Stabilization of high-voltage layered oxide cathode by utilizing residual lithium to form NASICON-type nanoscale functional coating

High-voltage medium-nickel low-cobalt lithium layered oxide cathode materials are becoming a popular development route for high-energy lithium-ion batteries due to their relatively high capacity, low cost, and improved safety. Unfortunately, capacity fading derived from surface lithium residue, electrode-electrolyte interfacial side reactions, and bulk structure degradation severely limits large-scale commercial utilization. In this work, an ultrathin and uniform NASICON-type Li3V2(PO4)(3) (LVP) nanoscale functional coating is formed in situ by utilizing residual lithium to enhance the lithium storage performance of LiNi0.6Co0.05Mn0.35O2 (NCM) cathode. The GITT and ex-situ EIS and XPS demonstrate exceptional Li+ diffusion and conductivity and attenuated interfacial side reactions, improving the electrode-electrolyte interface stability. The variable temperature in-situ XRD demonstrates delayed phase transition temperature to improve thermal stability. The battery in-situ XRD displays the single-phase H1-H2 reaction and weakened harmful H3 phase transition, minimizing the bulk mechanical degradation. These improvements are attributed to the removal of surface residual lithium and the formation of NASICON-type Li3V2(PO4)(3) functional coatings with stable structure and high ionic and electronic conductivity. Consequently, the obtained NCM@LVP delivers a higher capacity retention rate (97.1% vs. 79.6%) after 150 cycles and a superior rate capacity (87 mAh.g(-1) vs. 58 mAh.g(-1)) at a 5 C current density than the pristine NCM under a high cut-off voltage of 4.5 V. This work suggests a clever way to utilize residual lithium to form functional coatings in situ to improve the lithium storage performance of high-voltage medium-nickel low-cobalt cathode materials.

Automated summary

This study utilizes residual lithium to form nanoscale functional coatings in situ, addressing the performance issues of high-voltage medium-nickel low-cobalt lithium-ion batteries, including capacity fading, electrode-electrolyte interfacial side reactions, and bulk structure degradation. By optimizing the stability of the interface between electrolyte and electrode, improving the thermal stability and ion conductivity of the battery, better cycling stability and rate capacity were achieved.