In-depth understanding of the deterioration mechanism and modification engineering of high energy density Ni-rich layered lithium transition-metal oxide cathode for lithium-ion batteries

LiNi1_x_yCoxMnyO2/LiNi1_ x_yCoxAlyO2 (NCM/NCA) materials, the high energy density (>300 Wh kg_1) tran-sition metal layered oxide cathode, especially Ni-rich and low-Co materials are promoting the development of electric vehicles, while the poorer electrochemical cycling performance and safety that need to be addressed before dominant in commercialization. Understanding and targeting the bulk phase and interface mechanisms of Ni-rich NCM/NCA materials is the most effective means of solving the failures due to the migration of transition metal ions, the irreversible evolution of the structure within the bulk phase, the cracking and side reactions of particles at the interface of the cathode material. An in-depth explanation of the internal lattice distortion, lithium-nickel mixing, microcracking and oxygen generation mechanisms of high energy density layered oxide cathodes and some targeted component and structure design, interface modification methods are summarized by demonstrating the reaction and evolution mechanisms of NCM/NCA materials, as well as the theoretical calculation and means of in-situ advanced characterization of these deterioration mechanisms. This helps to accelerate the large-scale application and domination of high energy density Ni-rich and low-Co NCM/NCA materials in electric vehicles.