Co-reporter:Weimin Zhao, Yajuan Ji, Zhongru Zhang, Min Lin, ... Yong Yang
Current Opinion in Electrochemistry 2017 Volume 6, Issue 1(Volume 6, Issue 1) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.coelec.2017.10.012
•Functional electrolyte additives.•Lithium-ion batteries.•Solid electrolyte interfaces.•Working mechanism.•Theoretical calculation.•Characterization and imaging techniques.Functional electrolytes with additives are one of the key materials which affect the electrochemical performance of the Li-ion batteries such as energy density, power density and cycling performance. This paper gives a short overview of recent works on some new functional electrolyte additives involve P/N/F/S-containing and new type of lithium salts. The insights of working mechanism of these additives are summarized. The newly progress of in situ spectroscopic techniques and theoretical tools to characterize the composition, structure and growth of solid electrolyte interfaces (SEIs) are also briefly reviewed.Download high-res image (171KB)Download full-size image
Co-reporter:Dawei Wang;Ronghui Kou;Yang Ren;Cheng-Jun Sun;Hu Zhao;Ming-Jian Zhang;Yan Li;Ashifia Huq;J. Y. Peter Ko;Feng Pan;Yang-Kook Sun;Yong Yang;Khalil Amine;Jianming Bai;Zonghai Chen;Feng Wang
Advanced Materials 2017 Volume 29(Issue 39) pp:
Publication Date(Web):2017/10/01
DOI:10.1002/adma.201606715
AbstractNickel-rich layered transition metal oxides, LiNi1−x(MnCo)xO2 (1−x ≥ 0.5), are appealing candidates for cathodes in next-generation lithium-ion batteries (LIBs) for electric vehicles and other large-scale applications, due to their high capacity and low cost. However, synthetic control of the structural ordering in such a complex quaternary system has been a great challenge, especially in the presence of high Ni content. Herein, synthesis reactions for preparing layered LiNi0.7Mn0.15Co0.15O2 (NMC71515) by solid-state methods are investigated through a combination of time-resolved in situ high-energy X-ray diffraction and absorption spectroscopy measurements. The real-time observation reveals a strong temperature dependence of the kinetics of cationic ordering in NMC71515 as a result of thermal-driven oxidation of transition metals and lithium/oxygen loss that concomitantly occur during heat treatment. Through synthetic control of the kinetic reaction pathway, a layered NMC71515 with low cationic disordering and a high reversible capacity is prepared in air. The findings may help to pave the way for designing high-Ni layered oxide cathodes for LIBs.
Co-reporter:Yajuan Ji, Pengbo Zhang, Min Lin, Weimin Zhao, Zhongru Zhang, Yufen Zhao, Yong Yang
Journal of Power Sources 2017 Volume 359(Volume 359) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.jpowsour.2017.05.091
•(Phenoxy)Pentafluorocyclotriphosphazene N3P3(OPh)F5 as a bifunctional additive.•PFPN will be prior to oxidize and form a polymerization film on LiCoO2 surface.•The film of PFPN-derived can improve the electrochemical performance of LiCoO2.•The additive PFPN can help to enhance the thermal stability of LixCoO2.(Phenoxy)Pentafluorocyclotriphosphazene N3P3(OPh)F5 (PFPN) is investigated as a bifunctional additive in electrolyte to improve the electrochemical performance and thermal stability of LiCoO2 simultaneously when the electrodes cycled to high cutoff potentials. The results show that the electrochemical performance of the electrode material with the additive in the electrolyte is enhanced significantly, with a capacity retention of 91% after 300 cycles, which is a great improvement compared with that of only 67% in base electrolyte. More significantly, the thermal stability of LixCoO2 (x < 0.5) in the presence of PFPN or covered with decomposed products of PFPN is also remarkably improved. Our results show that the additive can be oxidized prior to EC and DMC, and the decomposition products of PFPN contribute to the LiCoO2/electrolyte interphase film (CEI) with more uniform and denser structure. This polymerized CEI processes an excellent electrochemical stability to assist in inhibiting the further decomposition of the electrolyte and reducing the interfacial impedance growth apparently of the cells with a long cycling condition.Download high-res image (234KB)Download full-size image
Co-reporter:Jian Wang;Yajuan Ji;Narayana Appathurai;Jigang Zhou;Yong Yang
Chemical Communications 2017 vol. 53(Issue 61) pp:8581-8584
Publication Date(Web):2017/07/27
DOI:10.1039/C7CC03960C
X-ray photoemission electron microscopy (X-PEEM) of cycled LiCoO2 composite electrodes has revealed the interfaces of various components within the composite electrodes and their dependence on additives in the electrolyte and the interplay of multiple components in the electrodes. This study visualizes CoF2 distribution and Co–O bonding variation along with local component agglomeration and degradation. The obtained new insights will assist further development of long-life high-voltage LiCoO2/C batteries.
Co-reporter:Yuanjun Shao, Hongjun Yue, Ruimin Qiao, Jiaqi Hu, Guiming Zhong, Shunqing Wu, Matthew J. McDonald, Zhengliang Gong, Zizhong Zhu, Wanli Yang, and Yong Yang
Chemistry of Materials 2016 Volume 28(Issue 4) pp:1026
Publication Date(Web):January 25, 2016
DOI:10.1021/acs.chemmater.5b03762
While a rechargeable battery based on Na/CFx has been proposed, its reversible mechanism has remained unclear. Here, a new fluorinated carbon fiber material with the formula CF0.75 is used as a cathode material for rechargeable sodium batteries, delivering an initial discharge capacity of 705 mA·h g–1 with a high discharge plateau of 2.75 V and a reversible high discharge capacity of 350 mA·h g–1 at 20 mA g–1. The first discharge plateau of 2.75 V is the highest value reported in this family of materials so far, even slightly higher than that of commercial fluorinated graphite tested in a lithium battery (2.7 V). The origins of the observed high voltage of the material are explored by a combination of theoretical calculations and galvanostatic intermittent titration technique data and determined to be related to the disordered structure of the carbon fiber. Soft X-ray absorption spectroscopy and 19F magic angle spinning nuclear magnetic resonance characterization results disclose a full view of the conversion reaction mechanism involved in the charge and discharge processes, both on the surface and in the bulk, and show evidence of reversible conversion between CFx and NaF. Although a suitable electrolyte is currently lacking and further research is necessary, the inherent advantages of the compound make it a promising cathode material for future rechargeable sodium batteries.
Co-reporter:Shiyao Zheng, Guiming Zhong, Matthew J. McDonald, Zhengliang Gong, Rui Liu, Wen Wen, Chun Yang and Yong Yang
Journal of Materials Chemistry A 2016 vol. 4(Issue 23) pp:9054-9062
Publication Date(Web):25 May 2016
DOI:10.1039/C6TA02230H
Na-ion batteries (NIBs) have recently attracted much attention, due to their low cost and the abundance of sodium resources. In this work, NaLi0.1Ni0.35Mn0.55O2 as a promising new kind of cathode material for Na-ion batteries was synthesized by a co-precipitation method. Powder XRD patterns show that the sample has a primary O3-type structure after Li+ substitution. The material delivers excellent electrochemical performance, with an initial discharge specific capacity of 128 mA h g−1 and a capacity retention of 85% after 100 cycles at a rate of 12 mA g−1 in the voltage range of 2.0–4.2 V. In a widened voltage range of 1.5–4.3 V, the specific capacity can reach up to 160 mA h g−1. The structural stability of the material is substantially improved compared with lithium-free NaNi0.5Mn0.5O2, which can be attributed to the formation of an O′3 phase caused by Li-substitution, as proven by in situ XRD and solid state NMR (ss-NMR) measurements.
Co-reporter:Xiang Han, Huixin Chen, Xin Li, Jianyuan Wang, Cheng Li, Songyan Chen and Yong Yang
Journal of Materials Chemistry A 2016 vol. 4(Issue 2) pp:434-442
Publication Date(Web):20 Nov 2015
DOI:10.1039/C5TA08297H
We report for the first time that the dehydrogenation process of PAN was suppressed and the silicon oxide of the MSP surface was reduced during annealing in Ar + H2. Consequently, the remaining –NH bonds of the carbon chain can interact with the fresh amorphous Si on the surface of the MSPs to form a Si–N–C layer, which improves the adhesion between Si and C and serves as a stable electrolyte blocking layer. In addition, based on micron-sized MSPs, the structural stability of the electrode is dramatically enhanced through in situ formation of Si nanocrystals of less than 5 nm. The low Li+ diffusion kinetics of the Si–N–C layer and self limiting inhomogeneous lithiation in MSPs jointly create unlithiated Si nanocrystals, acting as supporting frames to prevent pulverization of the anode material. Our nitriding MSP anode has exhibited for the first time a 100% capacity retention (394 mA h g−1) after 2000 cycles (10 cycles each at 0.1, 0.5, 1, 2, and 1 and then 1950 cycles at 0.5 A g−1) and a 100% capacity retention at 0.1 A g−1 (540 mA h g−1) after 400 cycles. Thus, our work proposes a novel avenue to engineer battery materials with large volume changes.
Co-reporter:Xiang Han, Huixin Chen, Xin Li, Shumei Lai, Yihong Xu, Cheng Li, Songyan Chen, and Yong Yang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 1) pp:673
Publication Date(Web):December 15, 2015
DOI:10.1021/acsami.5b09783
Conductive metal nanowire is a promising current collector for the Si-based anode material in high-rate lithium-ion batteries. However, to harness this remarkable potential for high power density energy storage, one has to address the interfacial potential barrier that hinders the electron injection from the metal side. Herein, we present that, solely by inserting ultrathin amorphous germanium (a-Ge) (∼5 nm) at the interface of NiSix/amorphous Si (a-Si), the rate capacity was substantially enhanced, 477 mAh g–1 even at a high rate of 40 A g–1. In addition, batteries containing the NiSix/Ge+Si anodes cycled over 1000 times at 10 A g–1 while the capacity retaining more than 877 mAh g–1, which is among the highest reported. The excellent electrochemical performance is directly correlated with the significantly improved electrical conductivity and mechanical stability throughout the entire electrode. The potential barrier between the NiSix and a-Si was modulated by a-Ge, which constructs an electron highway. Besides, the a-Ge interlayer enhances the interfacial adhesion by reducing void fraction and the inhomogeneous strain of the Li–Ge and Li–Si stacking structure was accommodated through the bending and twist of relatively thin NiSix, thus ensures a more stable high-rate cycling performance. Our work shows an effective way to fabricate metal/a-Si nanowires for high-rate lithium-ion battery anodes.Keywords: electron conductivity; germanium interlayer; high-rate lithium-ion anodes; NiSix/a-Si nanowire; structural integrity
Co-reporter:Xuehang Wu, Gui-Liang Xu, Guiming Zhong, Zhengliang Gong, Matthew J. McDonald, Shiyao Zheng, Riqiang Fu, Zonghai Chen, Khalil Amine, and Yong Yang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 34) pp:22227
Publication Date(Web):August 5, 2016
DOI:10.1021/acsami.6b06701
P2-type sodium nickel manganese oxide-based cathode materials with higher energy densities are prime candidates for applications in rechargeable sodium ion batteries. A systematic study combining in situ high energy X-ray diffraction (HEXRD), ex situ X-ray absorption fine spectroscopy (XAFS), transmission electron microscopy (TEM), and solid-state nuclear magnetic resonance (SS-NMR) techniques was carried out to gain a deep insight into the structural evolution of P2–Na0.66Ni0.33–xZnxMn0.67O2 (x = 0, 0.07) during cycling. In situ HEXRD and ex situ TEM measurements indicate that an irreversible phase transition occurs upon sodium insertion-extraction of Na0.66Ni0.33Mn0.67O2. Zinc doping of this system results in a high structural reversibility. XAFS measurements indicate that both materials are almost completely dependent on the Ni4+/Ni3+/Ni2+ redox couple to provide charge/discharge capacity. SS-NMR measurements indicate that both reversible and irreversible migration of transition metal ions into the sodium layer occurs in the material at the fully charged state. The irreversible migration of transition metal ions triggers a structural distortion, leading to the observed capacity and voltage fading. Our results allow a new understanding of the importance of improving the stability of transition metal layers.Keywords: cathode material; sodium ion battery; sodium nickel manganese oxide; structural transition; Zn doping
Co-reporter:Shouding Li, Jianghuai Guo, Zhuo Ye, Xin Zhao, Shunqing Wu, Jin-Xiao Mi, Cai-Zhuang Wang, Zhengliang Gong, Matthew J McDonald, Zizhong Zhu, Kai-Ming Ho, and Yong Yang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 27) pp:17233-17238
Publication Date(Web):June 15, 2016
DOI:10.1021/acsami.6b03969
A new cubic polymorph of sodium iron silicate, Na2FeSiO4, is reported for the first time as a cathode material for Na-ion batteries. It adopts an unprecedented cubic rigid tetrahedral open framework structure, i.e., F4̅3m, leading to a polyanion cathode material without apparent cell volume change during the charge/discharge processes. This cathode shows a reversible capacity of 106 mAh g–1 and a capacity retention of 96% at 5 mA g–1 after 20 cycles.
Co-reporter:Xuehang Wu, Guiming Zhong, Yong Yang
Journal of Power Sources 2016 Volume 327() pp:666-674
Publication Date(Web):30 September 2016
DOI:10.1016/j.jpowsour.2016.07.061
•Na4Fe3(PO4)2(P2O7)/C nanocomposite is prepared by a sol-gel route.•Na4Fe3(PO4)2(P2O7)/C exhibits excellent electrochemical performance.•Structural evolution during sodium extraction is investigated.A mixed polyanionic Na4Fe3(PO4)2(P2O7)/C nanocomposite is synthesized via a sol-gel route. The phosphate raw material is transformed to the mixed phosphate-pyrophosphate with high phase purity via a self-condensation reaction at 500 °C. Na4Fe3(PO4)2(P2O7)/C can deliver an initial capacity of 110 mAh g−1 at 0.05C with the average discharge voltage approaching 3.1 V. The nanocomposite shows excellent rate capability because of the presence of an in-situ formed 3-D network of carbon. At 10 C rate, the nanocomposite delivers a discharge capacity of 78 mAh g−1 at 25 mAh °C and 82 mAh g−1 at 55 °C. The nanocomposite has a good long-term cycling stability, retaining 89% of the initial discharge capacity after 300 cycles. In-situ XRD results demonstrate that the sodium insertion/extraction process in Na4Fe3(PO4)2(P2O7) is an imperfect solid-solution reaction with an obvious local lattice distortion instead of an ideal solid-solution reaction. Using a solid-state NMR technique, it is further found that the sodium extraction from the Na1, Na3, and Na4 sites causes an obvious change in local structure. However, the local structure of Na2 remains unchanged, which may aid the stability of the host structure.
Co-reporter:Wengao Zhao, Guiming Zhong, Matthew J. McDonald, Zhengliang Gong, Rui Liu, Jingyu Bai, Chun Yang, Shiguang Li, Weimin Zhao, Hongchun Wang, Riqiang Fu, Zheng Jiang, Yong Yang
Nano Energy 2016 Volume 27() pp:420-429
Publication Date(Web):September 2016
DOI:10.1016/j.nanoen.2016.07.011
•For the first time, Cu3(PO4)2/C is reported as a novel cathode vs Na+/Na.•High rechargeable specific capacity of the material as high as 290 mA h g−1.•Acceptable capacity retention of 210 mA h g−1(20 mA g−1) after 30 cycles.•The detailed conversion reaction mechanism of Cu3(PO4)2/C is disclosed.Conversion-type materials are an appealing alternative to conventional intercalation compounds as cathode materials for sodium ion batteries, due to their high capacities. In this paper, we report for the first time that carbon-coated copper phosphate (Cu3(PO4)2/C) can be used as a novel high-capacity cathode for rechargeable Na batteries. Cu3(PO4)2/C shows a reversible capacity up to 290 mA h g−1 at a current of 20 mA g−1and 190 mA h g−1 at 400 mA g−1, with capacity retention of 210 and 160 mA h g−1 respectively after 30 cycles. The detailed sodium storage mechanisms were studied by employing ex-situ XRD, HR-TEM, solid-state NMR and XAFS techniques. The results clearly indicate that Cu3(PO4)2 can transform into Na3PO4 and Cu particles after discharge. Furthermore, Cu can react with Na3PO4 to form copper phosphate and NaxCuyPO4 in the charge process, determining the rechargeability of Cu3(PO4)2.The schematic preparation approach of Cu3(PO4)2/C and its electrochemical (de)sodiation reaction at 1st rechargeable cycle.
Co-reporter:Dr. Qiaobao Zhang;Huixin Chen;Dr. Xiang Han;Dr. Junjie Cai; Yong Yang; Meilin Liu; Kaili Zhang
ChemSusChem 2016 Volume 9( Issue 2) pp:186-196
Publication Date(Web):
DOI:10.1002/cssc.201501151
Abstract
The appropriate combination of hierarchical transition-metal oxide (TMO) micro-/nanostructures constructed from porous nanobuilding blocks with graphene sheets (GNS) in a core/shell geometry is highly desirable for high-performance lithium-ion batteries (LIBs). A facile and scalable process for the fabrication of 3D hierarchical porous zinc–nickel–cobalt oxide (ZNCO) microspheres constructed from porous ultrathin nanosheets encapsulated by GNS to form a core/shell geometry is reported for improved electrochemical performance of the TMOs as an anode in LIBs. By virtue of their intriguing structural features, the produced ZNCO/GNS core/shell hybrids exhibit an outstanding reversible capacity of 1015 mA h g−1 at 0.1 C after 50 cycles. Even at a high rate of 1 C, a stable capacity as high as 420 mA h g−1 could be maintained after 900 cycles, which suggested their great potential as efficient electrodes for high-performance LIBs.
Co-reporter:Dr. Qiaobao Zhang;Huixin Chen;Dr. Xiang Han;Dr. Junjie Cai; Yong Yang; Meilin Liu; Kaili Zhang
ChemSusChem 2016 Volume 9( Issue 2) pp:
Publication Date(Web):
DOI:10.1002/cssc.201600017
Abstract
Invited for this month′s cover are the groups of Profs. Y. Yong (City University Hong Kong), M. Liu (Georgia Institute of Technology), and K. Zhang (Xiamen University). The image shows zinc–nickel–cobalt oxide microspheres coated with graphene nanosheets, which significantly enhances their cyclability when used in Li-ion batteries. The Full Paper itself is available at 10.1002/cssc.201501151.
Co-reporter:Dr. Qiaobao Zhang;Huixin Chen;Dr. Xiang Han;Dr. Junjie Cai; Yong Yang; Meilin Liu; Kaili Zhang
ChemSusChem 2016 Volume 9( Issue 2) pp:
Publication Date(Web):
DOI:10.1002/cssc.201600016
Co-reporter:Guiming Zhong, Jingyu Bai, Paul N. Duchesne, Matthew J. McDonald, Qi Li, Xu Hou, Joel A. Tang, Yu Wang, Wengao Zhao, Zhengliang Gong, Peng Zhang, Riqiang Fu, and Yong Yang
Chemistry of Materials 2015 Volume 27(Issue 16) pp:5736
Publication Date(Web):July 24, 2015
DOI:10.1021/acs.chemmater.5b02290
In the search for new cathode materials for rechargeable lithium batteries, conversion-type materials have great potential because of their ability to achieve high specific capacities via the full utilization of transition metal oxidation states. Here, we report for the first time that copper phosphate can be used as a novel high-capacity cathode for rechargeable Li batteries, capable of delivering a reversible capacity of 360 mAh/g with two discharge plateaus of 2.7 and 2.1 V at 400 mA/g. The underlying reaction involves the formation as well as the oxidation of metallic Cu. The solid-state NMR, in situ XAFS, HR-TEM, and XRD results clearly indicate that Cu can react with Li3PO4 to form copper phosphate and LixCuyPO4 during the charging process, largely determining the reversibility of Cu3(PO4)2. This new reaction scheme provides a new venue to explore polyanion-type compounds as high-capacity cathode materials with conversion reaction processes.
Co-reporter:Dawei Wang, Guiming Zhong, Wei Kong Pang, Zaiping Guo, Yixiao Li, Matthew J. McDonald, Riqiang Fu, Jin-Xiao Mi, and Yong Yang
Chemistry of Materials 2015 Volume 27(Issue 19) pp:6650
Publication Date(Web):September 18, 2015
DOI:10.1021/acs.chemmater.5b02429
The cubic garnet-type solid electrolyte Li7La3Zr2O12 with aliovalent doping exhibits a high ionic conductivity, reaching up to ∼10–3 S/cm at room temperature. Fully understanding the Li+ transport mechanism including Li+ mobility at different sites is a key topic in this field, and Li7–2x–3yAlyLa3Zr2–xWxO12 (0 ≤ x ≤ 1) are selected as target electrolytes. X-ray and neutron diffraction as well as ac impedance results show that a low amount of aliovalent substitution of Zr with W does not obviously affect the crystal structure and the activation energy of Li+ ion jumping, but it does noticeably vary the distribution of Li+ ions, electrostatic attraction/repulsion, and crystal defects, which increase the lithium jump rate and the creation energy of mobile Li+ ions. For the first time, high-resolution NMR results show evidence that the 24d, 96h, and 48g sites can be well-resolved. In addition, ionic exchange between the 24d and 96h sites is clearly observed, demonstrating a lithium transport route of 24d–96h–48g–96h–24d. The lithium mobility at the 24d sites is found to dominate the total ionic conductivity of the samples, with diffusion coefficients of 10–9 m2 s–1 and 10–12 m2 s–1 at the octahedral and tetrahedral sites, respectively.
Co-reporter:Huixin Chen, Qiaobao Zhang, Xiang Han, Junjie Cai, Meilin Liu, Yong Yang and Kaili Zhang
Journal of Materials Chemistry A 2015 vol. 3(Issue 47) pp:24022-24032
Publication Date(Web):29 Oct 2015
DOI:10.1039/C5TA07258A
Three-dimensional (3D) hierarchically porous transition metal oxides, particularly those involving different metal ions of mixed valence states and constructed from interconnected nano-building blocks directly grown on conductive current collectors, are promising electrode candidates for energy storage devices such as Li-ion batteries (LIBs) and supercapacitors (SCs). This study reports a facile and scalable chemical bath deposition process combined with simple calcination for fabricating 3D hierarchically porous Zn–Ni–Co oxide (ZNCO) nanosheet arrays directly grown on Ni foam with robust adhesion. The resulting nanostructures are then evaluated as a binder-free electrode for LIBs and SCs. Given its unique architecture and compositional advantages, the electrode exhibits a reversible capacity of 1131 mA h g−1 after 50 cycles at a current density of 0.2 A g−1, an excellent long-term cycling stability at a high current density of 1 A g−1 for 1000 cycles, and a desirable rate capability when tested as an anode for LIBs. When used for SCs, the electrode demonstrates a high specific capacitance (1728 F g−1 at 1 A g−1), an outstanding rate capability (72% capacitance retention from 1 A g−1 to 50 A g−1), and an excellent cycling stability (capacitance of 1655 F g−1 after 5000 cycles at a current density of 20 A g−1 with 108.6% retention). Overall, the unique 3D hierarchically porous ZNCO nanosheets hold a great promise for constructing high-performance energy storage devices.
Co-reporter:Xuehang Wu, Jianghuai Guo, Dawei Wang, Guiming Zhong, Matthew J. McDonald, Yong Yang
Journal of Power Sources 2015 Volume 281() pp:18-26
Publication Date(Web):1 May 2015
DOI:10.1016/j.jpowsour.2014.12.083
•Na0.66Ni0.33–xZnxMn0.67O2 are investigated for the first time as cathode materials.•Zn substitution can suppress Na+/vacancy ordering.•Zn substitution significantly improves capacity and voltage retention.•Na0.66Ni0.26Zn0.07Mn0.67O2 delivers a 3.6 V average discharge voltage.P2-type Na0.66Ni0.33–xZnxMn0.67O2 (x = 0, 0.07, 0.14) are prepared using a conventional solid state method and for the first time developed as promising cathode materials for high-voltage sodium-ion batteries. The XRD patterns show that Zn2+ ions are successfully incorporated into the lattice of the Na–Ni–Mn–O system and the P2-type structure remains unchanged after substitution. The introduction of Zn2+ in the Na–Ni–Mn–O system can effectively overcome the drawback of voltage decay when charged to a higher cutoff voltage (>4.0 V), and significantly improve capacity retention compared to the unsubstituted material during cycling. In addition, a smoother charge/discharge profile can be observed between 3.0 and 4.0 V for Zn-substituted samples, demonstrating that Na+/vacancy ordering can be suppressed during sodium insertion/extraction. Na0.66Ni0.26Zn0.07Mn0.67O2 can deliver an initial capacity of 132 mAh g−1 at 12 mA g−1 with a high average voltage of 3.6 V and a capacity retention of 89% after 30 cycles. EIS measurements demonstrate that Zn-substitution is an effective way to limit the increase of inter-particle contact resistance by suppressing any possible irreversible phase transformation found at low sodium contents.
Co-reporter:Xuehang Wu, Jianghuai Guo, Matthew J. McDonald, Shiguang Li, Binbin Xu, Yong Yang
Electrochimica Acta 2015 Volume 163() pp:93-101
Publication Date(Web):1 May 2015
DOI:10.1016/j.electacta.2015.02.134
•A new type of urchin-like Mn0.33Co0.67C2O4 is synthesized.•Urchin-like Mn0.33Co0.67C2O4 exhibits excellent lithium storage properties.•Role of SEI layers for enhanced electrochemical properties is analyzed in detail.A new type of hierarchical urchin-like Mn0.33Co0.67C2O4 (HU-Mn0.33Co0.67C2O4) is fabricated using a template-free chemical co-precipitation method. The morphology of this system is highly influenced by the Mn/Co ratio. The obtained urchin-like microspheres are composed of end-connected nanorods and accompanied by structural voids. When tested in lithium-ion batteries, HU-Mn0.33Co0.67C2O4 delivers a high reversible discharge capacity of 924 mAh g−1 at 500 mA g−1 in the 2nd cycle, with 83% capacity retention over 300 cycles. Rate capability testing shows that HU-Mn0.33Co0.67C2O4 can deliver discharge capacities of 734 mAh g–1 at 1 A g–1 and 414 mAh g–1 at 5 A g–1, respectively. Although the transition-metal content and conductivity of HU-Mn0.33Co0.67C2O4 are much lower than that of MnCo2O4, the material still exhibits a high specific capacity, good capacity retention, and excellent rate capability, suggesting that HU-Mn0.33Co0.67C2O4 is a promising anode material for future lithium-ion batteries (LIBs). In addition, a gradual electrochemical activation process is observed to occur in the first several cycles, relating to the gradual generation of SEI layers on the electrode surface. It is found that the SEI layers on the surface of oxalate materials are predominantly composed of lithium alkyl carbonates from the reductive decomposition of electrolyte and the catalytic products of Li2C2O4. We speculate that the formed SEI layers with high lithium ion conductivity play an important role in achieving the observed high specific capacities and excellent rate capabilities of oxalates.
Co-reporter:Xiang Han, Huixin Chen, Jingjing Liu, Hanhui Liu, Peng Wang, Kai Huang, Cheng Li, Songyan Chen, Yong Yang
Electrochimica Acta 2015 Volume 156() pp:11-19
Publication Date(Web):20 February 2015
DOI:10.1016/j.electacta.2015.01.051
•A novel, economical ball milling and heat treatment of porous silicon based anodes was introduced to boost the electrochemical performance of Li-ion batteries.•The compact C/SiO2-coated peanut shell-like electrodes could accommodate volume change effectively.•The electrodes exhibited outstanding cycling performance and rate capacities.•Our work gives a compelling look at a novel and large-scale production method of fabricating next generation Si/C anodes for high-performance LIBs.A novel, economical ball milling and heat treatment of porous silicon based anodes was introduced to boost the electrochemical performance and cycle capacity of Li-ion batteries. The resultant peanut shell-like electrodes combined multiple advantageous features, including a continuous, flexible electrically conductive carbon network, a synergistic C/SiO2 coating layer and improved interfacial contact, in a peanut shell structure with void space. The electrodes achieved an initial discharge capacity of 1909 mA h g−1 with coulombic efficiency of 88.8% as well as a high reversible capacity of 1179 mA h g−1 after 120 cycles at 0.1C. In addition, the material was capable of reaching a capacity of 493 mA h g−1 even at the high charge rate of 4C. This work gives a compelling look at a novel and large-scale production method of fabricating next generation Si/C anodes for high-performance LIBs.
Co-reporter:Sihui Wang, Yixiao Li, Jue Wu, Bizhu Zheng, Matthew J. McDonald and Yong Yang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 15) pp:10151-10159
Publication Date(Web):2015/03/12
DOI:10.1039/C5CP00853K
Layered lithium-rich oxides have several serious shortcomings such as fast voltage fading and poor cyclic stability of energy density which greatly hinder their practical applications. Fabrication of a stable framework of layered lithium-rich oxides during charging–discharging is crucial for addressing the above problems. In this work, we show that Ti modification is a promising way to realize this target with bifunctional roles. For example, it is able to substitute Mn in the lattice framework and form a stable surface layer. It therefore leads to an improved retention of energy density of the Ti-modified Li1.2Mn0.54−xTixNi0.13Co0.13O2 (x = 0.04, 0.08, and 0.15) materials during cycling. The evolution of dQ/dV curves show that the layered/spinel phase transformation is suppressed owing to the introduction of strong Ti–O bonds in the framework. In addition, SEM, TEM, and EIS results confirm that a more uniform and stable interface layer is formed on Ti-modified Li1.2Mn0.54−xTixNi0.13Co0.13O2 (x = 0.04, 0.08, and 0.15) materials compared with the Ti-free counterpart. The stable interface layer on the lithium-rich oxides is also beneficial for further reducing side reactions, resulting in stable interface layer resistance. Therefore, the improved cycling performance of the material is due to both contribution of the more stable framework and enhanced electrode/electrolyte interface by Ti modification.
Co-reporter:Dawei Wang, Guiming Zhong, Yixiao Li, Zhengliang Gong, Matthew J. McDonald, Jin-Xiao Mi, Riqiang Fu, Zhicong Shi, Yong Yang
Solid State Ionics 2015 Volume 283() pp:109-114
Publication Date(Web):15 December 2015
DOI:10.1016/j.ssi.2015.10.009
•The addition of lithium borate to Li3.5Si0.5P0.5O4 prominently increases the ionic conductivity.•11B MAS NMR results demonstrate that the boron exists in the form of BO4 and BO3, and plays a role as sintering assistant.•The synthesized electrolytes show prominence to another material with great potential for constructing solid state batteries.A series of lithium borate added electrolyte compounds, xLi3BO3-(1−x)Li3.5Si0.5P0.5O4 (0 ≤ x ≤ 0.2), are synthesized and characterized. This so-called LISICON electrolyte system is analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), solid state nuclear magnetic resonance (ss-NMR), electrochemical impedance spectra (EIS), and direct current (DC) polarization methods. From 11B MAS NMR spectra, it is demonstrated that a small fraction of boron exists in the form of BO4, while its majority settles at grain boundaries in the form of BO3, indicating that lithium borate glasses play a role as sintering assistant. This prominently increases the relative density of samples, and is beneficial to the ionic conductivity. Further results show that the electrical conduction of lithium borate added LISICONs is dominated by Li+ ions, with a transference number of tLi+ ≥ 0.996 and a corresponding ionic conductivity of about 6.5 × 10−6 S cm−1 at room temperature, almost two times that of pristine Li3.5Si0.5P0.5O4.
Co-reporter:Zigeng Liu, Yan-Yan Hu, Matthew T. Dunstan, Hua Huo, Xiaogang Hao, Huan Zou, Guiming Zhong, Yong Yang, and Clare P. Grey
Chemistry of Materials 2014 Volume 26(Issue 8) pp:2513
Publication Date(Web):March 24, 2014
DOI:10.1021/cm403728w
Na3V2(PO4)2F3 is a novel electrode material that can be used in both Li ion and Na ion batteries (LIBs and NIBs). The long- and short-range structural changes and ionic and electronic mobility of Na3V2(PO4)2F3 as a positive electrode in a NIB have been investigated with electrochemical analysis, X-ray diffraction (XRD), and high-resolution 23Na and 31P solid-state nuclear magnetic resonance (NMR). The 23Na NMR spectra and XRD refinements show that the Na ions are removed nonselectively from the two distinct Na sites, the fully occupied Na1 site and the partially occupied Na2 site, at least at the beginning of charge. Anisotropic changes in lattice parameters of the cycled Na3V2(PO4)2F3 electrode upon charge have been observed, where a (= b) continues to increase and c decreases, indicative of solid-solution processes. A noticeable decrease in the cell volume between 0.6 Na and 1 Na is observed along with a discontinuity in the 23Na hyperfine shift between 0.9 and 1.0 Na extraction, which we suggest is due to a rearrangement of unpaired electrons within the vanadium t2g orbitals. The Na ion mobility increases steadily on charging as more Na vacancies are formed, and coalescence of the resonances from the two Na sites is observed when 0.9 Na is removed, indicating a Na1–Na2 hopping (two-site exchange) rate of ≥4.6 kHz. This rapid Na motion must in part be responsible for the good rate performance of this electrode material. The 31P NMR spectra are complex, the shifts of the two crystallograpically distinct sites being sensitive to both local Na cation ordering on the Na2 site in the as-synthesized material, the presence of oxidized (V4+) defects in the structure, and the changes of cation and electronic mobility on Na extraction. This study shows how NMR spectroscopy complemented by XRD can be used to provide insight into the mechanism of Na extraction from Na3V2(PO4)2F3 when used in a NIB.
Co-reporter:Dawei Wang, Guiming Zhong, Oleksandr Dolotko, Yixiao Li, Matthew J. McDonald, Jinxiao Mi, Riqiang Fu and Yong Yang
Journal of Materials Chemistry A 2014 vol. 2(Issue 47) pp:20271-20279
Publication Date(Web):06 Oct 2014
DOI:10.1039/C4TA03591G
The cubic garnet-type solid electrolyte Li7La3Zr2O12 with aliovalent doping exhibits a high ionic conductivity. However, the synergistic effects of aliovalent co-doping on the ionic conductivity of garnet-type electrolytes have rarely been examined. In this work, the synergistic effects of co-dopants Al and Te on the ionic conductivity of garnets were investigated using X-ray diffraction (XRD), 27Al/6Li Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR), Energy Dispersive X-ray Spectroscopy (EDS), Neutron Powder Diffraction (NPD) and Alternating Current (AC) impedance measurements. It was shown that co-dopants Al and Te stabilized the cubic lattice of Li7−2x−3yAlyLa3Zr2−xTexO12 with specific Al/Te ratios, where additional Al had to be included in the structure if the amount of doped Te content x was below 0.5. In the Al and Te co-doped crystal structure, Al was incorporated into the tetrahedral 24d sites of lithium and Te occupied 16a sites of Zr. It was revealed that the occupancy of the latter could suppress the insertion of Al. High-resolution 6Li MAS NMR was able to differentiate the two lithium sites of interest in the garnet structure. Furthermore, it was shown that the mobility of Li ions at 24d sites mainly determined the bulk conductivities of garnet-type electrolytes.
Co-reporter:Huixin Chen, Qiaobao Zhang, Jiexi Wang, Daguo Xu, Xinhai Li, Yong Yang and Kaili Zhang
Journal of Materials Chemistry A 2014 vol. 2(Issue 22) pp:8483-8490
Publication Date(Web):25 Mar 2014
DOI:10.1039/C4TA00967C
Novel three-dimensional (3D) hierarchical NiSix/Co3O4 core–shell nanowire arrays composed of NiSix nanowire cores and branched Co3O4 nanosheet shells have been successfully synthesized by combining chemical vapor deposition and a simple but effective chemical bath deposition process followed by a calcination process. The resulting hierarchical NiSix/Co3O4 core–shell nanowire arrays directly serve as binder- and conductive-agent-free electrodes for lithium ion batteries, which demonstrate remarkably improved electrochemical performances with excellent capacity retention and high rate capability on cycling. They can maintain a stable reversible capacity of 1279 mA h g−1 after 100 cycles at a current density of 400 mA g−1 and a capacity higher than 340 mA h g−1 even at a current density as high as 8 A g−1. Such superior electrochemical performance of the electrodes made by directly growing electro-active highly porous Co3O4 on a nanostructured NiSix conductive current collector makes them very promising for applications in high-performance lithium ion batteries.
Co-reporter:Xiaobiao Wu, Sihui Wang, Xiaochen Lin, Guiming Zhong, Zhengliang Gong and Yong Yang
Journal of Materials Chemistry A 2014 vol. 2(Issue 4) pp:1006-1013
Publication Date(Web):05 Dec 2013
DOI:10.1039/C3TA13801A
High-voltage Li2CoPO4F (∼5 V vs. Li/Li+) with double-layer surface coating has been successfully prepared for the first time. The Li3PO4-coated Li2CoPO4F shows a high reversible capacity of 154 mA h g−1 (energy density up to 700 W h kg−1) at 1 C current rate, and excellent rate capability (141 mA h g−1 at 20 C). XRD and MAS NMR results show that Li2CoPO4F can be indexed as an orthorhombic structure with space group Pnma and coexists with Li3PO4. The XPS depth profiles and TEM analysis reveal that the as-prepared material has a double-layer surface coating, with a carbon outer layer and a Li3PO4 inner layer, which greatly enhances the transfer kinetics of the lithium ions and electrons in the material and stabilizes the electrode/electrolyte interface. Using LiBOB as an electrolyte additive is another way to further stabilize the electrode/electrolyte interface, and the LiBOB has a synergistic effect with the Li3PO4 coating layer. In this way, the Li2CoPO4F cathode material exhibits excellent long-term cycling stability, with 83.8% capacity retention after 150 cycles. The excellent cycling performance is attributed to the LiBOB electrolyte additive and the Li3PO4 coating layer, both of which play an important role in stabilizing the charge transfer resistance of Li2CoPO4F upon cycling.
Co-reporter:Sihui Wang, Jiong Yang, Xiaobiao Wu, Yixiao Li, Zhengliang Gong, Wen Wen, Min Lin, Jihui Yang, Yong Yang
Journal of Power Sources 2014 Volume 253() pp:432
Publication Date(Web):1 May 2014
DOI:10.1016/j.jpowsour.2013.11.009
Co-reporter:Sihui Wang, Jiong Yang, Xiaobiao Wu, Yixiao Li, Zhengliang Gong, Wen Wen, Min Lin, Jihui Yang, Yong Yang
Journal of Power Sources 2014 Volume 245() pp:570-578
Publication Date(Web):1 January 2014
DOI:10.1016/j.jpowsour.2013.07.021
•LiMn2−xTixO4 (x = 1) fulfill more than 1 Li+ ion insertion into the spinel structure.•Ti substitution improves the spinel cycling stability between 2 and 4.8 V.•Ti substitution can suppress the Jahn–Teller distortion associated with Mn3+ ions.•Ti substitution stabilizes the spinel structure by forming more stable framework.•The role of Ti substitution is explored by in situ XRD and ab initio calculations.LiMn2−xTixO4 (x = 0, 0.5, 1) cathode materials have been synthesized by a conventional solid state method. The capacity of the as-prepared LiMn2O4, LiMn1.5Ti0.5O4 and LiMnTiO4 are 252, 198 and 157 mAh g−1, respectively, when charging/discharging over the voltage range of 2.0–4.8 V at a current density of 40 mA g−1, all of which are consistent with more than 1 Li+ ion insertion into the spinel structure. Compared with the pristine LiMn2O4, Ti-substituted samples exhibit much better cycling stability both at room temperature and 60 °C between 2.0 V and 4.8 V. The underlying mechanism has been investigated by an in situ X-ray diffraction technique. The results demonstrate that Ti4+ ions can suppress the Jahn–Teller distortion associated with Mn3+, and stabilize the spinel structure during the charging/discharging process. Ti–O bond is stronger than Mn–O bond which yields a more stable spinel framework, i.e., [Mn2−xTix]O4. Moreover, Ti substitution helps lower the concentration of Jahn–Teller Mn3+ ions in the spinel structure during discharging process and consequently improves the structural stability. The role of Ti substitution is also confirmed by the ab initio calculations.
Co-reporter:Sihui Wang, Yan Wu, Yixiao Li, Jianming Zheng, Jihui Yang, Yong Yang
Electrochimica Acta 2014 Volume 133() pp:100-106
Publication Date(Web):1 July 2014
DOI:10.1016/j.electacta.2014.04.008
Layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2–Spinel LiMn1.5Ti0.5O4 composite cathodes have been prepared by mechanically mixing process and investigated in this work. The unoccupied 16c sites of spinel LiMn1.5Ti0.5O4 can be used as a reservoir to store the Li+ ions that are lost during the activation of Li2MnO3 component in lithium-rich Li[Li0.2Mn0.54Ni0.13Co0.13]O2 material. As a consequence, the initial irreversible capacity loss (ICL) of lithium-rich Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is significantly reduced in the presence of spinel LiMn1.5Ti0.5O4. When mixed with 35.7 wt% of LiMn1.5Ti0.5O4, the lithium-rich material shows an initial ICL of only 17 mAh g−1, and could still deliver an initial discharge capacity as high as 220 mAh g−1. More importantly, the composite materials show better cycling performance and rate capability as compared with the pristine Li[Li0.2Mn0.54Ni0.13Co0.13]O2. The material with 35.7 wt% LiMn1.5Ti0.5O4 shows the best cycling stability, retaining 90% of the initial discharge capacity at the current density of 20 mA g−1 after 40 cycles. The improved cycling stability and rate performance can be ascribed to the good conductivity of spinel LiMn1.5Ti0.5O4 with 3D fast Li+ diffusion path, which ensures the timely lithium ion intercalation and de-intercalation.
Co-reporter:Xiaochen Lin, Xu Hou, Xiaobiao Wu, Sihui Wang, Ming Gao and Yong Yang
RSC Advances 2014 vol. 4(Issue 77) pp:40985-40993
Publication Date(Web):31 Jul 2014
DOI:10.1039/C4RA05336B
A Na2MnPO4F/C nanocomposite material is successfully synthesized via spray drying, followed by a high-temperature sintering method. It is shown that the highly phase-pure Na2MnPO4F with symmetry of the P21/n space group is uniformly embedded in the carbon networks, which play a key role in building up a highly efficient, electron-flow channel and elevating the electronic conductivity of the nanocomposites. The electrochemical measurements show that the initial discharge capacity of Na2MnPO4F reaches up to 140 and 178 mA h g−1 at 30 °C and 55 °C, respectively. Furthermore, the capacity still maintains 135 mA h g−1 after 20 cycles at 55 °C. The Na+ diffusion coefficient in Na2MnPO4F is calculated at about 10−17 cm2 s−1 by the GITT method. The impressive cycling performance of the material is ascribed to the good structural reversibility and stability of Na2MnPO4F, which are confirmed by the ex situ XRD measurements during the first cycle and after 30 cycles.
Co-reporter:Qiaobao Zhang;Huixin Chen;Jiexi Wang;Daguo Xu;Xinhai Li;Yong Yang;Kaili Zhang
ChemSusChem 2014 Volume 7( Issue 8) pp:2325-2334
Publication Date(Web):
DOI:10.1002/cssc.201402039
Abstract
We demonstrate the facile and well-controlled design and fabrication of heterostructured and hierarchical 3D mesoporous NiSix/NiCo2O4 core/shell nanowire arrays on nickel foam through a facile chemical vapor deposition (CVD) technique combined with a simple but powerful chemical bath deposition (CBD) technique. The smart hybridization of NiCo2O4 and NiSix nanostructures results in an intriguing mesoporous hierarchical core/shell nanowire-array architecture. The nanowire arrays demonstrate enhanced electrochemical performance as binder- and conductive-agent-free electrodes for lithium ion batteries (LIBs) with excellent capacity retention and high rate capability on cycling. The electrodes can maintain a high reversible capacity of 1693 mA h g−1 after 50 cycles at 200 mA g−1. Given the outstanding performance and simple, efficient, cost-effective fabrication, we believe that these 3D NiSix/NiCo2O4 core/shell heterostructured arrays have great potential application in high-performance LIBs.
Co-reporter:Huixin Chen, Qiaobao Zhang, Jiexi Wang, Qiang Wang, Xiang Zhou, Xinhai Li, Yong Yang, Kaili Zhang
Nano Energy 2014 10() pp: 245-258
Publication Date(Web):
DOI:10.1016/j.nanoen.2014.09.020
Co-reporter:Shi Tan;Ya J. Ji;Dr. Zhong R. Zhang; Dr. Yong Yang
ChemPhysChem 2014 Volume 15( Issue 10) pp:1956-1969
Publication Date(Web):
DOI:10.1002/cphc.201402175
Abstract
Developing a stable and safe electrolyte that works at voltages as high as 5 V is a formidable challenge in present Li-ion-battery research because such high voltages are beyond the electrochemical stability of the conventional carbonate-based solvents available. In the past few years, extensive efforts have been carried out by the research community toward the exploration of high-voltage electrolytes. In this review, recent progress in the study of several promising high-voltage electrolyte systems, as well as their recipes, electrochemical performance, electrode compatibility, and characterization methods, are summarized and reviewed. These new electrolyte systems include high-voltage film-forming additives and new solvents, such as sulfones, ionic liquids, nitriles, and fluorinated carbonates. It appears to be very difficult to find a good high-voltage (∼5 V) electrolyte with a single-component solvent at the present stage. Using mixed fluorinated–carbonate solvents and additives are two realistic solutions for practical applications in the near term, while sulfones, nitriles, ionic liquids and solid-state electrolyte/polymer electrolytes are promising candidates for the next generation of high-voltage electrolyte systems.
Co-reporter:Dongping Lv, Jingyu Bai, Peng Zhang, Shunqing Wu, Yixiao Li, Wen Wen, Zheng Jiang, Jinxiao Mi, Zizhong Zhu, and Yong Yang
Chemistry of Materials 2013 Volume 25(Issue 10) pp:2014
Publication Date(Web):April 24, 2013
DOI:10.1021/cm303685p
The electrochemical mechanism of the cathode material Li2FeSiO4 with reversible extraction/insertion of more than one Li+ from/into the structure has been studied by techniques of in situ synchrotron X-ray absorption near edge structure (XANES) and X-ray diffraction (XRD). These advanced techniques provide effective solutions to address the limitations of characterization by traditional ex situ methods. The study of in situ Fe K-edge XANES indicates that the Fe ion in the Li2FeSiO4 is oxidized continuously to high valence during the charging process from open circuit potential to 4.8 V, which contributes to the high reversible capacities of the materials. In situ XRD and theoretical study from first-principles calculations have been employed to reveal the structural evolution of the Li2FeSiO4 underlying the high capacity during the charge/discharge process. The results of both experimental and theoretical studies are consistent and indicate that Li2FeSiO4 undergoes two two-phase reactions when the electrode is charged to a high voltage of 4.8 V.Keywords: cathode; electrochemistry; first principles calculation; lithium-ion battery; mechanism study; orthosilicate; synchrotron;
Co-reporter:Ying Xiao, Di Hao, Huixin Chen, Zhengliang Gong, and Yong Yang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 5) pp:1681
Publication Date(Web):February 4, 2013
DOI:10.1021/am302731y
Silicon is considered as one of the most promising anodes alternative, with a low voltage and a high theoretical specific capacity of ∼4200 mAh/g, for graphite in lithium-ion batteries. However, the large volume change and resulting interfacial changes of the silicon during cycling cause unsatisfactory cycle performance and hinder its commercialization. In this study, electrochemical performance and interfacial properties of silicon nanowires (SiNWs) which are prepared by the Cu-catalyzed chemical vapor deposition method, with 1 M LiPF6/EC + DMC (1:1 v/v) containing 2 wt % or no vinylene carbonate (VC) electrolyte, are investigated by using different electrochemical and spectroscopic techniques, i.e., cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques. It is shown that the addition of VC has greatly enhanced the cycling performance and rate capability of SiNWs and should have an impact on the wide utilization of silicon anode materials in Li-ion batteries.Keywords: Cu catalyst; cycling performance; rate capability; solid-state interphase;
Co-reporter:Xia Cao, Yixiao Li, Xiubin Li, Jianming Zheng, Jun Gao, Yuxing Gao, Xiaobiao Wu, Yufen Zhao, and Yong Yang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 22) pp:11494
Publication Date(Web):October 30, 2013
DOI:10.1021/am4024884
In this communication, a novel electrolyte additive, N,N-diallyic-diethyoxyl phosphamide (DADEPA), is described for the first time to improve the thermal stability of lithiated graphite anode in Li-ion batteries. The differential scanning calorimetry (DSC) measurement demonstrated that when the graphite was lithiated in the 5% DADEPA-containing electrolyte, the heat generation decreased sharply by half as compared with the reference, whereas the onset temperature for the main exothermic process was postponed by 20 °C. Electrochemical and XPS analyses indicated that the distinctive improvement in thermal safety came from a new interfacial chemistry, in which phosphorus-containing ingredients was embedded during the initial forming of the interphase.Keywords: lithium-ion batteries; phosphamide; safety; solid electrolyte interface (SEI);
Co-reporter:Jianming Zheng, Xiaobiao Wu, Yong Yang
Electrochimica Acta 2013 Volume 105() pp:200-208
Publication Date(Web):30 August 2013
DOI:10.1016/j.electacta.2013.04.150
•Fluorine doping leads to crystal growth and increases tap density.•Fluorine doping enhances the cycling performance of lithium-rich cathode material.•Surface fluorine modification similarly improves the cycling performance.•Stabilized electrode/electrolyte interface contributes to the improved cycling stability.High capacity cathode materials Li[Li0.2Mn0.54Ni0.13Co0.13]O2−xFx (x = 0, 0.05 and 0.10) have been synthesized by a sol–gel method using NH4F as F source. The effects of fluorine content on the structure, morphology and electrochemical performance of the Li[Li0.2Mn0.54Ni0.13Co0.13]O2−xFx have been extensively studied. With fluorine doping, cycling stability of Li[Li0.2Mn0.54Ni0.13Co0.13]O2−xFx is significantly improved because of the stabilization of the host structure. Li[Li0.2Mn0.54Ni0.13Co0.13]O1.95F0.05 shows a capacity retention of 88.1% after 50 cycles at 0.2 C at room temperature, much higher than that of 72.4% for pristine one. The improvement mechanism of fluorine doping has been investigated by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The results demonstrate that fluorine incorporation stabilizes the electrode/electrolyte interface by suppressing the formation of poorly conducting LiF in the SEI layer and thus maintains stable interfacial resistances. As compared to the enhanced material structure, the stabilized electrode/electrolyte interface is the primary factor contributing to the improved electrochemical performance. In addition, the thermal stability of fully delithiated electrode is also greatly improved by fluorine doping.
Co-reporter:Wei Zhang, Paul N. Duchesne, Zheng-Liang Gong, Shun-Qing Wu, Lin Ma, Zheng Jiang, Shuo Zhang, Peng Zhang, Jin-Xiao Mi, and Yong Yang
The Journal of Physical Chemistry C 2013 Volume 117(Issue 22) pp:11498-11505
Publication Date(Web):May 13, 2013
DOI:10.1021/jp401200u
The reactions and structural evolution of FeF3 during cell cycling are investigated in an in situ cell by using Fe K-edge X-ray absorption fine-structure (XAFS) spectroscopy. The results of X-ray absorption near-edge structure spectroscopic analysis demonstrate that there are three stages in the reaction of FeF3 with Li: (1) a two-phase intercalation reaction in the range of x = 0 to 0.46 Li, (2) a single-phase intercalation reaction in the range of x = 0.46 to 0.92 Li, and (3) a conversion reaction in the range of x = 0.92 to 2.78 Li. The coordination numbers (CNs) and bond lengths of the Fe–F bonds or Fe–Fe bonds for the lithiated FeF3 are obtained by performing XAFS fitting. The splitting trends of the Fe–F bond lengths and the Fe–F CNs in the range of x = 0 to 0.92 Li support the proposal that R-3c-structured FeF3 is transformed into R3c-structured Li0.92FeF3 after the intercalation of 0.92 equiv. of Li, and that the intermediate Li0.46FeF3 may be R3-structured. The small Fe–Fe CN of Li2.78FeF3 indicates that the average diameter of the Fe crystallites formed during discharge is <1 nm.
Co-reporter:Guiming Zhong, Zigeng Liu, Tao Li, Hu Cheng, Shenshui Yu, Riqiang Fu, Yong Yang
Journal of Membrane Science 2013 428() pp: 212-217
Publication Date(Web):
DOI:10.1016/j.memsci.2012.10.026
Co-reporter:Yanyan Tian, Hongjun Yue, Zhengliang Gong, Yong Yang
Electrochimica Acta 2013 90() pp: 186-193
Publication Date(Web):
DOI:10.1016/j.electacta.2012.12.008
Co-reporter:Wei Zhang, Lin Ma, Hongjun Yue and Yong Yang
Journal of Materials Chemistry A 2012 vol. 22(Issue 47) pp:24769-24775
Publication Date(Web):01 Oct 2012
DOI:10.1039/C2JM34391F
Here, a novel architecture of a core–shell structured FeF3@Fe2O3 composite with particle size of 100–150 nm and tunable Fe2O3 content is synthesized by a simple heat treatment process utilizing FeF3 with fine network structure as precursor. The structure, morphology and electrochemical performance of the pristine FeF3 and the FeF3@Fe2O3 composites are studied by XRD, SEM, TEM and discharge–charge measurements. XRD results show that the Bragg peaks of the FeF3@Fe2O3 composites are well indexed to FeF3 and Fe2O3. SEM and TEM images reveal the core–shell structure of the composites. The comparison of the electrochemical performance between the pristine FeF3 and the FeF3@Fe2O3 composites reveals that the in situ Fe2O3 coating (even with small amount, 0.6–5.2 wt%) has great influence on the improvement of electrochemical performance.
Co-reporter:Jingyu Bai, Zhengliang Gong, Dongping Lv, Yixiao Li, Huan Zou and Yong Yang
Journal of Materials Chemistry A 2012 vol. 22(Issue 24) pp:12128-12132
Publication Date(Web):18 Apr 2012
DOI:10.1039/C2JM30968H
A strategy is proposed and developed to promote Li+ diffusion in polyanion cathode materials such as 0.8Li2FeSiO4/0.4Li2SiO3/C with the incorporation of Li2SiO3 as a lithium ionic conductive matrix. It is shown that the presence of Li2SiO3 separates the Li2FeSiO4 particles into small domains of a few nanometres and provides a fast Li+ diffusion channel, thus effectively enhancing Li+ diffusion in the 0.8Li2FeSiO4/0.4Li2SiO3/C composite. As a result, the composite material shows enhanced electrochemical performance and delivers a capacity as high as 240 mA h g−1 (corresponding to 1.44 electrons exchange per active Li2FeSiO4 formula unit) with good cyclic stability at 30 °C. The XRD and FTIR results indicate that the Li2SiO3 component exists in an amorphous phase. SEM and TEM analyses show an aggregate structure consisting of primary nanocrystallites (about tens of nanometres in diameter). The primary particles consist of a crystal Li2FeSiO4 phase and an amorphous Li2SiO3 and C, and a nanocrystalline Li2FeSiO4 surrounded by amorphous Li2SiO3 and C which are well known as a lithium ion conductor and electron conductor. The smaller nanoparticles of Li2FeSiO4 and the presence of lithium ionic and electronic conducting amorphous Li2SiO3 and carbon matrix both contributed to the enhanced electrochemical performance of the composite.
Co-reporter:Xingkang Huang, Min Lin, Qingsong Tong, Xiuhua Li, Ying Ruan, Yong Yang
Journal of Power Sources 2012 Volume 202() pp:352-356
Publication Date(Web):15 March 2012
DOI:10.1016/j.jpowsour.2011.11.028
A LiCoMnO4 (5 V spinel) material has been synthesized by annealing a sol–gel precursor utilizing lithium acetate, cobalt acetate, manganese acetate, and citric acid. The as-prepared sample has been determined to be LiCo1.09Mn0.91O4 via inductive coupled plasma-atomic emission spectroscopy. The deviation of the molar ratio of Co/Mn from 1:1 is designed to minimize the amount of LiMn2O4 impurity in our sample. The produced spinel material possesses an initial discharge capacity of 87.1 mAh g−1 with two voltage plateaus at 5.1 and 4.9 V. The LiCo1.09Mn0.91O4 cathode has been assembled with a Li4Ti5O12 anode to form a full-cell which delivered a discharge capacity of 131.2 mAh g−1, centered at 3.2 V. It is of great interest that despite the low coulombic efficiency of the full-cell, it shows good cyclic performance. In addition, The LiCo1.09Mn0.91O4/Li4Ti5O12 cell shows an excellent rate capability, delivering a capacity of 84.2 mAh g−1, corresponding to a high power density of 4.70 kW kg−1 at the current density of 1700 mA g−1.Highlights► A LiCoMnO4 was synthesized via sol–gel method. ► The 4-V plateau was deliberately eliminated successfully. ► The LiCoMnO4/Li4Ti5O12 cell delivered 131.2 mAh g−1 at 170 mA (g(Li4Ti5O12))−1. ► The full-cell shows good cycleability despite its low initial coulombic efficient. ► The full-cell shows a high power density of 4.70 kW kg−1 at 1700 mA g−1.
Co-reporter:Jianming Zheng, Derong Zhu, Yong Yang, Yingsing Fung
Electrochimica Acta 2012 Volume 59() pp:14-22
Publication Date(Web):1 January 2012
DOI:10.1016/j.electacta.2011.09.069
The effects of ionic liquid (IL) N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Py14TFSI) based electrolyte on the electrochemical performance of cathode material Li[Li0.2Mn0.54Ni0.13Co0.13]O2 have been investigated. The results of thermogravimetric analysis (TGA), flammability and differential scanning calorimetry (DSC) tests indicate that Py14TFSI addition enhances thermal stability of the electrolyte and reduces the safety concern of Li-ion battery. Electrochemical measurements demonstrate that the cathode material shows good electrochemical performance in Py14TFSI-added electrolyte. The cathode material is able to deliver high initial discharge capacity of 250 mAh g−1 in electrolyte with Py14TFSI content up to 80% at 0.1 C. In addition, the cathode material delivers less initial irreversible capacity loss and higher initial coulombic efficiency in electrolyte with higher Py14TFSI content. However, increasing Py14TFSI content in the electrolyte affects rate capability of the cathode material distinctively. With 60% Py14TFSI-added electrolyte, Li[Li0.2Mn0.54Ni0.13Co0.13]O2 shows better cycling stability with a capacity retention of 84.4% after 150 cycles at 1.0 C than that in IL free electrolyte. The superior cycling performance of the cathode material cycled in Py14TFSI-added electrolyte is mainly ascribed to the formation of stable electrode/electrolyte interfaces, based on the results of scanning electron microscopy (SEM), X-ray photoelectron spectra (XPS) and electrochemical impedance spectroscopy (EIS) investigations.Highlights► The initial irreversible capacity loss of cathode Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is greatly reduced in Py14TFSI-added electrolyte. ► Cathode electrode Li[Li0.2Mn0.54Ni0.13Co0.13]O2 shows superior extended cycling stability in Py14TFSI-added electrolyte. ► The addition of Py14TFSI effectively suppresses side reaction between cathode electrode and electrolyte. ► The cathode electrode forms stable electrode/electrolyte interface in Py14TFSI-added electrolyte during cycling.
Co-reporter:Adel Attia;Qiong Wang;Xingkang Huang
Journal of Solid State Electrochemistry 2012 Volume 16( Issue 4) pp:1461-1471
Publication Date(Web):2012 April
DOI:10.1007/s10008-011-1543-0
Titanium phosphate materials were synthesized by evaporation-induced self assembly method by using Ti(OC4H9)4 and PCl3, in the presence of Pluronic (P123) as a non-ionic surfactant template. The molar ratios of P/Ti and the heat treatment of the materials affected their structures, particle geometries and electrochemical performances as indicated by X-ray powder diffraction, thermal gravimetric analysis, scanning electron and transmission electron microscopy and other electrochemical techniques. As expected, increasing the temperature to 800 °C for 3 h resulted in losing the mesoporosity and generally led to a decrease in capacity of these materials. Cyclic voltammetry showed that TiP2O7 is formed at 500 °C for 10 h at a molar ratio P/Ti = 0.412 as amorphous phase. On the other hand, at molar ratio P/Ti = 2.06 showed sharp peaks indicated TiP2O7 transformed into crystalline material showed lower peak separation potential indicated that kinetic reactions might be favored.
Co-reporter:Dongping Lv, Wen Wen, Xingkang Huang, Jingyu Bai, Jinxiao Mi, Shunqing Wu and Yong Yang
Journal of Materials Chemistry A 2011 vol. 21(Issue 26) pp:9506-9512
Publication Date(Web):31 May 2011
DOI:10.1039/C0JM03928D
A Li2FeSiO4/C composite material has been prepared via a solution-polymerization approach. The composite is characterized by X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and superconducting quantum interference device (SQUID). The electrochemical performance of the Li2FeSiO4 is greatly enhanced and the initial discharge capacity is ∼220 mA h g−1, when it is cycled between 1.5–4.8 V. This indicates that more than one lithium ion can be extracted out of the Li2FeSiO4 lattice. At high current densities, the Li2FeSiO4/C also exhibits excellent rate capability and cycling stability. This indicates that it is a very promising cathode material for next generation lithium-ion batteries.
Co-reporter:Xiaobiao Wu, Jianming Zheng, Zhengliang Gong and Yong Yang
Journal of Materials Chemistry A 2011 vol. 21(Issue 46) pp:18630-18637
Publication Date(Web):24 Oct 2011
DOI:10.1039/C1JM13578C
Fluorophosphates Na2Fe1−xMnxPO4F/C (x = 0, 0.1, 0.3, 0.7, 1) composite were successfully synthesized via a sol–gel method. The structure, morphology and electrochemical performance of the as prepared materials were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and charge/discharge measurements. XRD results show that, consistent with Na2FePO4F, Na2Fe0.9Mn0.1PO4F (x = 0.1) crystallize in a two-dimensional (2D) layered structure with space groupPbcn. However, increasing the content of Mn to x ≥ 0.3 results in a structure transition of Na2Fe1−xMnxPO4F from the 2D layered structure of Na2FePO4F to the three-dimensional (3D) tunnel structure of Na2MnPO4F. SEM and TEM analysis indicates nanostructured primary particles (about tens of nanometres in diameter) are obtained for all samples due to uniform carbon distribution and low calcining temperature used. Na2FePO4F is able to deliver a reversible capacity of up to 182 mA h g−1 (about 1.46 electrons exchanged per unit formula) with good cycling stability. Compared with Na2FePO4F, partial replacement of Fe by Mn in Na2Fe1−xMnxPO4F increases the discharge voltage plateau. Similar to Na2FePO4F, iron-manganese mixed solid solution Na2Fe1−xMnxPO4F (x = 0.1, 0.3, 0.7) also show good cycling performance. Furthermore, Na2MnPO4F with high electrochemical activity was successfully prepared for the first time, which is able to deliver a discharge capacity of 98 mA h g−1. The good electrochemical performance of Na2Fe1−xMnxPO4F materials can be attributed to the distinctive improvement of ionic/electronic conduction of the materials by formation of nanostructure composite with carbon.
Co-reporter:Kai Liu, Jianming Zheng, Guiming Zhong and Yong Yang
Journal of Materials Chemistry A 2011 vol. 21(Issue 12) pp:4125-4131
Publication Date(Web):28 Jan 2011
DOI:10.1039/C0JM03127E
An organic cathode material, poly(2,5-dihydroxyl-1,4-benzoquinonyl sulfide) (PDBS), has been synthesized and assessed as a cathode material for lithium ion batteries. The prepared polymer material is characterized by 13C solid state NMR, FTIR, XPS and elemental analysis techniques. The 13C solid state NMR, FTIR and XPS results indicate that the chlorine of chloranilic acid (CLA) is successfully substituted by sulfur after a sulfurization reaction. Elemental analysis shows that the prepared polymer is mainly composed of dimer and trimer. The electrochemical measurements show that the initial discharge capacity of PDBS is up to 350 mAh g−1, and 184 mAh g−1 still remains after 100 cycles at the current density of 15 mA g−1 in the voltage range of 1.5–3.6 V. The PDBS also shows high cycling stability, good rate capability and discharge/charge coulombic efficiency of higher than 98%, except for in the initial cycles. The good cycling stabilities and the high coulombic efficiency of the material are ascribed to the stable thioether bonds for stabilizing the framework of the polymer and the highly reversible carbonyl groups for energy storage.
Co-reporter:Huixin Chen, Ying Xiao, Lin Wang, Yong Yang
Journal of Power Sources 2011 Volume 196(Issue 16) pp:6657-6662
Publication Date(Web):15 August 2011
DOI:10.1016/j.jpowsour.2010.12.075
Silicon nanowires (Si NWs) with copper-coating as high capacity and improved cycle-life anode for lithium-ion batteries have been successfully prepared by chemical vapor deposition and magnetron sputtering methods. The morphology, structure, composition as well as the electrochemical performance of copper-coated Si NWs is characterized in detail. The results indicate that the copper-coated Si NWs electrodes show an initial coulombic efficiency of 90.3% when cycling between 0.02 V and 2.0 V (versus Li/Li+) at a current density of 210 mA g−1. The copper-coated Si NWs electrodes exhibit a capacity as high as 2700 mAh g−1 at the first cycle. They also show a good capacity retention and excellent rate capability compared with pristine and carbon-coated Si NWs.
Co-reporter:J.M. Zheng, X.B. Wu, Y. Yang
Electrochimica Acta 2011 Volume 56(Issue 8) pp:3071-3078
Publication Date(Web):1 March 2011
DOI:10.1016/j.electacta.2010.12.049
Li[Li0.2Mn0.54Ni0.13Co0.13]O2 as a cathode material for Li-ion battery has been successfully prepared by co-precipitation (CP), sol–gel (SG) and sucrose combustion (SC) methods. The prepared materials were characterized by XRD, SEM, BET and electrochemical measurements. The XRD result shows that the Li[Li0.2Mn0.54Ni0.13Co0.13]O2 materials prepared by different methods all form a pure phase with good crystallinity. SEM images and BET data present that the SC-material exhibited the smallest particle size (ca. 0.1 μm) and the highest surface area (7.4635 m2 g−1). The tap density of SC-material is lower than that of CP- and SG-materials. The result of rate performance tests indicates that the SC-material showed the best rate capability with the highest discharge capacity of 178 mAh g−1 at 5.0 C, followed by SG-material and then CP-material. However, the cycling stability of SC-material tested at 0.1 and 0.5 C is relatively poor as compared to that of SG-material and CP-material. The result of EIS measurements reveals that large surface area and small particle size of the SC-electrode result in more SEI layer formation because of the increased side reactions with the electrolyte during cycling, which deteriorates the electrode/electrolyte interface and thus leads to the faster capacity fading of the SC-material.
Co-reporter:Tao Li, Guiming Zhong, Riqiang Fu, Yong Yang
Journal of Membrane Science 2010 Volume 354(1–2) pp:189-197
Publication Date(Web):15 May 2010
DOI:10.1016/j.memsci.2010.02.038
A novel semi-interpenetrating polymer network (semi-IPN) membrane composed by Nafion117 and cross-linked poly (vinyl pyrrolidone) (PVP) has been prepared to improve the proton selectivity of perfluorosulfonic acid (PFSA) membrane. Its physico-chemical properties are characterized using scanning electron microscopy (SEM), diffuse-reflection Fourier-transform infrared spectroscopy (DRFTIR), wide-angle X-ray diffraction (WAXRD), thermo-gravimetric analysis (TGA), thermo-gravimetric mass spectrometry (TG-MS) and solid-state nuclear magnetic resonance (NMR). Our results indicate that the introduction of the cross-linked PVP mainly affects the configuration of the Nafion side-chains and thus indirectly influences the formation and interconnection of ion clusters. It is shown that this new semi-IPN membrane exhibits a better proton selectivity as compared to the pristine membrane. Under the optimal condition, the semi-IPN membrane exhibits 53% lower methanol permeability but 38% higher proton conductivity as compared to Nafion117, thus resulting in a factor of two improvement on the relative proton selection coefficient. Such improvement can be attributed to the unique Grotthuss mechanism (hopping mechanism) of proton transfer, instead of the diffusion of methanol molecular.
Co-reporter:Xingkang Huang, Dongping Lv, Qingshun Zhang, Haitao Chang, Jianlong Gan, Yong Yang
Electrochimica Acta 2010 Volume 55(Issue 17) pp:4915-4920
Publication Date(Web):1 July 2010
DOI:10.1016/j.electacta.2010.03.090
A highly crystalline macroporous β-MnO2 was hydrothermally synthesized using stoichiometric reaction between KMnO4 and MnCl2. The as-prepared material has a pore size of ca. 400 nm and a shell thickness of 300–500 nm. The formation of the macroporous morphology is related to self-assembling from nanowires of α-MnO2, and could be obtained at high reactant concentrations (e.g., 0.8 M KMnO4) but not at low ones (e.g., below 0.04 M KMnO4). Compared to conventional bulk β-MnO2 processing very low capacity, our macroporous material exhibits good electrochemical activity, e.g., obtaining an initial discharge capacity of 251 mAh g−1 and sustaining as ca. 165 mAh g−1 at 10 mA g−1. The electrochemical activity of the as-prepared β-MnO2 is related to its macroporous morphology and small shell thickness; the former leads to that electrolyte can flood pore of the material and its inner surface is available for lithium ion diffusion, while the latter helps to release the stress from phase transformation during the initial discharging. The X-ray diffraction characterizations of the macroporous β-MnO2 electrodes suggest that, upon initial discharging, such a β-MnO2 will be irreversibly transformed to an orthorhombic LixMnO2 and then cycled within the new developed phase in the subsequent lithium insertion/extraction processes.
Co-reporter:Hecheng Lin, Jianming Zheng, Yong Yang
Materials Chemistry and Physics 2010 Volume 119(Issue 3) pp:519-523
Publication Date(Web):15 February 2010
DOI:10.1016/j.matchemphys.2009.10.007
Submicron layered LiNi0.5Mn0.5O2 was synthesized via a co-precipitation and solid-state reaction method together with a quenching process. The crystal structure and morphology of the materials were investigated by X-ray diffraction (XRD), Brunauer–Emmett and Teller (BET) surface area and scanning electron microscopy (SEM) techniques. It is found that LiNi0.5Mn0.5O2 material prepared with quenching methods has smooth and regular structure in submicron scale with surface area of 0.43 m2 g−1. The initial discharge capacities are 175.8 mAh g−1 at 0.1 C (28 mA g−1) and 120.3 mAh g−1 at 5.0 C (1400 mA g−1), respectively, for the quenched samples between 2.5 and 4.5 V. It is demonstrated that quenching method is a useful approach for the preparation of submicron layered LiNi0.5Mn0.5O2 cathode materials with excellent rate performance. In addition, the cycling performance of quenched-LiNi0.5Mn0.5O2 material was also greatly improved by AlF3 coating technique.
Co-reporter:Huaijian Pan, Jing Zhang, Yunhua Chen, Xiangdong Zhuo, Yong Yang
Thin Solid Films 2010 Volume 519(Issue 2) pp:778-783
Publication Date(Web):1 November 2010
DOI:10.1016/j.tsf.2010.09.012
Silicon film and Metal/Si multilayer films of three different metals, Ti, Al and Zn, were prepared via magnetron sputtering. The electrochemical performance of these films was investigated, with a focus on the Li+ intercalation behaviour, using Auger electron spectroscopy and in-situ electrochemical dilatometry. Comparative studies of silicon film electrodes and Metal/Si multilayer film electrodes were also made. The results of in-situ electrochemical dilatometry indicate that Metal/Si multilayer film electrodes expand significantly less than silicon film electrodes when a similar amount of lithium ions are intercalated. Among films with a similar, sandwich-like structure, Ti/Si films exhibit the least volume expansion; whereas those composed of Al/Si films expand the most. Moreover, the expansion rates of multilayer film electrodes are slower than silicon film electrodes.
Co-reporter:Huixin Chen;Zhixin Dong;Yanpeng Fu;Yong Yang
Journal of Solid State Electrochemistry 2010 Volume 14( Issue 10) pp:1829-1834
Publication Date(Web):2010 October
DOI:10.1007/s10008-009-1001-4
Silicon nanowires (Si NWs) with and without carbon coating were successfully prepared by combination of chemical vapor deposition and thermal evaporation method. The morphologies, structures, and compositions of these nanomaterials were characterized in detail. Furthermore, the electrochemical performances of uncoated and carbon-coated Si NWs as anode materials were also studied. It shows that the carbon-coated Si NWs electrode has higher capacity, better cycle stability, and rate capability than the uncoated materials. For example, it delivers 3,702 and 3,082 mAh g−1 in the initial charge and discharge processes. When cycled between 0.02 and 2.0 V at a current density of 210 mA g−1, it yields a high coulombic efficiency of 83.2%. The discharge capacity still remains around 2,150 mAh g−1 after 30 cycles.
Co-reporter:Wanhao Yao, Zhongru Zhang, Jun Gao, Jie Li, Jie Xu, Zhoucheng Wang and Yong Yang
Energy & Environmental Science 2009 vol. 2(Issue 10) pp:1102-1108
Publication Date(Web):17 Jul 2009
DOI:10.1039/B905162G
Vinyl ethylene sulfite (VES) is studied as a new additive in propylene carbonate (PC)-based electrolyte for lithium ion batteries. The electrochemical results show that the artificial graphite material exhibits excellent electrochemical performance in a PC-based electrolyte with the addition of the proper amount of VES. According to our spectroscopic results, VES is reduced to ROSO2Li (R=C4H6), Li2SO3 and butadiene (C4H6) through an electrochemical process which precedes the decomposition of PC. Furthermore, some of the Li2SO3 could be further reduced to Li2S and Li2O. All of these products are proven to be components of the solid electrolyte interface (SEI) layer.
Co-reporter:Tao Li, Yong Yang
Journal of Power Sources 2009 Volume 187(Issue 2) pp:332-340
Publication Date(Web):15 February 2009
DOI:10.1016/j.jpowsour.2008.11.035
A series of organic silica/Nafion composite membranes has been prepared by using organic silane coupling agents (SCA) bearing different hydrophilic functional groups. The physico-chemical properties of the composite membranes have been characterized by electrochemical techniques, scanning electron microscopy (SEM), diffuse-reflection Fourier-transform infrared spectroscopy (DRFTIR), wide-angle X-ray diffraction (WAXRD), thermogravimetric analysis (TGA), and thermogravimetric mass spectrometry (TG-MS). It has been found that some organic silica/Nafion composite membranes modified by organic silane agents bearing amino groups exhibit extremely low methanol crossover and proton conductivity values, e.g., a composite membrane shows a proton conductivity that is about five orders of magnitude lower and a methanol permeability that is about three orders of magnitude lower than those of a Nafion117 membrane. However, under optimized conditions for controlling the basicity of the amino groups, we also obtained a composite membrane with 89% lower methanol permeability and 49% lower proton conductivity compared with Nafion117 membrane. The results clearly demonstrate that the diffusion of methanol and protons through the membrane can be controlled by adjusting the functional groups on the organic silica.
Co-reporter:Mi Lu, Yanyan Tian, Yong Yang
Electrochimica Acta 2009 Volume 54(Issue 27) pp:6792-6796
Publication Date(Web):30 November 2009
DOI:10.1016/j.electacta.2009.06.079
Natural graphite (NG) was sulfurized by heat-treating or by high energy ball-milling the blend of NG with sulfur powder. The effect of the surface functional groups, containing sulfur, on the performance of the NG anode for a lithium ion battery was then investigated. X-ray photoelectron spectroscopy revealed that the sulfur was introduced onto the surface of NG in both of these methods. The results of scanning electron microscopy and Raman spectroscopy showed that the surface disorder of NG increased after sulfurization. Charge/discharge tests showed that the reversible capacity of the first cycle was increased after surface sulfurization and that the coulombic efficiency of the first cycle increased for the heat-treated sample but decreased for the ball-milled one. The change in the electrochemical performance was due to a number of factors including an increase in new active sites for lithium storage and an increase in surface area and increased disorder of the sulfurized NG samples.
Co-reporter:HongJun Yue, XingKang Huang, DongPing Lv, Yong Yang
Electrochimica Acta 2009 Volume 54(Issue 23) pp:5363-5367
Publication Date(Web):30 September 2009
DOI:10.1016/j.electacta.2009.04.019
A spinel LiMn2O4/C composite was synthesized by hydrothermally treating a precursor of manganese oxide/carbon (MO/C) composite in 0.1 M LiOH solution at 180 °C for 24 h, where the precursor was prepared by reducing potassium permanganate with acetylene black (AB). The AB in the precursor serves as the reducing agent to synthesize the LiMn2O4 during the hydrothermal process; the excess of AB remains in the hydrothermal product, forming the LiMn2O4/C composite, where the remaining AB helps to improve the electronic conductivity of the composite. The contact between LiMn2O4 and C in our composite is better than that in the physically mixed LiMn2O4/C material. The electrochemical performance of the LiMn2O4/C composite was investigated; the material delivered a high capacity of 83 mAh g−1 and remained 92% of its initial capacity after 200 cycles at a current density of 2 A g−1, indicating its excellent rate capability as well as good cyclic performance.
Co-reporter:Xingkang Huang;Adel Attia;Hongjun Yue
Journal of Solid State Electrochemistry 2009 Volume 13( Issue 5) pp:697-703
Publication Date(Web):2009 May
DOI:10.1007/s10008-008-0584-5
Potassium type birnessite (K-bir) was synthesized by O2 oxidizing Mn2+ in aqueous solution of KOH. Co3O4-coated K-bir (Co-K-bir) was prepared by employing a novel coating method, in which the remaining OH− ions on the particle surface of the as-precipitated K-bir reacted with Co2+ ions in aqueous solution, forming CoOOH coverage; the coating layer of CoOOH was subsequently annealed at 300 °C to transform into Co3O4. All the K-bir and Co-K-birs were investigated by scanning electron microscopy, transmission electron microscopy, inductive coupled plasma–atomic emission spectroscopy, Brunauer–Emmett–Teller specific area, and laser particle size analyzing techniques. Their electrochemical properties were also studied by discharging–charging at constant current. The results show that the covering layers of Co3O4 are incompact, and their average thickness are about 0.65–0.78 μm. Compared to the as-prepared and the annealed K-bir, the Co3O4-coated samples have higher initial discharge capacities and show distinctly improved cycleability performance.
Co-reporter:J.M. Yan, H.Z. Huang, J. Zhang, Y. Yang
Journal of Power Sources 2008 Volume 175(Issue 1) pp:547-552
Publication Date(Web):3 January 2008
DOI:10.1016/j.jpowsour.2007.06.074
The study of Mg2Si/C composites as anode materials for lithium ion batteries is reported in this paper. Firstly, Mg2Si was synthesized by mechanically activated annealing (MAA) technique and the preparing conditions for pure Mg2Si alloy were investigated and optimized. Then the composite materials of Mg2Si and carbon materials such as CNTs and CMS with different ratios were prepared by the followed ball-milling techniques. Their electrochemical performances were compared by the galvanostatically charge/discharge and EIS experiments. The pure Mg2Si alloy delivers a large initial capacity, but the capacity decreases rapidly with cycling. In contrast, the composites show good cyclic stability and deliver a reversible capacity of about 400 mAh g−1 with 40% carbon in the composite. The results of EIS indicate that the composite of Mg2Si/CMS has better interface stability than that of pure Mg2Si materials.
Co-reporter:Xiao-Jian Guo, Yi-Xiao Li, Min Zheng, Jian-Ming Zheng, Jie Li, Zheng-Liang Gong, Yong Yang
Journal of Power Sources 2008 Volume 184(Issue 2) pp:414-419
Publication Date(Web):1 October 2008
DOI:10.1016/j.jpowsour.2008.04.013
A series of cathode materials with molecular notation of xLi[Li1/3Mn2/3]O2·(1 − x)Li[Ni1/3Mn1/3Co1/3]O2 (0 ≤ x ≤ 0.9) were synthesized by combination of co-precipitation and solid state calcination method. The prepared materials were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, and their electrochemical performances were investigated. The results showed that sample 0.6Li[Li1/3Mn2/3]O2·0.4Li[Ni1/3Mn1/3Co1/3]O2 (x = 0.6) delivers the highest capacity and shows good capacity-retention, which delivers a capacity ∼250 mAh g−1 between 2.0 and 4.8 V at 18 mA g−1.
Co-reporter:Hongjun Yue, Xingkang Huang, Yong Yang
Materials Letters 2008 Volume 62(Issue 19) pp:3388-3390
Publication Date(Web):15 July 2008
DOI:10.1016/j.matlet.2008.03.014
Manganese oxide/carbon nanotubes (MO/CNTs) composite was prepared by hydrothermally reducing KMnO4 with CNTs, where the used CNTs are of dual role, i.e., they serve as reductant during reaction and the remaining CNTs act as conducting agent in the composite. This composite was characterized by X-ray diffraction and scanning electron microscopy techniques. In addition, the electrochemical performances of the composite were investigated, which suggested an excellent rate-capability of this material; e.g., it delivered a high discharge capacity as 131 mAh g− 1 at a high current density of 4 A g− 1 (20 C), and high capacity at low discharge current density, e.g., about 209 mAh g− 1 at 0.2 C rate. Therefore, such a MO/CNTs composite is promising in high power application of lithium battery and electrochemical capacitor.
Co-reporter:Jie Li ; Wanhao Yao ; Ying S. Meng ;Yong Yang
The Journal of Physical Chemistry C 2008 Volume 112(Issue 32) pp:12550-12556
Publication Date(Web):July 22, 2008
DOI:10.1021/jp800336n
The addition of 2% vinyl ethylene carbonate (VEC) into LiPF6/EC + DMC electrolyte can significantly improve the cyclic performance of a LiNi0.8Co0.2O2/Li cell at elevated temperatures such as 50 °C. In situ electrochemical mass spectrometry (EMS) was used to investigate the gas evolution spectroscopy in the cell during a charge/discharge process with and without VEC additive. Fourier transform infrared (FTIR), ultraviolet−visible (UV−vis), and liquid nuclear magnetic resonance (NMR) spectroscopies were also carried out to investigate the reactions between various electrolyte components and VEC without the electrochemical reaction. We propose the possible polymerized products based on the spectroscopy and the acting mechanism of the VEC additives.
Co-reporter:Hu Cheng, Changbao Zhu, Mi Lu, Yong Yang
Journal of Power Sources 2007 Volume 173(Issue 1) pp:531-537
Publication Date(Web):8 November 2007
DOI:10.1016/j.jpowsour.2007.04.027
The passive layer formed on lithium in a PEO20–LiTFSI–5%PC gel polymer electrolyte after different electrochemical processes was characterized using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and electrochemical impedance spectroscopy (EIS). EIS indicates that the interface resistance of lithium electrodes increases with time after fresh lithium deposition, whereas the interfacial resistance has no change with time after lithium deposition/dissolution process. The XPS analysis as well as FTIR data show that the main compositions of the passive layer are ROCO2Li, Li2CO3, LiOH, LiX (X = F, S, N, SO2CF3) and Li oxides, mostly due to the reactions occurred between lithium and PC, LiTFSI, and trace impurities (H2O, O2), and the lithium dissolution process has no distinctive effect on the composition of passive layer. XPS depth profile of the passive film detected by XPS and sputtering experiments further demonstrates that the presence of Li2CO3/LiOH is in the outer layer and Li2O, LiF mainly in the inner part of the passive layer.
Co-reporter:Yi-Xiao Li, Zheng-Liang Gong, Yong Yang
Journal of Power Sources 2007 Volume 174(Issue 2) pp:528-532
Publication Date(Web):6 December 2007
DOI:10.1016/j.jpowsour.2007.06.126
A high capacity Li2MnSiO4/C nanocomposite cathode material with good rate performance for lithium ion batteries through a solution route has been successfully prepared. The material is able to deliver a reversible capacity of 209 mAh g−1 in the first cycle, i.e. more than one electron exchange can be reversible cycled in the materials. The highly dispersion of nanocrystalline Li2MnSiO4 which was surround by a thin film of carbon was attributed to the cause of excellent performance of the materials. Ex situ XRD and IR results show that poor cycling behavior of Li2MnSiO4 might be due to an amorphization process of the materials.
Co-reporter:Z.L. Gong, Y.X. Li, Y. Yang
Journal of Power Sources 2007 Volume 174(Issue 2) pp:524-527
Publication Date(Web):6 December 2007
DOI:10.1016/j.jpowsour.2007.06.250
Li2CoSiO4 has been prepared successfully by a solution route or hydrothermal reaction for the first time, and its electrochemical performance has been investigated primarily. Reversible extraction and insertion of lithium from and into Li2CoSiO4 at 4.1 V versus lithium have shown that this material is a potential candidate for the cathode in lithium ion batteries. At this stage reversible electrochemical extraction was limited to 0.46 lithium per formula unit for the Li2CoSiO4/C composite materials, with a charge capacity of 234 mAh g−1 and a discharge capacity of 75 mAh g−1.
Co-reporter:C. Li;Z. T. Liu;C. Gu;X. Xu;Y. Yang
Advanced Materials 2006 Volume 18(Issue 2) pp:228-234
Publication Date(Web):11 JAN 2006
DOI:10.1002/adma.200500202
Amorphous silicon nanotubes with periodically aligned dome-shaped interiors (see Figure) are fabricated by chemical vapor deposition using a gold catalyst. As-grown materials have a length of several tens of micrometers and diameters of 70–100 nm. The inner shape and size of the interiors in the products may be tuned by controlling the silane flow rate, producing structures ranging from nanowires to tubular structures. A growth model based on surface tension is proposed.
Co-reporter:Hansan Liu, Yong Yang, Jiujun Zhang
Journal of Power Sources 2006 Volume 162(Issue 1) pp:644-650
Publication Date(Web):8 November 2006
DOI:10.1016/j.jpowsour.2006.07.028
LiNi0.8Co0.2O2 cathode material showed a performance loss after storage in air. The surface species on the material formed during the exposure to air were identified through TG, SEM, TPD-MS, XRD and XPS. Two thin layers were found on the surface. The first layer in contact with the bulk material contains NiO-like species, and the top layer consists of adsorbed hydroxyl, bicarbonate, carbonate, and crystalline Li2CO3. These two layers are both electrochemically inactive and poor conductors for Li+ ions, which are believed to be responsible for the storage loss. A chemical reaction mechanism, involving atmospheric H2O and CO2, and the particle surface of LiNi0.8Co0.2O2 material, was proposed to explain the formation process of those surface species. For storage loss prevention, a doping approach to reduce nickel content and a storage approach to isolate the material from H2O and CO2 were found to be effective to improve the storage property of LiNiO2-based materials. For storage loss recovery, a heat-treatment process at 725 °C was demonstrated to be a feasible approach for full recovery of the performance.
Co-reporter:Junmin Nan, Yong Yang, Zugeng Lin
Electrochimica Acta 2006 Volume 51(Issue 23) pp:4873-4879
Publication Date(Web):15 June 2006
DOI:10.1016/j.electacta.2006.01.031
The oxide films of nickel electrode formed in 30 wt.% KOH solution under potentiodynamic conditions were characterized by means of electrochemical, in situ PhotoElectrochemistry Measurement (PEM) and Confocal Microprobe Raman spectroscopic techniques. The results showed that a composite oxide film was produced on nickel electrode, in which aroused cathodic or anodic photocurrent depending upon polarization potentials. The cathodic photocurrent at −0.8 V was raised from the amorphous film containing nickel hydroxide and nickel monoxide, and mainly attributed to the formation of NiO through the separation of the cavity and electron when laser light irradiates nickel electrode. With the potential increasing to more positive values, Ni3O4 and high-valence nickel oxides with the structure of NiO2 were formed successively. The composite film formed in positive potential aroused anodic photocurrent from 0.33 V. The anodic photocurrent was attributed the formation of oxygen through the cavity reaction with hydroxyl on solution interface. In addition, it is demonstrated that the reduction resultants of high-valence nickel oxides were amorphous, and the oxide film could not be reduced completely. A stable oxide film could be gradually formed on the surface of nickel electrode with the cycling and aging in 30 wt.% KOH solution.
Co-reporter:Zhicong Shi, Qiong Wang, Weiling Ye, Yixiao Li, Yong Yang
Microporous and Mesoporous Materials 2006 Volume 88(1–3) pp:232-237
Publication Date(Web):21 January 2006
DOI:10.1016/j.micromeso.2005.09.013
Mesoporous titanium pyrophosphates have been synthesized by a sol–gel template method with further calcinations at or below the temperature of 700 °C. When calcined at 800 °C, crystalline TiP2O7 will be formed accompanied with the break down of meso-structure in the precursor. Mesoporous TiP2O7 shows a similar lithium ion intercalation behavior to that of solid solution in the electrochemical tests. When cycled at high charge/discharge rate, mesoporous TiP2O7 calcined at 700 °C delivers a higher specific discharge capacity than that of crystalline TiP2O7, indicating that mesoporous structure is beneficial for improving the transportation and intercalation/deintercalation behavior of lithium ions in the materials, thus improving the charge/discharge performance of the materials at high charge/discharge rate.
Co-reporter:Chen Li, Chi Gu, Zengtao Liu, Jinxiao Mi, Yong Yang
Chemical Physics Letters 2005 Volume 411(1–3) pp:198-202
Publication Date(Web):5 August 2005
DOI:10.1016/j.cplett.2005.05.117
Abstract
Single-crystal silicon nanowires with the prism structures were synthesized by chemical vapor deposition of SiH4 gas at 450 °C. Fe particles which were located at the tip of the CNTs were employed as a catalyst for the growth of silicon nanowires (SiNWs). Transmission electron microscopy studies of the materials showed that the nanowires have a diameter of 50–70 nm and a length of several micrometers. High-resolution transmission electron microscopy demonstrated that the nanowires have excellent single-crystal characteristics. Both the CNTs and Fe play a key role in the growth process of the SiNWs. A growth mechanism was proposed for the growth of silicon nanowires under our experimental conditions.
Co-reporter:Z.R. Zhang, H.S. Liu, Z.L. Gong, Y. Yang
Journal of Power Sources 2004 Volume 129(Issue 1) pp:101-106
Publication Date(Web):15 April 2004
DOI:10.1016/j.jpowsour.2003.11.015
Electrochemical performance and spectroscopic characterization of native and TiO2-coated LiNi0.8Co0.2O2 were investigated. The electrochemical results showed TiO2-coated materials exhibited better cycle stability in the different potential regions (i.e. 3.0–4.3 and 3.0–4.6 V) and the decomposition of the electrolytes was suppressed on coated materials surface. In addition, FT-IR and temperature-programmed desorption–mass spectroscopy (TPD–MS) results demonstrated that different oxidation products were formed on the native and coated electrodes. A possible decomposition mechanism of the electrolytes has been proposed based on our results.
Co-reporter:Junmin Nan, Yong Yang, Zugeng Lin
Electrochimica Acta 2001 Volume 46(Issue 12) pp:1767-1772
Publication Date(Web):30 March 2001
DOI:10.1016/S0013-4686(01)00427-3
In conjunction with electrochemical techniques, the microscopic properties and Raman spectra of AB5-type metal hydride (MH) electrodes at different potentials or after different charge–discharge cycles were characterized by the confocal microprobe Raman method. The experimental results indicate that a composite oxide layer was produced and different Raman spectra were observed for MH electrode at different charge–discharge stages. It is proposed that nickel plays a main role in the composite surface oxide layer as reactive sites for electrochemical reaction while other components are dispersed evenly to provide a stable corrosion resistance layer to the corrosive electrolyte. Moreover, it was demonstrated that Co, Mn and other alloy components due to their affinity with water, segregated and were enriched progressively in the alloy surface layer, where they subsequently produced oxides, which should be an important cause for the deterioration of MH electrodes.
Co-reporter:Junmin Nan, Yong Yang, Zugeng Lin
Journal of Alloys and Compounds 2001 Volume 316(1–2) pp:131-136
Publication Date(Web):2 March 2001
DOI:10.1016/S0925-8388(00)01412-2
A novel surface treatment method using a weak acid solution containing Ni2+ ions (WANi) for AB5-type hydrogen storage alloys is introduced. The properties of treated and untreated metal-hydride (MH) electrodes were investigated using several electrochemical and spectroscopic methods. Ex-situ scanning tunnelling microscopy (STM) and electrochemical results showed that the WANi process modified the alloy surface layer under modest reaction conditions and enhanced the initial electrochemical performances of the electrodes. In-situ confocal microprobe Raman spectroscopic results demonstrated that the formation, growth and properties of alloy surface oxide layers exhibited some differences on the microscopic level. In addition, manganese and cobalt segregated and progressively enriched the alloy surface and were subsequently oxidized/reduced during charge–discharge processes. The changes in the composition and structure of the surface layer of the electrodes are believed to be an important factor causing the deterioration of MH electrodes.
Co-reporter:Fengju Bian, Zhongru Zhang, Yong Yang
Journal of Energy Chemistry (May 2014) Volume 23(Issue 3) pp:383-390
Publication Date(Web):1 May 2014
DOI:10.1016/S2095-4956(14)60161-3
The effects of methylene methanedisulfonate (MMDS) on the high-temperature (~50 °C) cycle performance of LiMn2O4/graphite cells are investigated. By addition of 2 wt% MMDS into a routine electrolyte, the high-temperature cycling performance of LiMn2O4/graphite cells can be significantly improved. The analysis of differential capacity curves and energy-dispersive X-ray spectrometry (EDX) indicates that MMDS decomposed on both cathode and anode. The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells. It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMn2O4 material, while the capacity fading of cell with 2 wt% MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.The high-temperature cycling performance of LiMn2O4/graphite cells is significantly improved by addition of 2 wt% methylene methanedisulfonate (MMDS) into a routine electrolyte. A three-electrode system of pouch cell is used to study the acting mechanism of the additives.Download full-size image
Co-reporter:Jian Wang, Yajuan Ji, Narayana Appathurai, Jigang Zhou and Yong Yang
Chemical Communications 2017 - vol. 53(Issue 61) pp:NaN8584-8584
Publication Date(Web):2017/07/11
DOI:10.1039/C7CC03960C
X-ray photoemission electron microscopy (X-PEEM) of cycled LiCoO2 composite electrodes has revealed the interfaces of various components within the composite electrodes and their dependence on additives in the electrolyte and the interplay of multiple components in the electrodes. This study visualizes CoF2 distribution and Co–O bonding variation along with local component agglomeration and degradation. The obtained new insights will assist further development of long-life high-voltage LiCoO2/C batteries.
Co-reporter:Xiang Han, Huixin Chen, Ziqi Zhang, Donglin Huang, Jianfang Xu, Cheng Li, Songyan Chen and Yong Yang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 45) pp:NaN17763-17763
Publication Date(Web):2016/10/20
DOI:10.1039/C6TA07274G
Micrometer Si (MSi) particles are an attractive alternative as high energy-density lithium-ion battery anodes. To maintain the structural integrity and resolve the electrical conduction problem of MSi-based anodes, we propose novel MSi/C/reduced graphene oxide (RGO) through simple ball milling liquid polyacrylonitrile (PAN) with MSi and graphene oxide nanosheets, followed by thermal reduction. This structure capitalizes on the interaction of MSi and carbonized PAN with RGO sheets to provide a robust microarchitecture. The mechanical integrity of the in situ formed porous configuration can be dramatically improved by manipulating the size of unreacted Si nanocrystals. In addition, the Si–N–C layer serves as an electrolyte blocking layer, which helps to build a stable SEI layer and results in a high initial coulombic efficiency of 91.7%. Furthermore, the RGO binding to MSi/C acts as a flexible buffer during galvanostatic cycling, allowing microparticles to expand and fractured nanoparticles to anchor, while retaining electrical connectivity at both the particle and electrode levels. As a result, this hierarchical structure exhibits a superior reversible capacity of 1572 mA h g−1 with no capacity loss for 160 cycles at 0.2 A g−1 and over 628 mA h g−1 for 1000 cycles at 2 A g−1.
Co-reporter:Sihui Wang, Yixiao Li, Jue Wu, Bizhu Zheng, Matthew J. McDonald and Yong Yang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 15) pp:NaN10159-10159
Publication Date(Web):2015/03/12
DOI:10.1039/C5CP00853K
Layered lithium-rich oxides have several serious shortcomings such as fast voltage fading and poor cyclic stability of energy density which greatly hinder their practical applications. Fabrication of a stable framework of layered lithium-rich oxides during charging–discharging is crucial for addressing the above problems. In this work, we show that Ti modification is a promising way to realize this target with bifunctional roles. For example, it is able to substitute Mn in the lattice framework and form a stable surface layer. It therefore leads to an improved retention of energy density of the Ti-modified Li1.2Mn0.54−xTixNi0.13Co0.13O2 (x = 0.04, 0.08, and 0.15) materials during cycling. The evolution of dQ/dV curves show that the layered/spinel phase transformation is suppressed owing to the introduction of strong Ti–O bonds in the framework. In addition, SEM, TEM, and EIS results confirm that a more uniform and stable interface layer is formed on Ti-modified Li1.2Mn0.54−xTixNi0.13Co0.13O2 (x = 0.04, 0.08, and 0.15) materials compared with the Ti-free counterpart. The stable interface layer on the lithium-rich oxides is also beneficial for further reducing side reactions, resulting in stable interface layer resistance. Therefore, the improved cycling performance of the material is due to both contribution of the more stable framework and enhanced electrode/electrolyte interface by Ti modification.
Co-reporter:Kai Liu, Jianming Zheng, Guiming Zhong and Yong Yang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 12) pp:NaN4131-4131
Publication Date(Web):2011/01/28
DOI:10.1039/C0JM03127E
An organic cathode material, poly(2,5-dihydroxyl-1,4-benzoquinonyl sulfide) (PDBS), has been synthesized and assessed as a cathode material for lithium ion batteries. The prepared polymer material is characterized by 13C solid state NMR, FTIR, XPS and elemental analysis techniques. The 13C solid state NMR, FTIR and XPS results indicate that the chlorine of chloranilic acid (CLA) is successfully substituted by sulfur after a sulfurization reaction. Elemental analysis shows that the prepared polymer is mainly composed of dimer and trimer. The electrochemical measurements show that the initial discharge capacity of PDBS is up to 350 mAh g−1, and 184 mAh g−1 still remains after 100 cycles at the current density of 15 mA g−1 in the voltage range of 1.5–3.6 V. The PDBS also shows high cycling stability, good rate capability and discharge/charge coulombic efficiency of higher than 98%, except for in the initial cycles. The good cycling stabilities and the high coulombic efficiency of the material are ascribed to the stable thioether bonds for stabilizing the framework of the polymer and the highly reversible carbonyl groups for energy storage.
Co-reporter:Wei Zhang, Lin Ma, Hongjun Yue and Yong Yang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 47) pp:NaN24775-24775
Publication Date(Web):2012/10/01
DOI:10.1039/C2JM34391F
Here, a novel architecture of a core–shell structured FeF3@Fe2O3 composite with particle size of 100–150 nm and tunable Fe2O3 content is synthesized by a simple heat treatment process utilizing FeF3 with fine network structure as precursor. The structure, morphology and electrochemical performance of the pristine FeF3 and the FeF3@Fe2O3 composites are studied by XRD, SEM, TEM and discharge–charge measurements. XRD results show that the Bragg peaks of the FeF3@Fe2O3 composites are well indexed to FeF3 and Fe2O3. SEM and TEM images reveal the core–shell structure of the composites. The comparison of the electrochemical performance between the pristine FeF3 and the FeF3@Fe2O3 composites reveals that the in situ Fe2O3 coating (even with small amount, 0.6–5.2 wt%) has great influence on the improvement of electrochemical performance.
Co-reporter:Huixin Chen, Qiaobao Zhang, Jiexi Wang, Daguo Xu, Xinhai Li, Yong Yang and Kaili Zhang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 22) pp:NaN8490-8490
Publication Date(Web):2014/03/25
DOI:10.1039/C4TA00967C
Novel three-dimensional (3D) hierarchical NiSix/Co3O4 core–shell nanowire arrays composed of NiSix nanowire cores and branched Co3O4 nanosheet shells have been successfully synthesized by combining chemical vapor deposition and a simple but effective chemical bath deposition process followed by a calcination process. The resulting hierarchical NiSix/Co3O4 core–shell nanowire arrays directly serve as binder- and conductive-agent-free electrodes for lithium ion batteries, which demonstrate remarkably improved electrochemical performances with excellent capacity retention and high rate capability on cycling. They can maintain a stable reversible capacity of 1279 mA h g−1 after 100 cycles at a current density of 400 mA g−1 and a capacity higher than 340 mA h g−1 even at a current density as high as 8 A g−1. Such superior electrochemical performance of the electrodes made by directly growing electro-active highly porous Co3O4 on a nanostructured NiSix conductive current collector makes them very promising for applications in high-performance lithium ion batteries.
Co-reporter:Huixin Chen, Qiaobao Zhang, Xiang Han, Junjie Cai, Meilin Liu, Yong Yang and Kaili Zhang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 47) pp:NaN24032-24032
Publication Date(Web):2015/10/29
DOI:10.1039/C5TA07258A
Three-dimensional (3D) hierarchically porous transition metal oxides, particularly those involving different metal ions of mixed valence states and constructed from interconnected nano-building blocks directly grown on conductive current collectors, are promising electrode candidates for energy storage devices such as Li-ion batteries (LIBs) and supercapacitors (SCs). This study reports a facile and scalable chemical bath deposition process combined with simple calcination for fabricating 3D hierarchically porous Zn–Ni–Co oxide (ZNCO) nanosheet arrays directly grown on Ni foam with robust adhesion. The resulting nanostructures are then evaluated as a binder-free electrode for LIBs and SCs. Given its unique architecture and compositional advantages, the electrode exhibits a reversible capacity of 1131 mA h g−1 after 50 cycles at a current density of 0.2 A g−1, an excellent long-term cycling stability at a high current density of 1 A g−1 for 1000 cycles, and a desirable rate capability when tested as an anode for LIBs. When used for SCs, the electrode demonstrates a high specific capacitance (1728 F g−1 at 1 A g−1), an outstanding rate capability (72% capacitance retention from 1 A g−1 to 50 A g−1), and an excellent cycling stability (capacitance of 1655 F g−1 after 5000 cycles at a current density of 20 A g−1 with 108.6% retention). Overall, the unique 3D hierarchically porous ZNCO nanosheets hold a great promise for constructing high-performance energy storage devices.
Co-reporter:Xiaobiao Wu, Sihui Wang, Xiaochen Lin, Guiming Zhong, Zhengliang Gong and Yong Yang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 4) pp:NaN1013-1013
Publication Date(Web):2013/12/05
DOI:10.1039/C3TA13801A
High-voltage Li2CoPO4F (∼5 V vs. Li/Li+) with double-layer surface coating has been successfully prepared for the first time. The Li3PO4-coated Li2CoPO4F shows a high reversible capacity of 154 mA h g−1 (energy density up to 700 W h kg−1) at 1 C current rate, and excellent rate capability (141 mA h g−1 at 20 C). XRD and MAS NMR results show that Li2CoPO4F can be indexed as an orthorhombic structure with space group Pnma and coexists with Li3PO4. The XPS depth profiles and TEM analysis reveal that the as-prepared material has a double-layer surface coating, with a carbon outer layer and a Li3PO4 inner layer, which greatly enhances the transfer kinetics of the lithium ions and electrons in the material and stabilizes the electrode/electrolyte interface. Using LiBOB as an electrolyte additive is another way to further stabilize the electrode/electrolyte interface, and the LiBOB has a synergistic effect with the Li3PO4 coating layer. In this way, the Li2CoPO4F cathode material exhibits excellent long-term cycling stability, with 83.8% capacity retention after 150 cycles. The excellent cycling performance is attributed to the LiBOB electrolyte additive and the Li3PO4 coating layer, both of which play an important role in stabilizing the charge transfer resistance of Li2CoPO4F upon cycling.
Co-reporter:Shiyao Zheng, Guiming Zhong, Matthew J. McDonald, Zhengliang Gong, Rui Liu, Wen Wen, Chun Yang and Yong Yang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 23) pp:NaN9062-9062
Publication Date(Web):2016/05/25
DOI:10.1039/C6TA02230H
Na-ion batteries (NIBs) have recently attracted much attention, due to their low cost and the abundance of sodium resources. In this work, NaLi0.1Ni0.35Mn0.55O2 as a promising new kind of cathode material for Na-ion batteries was synthesized by a co-precipitation method. Powder XRD patterns show that the sample has a primary O3-type structure after Li+ substitution. The material delivers excellent electrochemical performance, with an initial discharge specific capacity of 128 mA h g−1 and a capacity retention of 85% after 100 cycles at a rate of 12 mA g−1 in the voltage range of 2.0–4.2 V. In a widened voltage range of 1.5–4.3 V, the specific capacity can reach up to 160 mA h g−1. The structural stability of the material is substantially improved compared with lithium-free NaNi0.5Mn0.5O2, which can be attributed to the formation of an O′3 phase caused by Li-substitution, as proven by in situ XRD and solid state NMR (ss-NMR) measurements.
Co-reporter:Xiang Han, Huixin Chen, Xin Li, Jianyuan Wang, Cheng Li, Songyan Chen and Yong Yang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 2) pp:NaN442-442
Publication Date(Web):2015/11/20
DOI:10.1039/C5TA08297H
We report for the first time that the dehydrogenation process of PAN was suppressed and the silicon oxide of the MSP surface was reduced during annealing in Ar + H2. Consequently, the remaining –NH bonds of the carbon chain can interact with the fresh amorphous Si on the surface of the MSPs to form a Si–N–C layer, which improves the adhesion between Si and C and serves as a stable electrolyte blocking layer. In addition, based on micron-sized MSPs, the structural stability of the electrode is dramatically enhanced through in situ formation of Si nanocrystals of less than 5 nm. The low Li+ diffusion kinetics of the Si–N–C layer and self limiting inhomogeneous lithiation in MSPs jointly create unlithiated Si nanocrystals, acting as supporting frames to prevent pulverization of the anode material. Our nitriding MSP anode has exhibited for the first time a 100% capacity retention (394 mA h g−1) after 2000 cycles (10 cycles each at 0.1, 0.5, 1, 2, and 1 and then 1950 cycles at 0.5 A g−1) and a 100% capacity retention at 0.1 A g−1 (540 mA h g−1) after 400 cycles. Thus, our work proposes a novel avenue to engineer battery materials with large volume changes.
Co-reporter:Dawei Wang, Guiming Zhong, Oleksandr Dolotko, Yixiao Li, Matthew J. McDonald, Jinxiao Mi, Riqiang Fu and Yong Yang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 47) pp:NaN20279-20279
Publication Date(Web):2014/10/06
DOI:10.1039/C4TA03591G
The cubic garnet-type solid electrolyte Li7La3Zr2O12 with aliovalent doping exhibits a high ionic conductivity. However, the synergistic effects of aliovalent co-doping on the ionic conductivity of garnet-type electrolytes have rarely been examined. In this work, the synergistic effects of co-dopants Al and Te on the ionic conductivity of garnets were investigated using X-ray diffraction (XRD), 27Al/6Li Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR), Energy Dispersive X-ray Spectroscopy (EDS), Neutron Powder Diffraction (NPD) and Alternating Current (AC) impedance measurements. It was shown that co-dopants Al and Te stabilized the cubic lattice of Li7−2x−3yAlyLa3Zr2−xTexO12 with specific Al/Te ratios, where additional Al had to be included in the structure if the amount of doped Te content x was below 0.5. In the Al and Te co-doped crystal structure, Al was incorporated into the tetrahedral 24d sites of lithium and Te occupied 16a sites of Zr. It was revealed that the occupancy of the latter could suppress the insertion of Al. High-resolution 6Li MAS NMR was able to differentiate the two lithium sites of interest in the garnet structure. Furthermore, it was shown that the mobility of Li ions at 24d sites mainly determined the bulk conductivities of garnet-type electrolytes.
Co-reporter:Jingyu Bai, Zhengliang Gong, Dongping Lv, Yixiao Li, Huan Zou and Yong Yang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 24) pp:NaN12132-12132
Publication Date(Web):2012/04/18
DOI:10.1039/C2JM30968H
A strategy is proposed and developed to promote Li+ diffusion in polyanion cathode materials such as 0.8Li2FeSiO4/0.4Li2SiO3/C with the incorporation of Li2SiO3 as a lithium ionic conductive matrix. It is shown that the presence of Li2SiO3 separates the Li2FeSiO4 particles into small domains of a few nanometres and provides a fast Li+ diffusion channel, thus effectively enhancing Li+ diffusion in the 0.8Li2FeSiO4/0.4Li2SiO3/C composite. As a result, the composite material shows enhanced electrochemical performance and delivers a capacity as high as 240 mA h g−1 (corresponding to 1.44 electrons exchange per active Li2FeSiO4 formula unit) with good cyclic stability at 30 °C. The XRD and FTIR results indicate that the Li2SiO3 component exists in an amorphous phase. SEM and TEM analyses show an aggregate structure consisting of primary nanocrystallites (about tens of nanometres in diameter). The primary particles consist of a crystal Li2FeSiO4 phase and an amorphous Li2SiO3 and C, and a nanocrystalline Li2FeSiO4 surrounded by amorphous Li2SiO3 and C which are well known as a lithium ion conductor and electron conductor. The smaller nanoparticles of Li2FeSiO4 and the presence of lithium ionic and electronic conducting amorphous Li2SiO3 and carbon matrix both contributed to the enhanced electrochemical performance of the composite.
Co-reporter:Xiaobiao Wu, Jianming Zheng, Zhengliang Gong and Yong Yang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 46) pp:NaN18637-18637
Publication Date(Web):2011/10/24
DOI:10.1039/C1JM13578C
Fluorophosphates Na2Fe1−xMnxPO4F/C (x = 0, 0.1, 0.3, 0.7, 1) composite were successfully synthesized via a sol–gel method. The structure, morphology and electrochemical performance of the as prepared materials were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and charge/discharge measurements. XRD results show that, consistent with Na2FePO4F, Na2Fe0.9Mn0.1PO4F (x = 0.1) crystallize in a two-dimensional (2D) layered structure with space groupPbcn. However, increasing the content of Mn to x ≥ 0.3 results in a structure transition of Na2Fe1−xMnxPO4F from the 2D layered structure of Na2FePO4F to the three-dimensional (3D) tunnel structure of Na2MnPO4F. SEM and TEM analysis indicates nanostructured primary particles (about tens of nanometres in diameter) are obtained for all samples due to uniform carbon distribution and low calcining temperature used. Na2FePO4F is able to deliver a reversible capacity of up to 182 mA h g−1 (about 1.46 electrons exchanged per unit formula) with good cycling stability. Compared with Na2FePO4F, partial replacement of Fe by Mn in Na2Fe1−xMnxPO4F increases the discharge voltage plateau. Similar to Na2FePO4F, iron-manganese mixed solid solution Na2Fe1−xMnxPO4F (x = 0.1, 0.3, 0.7) also show good cycling performance. Furthermore, Na2MnPO4F with high electrochemical activity was successfully prepared for the first time, which is able to deliver a discharge capacity of 98 mA h g−1. The good electrochemical performance of Na2Fe1−xMnxPO4F materials can be attributed to the distinctive improvement of ionic/electronic conduction of the materials by formation of nanostructure composite with carbon.
Co-reporter:Dongping Lv, Wen Wen, Xingkang Huang, Jingyu Bai, Jinxiao Mi, Shunqing Wu and Yong Yang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 26) pp:NaN9512-9512
Publication Date(Web):2011/05/31
DOI:10.1039/C0JM03928D
A Li2FeSiO4/C composite material has been prepared via a solution-polymerization approach. The composite is characterized by X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and superconducting quantum interference device (SQUID). The electrochemical performance of the Li2FeSiO4 is greatly enhanced and the initial discharge capacity is ∼220 mA h g−1, when it is cycled between 1.5–4.8 V. This indicates that more than one lithium ion can be extracted out of the Li2FeSiO4 lattice. At high current densities, the Li2FeSiO4/C also exhibits excellent rate capability and cycling stability. This indicates that it is a very promising cathode material for next generation lithium-ion batteries.
