锂层状氧化物LiNi_0.6Co_0.2Mn_0.2O₂（NCM622）是电动汽车高能锂离子电池中最有前途的正极材料之一。然而，目前NCM622的一个问题是其初始库仑效率（ICE）只有约87%，比LiCoO₂或LiFePO₄至少低6%。在本工作中，我们研究了在烧结过程中形成的表面化学残留物（如LiOH和Li₂CO₃）和Li/Ni阳离子混排对ICE的影响。结果表明，当烧结温度从825 ^oC提高到900 ^oC时，样品的ICE从80.80%提高到86.68%，而相应的Li/Ni阳离子混排和表面化学残留物也有所减少。进一步地，我们使用HNO₃溶液洗涤去除825 ^oC烧结后的样品的表面残留物，发现尽管Li/Ni阳离子紊乱有所增加，但ICE提高3.57%。这些结果表明，通过适当的烧结工艺和后处理技术将表面残留量和Li/Ni阳离子混排降至最低是获得高ICE并改善NCM622电化学性能的关键。

Lithium layered oxide LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) is one of the most promising cathode materials in high-energy lithium-ion batteries for electric vehicles. However, one drawback for NCM622 is that its initial coulombic efficiency (ICE) is only about 87%, which is at least 6% lower than that of LiCoO₂ or LiFePO₄. In this work, we investigated the effects of surface chemical residues (e.g., LiOH and Li₂CO₃) and Li/Ni cation disorder resulted during the sintering on the ICE. We found that the ICE of the as-prepared samples could be boosted from 80.80% to 86.68% as the sintering temperatures were increased from 825 to 900 ^oC. The corresponding Li/Ni cation disorder and surface chemical residues were also reduced with the increasing sintering temperatures. Furthermore, the ICE of the sample sintered at 825 ^oC could be enhanced by 3.57% after washing with HNO₃ solution to remove the surface residues despite the Li/Ni cation disorder being increased. These results demonstrate that minimizing the amount of surface residuals and the degree of Li/Ni cation disorder through an appropriate sintering process and post-treatment technology is critical to achieve a high ICE and improve the electrochemical performances of NCM622.