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Changsha, China

Jin G.,Central South University | Wang H.,Central South University | Xie H.,Yangtze Normal University | He K.,Central South University | And 5 more authors.
Electrochimica Acta | Year: 2014

In this paper, we reported the synthesis of single-crystalline octahedral LiMn2O4 particles by a two-step method in which well-shaped octahedral Mn3O4 was easily obtained by the hydrothermal reaction of KMnO4 in water/N, N-dimethyl formamide (DMF) mixed solution and then transferred to LiMn2O4 by the solid-state lithiation process. High crystallinity and phase purity were also observed. When used as a cathode for Li-ion battery, the octahedral LiMn2O4 particles have demonstrated superior electrochemical properties in comparison with the LiMn2O4 particles by sol-gel method. A high initial discharge capacity of 122.7 mAhg-1 was exhibited at 1C-rate and 104 mAh g-1 maintained after 200 cycles for octahedral LiMn2O4. And good rate capability has also been achieved. The excellent electrochemical properties should be mainly attributed to the special octahedral morphology, single crystalline nature and high crystallinity. © 2014 Elsevier Ltd. All rights reserved. Source


Huang C.,Hunan Changyuan Lico Co. | Huang C.,Central South University | Zhuang S.,Central South University | Zhuang S.,Xiamen University of Technology | Tu F.,Central South University
Journal of the Electrochemical Society | Year: 2013

Interfacial properties of Li-ion cells containing LiCoO2 and a mixture of natural and artificial graphite in a LiPF6-based nonaqueous electrolyte were studied during storage and operation under various temperatures. The graphite/electrolyte interface showed a higher activation energy of Li-ion transfer than the LiCoO2/electrolyte interface for a cell with 100% state of charge. Li-plating occurred on graphite in charging at low temperature, where the charge transfer resistance of graphite electrode became dominating in the fully charged cell. The instability of solid electrolyte interphase (SEI) film on graphite during storage and cycles led to a decrease in impedance and capacity loss. Mechanisms of reversible capacity loss of an aged cell during storage were discussed. © 2012 The Electrochemical Society. Source


Wang H.,Central South University | Li Y.,Central South University | Huang C.,Hunan Changyuan Lico Co. | Zhong Y.,Central South University | Liu S.,Central South University
Journal of Power Sources | Year: 2012

Carbon-coated monoclinic Li 3V 2(PO 4) 3 (LVP/C) cathode materials are successfully prepared via a polyvinylpyrrolidone (PVP)-assisted sol-gel method. LVP/C composites are investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and electrochemical methods. The results indicate that the sample synthesized with 9 wt% PVP is coated with a carbon layer in a thickness of about 12 nm, which presents excellent rate capability and good cyclic performance. In the potential range of 3.0-4.3 V, it shows a capacity of 127.2 and 115.1 mAh g -1 at 1 and 10 C, respectively. Even at discharge rate of 20 C, it still has 81.8 mAh g -1 with 10.7% capacity loss after 120 cycles. The lithium diffusion coefficient of the as-prepared material is in the order of 10 -8 cm 2 s -1. Our experiment results demonstrate that the LVP/C composites prepared via a PVP-assisted sol-gel method can be an attractive candidate as cathode materials in high-power lithium-ion batteries. © 2011 Elsevier Ltd. All rights reserved. All rights reserved. Source


Wang L.,Hunan University of Commerce | Zhou X.,Hunan Changyuan Lico Co.
Proceedings - 2013 International Conference on Mechatronic Sciences, Electric Engineering and Computer, MEC 2013 | Year: 2013

Aiming at the characteristics of vagueness and uncertainty of information existed in the alloy powder production, a LS-SVM prediction model based on VPRS is presented in this paper, in which variable precision rough set is analyzed with set pair situation and mixture kernels function is used as a modeling tool. Firstly, an initial decision table is constructed after information pretreatment, and the cupidity algorithm is used to reduce the redundant embedding and variables to acquire the reduced sample space. And then, the reduced result is input into LS-SVM model to identify and optimize the key variables or parameters. The simulation results show that the model has better performance than that of which based on gauss kernels and has fine generalization performance and high prediction precision. © 2013 IEEE. Source


Zhang H.,Central South University | Qiao H.,Central South University | Wang H.,Central South University | Zhou N.,Hunan Agricultural University | And 4 more authors.
Nanoscale | Year: 2014

High-performance, low cost catalyst for oxygen reduction reaction (ORR) remains a big challenge. Herein, nanostructured NiCo2O 4/CNTs hybrid was proposed as a high-performance catalyst for metal/air battery for the first time. The well-formed NiCo2O 4/CNTs hybrid was studied by steady-state linear polarization curves and galvanostatic discharge curves in comparison with CNTs-free NiCo 2O4 and commercial carbon-supported Pt. Because of the synergistic effect, NiCo2O4/CNTs hybrid exhibited significant improvement of catalytic performance in comparison with NiCo 2O4 or CNTs alone, even outperforming Pt/C hybrid in ORR process. In addition, the benefits of Ni incorporation were demonstrated by the improved catalytic performance of NiCo2O4/CNTs compared to Co3O4/CNTs, which should be attributed to improved electrical conductivity and new, highly efficient, active sites created by Ni cation incorporation into the spinel structure. NiCo2O 4/CNTs hybrid could be used as a promising catalyst for high power metal/air battery. © 2014 the Partner Organisations. Source

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