BE = 292.5 eV) of CO2 is clearly identified from a treated surface. After the thermal treatment, the hydrogen permeability of the membrane is increased by a factor of 2.5, such behavior can be mainly attributed to the removing of the carbon contaminate initially present in the surface.
Co-reporter:Li Yang, Zhengxi Zhang, Yaju Guo, Xuhui Gao, Hiroshi Takeuchi
Separation and Purification Technology 2005 Volume 47(1–2) pp:88-94
Publication Date(Web):December 2005
DOI:10.1016/j.seppur.2005.06.007
A liquid surfactant membrane process for separating U(VI) from sulfuric acid media was investigated using N-alkylcaprolactam (Bs) as a carrier. The operating conditions, including the concentrations of the extractant and stripping agent and the volume ratios of the (W/O)/W emulsion were optimized for the U(VI) extraction, from the viewpoint of their effect on the kinetics and recovery efficiency as well as the stability of the (W/O) emulsion drops. It was found that the liquid membrane containing n-dodecane used as a solvent, ECA4360J as a surfactant and B8 as a carrier is an effective membrane for extracting U(VI) from sulfuric acid, and the concentrations of B8 should be within the range between 0.03 and 0.05 M for keeping the emulsion stability. At the same time, a two-stage counter-current operation was demonstrated and results showed that LSM process in two-stage operation is effective.
Co-reporter:Qinghua Tian, Zhengxi Zhang, Li Yang, Yixin Xiang
Journal of Alloys and Compounds (25 May 2017) Volume 705() pp:
Publication Date(Web):25 May 2017
DOI:10.1016/j.jallcom.2017.02.175
•The Li4Ti5O12 nanobelts with dual-phase had been facilely prepared.•The unique nanostructure brought it versatile synergistic effect.•It exhibited high lithium storage and ultra-long life.The main issues spinel lithium titanate (Li4Ti5O12) anodes suffered from are poor electrical conductivity and low theoretical capacity, which impede the practical application of Li4Ti5O12 anodes in power lithium-ion batteries. Herein, the improvement in rate capability and specific capacity of Li4Ti5O12 anodes has been achieved by facile two-phase formation and nanostructure engineering strategy. When evaluated as anode material for lithium-ion batteries, the as-prepared TiO2in-situ decorated Li4Ti5O12 nanobelts exhibit impressive performance, delivering a high reversible specific capacity of 185.1 and 161.2 mAh g−1 at 20 and 200 mA g−1 after 250 and 2000 cycles, respectively. More importantly, a capacity of 135.6 mAh g−1 could be retained at a high rate of 2000 mA g−1 even after 5000 cycles, showing excellent rate property and cycle life. Thus excellent performance may make them a promising anode material for advanced lithium-ion batteries.
Co-reporter:Qinghua Tian, Yang Tian, Wei Zhang, Jun Huang, Zhengxi Zhang, Li Yang
Journal of Alloys and Compounds (25 April 2017) Volume 702() pp:
Publication Date(Web):25 April 2017
DOI:10.1016/j.jallcom.2017.01.253
•Heterostructure SnO2@TiO2 with a yolk-like core was fabricated by novel approach.•The SnO2@TiO2 possessed sufficient structure stability.•The SnO2@TiO2 exhibited impressive lithium storage performance.A unique structure of yolk-like SnO2@TiO2 nanospheres has been fabricated via SnO2 nanoparticles self-assembled into a core during calcination process. Moreover, this as-prepared composite owns a mesoporous structure, which can accelerate the diffusion of both electrons and lithium-ions by providing a high electrode-electrolyte contact area. When evaluated as anode material for lithium-ion batteries, the SnO2@TiO2 gives a high reversible capacity of 472.7 mAh g−1 even at 2 A g−1 after 800 cycles, exhibiting significantly improved electrochemical performance. This work may provide a broader vision into fabricating yolk-like SnO2@TiO2 heterostructures for high-performance anode materials of lithium-ion batteries.
Co-reporter:Qinghua Tian, Jizhang Chen, Zhengxi Zhang, Li Yang
Electrochimica Acta (20 March 2017) Volume 231() pp:
Publication Date(Web):20 March 2017
DOI:10.1016/j.electacta.2017.02.084
•The hierarchical structure of Li4Ti5O12 with dual-phase had been prepared.•The well-designed structure provided it with versatile synergistic effect.•It exhibited good lithium storage and ultra-long life.The current research priorities about spinel lithium titanate (Li4Ti5O12) mainly focus on the improvement of specific capacity and rate capacity due to the intrinsic issues of Li4Ti5O12, such as low specific capacity and poor electrical conductivity, which limit the practical application of Li4Ti5O12 anodes in lithium-ion batteries. Herein, it is demonstrated that the Li4Ti5O12 with improved performance can be obtained by proper hierarchical structure construction and TiO2in-situ decoration. In consequence, it delivers a high reversible specific capacity of 162.5 and 148.6 mAh g−1 at 50 and 200 mA g−1 after 900 and 2400 cycles, respectively. In addition, a capacity of 110.8 mAh g−1 could be retained at a high rate of 20C even after 5000 cycles, exhibiting improved rate property and ultra-long life. This work may pave the way to facilely prepare advanced Li4Ti5O12-based anode materials for lithium-ion batteries.
Co-reporter:Qinghua Tian, Jizhang Chen, Zhengxi Zhang, Li Yang
Materials Letters (1 May 2017) Volume 194() pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.matlet.2017.02.037
•The interestingly hierarchical structure of Li4Ti5O12 had been prepared.•It had improved diffusion dynamics of ions and electrons.•It had good lithium storage and ultra-long life.Herein, a unique hierarchical structure of interconnected microspheres constructed by regular lithium titanate (Li4Ti5O12) nanosheets has been prepared via a facile and smart approach. When evaluated as anode materials for lithium-ion batteries (LIBs), the as-prepared Li4Ti5O12 shows outstanding lithium storage performance, delivering a high reversible specific capacity of 161.9 and 141.1 mAh g−1 after 300 and 1200 cycles at 20 and 200 mA g−1, respectively. This work may open up a broader vision into developing advanced Li4Ti5O12 anode materials for LIBs.The novel hierarchical structure of Li4Ti5O12 exhibits good lithium storage and ultra-long life.
Co-reporter:Jizhang Chen, Li Yang, Zhengxi Zhang, Shaohua Fang and Shin-ichi Hirano
Chemical Communications 2013 - vol. 49(Issue 27) pp:NaN2794-2794
Publication Date(Web):2013/02/18
DOI:10.1039/C3CC40671G
Using amorphous TiO2 microspheres as precursors, we obtain mesoporous TiO2–Sn@C core–shell microspheres. Sn is encapsulated into a TiO2 matrix, and carbon is coated outside. This intriguing architecture can effectively buffer volume change and structural stress, thus contributing to excellent long-term cycling stability and superior high-rate cyclability.
Co-reporter:Kun Yin, Zhengxi Zhang, Xiaowei Li, Li Yang, Kazuhiro Tachibana and Shin-ichi Hirano
Journal of Materials Chemistry A 2015 - vol. 3(Issue 1) pp:NaN178-178
Publication Date(Web):2014/11/05
DOI:10.1039/C4TA05106H
Polymeric ionic liquids (PILs) have stirred up great interest for their potential applications as electrolyte hosts in lithium metal batteries (LMBs) because of their desirable performance. In this work, PIL-based gel polymer electrolytes applied in lithium metal batteries (LMBs) at low–medium temperatures (25 °C, 30 °C and 40 °C) are first reported. A novel imidazolium-tetraalkylammonium-based dicationic polymeric ionic liquid, poly(N,N,N-trimethyl-N-(1-vinlyimidazolium-3-ethyl)-ammonium bis(trifluoromethanesulfonyl)imide) is successfully synthesized, and its structure and purity are confirmed by 1H NMR, FTIR and elemental analysis. Subsequently, the ternary gel polymer electrolytes are prepared by blending the as-synthesized dicationic PIL as the polymer host with 1,2-dimethyl-3-ethoxyethyl imidazolium bis(trifluoromethanesulfonyl)imide (IM(2o2)11TFSI) ionic liquid and LiTFSI salt in different weight ratios. The PIL-LiTFSI-IM(2o2)11TFSI electrolytes reveal low glass transition temperatures around −54 °C and high thermal stability to about 330 °C. Moreover, the ternary gel polymer electrolytes show good ion conductivity around 10−4 S cm−1 at low–medium temperatures, high electrochemical stability and good interfacial stability with lithium metal. Particularly, the Li/LiFePO4 cells assembled with polymer electrolytes at a rate of 0.1 C are able to deliver discharge capacities of about 160 mA h g−1, 140 mA h g−1 and 120 mA h g−1 at 40 °C, 30 °C and 25 °C, respectively, with excellent capacity retention, as well as exhibiting acceptable rate capability. These findings reveal that dicationic PIL-based electrolytes have great potential for use as safe electrolytes in LMBs.
Co-reporter:Jun Huang, Kaihua Yang, Zhengxi Zhang, Li Yang and Shin-ichi Hirano
Chemical Communications 2017 - vol. 53(Issue 55) pp:NaN7803-7803
Publication Date(Web):2017/06/16
DOI:10.1039/C7CC03933F
∼1 V lithium intercalation materials are promising anodes for lithium-ion batteries, because such materials give consideration to both the tolerance of lithium plating (e.g., graphite with ∼0.1 V versus Li+/Li easily results in lithium plating due to a too low potential) and the energy density of the batteries (e.g., Li4Ti5O12 with ∼1.55 V decreases the battery voltage, and thus reduces the energy density). Herein, the layered perovskite compound LiEuTiO4 with a 0.8 V lithium intercalation/deintercalation potential plateau was successfully synthesized by the ion-exchange reaction with NaEuTiO4 prepared via a sol–gel method. LiEuTiO4 can deliver a high capacity of 219.2 mA h g−1 (2nd discharge) at a rate of 100 mA g−1. Even after 500 cycles, the discharge capacity remains at ∼217 mA h g−1 and the Coulombic efficiency is 99.2%. To our knowledge, the cycle stability of LiEuTiO4 exceeds all previous ∼1 V electrodes. Different from the common lithium intercalation Ti-based electrodes (such as Li4Ti5O12) based on the reduction of the Ti4+ to Ti3+, electrochemical lithium intercalation into LiEuTiO4 leads to the reduction of the Eu3+ to Eu2+.
Co-reporter:Dong Luo, Pei Shi, Shaohua Fang, Wenbin Guo, Li Yang and Shin-ichi Hirano
Inorganic Chemistry Frontiers 2017 - vol. 4(Issue 4) pp:NaN658-658
Publication Date(Web):2017/01/18
DOI:10.1039/C6QI00571C
Assembled microspherical cathodes have attracted great attention thanks to their high tap density, good rate capability and cycling stability. However, for layered Li-rich transition-metal oxides (LROs), the preparation of uniformly assembled microspheres still faces many challenges due to harsh synthetic conditions and the nature of multiple metal elements. In this work, Li1.17Mn0.50Ni0.16Co0.17O2 assembled microspheres have been prepared by a new route tactfully combining a solvothermal process and a molten-salt method. The use of a solvothermal process is helpful for the preparation of precursors with assembled microspherical morphology, and the addition of complex salts (NaCl and KCl), can increase the uniformity of cation distribution. The product obtained at 800 °C delivers the best electrochemical performances among all samples. At a current density of 300 mA g−1, its initial discharge capacity is larger than 228 mA h g−1, corresponding to a capacity retention ratio of 86.8% after 200 cycles. Even if the current density increases to 2000 mA g−1, its discharge capacity is still as large as 156 mA h g−1. What's more, we discover the moving rate of Li-ions during the sintering process will affect the uniformity of Li2MnO3-like and LiMO2 components in LRO assembled microspheres. This discovery is helpful for the preparation of LRO assembled microspheres with excellent electrochemical performances.
Co-reporter:Yufeng Tang, Li Yang, Zheng Qiu and Jianshu Huang
Journal of Materials Chemistry A 2009 - vol. 19(Issue 33) pp:NaN5984-5984
Publication Date(Web):2009/06/30
DOI:10.1039/B907480E
Mesoporous spinel lithium titanate Li4Ti5O12 microspheres were prepared by template-free hydrothermal process in ethanol–water mixed solution and subsequent heat treatment. The role of ethanol helps the formation of a mesoporous structure during the hydrothermal process. A mechanism analogous to the Kirkendall effect was proposed to account for the template-free formation of these mesoporous nanostructures. As anode materials for high-rate lithium ion battery, the Li4Ti5O12 mesoporous spheres exhibited superior high-rate performance of 114 mA h g−1 at 30C and good capacity retention of 125 mA h g−1 after 200 cycles at 20C, which indicates promising application in high-rate lithium ion batteries.
Co-reporter:Qinghua Tian, Zhengxi Zhang, Li Yang and Shin-ichi Hirano
Journal of Materials Chemistry A 2014 - vol. 2(Issue 32) pp:NaN12887-12887
Publication Date(Web):2014/06/11
DOI:10.1039/C4TA02059F
In this work, a peculiar nanostructure of SnO2/Sn@carbon nanospheres dispersed in the interspaces of a three-dimensional SnO2/Sn@carbon nanowires network composite (denoted as SnO2/Sn@C) has been successfully fabricated by a facile strategy and confirmed by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, laser Raman spectroscopy, Brunauer–Emmett–Teller method, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy characterization, illustrating the combination of the nanospheres and the 3-dimensional nanowires network. This architecture effectively withstands the volume change and restricts the agglomeration of SnO2/Sn during the cycling process. Moreover, the SnO2/Sn distributed in carbon matrix and the SnO2/Sn@carbon nanospheres dispersed in interspaces of three-dimensional SnO2/Sn@carbon nanowires network facilitate electron and ion transport throughout the electrode. As a result, this composite exhibits excellent performance as a potential anode material for lithium ion batteries and delivers a reversible capacity of 678.6 mA h g−1 at 800 mA g−1, even after 500 cycles.
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