表面化学侵蚀改性富锂层状正极材料Li[Li0.2Mn0.54Ni0.13Co0.13]O2

采用3种不同pH值的去离子水，NH₄NO₃和H₂C₂O₄溶液对富锂层状正极材料LiLi_0.2Mn_0.54Ni_0.13Co_0.13]O₂进行表面化学侵蚀改性，旨在改善其整体电化学性能。ICP结果表明pH值对材料中Li的析出具有显著影响。X射线衍射（XRD）表明表面化学侵蚀对材料的结构有影响。拉曼光谱（Raman spectroscopy）表明材料表面结构发生了变化。H₂C₂O₄溶液侵蚀过的样品的首次效率有了极大提高，但同时中值电压和循环性能显著恶化。NH₄NO₃溶液侵蚀过的样品的首次效率从63%提高到了85%，1C倍率下的放电比容量从149 mAh·g^-1提高到194 mAh·g^-1，同时保持了温和的中值电压变化曲线。通过高分辨透射电镜（HRTEM），X射线光电子能谱（XPS）和电化学阻抗谱（EIS）对改性机理进行了研究。

Surface Modification by Chemical Leaching of Over-Lithiuated Cathode Material Li[Li0.2Mn0.54Ni0.13Co0.13]O2

With a purpose to improve the comprehensive electrochemical performance of over-lithiuated cathode material, surface modification was adopted using three solutions with specific pH value, including deionized water, NH₄NO₃ and H₂C₂O₄. The structure, morphology and electrochemical performance of the samples were extensively studied. ICP results show pH value has significant effect on the extraction of Li element in the materials. XRD demonstrates that the structure of the pretreated samples changed compared with the pristine sample. Raman Spectroscopy detects structural changes on the sample surface. The initial efficiency of H₂C₂O₄ treated sample is improved greatly but its mean voltage and cyclability is deteriorated simultaneously. The NH₄NO₃ treated sample shows the optimal comprehensive performance. Compared to the pristine sample, its initial coulombic efficiency is improved from 63% to 85% and capacity at 1C is enhanced from 149 to 194 mAh·g^-1 while maintaining a mild mean voltage decay rate. The improvement mechanism has been investigated by high resolution transmission electron microscopy (HRTEM), X-ray Photoelectron Spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS).