With the increasing demand for higher energy density in lithium-ion batteries (LIBs), designing high-Ni cathodes with maximized Ni content is becoming essential. This pursuit leads to an increase in surface residual Li compounds (Li₂CO₃ and LiOH), triggering notorious issues such as severe side reactions, gas evolution, and the necessity for additional manufacturing processes. However, an understanding of the residual Li chemistry is still lacking. In this study, the presence of residual Li compounds in both the primary and secondary particle levels in conventional polycrystalline high-Ni cathodes was investigated. Residual Li compounds exist in a crystalline phase not only on the surfaces of secondary particles, but also within the intergranular pores between the primary particles. The identification of residual Li implies that designing and controlling the intergranular pores in high-Ni cathodes is necessary. Finally, post-treatment strategies aimed at controlling residual Li compounds in high-Ni cathodes are proposed and the characteristics of each strategy are described.

中文翻译：

---

鉴定锂离子电池高镍正极中残余锂的纳米结构


随着锂离子电池 （LIB） 对更高能量密度的需求不断增长，设计具有最大 Ni 含量的高 Ni 阴极变得至关重要。这种追求导致表面残留的锂化合物（Li₂CO₃ 和 LiOH）的增加，引发了臭名昭著的问题，例如严重的副反应、气体逸出以及需要额外的制造工艺。然而，对残余 Li 化学性质的理解仍然缺乏。在这项研究中，研究了常规多晶高镍阴极中初级和次级颗粒水平中残留的 Li 化合物的存在。残余锂化合物不仅以结晶相形式存在于次级颗粒的表面，还存在于初级颗粒之间的晶间孔隙中。残余 Li 的鉴定意味着设计和控制高 Ni 阴极中的晶间孔隙是必要的。最后，提出了旨在控制高镍正极中残留 Li 化合物的后处理策略，并描述了每种策略的特点。