Co-reporter:Yuguang Zhao;Zhanyu Li;Kai Yang;Fei Gao
Ionics 2017 Volume 23( Issue 3) pp:597-605
Publication Date(Web):2017 March
DOI:10.1007/s11581-016-1851-6
Pr-doped Li4Ti5O12 in the form of Li4−x/3Ti5−2x/3PrxO12 (x = 0, 0.01, 0.03, 0.05, and 0.07) was synthesized successfully by an electrospinning technique. ICP shows that the doped samples are closed to the targeted samples. XRD analysis demonstrates that traces of Pr3+ can enlarge the lattice parameter of Li4Ti5O12 from 8.3403 to 8.3765 Å without changing the spinel structure. The increase of lattice parameter is beneficial to the intercalation and de-intercalation of lithium-ion. XPS results identify the existence form of Ti is mainly Ti4+ and Ti3+ in minor quantity in Li4−x/3Ti5−2x/3PrxO12 (x = 0.05) samples due to the small amount of Pr3+. The transition from Ti4+ to Ti3+ is conducive to the electronic conductivity of Li4Ti5O12. FESEM images show that all the nanofibers are well crystallized with a diameter of about 200 nm and distributed uniformly. The results of electrochemical measurement reveal that the 1D Li4−x/3Ti5−2x/3PrxO12 (x = 0.05) nanofibers display enhanced high-rate capability and cycling stability compared with that of undoped nanofibers. The high-rate discharge capacity of the Li4−x/3Ti5−2x/3PrxO12 (x = 0.05) samples is excellent (101.6 mAh g−1 at 50 °C), which is about 58.48 % of the discharge capacity at 0.2 °C and 4.3 times than that of the bare Li4Ti5O12 (23.5 mA g−1). Even at 10 °C (1750 mA g−1), the specific discharge capacity is still 112.8 mAh g−1 after 1000 cycles (87.9 % of the initial discharge capacity). The results of cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) illustrate that the Pr-doped Li4Ti5O12 electrodes possess better dynamic performance than the pure Li4Ti5O12, further confirming the excellent electrochemical properties above.
Co-reporter:Jiguang Li, Jianling Li, Tianheng Yu, Feixiang Ding, Guofeng Xu, Zhanyu Li, Yuguang Zhao, Feiyu Kang
Ceramics International 2016 Volume 42(Issue 16) pp:18620-18630
Publication Date(Web):December 2016
DOI:10.1016/j.ceramint.2016.08.206
Abstract
The development of Li-rich layer cathode materials has been limited by poor cycle, rate performance, phase transformation and voltage decay. To improve these properties, a facile and low-cost wet method is employed to fabricate Pr6O11 coating layer on Li[Li0.2Mn0.54Co0.13Ni0.13]O2 nanoparticles. The 3–6 nm Pr6O11 coating layer is observed on the surface of Li[Li0.2Mn0.54Co0.13Ni0.13]O2 by HRTEM. Interestingly, HAADF-STEM and EDS analyses show that the transition metal ions and the praseodymium ions mutually infiltrate in the Pr6O11 coating layer and Li[Li0.2Mn0.54Co0.13Ni0.13]O2 nanoparticles during calcination. A combination of HAADF-STEM with EDS and XPS studies reveals that Pr6O11 coating layer is bridged to Li[Li0.2Mn0.54Co0.13Ni0.13]O2 nanoparticles by the chemical bonds of transition phase Li1.2MXPr1−xO2. XRD patterns show that all samples are indexed to the layered structure α-NaFeO2, but the lattice parameters are influenced lightly after Pr6O11 coating. HRTEM and SAED analyses elucidate that the super large Pr ions surface-doping and the Pr6O11 coating are verified to suppress the transformation of layer to spinel structure in the bulk nanoparticles after cycles. The sample coated with 3 wt% Pr6O11 exhibits wonderful electrochemical performance with the first coulomb efficiency of 85.6%, the capacity retention ratio of 97.9% after 50 cycles and the discharge capacity of 162.2 mAh g−1 at 5 C. The resistant of charge transfer and the electrodes polarization are reduced by Pr6O11 coating according to EIS. Therefore, Pr6O11, which contains the super large Pr ions, plays two roles: the first one, it is coated on the Li[Li0.2Mn0.54Co0.13Ni0.13]O2 nanoparticles to optimize the environment of the interface reaction between electrodes and electrolyte; the other one, its Pr ions surface-doping stabilizes the structure in the superficial region of Li[Li0.2Mn0.54Co0.13Ni0.13]O2 nanoparticles and suppresses the voltage decay. The multifunctional Pr6O11 can play a significant role in accelerating development of new materials with excellent stabilization and high capacity.
Co-reporter:Yong Zheng, Kun Qian, Dan Luo, Yiyang Li, Qingwen Lu, Baohua Li, Yan-Bing He, Xindong Wang, Jianling Li and Feiyu Kang
RSC Advances 2016 vol. 6(Issue 36) pp:30474-30483
Publication Date(Web):02 Mar 2016
DOI:10.1039/C6RA01677D
In this study, the degradation of a LiFePO4/graphite battery under an over-discharge process and its effect on further cycling stability are investigated. Batteries are over-discharged to 1.5, 1.0, 0.5 or 0.0 V and then cycled 110 times under over-discharge conditions. The batteries over-discharged to 0.5 and 0.0 V experience serious irreversible capacity losses of 12.56% and 24.88%, respectively. The same batteries lost 7.79 and 24.46% more capacity after they were further subjected to 110 cycles between 3.65 and 2.0 V at 1C/1C, respectively. This shows that a serious loss of active lithium and loss of anode material occur at 0.0 V during both over-discharging and the normal cycling stage. Dissolution and breakdown of solid electrolyte interphase (SEI) films are suggested to be the main reason for degradation under over-discharge at low voltage and further lead to a poor cycling performance. Gas generation can be found on the cycled batteries below 1 V and the gas mainly contains H2, CH4 and C2H6. The structures of LiFePO4 and graphite materials have almost no change according to the results of XRD tests. Half-cell study suggests that almost no irreversible capacity loss occurs at the LiFePO4 cathode, whereas a decline in the capacity is observed at the graphite anode, especially for the batteries over-discharging bellow 1.0 V. Evidence for fierce side reactions at 0.5 and 0.0 V is provided as well, as demonstrated by the developed rich surface chemistry and an significant impedance increase for the aged electrodes.
Co-reporter:Cheng Chen, Xinping Li, Fuhai Deng and Jianling Li
RSC Advances 2016 vol. 6(Issue 83) pp:79894-79899
Publication Date(Web):10 Aug 2016
DOI:10.1039/C6RA17794H
Nickel Schiff base complexes Ni(salen), Ni(salphen) and Ni(saldmp) are synthesized and electropolymerized on multiwalled carbon nanotube electrodes. The structures of the three monomers are similar except for the groups between the imine linkages, so the difference in electrochemical behavior can be related to the influence of the groups. Polymerization parameters such as the consumed charge, the apparent surface coverage and the doping level are investigated to elucidate the effects of groups between imine linkages. The results show that poly[Ni(salen)] has higher consumed charge and apparent surface coverage than others, which means that poly[Ni(salen)] can be deposited more easily on the electrodes. While poly[Ni(salphen)] has the highest doping level, there are more electrons transferred per monomer unit, indicating a better capacitance for energy storage. The electrochemical characteristics are also evaluated and the peak potential in cyclic voltammetry plots is about 0.9 V for Ni(salen) and Ni(salphen), and about 0.7 V for Ni(saldmp). The different peak potentials indicate the redox potential will be related to the various groups. Meanwhile the galvanostatic charge/discharge curves display a specific capacitance of about 200 F g−1 for poly[Ni(salphen)], and about 150 F g−1 for poly[Ni(salen)] and poly[Ni(saldmp)]. The variation in electrochemical behavior is mainly caused by the different molecular structure and the groups between imine linkages are the unique differences in structure. So we propose a new electronic transmission mechanism that the electrons will transmit via the Ph–CN–Y–NC–Ph path (Y represents groups between imine linkages), and these groups can provide an electronic transmission path as imine bridges and then influence the electrochemical behavior.
Co-reporter:Zhanyu Li, Jianling Li, Yuguang Zhao, Kai Yang, Fei Gao and Xiao Li
RSC Advances 2016 vol. 6(Issue 19) pp:15492-15500
Publication Date(Web):21 Jan 2016
DOI:10.1039/C5RA27142H
Sm-doped Li4Ti5O12 (LTO) in the form of Li4−x/3Ti5−2x/3SmxO12 (x = 0, 0.01, 0.03, 0.05 and 0.10) is synthesized successfully by a simple solid-state reaction in air. XRD analysis and Rietveld refinement demonstrate that traces of the doped Sm3+ ions have successfully entered the lattice structure of the bulk LTO and the Sm doping does not change the spinel structure of LTO. However, of interest is that the lattice parameter increases gradually with the increase of the Sm doping amount, which is potentially beneficial for intercalation and de-intercalation of lithium ions. XPS results further identify the existence of Ti3+ ions and the transition of a small quantity of Ti ions from Ti4+ to Ti3+, which will improve the conductivity of LTO. All materials are well crystallized with a uniform and narrow size distribution in the range of 0.5–1.2 μm. The results of electrochemical measurement reveal that the Sm doping can improve the rate capability and cycling stability of LTO. Among all samples, Li4−x/3Ti5−2x/3SmxO12 (x = 0.03) exhibits the best electrochemical properties. The specific capacities of the Li4−x/3Ti5−2x/3SmxO12 (x = 0.03) sample at charge and discharge rates of 5C and 10C are 131.1 mA h g−1 and 119.2 mA h g−1, respectively, compared with 64 mA h g−1 (5C) and 47 mA h g−1 (10C) for the pristine LTO in the potential range 1.0–2.5 V (vs. Li/Li+). This result can be attributed to Li4−x/3Ti5−2x/3SmxO12 (x = 0.03) with a diffusion coefficient of 1.3 × 10−12 cm2 s−1, which is higher than the 7.4 × 10−14 cm2 s−1 for the LTO electrode without Sm doping. In the meantime, the discharge capacity of Li4−x/3Ti5−2x/3SmxO12 (x = 0.03) can still reach 125.1 mA h g−1 even after 100 cycles and maintain 95.2% of its initial discharge capacity at 5C. Therefore, Sm doping has a great impact on discharge capacity, rate capability and cycling performance of LTO anode materials for lithium-ion batteries.
Co-reporter:Zhanyu Li, Feixiang Ding, Yuguang Zhao, Yudong Wang, Jianling Li, Kai Yang, Fei Gao
Ceramics International 2016 Volume 42(Issue 14) pp:15464-15470
Publication Date(Web):1 November 2016
DOI:10.1016/j.ceramint.2016.06.198
Abstract
The TiN coated Li4Ti5O12 (LTO) submicrospheres with high electrochemical performance as anode materials for lithium-ion battery were synthesized successfully by solvothermal method and subsequent nitridation process in the presence of ammonia. The XRD results revealed that the crystal structure of LTO did not change after thermal nitridation process. The submicrospheres morphology of LTO and TiN film on the surface of LTO submicrospheres were characterized by FESEM and HRTEM, respectively. XPS result confirmed that a small amount of Ti changed from Ti4+ to Ti3+ after nitridation process, which will increase the electronic conductivity of LTO. Electrochemical results showed that electrochemical performance of TiN coated LTO anode materials compared favorably with that of pure LTO. Also its rate capability and cycling performance were apparently superior to those of pure LTO. The reversible capacity of TiN-LTO is 105.2 mA h g−1 at a current density of 10 C after 100 cycles and maintain 92.9% of its initial discharge capacity, while that of pure LTO is only 83.6 mA h g−1 with a capacity retention of 90.3%. Even at 20 C, the discharge capacity of TiN coated LTO sample is 101.3 mA h g−1, compared with 77.3 mA h g−1 for pristine LTO in the potential range 1.0–2.5 V (vs. Li/Li+).
Co-reporter:Guofeng Xu, Qingrui Xue, Jianling Li, Zhanyu Li, Xinping Li, Tianheng Yu, Jiguang Li, Xindong Wang, Feiyu Kang
Solid State Ionics 2016 Volume 293() pp:7-12
Publication Date(Web):1 October 2016
DOI:10.1016/j.ssi.2016.04.025
•The Sm-substituted electrode shows elevated electrochemical performance.•Enlarged Li layer space, inhibited oxygen release and better electrical conductivity are achieved.•The rare earth elements series are hoped to further used on other layered cathode materials.Lithium-excess layered cathode materials Li[Li0.2Mn0.54 − xSmxCo0.13Ni0.13]O2 (x = 0, 0.01, 0.03, 0.05) with different quantities of Sm were synthesized by the coprecipitation-calcination method. The rare earth element samarium (Sm) was introduced into the structure of Li[Li0.2Mn0.54Co0.13Ni0.13]O2 as the replacement at Mn sites. The refinement unit cell parameters from the X-ray powder diffraction patterns illustrate the doping of Sm facilitates enlarging the lithium ions diffusion passageway space of the Li[Li0.2Mn0.54Co0.13Ni0.13]O2 structure. The Li[Li0.2Mn0.51Sm0.03Co0.13Ni0.13]O2 electrode presented the best electrochemistry properties. The initial discharge capacity is 287.5 mAh g− 1 and the initial coulombic efficiency increases from 81.31% to 85.34% with a constant current density of 12.5 mA g− 1, which can be attributed to the suppression of the oxygen release from the structure at the initial charge-discharge process. The Li[Li0·2Mn0.51Sm0.03Co0.13Ni0.13]O2 electrode delivers 236.1 mAh g− 1 after 40 cycles and the capacity retention ratio is 82.12% while only 206.8 mAh g− 1 and 70.85% are obtained after 40 times of cycling for the pristine electrode. The Nyquist plots indicate that the electrical conductivity and interfacial electrochemical reaction activity increase as well.
Co-reporter:Zhanyu Li;Yuguang Zhao;Kai Yang;Fei Gao;Xiao Li
Ionics 2016 Volume 22( Issue 6) pp:789-795
Publication Date(Web):2016 June
DOI:10.1007/s11581-015-1610-0
Li4Ti5O12 (LTO) was synthesized with two different cooling methods by solid-state method, namely fast cooling and air cooling. The samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), galvanostatic charge–discharge test, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), respectively. XRD revealed that the basic LTO structure was not changed. FESEM images showed that fast cooling effectively reduced the particle sizes and the agglomeration of particles. Galvanostatic charge–discharge test showed that the air cooling sample exhibited a mediocre performance, having an initial discharge capacity of 136.3mAh · g−1 at 0.5 C; however, the fast cooling sample demonstrated noticeable improvement in both of its discharge capacity and rate capability, with a high initial capacity value of 142.7 mAh · g−1 at 0.5 C. CV measurements also revealed that fast cooling enhanced the reversibility of the LTO. EIS confirmed that fast cooling resulted in lower electrochemical polarization and a higher lithium-ion diffusion coefficient. Therefore, fast cooling have a great impact on discharge capacity, rate capability, and cycling performance of LTO anode materials for lithium-ion batteries.
Co-reporter:Xinping Li;Gang Yan;Zhixun Zhu
Chemical Research in Chinese Universities 2016 Volume 32( Issue 1) pp:82-89
Publication Date(Web):2016 February
DOI:10.1007/s40242-016-5316-2
Hollow tube-like activated carbon(HTAC) was fabricated by a simple and efficient carbonization method with cotton as carbon precursor activated by KOH without any template. The activation time from 0 to 90 min showed no significant effect on the micro-morphology, but greatly influenced the specific surface area and electrochemical performance. In the end, it was found that the sample activated for 60 min(HTAC-60) has a higher specific surface area of 2600 m2/g, a larger pore volume of 1.52 cm3/g and a greater specific capacitance of 483 F/g at a current density of 0.2 A/g in 1 mol/L H2SO4. Moreover, the sample HTAC-60 shows excellent cycle stability(only 12.2% loss after 5000 cycles) and a high energy density of 67.1 or 37.2 W·h·kg–1 at a power density of 200 or 1000 W/kg, respectively, operated in a voltage range of 0—1.0 V in 1 mol/L H2SO4. The results indicate that cotton can potentially be used as a raw material for producing low cost and high performance activated carbon electrode materials for electric double layer capacitor.
Co-reporter:Yong Zheng, Yan-Bing He, Kun Qian, Baohua Li, Xindong Wang, Jianling Li, Sum Wai Chiang, Cui Miao, Feiyu Kang, Jianbo Zhang
Electrochimica Acta 2015 Volume 176() pp:270-279
Publication Date(Web):10 September 2015
DOI:10.1016/j.electacta.2015.06.096
•Decay of battery during cycling under high discharge current is investigated.•A decline in the capability of LiFePO4 electrode is observed at higher rates.•The detailed degradation mechanism is proven by post-mortem analysis.•Increased resistance in the LiFePO4 cathode is suggested to be the root cause of power fading under high-rate discharge.In this study, the deterioration of lithium iron phosphate (LiFePO4) /graphite batteries during cycling at different discharge rates and temperatures is examined, and the degradation under high-rate discharge (10C) cycling is extensively investigated using full batteries combining with post-mortem analysis. The results show that high discharge current results in an instability of electrode/electrolyte interface and unstable solid electrolyte interphase (SEI) layers are expected to form on the newly exposed graphite anode surface, which cause sustainable consumption of active lithium and further lead to the performance degradation of active materials. For LiFePO4 cathode, the initial capacity is largely recovered under low rate (0.1-0.2C), whereas a decline in the capability is observed at higher rates (0.5-3.0C). For graphite anode, half-cell study shows that considerable capacity loss occurs even at low rates. A small amount of Fe deposition is observed on graphite anode after cycling under 10C discharge at 55 °C. X-ray photoelectron spectroscopy (XPS) analysis confirms that a layer composed of lithium compounds is formed on the surface of anode, which can not participate in the reversible electrochemical reaction again. In addition, electrochemical impedance spectrum (EIS) measurements of half-cell indicate that the increased resistance of the positive electrode is suggested to be the root cause of power fading under high-rate discharge cycling, especially at high temperature.
Co-reporter:Guofeng Xu, Jianling Li, Xinping Li, Hongwei Zhou, Xianan Ding, Xindong Wang, Feiyu Kang
Electrochimica Acta 2015 Volume 173() pp:672-679
Publication Date(Web):10 August 2015
DOI:10.1016/j.electacta.2015.05.083
•Li-rich 0.6Li[Li1/3Mn2/3]O2-0.4Li[Ni1/3Co1/3Mn1/3]O2 nanofibers are successfully synthesized by the electrostatic spinning method.•The step-by-step CV tests revealed that nanofibers electrode presents higher discharge voltage platform and increased discharge energy density.•The enhanced electrochemical performance is attributed to the neat ion arrangement in crystal structure and the better electrochemical kinetics of nanofibers electrode.Solid solution cathode materials 0.6Li[Li1/3Mn2/3]O2-0.4Li[Ni1/3Co1/3Mn1/3]O2 with different morphologies were synthesized by electrospinning and coprecipitation method respectively. The field-emission scanning electron microscope images verified the successful formation of nanofibers for electrospinning and nanoparticles for coprecipitation and the nanofibers showed larger specific surface area according to the Brurauer Emmerr Teller procedure. The X-ray powder diffraction patterns and the corresponding lattice parameter refinements showed that both samples can be indexed to hexagonal α-NaFeO2 layered structure with space group of R-3m. And the material prepared by electrostatic spinning method has a tight atomic arrangement in the layer yet the different dimensions do not influence the intercalation and deintercalation of lithium ion through the interlayer. The discharge capacity of nanofibers electrode is 302.3 mAh g−1 at 0.05 C and the initial columbic efficiency is 76.2%, which are higher than 282.7 mAh g−1 and 68.2% of the nanoparticles electrode. The nanofibers electrode also presented better cycleability and rate capability, especially performed capacity of 126.6 mAh g−1 at 5 C, much higher than that of 109.4 mAh g−1 for nanoparticles electrode. The step-by-step cyclic voltammetry revealed that the nanofibers electrode performs higher discharge voltage platform and enhanced discharge energy density. The excellent electrochemical performance of nanofibers electrode is ascribed to the better conductivity and superior lithium ion diffusion ability according to the electrochemical impedance spectrum measurement.
Co-reporter:Yong Zheng, Yan-Bing He, Kun Qian, Baohua Li, Xindong Wang, Jianling Li, Cui Miao, Feiyu Kang
Journal of Alloys and Compounds 2015 Volume 639() pp:406-414
Publication Date(Web):5 August 2015
DOI:10.1016/j.jallcom.2015.03.169
•Degradation of LiFePO4/graphite batteries under different state of charge at 55 °C is investigate.•Side reactions caused by self-discharge are the main reason for performance fade during storage.•The detailed degradation mechanism is proven by post-mortem analysis.•Increased electrode resistance in LiFePO4 cathode suggests that side reactions also happen at positive electrode.In this paper, the degradation of LiFePO4/graphite batteries during 10 months of storage under different temperatures and states of charge (SOCs) is studied. The effects of SOC during storage process are systematically investigated using electrochemical methods and post-mortem analysis. The results show that at elevated temperature of 55 °C, higher stored SOC results in more significant increase in bulk resistance (Rb) and charge-transfer resistance (Rct) of full battery, whereas the rate-discharge capability of stored battery is unchanged. The side reactions at the electrode/electrolyte interface caused by self-discharge are the main reasons for the performance fading during storage. For LiFePO4 cathode, long-time storage does not influence the framework structure under various SOCs. The existence of little irreversible capacity loss and impedance increase indicates that side reactions also occur at the positive electrode. For graphite anode, only a little capacity loss is found upon storage. There is a significant increase in impedance and a small amount of Fe deposition on graphite anode after storage at 100% SOC and 55 °C. The lithium ion loss arises from side reactions taking place at the graphite anode, which is responsible for the capacity degradation of battery during the storage process. XPS analysis confirms that a deposit layer composed of Li2CO3 and LiF is formed on the surface of anode.
Co-reporter:Yu Dai, Jianling Li, Gang Yan, Guofeng Xu, Qingrui Xue, Feiyu Kang
Journal of Alloys and Compounds 2015 Volume 621() pp:86-92
Publication Date(Web):5 February 2015
DOI:10.1016/j.jallcom.2014.09.183
•The cactus-like porous MnO2 was synthesized by hydrothermal method assisted with SDS.•The MnO2 exhibits a max specific capacitance of 187.8 F g−1 (0.2 A g−1, 1 M Na2SO4).•Excellent cycling stability: 92.9% capacitance retention after 1000 cycles.The cactus-like porous manganese dioxide (MnO2) was synthesized by a simple hydrothermal method assisted with the surfactant sodium dodecyl sulfate (SDS). The morphology, composition, property of the prepared materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET), Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM) measurements. It was found that the sample without surfactant was composed of nanoflakes which piling up together, whereas in the presence of the surfactant, the MnO2 samples with the max specific surface of 321.9 m2 g−1 showed a porous cactus-like microstructure, consisted of uniform nanowires and porous nanoflakes. The electrochemical performances of the MnO2 with and without surfactant were analyzed using Cyclic Voltammetry (CV), Electrochemical Impedance Spectrometry (EIS) and Galvanostatic Charge–Discharge (GCD) tests. The results showed that the MnO2 assisted with 1 wt.% SDS displayed a higher specific capacitance of 187.8 F g−1 at the current density of 0.2 A g−1 compared with the MnO2 without surfactant (134.8 F g−1). And such MnO2 samples with higher specific capacitance also afford an excellent cyclic stability with the capacity retention of approximately 92.9% after 1000 cycles in 1 M Na2SO4 solution at a current density of 1 A g−1. The superior capacitive performance of the as-prepared materials could be attributed to its unique cactus-like porous structure, which provided good electronic conductivity, large specific surface area as well as fast electron and ion transport.
Co-reporter:Pengfei Hou;Penglei Cui;Hui Liu;Jun Yang
Nano Research 2015 Volume 8( Issue 2) pp:512-522
Publication Date(Web):2015 February
DOI:10.1007/s12274-014-0663-0
Noble metal nanoparticles with hollow interiors and customizable shell compositions have immense potential for a wide variety of applications. Herein, we present a facile, general, and cost-effective strategy for the synthesis of noble metal nanoparticles with hollow structures, which is based on the inside-out diffusion of Ag in solid-state core-shell nanoparticles. This approach starts with the preparation of core-shell nanoparticles with Ag residing in the core region, which are then loaded on a solid substrate and aged in air to allow the inside-out diffusion of Ag from the core region, leading to the formation of monometallic or alloy noble metal nanoparticles with a hollow interior. The synthesis was carried out at room temperature and could be achieved on different solid substrates. In particular, the inside-out diffusion of Ag calls for specific concern with respect to the evaluation of the catalytic performance of the Ag-based core-shell nanoparticles since it may potentially interfere with the physical and chemical properties of the core-shell particles.
Co-reporter:Qingrui. Xue, Jianling. Li, Guofeng. Xu, Hongwei. Zhou, Xindong. Wang and Feiyu. Kang
Journal of Materials Chemistry A 2014 vol. 2(Issue 43) pp:18613-18623
Publication Date(Web):10 Sep 2014
DOI:10.1039/C4TA04024D
Lithium-rich layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is prepared by a fast co-precipitation method and surface modified with conducting polyaniline (PANI, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt% theoretically) via in situ chemical oxidation polymerization to optimize the electrochemical properties. The uniform PANI layer with a thickness of 5 nm (10 wt%) has been successfully coated on the surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 particles, as observed by field-emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The X-ray powder diffraction (XRD) results show that all the prepared samples have a typical layered hexagonal α-NaFeO2 structure. The PANI layer maintains the integrity of the surface material crystal structure of the Li[Li0.2Mn0.54Ni0.13Co0.13]O2 particles by protecting the electrodes from external erosion during continuous charge–discharge cycles. PANI-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 electrodes present excellent electrochemical properties at room temperature. The initial discharge capacity is 313.5 mA h g−1 (0.05 C) with a coulombic efficiency of 89.01% (PANI, 10 wt%), compared with 291.9 mA h g−1 (0.05 C) for the pristine Li[Li0.2Mn0.54Ni0.13Co0.13]O2 with a coulombic efficiency of 81.31% in the potential range 2.0–4.8 V (vs. Li/Li+). The discharge capacity is retained at 282.1 mA h g−1 after 80 cycles at 0.1 C. Moreover, the PANI-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 exhibits an excellent high rate capacity of 198.6 mA h g−1 at 10 C. The electrochemical impedance spectra (EIS) measurements reveal that the thin PANI coating layer significantly optimizes the interfacial electrochemical reaction activity by reducing the charge transfer resistance. Moreover, the special H+/Li+ exchange reaction during the proton acid doping procedure also promotes the improvement of the electrochemical performance.
Co-reporter:Guofeng Xu, Jianling Li, Qingrui Xue, Xianping Ren, Gang Yan, Xindong Wang, Feiyu Kang
Journal of Power Sources 2014 Volume 248() pp:894-899
Publication Date(Web):15 February 2014
DOI:10.1016/j.jpowsour.2013.10.002
•The H+/Li+ exchange reaction is triggered by a mild acid solution.•In-situ CV method is adopted to explain the mechanism of acid treatment.•The treated electrode shows elevated initial cycle efficiency and rate performance.•The elevated capability is attributed to the enhanced oxygen reducibility.Solid solution cathode material 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2 has been synthesized by a co-precipitation method and a mild acid was adopted to give rise to the H+/Li+ exchange reaction. The inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic absorption spectroscopy (AAS) data show that the H+/Li+ exchange reaction actually occurs and the chemical composition is H0.06Li1.15Ni0.13Co0.14Mn0.55O2.03 after the material was treated. The X-ray powder diffraction patterns indicates that the structure doesn't change through the H+/Li+ exchange reaction and remains the hexagonal α-NaFeO2 layered structure with space group of R-3m. The field-emission scanning electron microscope (SEM) and transmission electron microscope (TEM) images show that there are traces of erosion on the surface of the H+/Li+ exchanged sample. The initial charge–discharge curve measured at 0.05C (12.5 mA g−1) demonstrates that the H+/Li+ exchanged electrode delivers a capacity of up to 314.0 mAh g−1 and coulombic increased initial efficiency. Cycle voltammetry (CV) measurement confirms this is attributed to the improvement of the reduction catalytic activity of oxygen released during the initial charging. The processed electrode also displays improved rate performance.
Co-reporter:Guofeng Xu, Jianling Li, Qingrui Xue, Yu Dai, Hongwei Zhou, Xindong Wang, Feiyu Kang
Electrochimica Acta 2014 Volume 117() pp:41-47
Publication Date(Web):20 January 2014
DOI:10.1016/j.electacta.2013.11.064
A novel wet method of (NH4)3AlF6 coating was explored to enhance the electrochemical performance of Mn-based solid-solution cathode material 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2. The X-ray powder diffraction patterns show that the coating material is pure-phase (NH4)3AlF6 and both pristine and coated samples can be indexed to hexagonal α-NaFeO2 layered structure with space group of R-3 m. The field-emission scanning electron microscope images and the energy dispersive X-ray spectroscopy show that (NH4)3AlF6 is successfully coated on the surface of active particle. The (NH4)3AlF6 coated electrodes exhibit improved electrochemical performance, for instance, the initial charge-discharge efficiency was promoted by 5% (NH4)3AlF6 coating, the 1 wt.% and 3 wt.% coated electrodes deliver elevated cycling ability which is ascribed to the lower resistance between electrode and electrolyte as indicated by AC impedance measurement at different cycles. In addition, the coated-electrodes also give enhanced rate capability particularly for 1 wt.% NAF-coated electrode performing surprising capacity of 143.4 mAh g−1 at 5 C higher than that of 109.4 mAh g−1 for pristine electrode. Furthermore, the 1 wt.% NAF-coated electrode also shows improved cycle and rate performance at 55°C.
Co-reporter:Yakun Zhang;Xindong Wang;Feng Ye;Jun Yang
Journal of Applied Polymer Science 2014 Volume 131( Issue 3) pp:
Publication Date(Web):
DOI:10.1002/app.39561
ABSTRACT
N,N′-ethylene–bis(salicylideneiminato)]–nickel(II) [Ni(salen)] was synthesized in situ onto the surface of multiwalled carbon nanotubes via a one-step potentiostatic electrodeposition as one-dimensional nanobelts. The synthetic process was free of any templates or additives. Potential played a key role in the formation of the poly[N,N′-ethylene–bis(salicylideneiminato)]–nickel(II)] {poly[Ni(salen)]} nanobelts, and the electrical conductivities of the poly[Ni(salen)] decreased with increasing deposition time. The capacitance values of poly[Ni(salen)] were 272, 195, and 146 F/g at 0.05 mA/cm2 for deposition times of 10, 20, and 30 min, respectively. The capacitance of the sample with a particle structure was much lower than that of poly[Ni(salen)] with a nanobelt structure. The poly[Ni(salen)] nanobelts exhibited a better capacitive behavior than the poly[Ni(salen)] particles because the nanobelt structure made access for the charge and ion to the inner part of the electrode easier. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39561.
Co-reporter:Gang Yan ; Jianling Li ; Yakun Zhang ; Fei Gao ;Feiyu Kang
The Journal of Physical Chemistry C 2014 Volume 118(Issue 19) pp:9911-9917
Publication Date(Web):April 14, 2014
DOI:10.1021/jp500249t
Nanobelt-like poly[Ni(salen)] obtained by electrodeposition of potentiostatic method has been characterized by field emission scanning electron microscopy and transmission electron microscope. The polymerization mode and the energy storage mechanism were investigated through the methyl replacement in the para-position of phenyl rings in Ni(salen) monomer and the removal of center metal ion Ni. The electrode samples were characterized by cyclic voltammetry and galvanostatic charge/discharge methods.
Co-reporter:Zhong Chen, Jianling Li, Yu Chen, Yakun Zhang, Guofeng Xu, Jun Yang, Ye Feng
Particuology 2014 Volume 15() pp:27-33
Publication Date(Web):August 2014
DOI:10.1016/j.partic.2012.12.008
Graphene/hierarchy structure manganese dioxide (GN/MnO2) composites were synthesized using a simple microwave-hydrothermal method. The properties of the prepared composites were analyzed using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) measurements. The electrochemical performances of the composites were analyzed using cyclic voltammetry, electrochemical impedance spectrometry (EIS), and chronopotentiometry. The results showed that GN/MnO2 (10 wt% graphene) displayed a specific capacitance of 244 F/g at a current density of 100 mA/g. An excellent cyclic stability was obtained with a capacity retention of approximately 94.3% after 500 cycles in a 1 mol/L Li2SO4 solution. The improved electrochemical performance is attributed to the hierarchy structure of the manganese dioxide, which can enlarge the interface between the active materials and the electrolyte. The preparation route provides a new approach for hierarchy structure graphene composites; this work could be readily extended to the preparation of other graphene-based composites with different structures for use in energy storage devices.Graphical abstractSchematic illustration of fabrication process for GN/MnO2 composite.Highlights► Graphene/hierarchy structure MnO2 composites were synthesized by microwave-hydrothermal method. ► The hierarchy structure of MnO2 is composed of MnO2 nanospheres and MnO2 sheets. ► GN/MnO2-10% electrode showed a specific capacitance of 244 F/g at 100 mA/g in 1 mol/L Li2SO4. ► Capacity retention of 94.3% was obtained after 500 cycles in a 1 mol/L Li2SO4 solution.
Co-reporter:Yu Chen, Guofeng Xu, Jianling Li, Yakun Zhang, Zhong Chen, Feiyu Kang
Electrochimica Acta 2013 Volume 87() pp:686-692
Publication Date(Web):1 January 2013
DOI:10.1016/j.electacta.2012.09.024
Solid solution material of 0.5Li2MnO3·0.5LiNi0.33Co0.33Mn0.33O2 (alternatively Li[Li0.2Mn0.54Ni0.13Co0.13]O2) was synthesized by a fast co-precipitation method which takes sulfates with high solubility as the transition metal sources of mixed hydroxide precursor. The optimal synthetic conditions were determined through the design of orthogonal experiments. The properties of samples synthesized under the best conditions were investigated in detail. The XRD pattern of 0.5Li2MnO3·0.5LiNi0.33Co0.33Mn0.33O2 revealed a well ordered hexagonal layered structure with the evident feature of super lattice caused by Li2MnO3. FESEM images showed that the powders possess small and unagglomerated particles with size range of 100–300 nm. XPS analysis results demonstrated that the valence states of Ni, Co, Mn are +2, +3, and +3.52 respectively. The electrochemical measurements showed that the optimal material delivers initial discharge capacity of 315.3 mAh g−1 at 1/20 C between 2.0 and 4.8 V with good cycle stability after firstly several cycles. CV test proved that the high capacity performance is ascribed to the redox of oxygen or its species at the electrode surface. Rate test showed that 179.5 mAh g−1 was obtained at 2 C which is considerably high, as far as we concerned.
Co-reporter:Bangsheng Ming, Jianling Li, Feiyu Kang, Guoyao Pang, Yakun Zhang, Liang Chen, Junyuan Xu, Xindong Wang
Journal of Power Sources 2012 Volume 198() pp:428-431
Publication Date(Web):15 January 2012
DOI:10.1016/j.jpowsour.2011.10.003
Birnessite-type MnO2 (Bir-MnO2) nanospheres have been successfully synthesized by the microwave–hydrothermal (M–H) method at 75 °C for 30 min under low pressure. The properties and electrochemical performance of the as-prepared MnO2 are analyzed and evaluated by the field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) measurements and electrochemical tests. The Bir-MnO2 appears mesoporous nanosphere structure with 70–90 nm in diameter, and it exhibits a large specific surface (SS) of 213.6 m2 g−1 by the results of FE-SEM, XRD and BET. The electrochemical test results show that the specific capacitance (SC) is 210 F g−1 at 200 mA g−1 in 1.0 M Na2SO4 electrolyte, and the SC retention and coulombic efficiency are over 96% and 98% respectively after 300 cycles at 1.6 A g−1. Compared with the conventional syntheses of MnO2, the performance of the Bir-MnO2 nanospheres synthesized by M–H method is significantly improved.Highlights► Birnessite-type MnO2 nanospheres are synthesized by microwave–hydrothermal method. ► Synthesis process is fast (30 min), at low temperature (75 °C) under low pressure. ► As-prepared MnO2 has interesting nanosphere structure. ► The specific surface of the as-prepared MnO2 is as large as 213.6 m2 g−1. ► The nanospheres show high coulombic efficiency (98%) and excellent cycle stability.
Co-reporter:Yakun Zhang, Jianling Li, Fei Gao, Feiyu Kang, Xindong Wang, Feng Ye, Jun Yang
Electrochimica Acta 2012 Volume 76() pp:1-7
Publication Date(Web):1 August 2012
DOI:10.1016/j.electacta.2012.03.182
N,N′-ethylenebis(salicylideneaminato) nickel(II), (Ni(salen)), which is the archetype of Schiff base metal complexes, was easily synthesized onto the surface of activated carbon (AC), mesoporous carbon (MC) and multi-walled carbon nanotube (MWCNT) by the route of linear potential sweep, respectively. The microstructure of the poly[Ni(salen)] homogeneously grown on the different carbon supports was evidenced by field emission scanning electron microscopy (FESEM). Growth parameters such as the apparent surface coverage and the doping level were investigated to confirm the effects of supports on the Ni(salen) polymerization. Diffusion coefficient was calculated from the chronoamperometry test to characterize the charge transport ability with the different pore size distributions of the supports, and the result indicates that MWCNT support with abundant macro porous is more active to the growth of the polymer and the charge diffusion. Capacitance performance of the electrodes was discussed by constant charge/discharge and alternating current impedance tests. A 3.79 times capacitance increase of the poly[Ni(salen)] electrode with MWCNT as a support was observed. The exceptional electrochemical properties make the use of MWCNT an attractive support for poly[Ni(salen)] as a supercapacitor material.
Co-reporter:Yakun Zhang, Jianling Li, Feiyu Kang, Fei Gao, Xindong Wang
International Journal of Hydrogen Energy 2012 Volume 37(Issue 1) pp:860-866
Publication Date(Web):January 2012
DOI:10.1016/j.ijhydene.2011.04.034
A nanoporous manganese oxide (MnO2) film was fabricated via a polystyrene templated electrodeposition in the solution containing MnSO4. The nanoporous MnO2 film obtained has been characterized by field emission scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge methods. The specific capacitance of 1018 F g−1 was observed at a low current density of 500 mA g−1. When the current density increased to 30.0 A g−1, the specific capacitance of 277 F g−1 remained. The high capacitance retention at high rates makes the prepared MnO2 a promising candidate for supercapacitor applications.Highlights► An array of manganese oxide (MnO2) nanowall-spheres was fabricated using template via potentiodynamic electrodeposition. ► High specific capacitance of 1018 F g−1 was obtained at a low current density of 500 mA g−1. ► The maximum specific energy of sample reached 90.5 Wh kg−1, and almost 30% remained as stable value.
Co-reporter:JianLing Li;Fei Gao;YaKun Zhang;FeiYu Kang;XinDong Wang
Science China Chemistry 2012 Volume 55( Issue 7) pp:1338-1344
Publication Date(Web):2012/07/01
DOI:10.1007/s11426-012-4585-y
The composites of poly[Ni(salen)] and multi-walled carbon nanotube (MWCNT) were synthesized by pulse potentiostatic method. The composites were characterized by field emission scanning electron microscopy, Fourier transform infrared spectra, and electrochemical impedance spectroscopy. The wrapping of carbon nanotubes with poly[Ni(salen)] varied significantly with anodic pulse duration. Variance of structure of poly[Ni(salen)] caused by anodic pulse duration affected the ability of absorption to solvent molecules or solvated ions, which was indicated by ν (C≡N) intensity. The ability to store/release charge of poly[Ni(salen)] caused by redox switching was evaluated in the form of low-frequency capacitance. Correlations of charge-transfer resistance/ionic diffusion resistance with potential and anodic pulse duration were investigated.
Co-reporter:Fei Gao ; Jianling Li ; Feiyu Kang ; Yakun Zhang ; Xindong Wang ; Feng Ye ;Jun Yang
The Journal of Physical Chemistry C 2011 Volume 115(Issue 23) pp:11822-11829
Publication Date(Web):May 20, 2011
DOI:10.1021/jp111831y
A composite of poly[Ni(salen)] and multiwalled carbon nanotubes (MWCNTs) was synthesized by in situ electropolymerization. As-grown poly[Ni(salen)] filled gaps between MWCNTs and formed a ferroconcrete-like microstructure. It was found that the doping level and electrochemical reversibility of poly[Ni(salen)] were greatly improved because of the support of MWCNTs. Values of the charge diffusion transport coefficient estimated by cyclic voltammetry revealed the effect of the mass of poly[Ni(salen)] on the charge transport behavior of composites. Both the direct ohmic resistance and the alternating ohmic resistance of a composite with small mass ratios (0.29/1 and 0.63/1) were obviously lower than those of MWCNTs which was demonstrated by electrochemical impedance spectroscopy and galvanostatic charge/discharge tests. Galvanostatic charge/discharge tests also showed that the ability to store charge was improved significantly for composites by incorporating poly[Ni(salen)].
Co-reporter:Fei Gao, Jianling Li, Yakun Zhang, Xindong Wang, Feiyu Kang
Electrochimica Acta 2010 Volume 55(Issue 20) pp:6101-6108
Publication Date(Web):1 August 2010
DOI:10.1016/j.electacta.2010.05.076
The complex (2,2-dimethyl-1,3-propanediaminebis(salicylideneaminato))–nickel(II), [Ni(saldMp)], was oxidatively electropolymerized on activated carbon (AC) electrode in acetonitrile solution. The poly[Ni(saldMp)] presented an incomplete coated film on the surface of carbon particles of AC electrode by field emission scanning electron microscopy. The electrochemical behaviors of poly[Ni(saldMp)] modified activated carbon (PAC) electrode were evaluated in different potential ranges by cyclic voltammetry. Counterions and solvent swelling mainly occurred up to 0.6 V for PAC electrode by the comparison of D1/2C values calculated from chronoamperometry experiments. Both the Ohmic resistance and Faraday resistance of PAC electrode gradually approached to those of AC electrode when its potential was ranging from 1.2 V to 0.0 V. Galvanostatic charge/discharge experiments indicated that both the specific capacitance and energy density were effectively improved by the reversible redox reaction of poly[Ni(saldMp)] film under the high current density up to 10 mA cm−2 for AC electrode. The specific capacitance of PAC electrode decreased during the first 50 cycles but thereafter it remained constant for the next 200 cycles. This study showed the redox polymer may be an attractive material in supercapacitors.
Co-reporter:Jian-ling Li 李建玲;Fei Gao;Ya-kun Zhang
Chinese Journal of Polymer Science 2010 Volume 28( Issue 5) pp:667-671
Publication Date(Web):2010 September
DOI:10.1007/s10118-010-0083-x
The polymer of complex [Ni(salen)], (N,N′-ethylenebis (salicylideneaminato) nickel(II)), was prepared on graphite electrode by the route of linear sweep potential method. The nano-micro sheaf/wire structures of poly[Ni(salen)] have been obtained by adjusting the polymerization sweep rate of 5, 20 and 40 mV·s−1. The polymer prepared at 20 mV·s−1 had nanoscaled wire structure of ca. 100 nm in diameter. The good electrochemical reversibility of poly[Ni(salen)] was investigated by cyclic voltammetry and galvanostatic test in 1.0 mol/L Et3MeNBF4/acetonitrile solution. The initial specific gravimetric capacitance of poly[Ni(salen)] at the current density of 0.1 mA·cm−2 reached 270.2 F·g−1, however, the cycle stability needs to be improved.
Co-reporter:Tianheng Yu, Jianling Li, Guofeng Xu, Jiguang Li, Feixiang Ding, Feiyu Kang
Solid State Ionics (March 2017) Volume 301() pp:64-71
Publication Date(Web):March 2017
DOI:10.1016/j.ssi.2017.01.008
Co-reporter:Qingrui. Xue, Jianling. Li, Guofeng. Xu, Hongwei. Zhou, Xindong. Wang and Feiyu. Kang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 43) pp:NaN18623-18623
Publication Date(Web):2014/09/10
DOI:10.1039/C4TA04024D
Lithium-rich layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is prepared by a fast co-precipitation method and surface modified with conducting polyaniline (PANI, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt% theoretically) via in situ chemical oxidation polymerization to optimize the electrochemical properties. The uniform PANI layer with a thickness of 5 nm (10 wt%) has been successfully coated on the surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 particles, as observed by field-emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The X-ray powder diffraction (XRD) results show that all the prepared samples have a typical layered hexagonal α-NaFeO2 structure. The PANI layer maintains the integrity of the surface material crystal structure of the Li[Li0.2Mn0.54Ni0.13Co0.13]O2 particles by protecting the electrodes from external erosion during continuous charge–discharge cycles. PANI-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 electrodes present excellent electrochemical properties at room temperature. The initial discharge capacity is 313.5 mA h g−1 (0.05 C) with a coulombic efficiency of 89.01% (PANI, 10 wt%), compared with 291.9 mA h g−1 (0.05 C) for the pristine Li[Li0.2Mn0.54Ni0.13Co0.13]O2 with a coulombic efficiency of 81.31% in the potential range 2.0–4.8 V (vs. Li/Li+). The discharge capacity is retained at 282.1 mA h g−1 after 80 cycles at 0.1 C. Moreover, the PANI-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 exhibits an excellent high rate capacity of 198.6 mA h g−1 at 10 C. The electrochemical impedance spectra (EIS) measurements reveal that the thin PANI coating layer significantly optimizes the interfacial electrochemical reaction activity by reducing the charge transfer resistance. Moreover, the special H+/Li+ exchange reaction during the proton acid doping procedure also promotes the improvement of the electrochemical performance.
