Study on the Surface Modification of Regenerated and Repaired LiNi0.5Co0.2Mn0.3O2 Single Crystal

Abstract

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.