Due to the relatively small particle size of single crystals, the high specific surface area increases the side reactions between the electrode and the electrolyte. Without proper surface modification, single-crystal particles tend to interact directly with the electrolyte, leading to side reactions that impair the electrochemical performance of the material. To address this issue, constructing a coating layer on the material's surface is one effective solution. In this study, a wet-coating technique was employed to co-coat single-crystal LiNi_0.5Co_0.2Mn_0.3O₂ cathode material with vanadium (V) and samarium (Sm). SEM and TEM tests revealed the presence of a V-Sm coating layer with a thickness of approximately 1-3 nm on the surface of the coated samples. The coated material demonstrated a capacity retention rate of 86.5% after 450 cycles at a 1 C rate (1 C=160 mAh·g^-1), which represents an improvement of about 6.7% compared to the original material. EIS results indicated that the V-Sm coating stabilized the surface SEI film of the material and inhibited the growth of charge transfer resistance (Rct). XPS analysis of the electrodes after cycling showed that the V-Sm coating effectively protected the material by isolating it from direct contact with the electrolyte, suppressing the decomposition of the electrolyte during cycling, and reducing adverse side reactions between the material and the electrolyte, thereby enhancing the overall electrochemical performance of the material.

中文翻译：

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再生修复LiNi0.5Co0.2Mn0.3O2单晶表面改性研究


由于单晶的粒径相对较小，高比表面积增加了电极和电解质之间的副反应。如果没有适当的表面改性，单晶颗粒往往会直接与电解质相互作用，导致副反应，从而损害材料的电化学性能。为了解决这个问题，在材料表面构建涂层是一种有效的解决方案。在本研究中，采用湿法涂层技术将单晶 LiNi_0.5Co_0.2Mn_0.3O₂ 正极材料与钒 （V） 和钐 （Sm） 共涂。SEM 和 TEM 测试显示，涂层样品表面存在厚度约为 1-3nm 的 V-Sm 涂层。涂层材料在 1C 速率 （1C=160 mAh·^g-1） 下循环 450 次后，容量保持率为 86.5%，与原始材料相比提高了约 6.7%。EIS 结果表明，V-Sm 涂层稳定了材料的表面 SEI 膜并抑制了电荷转移电阻 （Rct） 的增长。循环后电极的 XPS 分析表明，V-Sm 涂层通过隔离材料与电解质直接接触，抑制电解质在循环过程中的分解，减少材料与电解质之间的不良副反应，从而增强材料的整体电化学性能，从而有效地保护材料。