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29 results on '"Kang, Xueya"'

12. Electrochemical Performances of Maricite NaFePO4/C as cathode material for Sodium-Ion and Lithium-Ion Batteries

Author

Yan, Xw (Yan, Xianwei), Kang, Xy (Kang, Xueya), Zhao, L (Zhao, Ling), Huang, Wx (Huang, Wanxia), Zhou, Dm (Zhou, Dengmei), Deng, Zl (Deng, Zhilin), Yu, Yb (Yu, Yongbo), and Shi, Qw (Shi, Qiwu)

Subjects
Materials science, Sodium, chemistry.chemical_element, 02 engineering and technology, Maricite, 010402 general chemistry, 021001 nanoscience & nanotechnology, Electrochemistry, 01 natural sciences, Cathode, 0104 chemical sciences, Ion, law.invention, Chemical engineering, chemistry, Cathode material, law, Carbon source, Lithium, 0210 nano-technology
Abstract

Carbon-coated NaFePO4 (NaFePO4/C) with a maricite structure was synthesized by a two-step solidstate method with sucrose as carbon source. The electrochemical performances of NaFePO4/C were evaluated for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs), respectively. For SIBs, the initial reversible capacity of 48.8 mAh g(-1) at 0.05 C (1 C=154 mAh g(-1)) has obtained. For LIBs, the initial discharge capacity of NaFePO4 can reach up to 75.7 mAh g(-1) at 0.05 C. The reversible capacity of 50.6 and 38 mAh g(-1) can be obtained at 0.1 C, 0.2 C, respectively. With a simple synthetic process, cost-effective chemicals, and desirable electrochemical performance, the maricite NaFePO4/C is a possible application for large-scale energy devices and stationary storage.

Published
2017

13. Synthesis Of LiCo1/3Ni1/3Mn1/3O2As A Layered Cathode Material Prepared By The Pechini Process

Author

Zhigang Li, Tiandiao Wang, Han Ying, and Kang Xueya

Subjects
Materials science, Aqueous solution, Scanning electron microscope, Mechanical Engineering, Non-blocking I/O, Analytical chemistry, Layered double hydroxides, Mineralogy, engineering.material, Condensed Matter Physics, Electrochemistry, Metal, chemistry.chemical_compound, chemistry, Mechanics of Materials, visual_art, visual_art.visual_art_medium, engineering, Hydroxide, General Materials Science, Stoichiometry
Abstract

In a study, a layered LiCO1/ 3Mn1/3Ni1/ 3O2 include a solid-state solution method, co-precipitation, mixed hydroxide method, layered double hydroxides solid state reaction, spray dry method and the metal ecetate decomposition method. In the study, layered LiCO1/ 3Mn1/ 3Ni1/ 3O2 was first prepared by the Pechini process. Ni(NO3)2·6H2O(AR), Co(NO3)2·6H2O(AR) and Mn(NO3)2(AR) were mixed and dissolved in deionized water in a molar ration of Ni/Co/Mn =1:1:1. The aqueous solution was slowly dripped into a mixed solution of NH3·H2O and NaOH at a constant rate. The stoichiometric starting materials NiO(AR), Co(NO3)2·6H2O(AR) and Mn(CH3COO)2·H2O(AR) were dispersed in acetone and mixed. The structure and morphology of the prepared powders was characterized using Xray difraction and scanning electron microscopy. Results show that Sample 1 had a phase pure a-NaFeO2 structure and the least ion mixing degree in the lattice with fine, uniform particle sizes. They developed a well layered structure and are anticipated to display an excellent electrochemical performance. The new approach requires only low temperatures and saves on energy consumption.

Published
2006

19. The first principles and experimental study on Mn-doped LiFePO4

Author

Han Ying, Tuerdi Wumair, Dou Junqing, Kang Xueya, and Hua Ning

Subjects
Materials science, Computational chemistry, Band gap, Doping, Energy density, Analytical chemistry, General Physics and Astronomy, Ionic conductivity, High capacity, Density functional theory, Mn doped, Electrochemistry
Abstract

The electronic structures of pure and Mn-doped LiFePO4 are studied using density functional theory (DFT). The results demonstrate that the pure LiFePO4 has a band gap of 0.725 eV, while the 25% Mn doped LiFe0.75Mn0.25PO4 has the smallest band gap (0.469 eV), and the weakest FeO and LiO bond, which indicates that the electronic conductivity and the ionic conductivity of the doped LiFePO4 are improved due to doping. On the other hand, the experimental results also show that the LiFe0.75Mn0.25PO4 has the best electrochemical performance and it delivers a very high capacity of 158 mAh? g-1 and a high energy density of 551 Whkg-1.

Published
2012

25. Synthesis of carbon microtubules core structure LiFePO4 via a template-assisted method.

Author

Wumair, Turdi, Dou, Junqing, Zhang, Lu, Chen, Mingde, and Kang, Xueya

Abstract

The carbon microtubules core structure LiFePO 4 is synthesized using a cotton fiber template-assisted method. The crystalline structure and morphology of the product is characterized by X-ray diffraction and field emission scanning electron microscopy. The charge–discharge kinetics of the LiFePO 4 electrode is investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The result shows that the well-crystallized carbon microtubules core structure LiFePO 4 is successfully synthesized. The as-synthesized material exhibits a high initial discharge capacity of 167 mAh g −1 at 0.2 C rate. The material also shows good high-rate discharge performance and cycling stability, about 127 mAh g −1 and 94.7 % capacity retention after 100 cycles even at 5.0 C rate. [ABSTRACT FROM AUTHOR]

Published
2013
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27. Synthesis of the Stoichiometrical LixLi'1-xNa0.06MnO2 Containing Li2MnO3 Phase by Ion-Exchange Method

Author

Wang, Huanhuan, Kang, Xueya, Xu, Jinbao, Wumaier, Tuerdi, Wang, Lei, Chen, Mingde, and Zhang, Bingbing

Abstract

Using ion-exchange method, previous researchers have successfully synthesized cathode materials with excellent electrochemical properties. In this paper, the stoichiometrical LixLi'1-xNa0.06MnO2 containing Li2MnO3 phase was synthesized depending on the two stages which was the characteristic of the ion-exchange route. The additive proportion of Li in the first and second steps of the ion exchange process was changed in the purpose of regulating the proportional relation of the layered LiyNa0.06MnO2 and the monoclinic Li2MnO3 (m-Li2MnO3) phases. The LixLi'1-xNa0.06MnO2 cathode material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and galvanostatic charge-discharge cycling technique in order to investigate the crystalline structure, surface morphology and electrochemical property. Through our experiments, Li0.25Li'0.75Na0.06MnO2 and Li0.35Li'0.65Na0.06MnO2 behaved the excellent electrochemical performance. Li0.25Li'0.75Na0.06MnO2 could deliver the capacity of 206 mAhg[?]1 at 10 mAg[?]1 in the first charge process, and Li0.35Li'0.65Na0.06MnO2 showed outstanding cycle stability. Its average discharge specific capacity reached 150 mAhg[?]1. The improved performance might arise from the existence of the optimal proportion of m-Li2MnO3 phase. This stoichiometrical LixLi'1-xNa0.06MnO2 might be a good substitute for the cathodes containing poisonous or expensive metals.

Published
2013

28. Studies of V doping for the LiFePO4-based Li Ion batteries

Author

Hua, Ning, Wang, Chenyun, Kang, Xueya, Wumair, Tuerdi, and Han, Ying

Subjects
*LITHIUM-ion batteries, *VANADIUM, *ELECTROCHEMICAL analysis, *CATHODES, *CHEMICAL reduction, *MOLECULAR structure, *DIFFUSION, *SCANNING electron microscopy
Abstract

Abstract: Alien atom doping has been adopted to modify the electrochemical performance of olivine type LiFePO4 for cathode material. Here, we report that vanadium-doping can improve the performance of LiFePO4/C immensely. LiFePO4/C and V-doped LiFePO4/C cathode materials were first synthesized by carbothermal reduction method. Physico-chemical characterizations were done by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Electrochemical behavior of the cathode materials was analyzed using cyclic voltammetry (CV) and galvanostatic measurements. ICP and XRD analyses indicated that V ions were sufficiently doped in LiFePO4 and did not alter its crystal structure and exhibited the variation of lattice parameters with the doped degree. From the CV, the V ion doping affected the Li+ ionic diffusion coefficient during both the delithiation and lithiation processes and it became larger with an appropriate amount doping. From the results, it is noted that vanadium ions doping can improve performance of LiFePO4, especially on the aspect of stable cycle-life at higher C rate. [Copyright &y& Elsevier]

Published
2010
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29. Effect of Mn2+-doping in LiFePO4 and the low temperature electrochemical performances

Author

Li, Chengfeng, Hua, Ning, Wang, Chengyun, Kang, Xueya, Tuerdi Wumair, and Han, Ying

Subjects
*SEMICONDUCTOR doping, *LOW temperatures, *ELECTROCHEMISTRY, *MANGANESE, *LITHIUM compounds, *OLIVINE, *COMPOSITE materials, *X-ray diffraction, *VOLTAMMETRY
Abstract

Abstract: Olivine composites LiFe1−x Mn x PO4/C (x =0, 0.05, 0.1) were prepared by chelation assisted mechanochemical activation method using C2H2O4 as the chelating reagent. The structures of the prepared composites were characterized by X-ray diffraction (XRD). Cyclic voltammetry, ac impedance spectroscopy, galvanostatic charge/discharge performances were studied at room temperature. The discharge capacity of LiFe0.95Mn0.05PO4 was 155.6mAhg−1 and 102.9mAhg−1 at 1C and 10C rate, respectively. The results indicated Mn2+-doping in LiFePO4 could effectively enhance the electrochemical performances of this olivine compound especially at high charge/discharge rate. In addition, charge/discharge method was also used to characterize the low temperature properties of the different samples. The results showed that the lower the operation temperature was, the poorer the performances were. Furthermore, ac impedance measurement was used to understand the factors of the poor performances at low temperature. [ABSTRACT FROM AUTHOR]

Published
2011
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