LiNi0.5Co0.2Mn0.3O2@WO3复合正极材料的制备与性能

为改善LiNi_0.5Co_0.2Mn_0.3O₂（NCM）锂离子电池三元正极材料的电化学性能，采用液相蒸发法将WO₃包覆于NCM表面，得到NCM@WO₃复合正极材料。通过XRD、SEM和TEM对NCM@WO₃复合材料的结构和形貌进行表征，利用充放电测试、循环伏安及交流阻抗测试对其电化学性能进行表征。结果表明，当WO₃包覆量为3wt%时，NCM@WO₃复合材料性能最佳，在0.5 C下的首次放电比容量为179.9 mA·hg-1，不可逆容量损失降低至42.4 mA·hg-1，循环50圈后容量保持率为98.3%。WO₃的包覆提高了锂离子扩散速率，减少了电极材料与电解液的副反应，NCM@WO₃复合材料的电化学性能得到提升。 

Preparation and properties of LiNi0.5Co0.2Mn0.3O2@WO3 composite cathode materials

In order to improve the electrochemical performance of LiNi_0.5Co_0.2Mn_0.3O₂ (NCM), WO₃ coated NCM (NCM@WO₃) composite cathode materials were synthesized with a liquid phase evaporation process. The structure and morphology of the NCM@WO₃ composite were characterized by XRD, SEM and TEM. The electrochemical performance of the NCM@WO₃ composite was characterized by charge-discharge test, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the NCM@WO₃ composite with 3wt% WO₃ has the best performance, it delivers an initial discharge capacity of 179.9 mA·hg-1 with a low irreversible capacity loss of 42.4 mA·hg-1 at 0.5 C, and the capacity retention after 50 cycles is 98.3%. The improved electrochemical properties of the NCM@WO₃ composite are mainly attributed to the WO₃ coating, which improves the lithium ions diffusion rate and suppresses the interface reaction between the cathode and the electrolyte.