Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (9): 1667-1673.doi: 10.3866/PKU.WHXB201406251

• ELECTROCHEMISTRY AND NEW ENERGY • Previous Articles     Next Articles

Effects of Surface Modification with Ag/C on Electrochemical Properties of Li[Li0.2Mn0.54Ni0.13Co0.13]O2

XUE Qing-Rui1, LI Jian-Ling1, XU Guo-Feng1, HOU Peng-Fei1, YAN Gang1, DAI Yu1, WANG Xin-Dong1, GAO Fei2   

  1. 1. School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China;
    2. China Electric Power Research Institute, Beijing 100085, P. R. China
  • Received:2014-05-09 Revised:2014-06-25 Published:2014-08-29
  • Contact: LI Jian-Ling E-mail:lijianling@ustb.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (51172023, 51372021), National High Technology Research and Development Program of China (863) (2012AA110302), and Basic Forward-Looking Technology Project of the State Grid Corporation, China (DG71-13-009).

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Abstract:

A lithium-rich solid-solution layered cathode material, Li[Li0.2Mn0.54Ni0.13Co0.13]O2, was synthesized using a fast co-precipitation method, and surface modified withAg/C via chemical deposition. The electrochemical properties, structures, and morphologies of the prepared samples were investigated using X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), galvanostatic charge-discharge cycling, cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and energy dispersive X-ray spectroscopy (EDS). The XRD results showed that the pristine and Ag/Ccoated cathode materials both have hexagonal α-NaFeO2 layered structures with the R3m space group. Microscopic morphological observations and EDS elemental mapping showed that a uniform Ag/C coating layer of thickness 25 nm was deposited on the surfaces of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 particles. The Ag/C-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 material gave an excellent electrochemical performance. The initial discharge capacity (0.05C) of the Ag/C- coated sample was 272.4 mAh ·g-1, with an initial coulombic efficiency of 77.4%, corresponding to 242.6 mAh·g-1 for the pristine sample, with an initial coulombic efficiency of 67.6%, in the potential range 2.0-4.8 V (vs Li/Li+). After 30 cycles (0.2C), the Ag/C-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 retained a capacity of 222.6 mAh·g-1, which was 14.45% higher than that of Li[Li0.2Mn0.54Ni0.13Co0.13]O2. We also found that the Ag/C coating improved the rate capability of the solid-solution material Li[Li0.2Mn0.54Ni0.13Co0.13]O2. The capacity retention (1C) of the Ag/C-coated sample was 81.3%, compared with the capacity at 0.05C. CV and EIS results showed that the Ag/C coating layer suppressed the oxygen release in the initial charge progress and lowered the surface film resistance and electrochemical reaction resistance of the pristine sample.

Key words: Lithium ion battery, Solid solution material, Chemical deposition method, Surface modification, Compound coating