物理化学学报 >> 2014, Vol. 30 >> Issue (9): 1667-1673.doi: 10.3866/PKU.WHXB201406251

电化学和新能源 上一篇    下一篇

Ag/C包覆对Li[Li0.2Mn0.54Ni0.13Co0.13]O2电化学性能的影响

薛庆瑞1, 李建玲1, 徐国峰1, 侯朋飞1, 晏刚1, 代宇1, 王新东1, 高飞2   

  1. 1. 北京科技大学冶金与生态工程学院, 北京 100083;
    2. 中国电力科学研究院, 北京 100085
  • 收稿日期:2014-05-09 修回日期:2014-06-25 发布日期:2014-08-29
  • 通讯作者: 李建玲 E-mail:lijianling@ustb.edu.cn
  • 基金资助:

    国家自然科学基金（51172023，51372021），国家高技术研究发展计划项目（863）（2012AA110302）和国家电网公司基础性前瞻性科技项目（DG71-13-009）资助

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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摘要：

运用共沉淀和元素化学沉积相结合的方法，制备出了具有Ag/C 包覆层的层状富锂固溶体材料Li[Li0.2Mn0.54Ni0.13Co0.13]O2. 通过X 射线衍射（XRD）、场发射扫描电子显微镜（SEM）、透射电子显微镜（TEM）、恒流充放电、循环伏安（CV），电化学阻抗谱（EIS）和X 射线能量散射谱（EDS）方法，研究了Ag/C 包覆层对Li[Li0.2Mn0.54Ni0.13Co0.13]O2电化学性能的影响. 结果表明，Ag/C 包覆层的厚度约为25 nm，Ag/C 包覆在保持了固溶体材料α-NaFeO2 六方层状晶体结构的前提下，显著地改善了Li[Li0.2Mn0.54Ni0.13Co0.13]O2 的电化学性能. 在2.0-4.8 V（vs Li/Li+）的电压范围内，首次放电（0.05C）容量由242.6 mAh·g-1提高到272.4 mAh·g-1，库仑效率由67.6%升高到77.4%；在0.2C倍率下，30 次循环后，Ag/C 包覆的电极材料容量为222.6 mAh·g-1，比未包覆电极材料的容量高出14.45%；包覆后的电极材料在1C下的容量仍为0.05C下的81.3%. 循环伏安及电化学交流阻抗谱研究表明，Ag/C包覆层抑制了材料在充放电过程中氧的损失，有效降低了Li[Li0.2Mn0.54Ni0.13Co0.13]O2颗粒的界面膜电阻与电化学反应电阻.

关键词: 锂离子电池, 固溶体材料, 化学沉积法, 表面改性, 复合包覆

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