A novel perspective on behavior and improvement of Li-rich cathodes in commercial pouch cells

Lithium-rich layered cathode material has aroused considerable interest both in scientific and industrial fields owing to their special high capacity. It is generally regarded as a solid solution or as a combination of LiTMO 2 (TM = Ni, Co, Mn, R-3 m ) phase and Li 2 MnO 3 ( C/2 m ) phase. The main challenges are gas generation and voltage fade during cycling. Since the behavior in full battery will be quite different in an easier gas-generating system, in this work, a pouch full battery composed of lithium-rich layered oxides (Li 1.144 Ni 0.136 Co 0.136 Mn 0.544 O 2 ) is prepared. The electrochemical performances are compared with those of coin half-cell. More importantly, gas evolution is visually monitored for the first time. The quantitative analyzation shows that CO 2 accounts for the dominant volume (82%). It is mainly caused by the structural deterioration of thin surface layer and side reaction with electrolyte of cathode materials. Subsequently, surface-modified material and complex electrolyte are introduced, cycle life is significantly improved to 600, and gas evolution is effectively suppressed during early cycling. This work reveals the practical performance of Li-rich cathodes in commercial full battery, which is beneficial to address the vital issues and offer instructions to optimize Li-rich system for an early industrial application.