锂离子电池正极材料LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2的LaF_3包覆改性研究

Surface Modification of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2 Cathode Materials with LaF_3 for lithium-ion Batteries

通过沉淀法对高镍LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2正极材料进行了LaF_3包覆,采用了X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能谱仪(EDS)、恒流充放电测试和电化学交流阻抗(EIS)对材料的结构、形貌、成分和电化学性能进行了表征,系统的研究了LaF_3包覆对材料的性能影响。结果表明,LaF_3在Li Ni0.6Co0.2Mn0.2O2材料表明形成了均匀的包覆层,LaF_3包覆后未影响主体材料的晶体结构。LaF_3包覆后的材料倍率性能和循环性能均优于未包覆的原材料。在3.0~4.6 V电压范围和170 m A·g-1的电流密度下循环100周后,包覆量为1.0 wt%的材料容量保持率为84.6%,而未包覆的材料容量保持率仅为66.7%。包覆层的存在避免了电解液和主体材料的直接接触,减少了电解液的氧化和HF的腐蚀,稳定了材料的结构,极大的减小了电极极化程度,从而提高了材料的电化学性能。

The LiNi（0.6）Co（0.2）Mn（0.2）O2 cathode material was coated with LaF3 by precipitation method.X-ray diffraction（XRD）, scanning electron microscopy（SEM）, X-ray energy dispersive spectroscopy（EDS）, electrochemical impedance spectroscopy（EIS） and galvanostatic charge-discharge test were used.The structure, morphology, composition and electrochemical properties of the as-prepared materials were characterized by testing.The results show that the LaF3 does not affect the crystal structure of the host material.It shows that a uniform coating layer is formed on the Li Ni0.6 Co0.2 Mn0.2 O2 material, and the rate capability and cycle performance of the coated material are better than raw materials.In the voltage range of 3.0-4.6 V and the current density of 170 m A·g-1, the capacity retention rate of the Li Ni0.6 Co0.2 Mn0.2 O2 material coated with 1.0 wt% LaF3 is 84.66 % after 100 cycle, while the capacity retention of the raw material is only 66.77 %. The existence of the coating layer avoids the direct contact between the electrolyte and the host material, reduces the oxidation of the electrolyte and the corrosion of the HF, greatly reduces the polarization of the electrode, and effectively improves the electrochemical performance of the material.