Improved Electrochemical Performance of LiCoO2 Electrodes with ZnO Coating by Radio Frequency Magnetron Sputtering

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• 作者：Xinyi Dai ; Liping Wang ; Jin Xu ; Ying Wang ; Aijun Zhou ; Jingze Li
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2014
• 出版时间：September 24, 2014
• 年：2014
• 卷：6
• 期：18
• 页码：15853-15859
• 全文大小：492K
• ISSN：1944-8252

文摘

Surface modification of LiCoO₂ is an effective method to improve its energy density and elongate its cycle life in an extended operation voltage window. In this study, ZnO was directly coated on as-prepared LiCoO₂ composite electrodes via radio frequency (RF) magnetron sputtering. ZnO is not only coated on the electrode as thin film but also diffuses through the whole electrode due to the intrinsic porosity of the composite electrode and the high diffusivity of the deposited species. It was found that ZnO coating can significantly improve the cycling performance and the rate capability of the LiCoO₂ electrodes in the voltage range of 3.0鈥?.5 V. The sample with an optimum coating thickness of 17 nm exhibits an initial discharge capacity of 191 mAh g^鈥? at 0.2 C, and the capacity retention is 81% after 200 cycles. It also delivers superior rate performance with a reversible capacity of 106 mAh g^鈥? at 10 C. The enhanced cycling performance and rate capability are attributed to the stabilized phase structure and improved lithium ion diffusion coefficient induced by ZnO coating as evidenced by X-ray diffraction, cyclic voltammetry, respectively.

Keywords:

lithium cobalt oxide; zinc oxide coating; RF magnetron sputtering; structure stability; lithium ion diffusion coefficient