Stabilizing Ni‐Rich LiNi0.92Co0.06Al0.02O2 Cathodes by Boracic Polyanion and Tungsten Cation Co‐Doping for High‐Energy Lithium‐Ion Batteries

Abstract Layered nickel‐rich transition metal oxide has been receiving much attention as high‐energy‐density cathode materials for rechargeable lithium‐ion batteries. However, the severe capacity fading caused by bulk structural degradation of Ni‐rich cathodes during lithiation/delithiation obstructs their commercialization. Herein, we modify the LiNi 0.92 Co 0.06 Al 0.02 O 2 (NCA92) cathode materials by W 6+ cation and BO 3 3− polyanion co‐doping to improve the structural stability and upgrade the electrochemical reversibility. The co‐doped NCA92 materials show remarkably improved cycling stability at 1 C with a capacity retention of 93.4 % after 100 cycles, whereas the pristine cathodes exhibit poor capacity retention of 53.0 % and suffer severe structural deterioration. Further studies reveal that the particle fragmentation resulted from the inherent internal strain and the structural degradation upon cycling can be effectively mitigated by W 6+ cation and BO 3 3− polyanion co‐doping. Besides, W 6+ and BO 3 3− co‐doping could enlarge the interlayer spacing of NCA92, thus increasing lithium‐ion diffusion coefficient, which is conducive to enhancing the rate capability. The present work demonstrates that cationic‐anionic co‐doping is an effective strategy to maintain the structural stability of Ni‐rich cathode materials, and it promotes the development of stable cathode materials for high energy density lithium‐ion batteries.