偏铝酸锂/环化聚丙烯腈共包覆改性高镍层状正极材料的制备

Preparation of modified high‑nickel layered cathode with LiAlO2/cyclopolyacrylonitrile dual‑functional coating

构建表面无机-有机复合包覆层,用于改善高镍层状(NCM811)正极材料结构和界面不稳定问题。复合包覆层由纳米偏铝酸锂(LiAlO_(2),LAO)和环化聚丙烯腈(cPAN)构成。该复合包覆层中LAO是一种典型的锂离子导体,可提供Li^(+)迁移通道;PAN环化后,可产生离域的π键,形成具有电子导电性的cPAN。材料表面复合包覆层的结构及成分研究表明,该复合包覆层均匀分布在NCM811材料表面。半电池测试结果表明,在2.7~4.3 V(vs Li/Li^(+))电压范围内,在180 mA·g^(-1)电流密度下,改性后的NCM811材料循环150周后容量保持率为84.8%。而同样条件下,原始NCM811材料容量保持率为65.5%。该复合包覆层可有效提升NCM811结构和界面稳定性,减少电解液分解,降低界面阻抗。

The structural and interfacial instability of high⁃nickel layered cathode material(NCM811)were improved by the construction of inorganic⁃organic dual⁃coating.The dual⁃coating layer was composed of nano lithi⁃um metaluminate(LiAlO_(2),LAO)and cyclopolyacrylonitrile(cPAN).The LAO is a typical lithium⁃ion conductor,which can be used as a surface coating material to ensure rapid Li^(+)migration at the interface.In addition,the polyac⁃rylonitrile(PAN)undergoes cross⁃linked cyclization reactions,resulting in the formation of a delocalizedπbond and the formation of the cPAN with electronic conductivity after low⁃temperature heat treatment.The structure and composition of the dual⁃coating layer were carefully characterized,which indicates its uniform distribution on the surface of the NCM811 material.The as⁃obtained modified sample showed an electrochemical capacity retention of 84.8%after 150 cycles in the voltage range of 2.7⁃4.3 V(vs Li/Li^(+))at the current density of 1C(180 mA·g^(-1)).Under the same test conditions,the capacity retention of pristine NCM811 was only 65.5%.The dual⁃coating layer can effectively protect the active material and could reduce the electrolyte decomposition on the material surface to a certain extent,leading to a decrease in interfacial impedance.