Review on Oxygen Release Mechanism and Modification Strategy of Nickel-Rich NCM Cathode Materials for Lithium-Ion Batteries: Recent Advances and Future Directions

With the commercialization of lithium-ion battery (LIB) powered electric vehicles, they have been recognized as an important green technology due to the merit of zero CO2 emissions to mitigate global climate change. As for the cathode materials, nickel-rich LiNixCoyMn1-x-yO2 (NCM) stand out due to high energy density. However, key issues of cation migration, phase transition, formation of oxygen vacancies and battery overcharge would cause oxygen release problems when operating at high voltages, which seriously harms battery performance. When applied in large-scale battery packs, the problemes mentioned above of individual cells may affect the overall battery pack due to their close stack. Therefore, study to avoid the phenomenon of oxygen release generation is necessary, while, a systematic summary of its mechanism can help to improve the thermal stability of LIBs. Herein, this review initiates to systematically elucidate the mechanism of oxygen release in nickel-rich NCM followed by further summarizing the effective strategies to deal with the oxygen release phenomenon, and finally give an outlook on the future prospects of nickel-rich NCM.