Reversible Configurations of 3‐Coordinate and 4‐Coordinate Boron Stabilize Ultrahigh‐Ni Cathodes with Superior Cycling Stability for Practical Li‐Ion Batteries

Abstract Ultrahigh‐Ni layered oxide cathodes are the leading candidate for next‐generation high‐energy Li‐ion batteries owing to their cost‐effectiveness and ultrahigh capacity. However, the increased Ni content causes larger volume variations and worse lattice oxygen stability during cycling, resulting in capacity attenuation and kinetics hysteresis. Herein, a Li 2 SiO 3 ‐coated Li(Ni 0.95 Co 0.04 Mn 0.01 ) 0.99 B 0.01 O 2 ultrahigh‐Ni cathode that well‐addresses all the above issues, which is also the first time to realize the real doping of B ions is demonstrated. The as‐obtained cathode delivers a reversible capacity of up to 237.4 mAh g −1 (924 Wh kg −1 cathode ) and a superior capacity retention of 84.2% after 500 cycles at 1C in pouch‐type full‐cells. Advanced characterizations and calculations verify that the boron‐doping is existed in terms of 3‐coordinate and 4‐coordinate configurations and their high electrochemical reversibility during de‐/lithiation, which greatly stabilizes oxygen anions and impedes Ni‐ion migration to Li layer. Furthermore, the B‐doping engineers the primary particle microstructure for better relaxing the lattice strain and accelerating Li‐ion diffusion. This work advances the energy density of cathode materials into the domain of above 900 Wh kg −1 , and the concept will inspire more intensive study on ultrahigh‐Ni cathodes.