Tungsten Boride Stabilized Single‐Crystal LiNi 0.83 Co 0.07 Mn 0.1 O 2 Cathode for High Energy Density Lithium‐Ion Batteries: Performance and Mechanisms

Abstract Transition metal doped LiNiO 2 layered compounds have attracted significant interest as cathode materials for lithium‐ion batteries (LIBs) in recent years due to their high energy density. However, a critical issue of LiNiO 2 ‐based cathodes is caused particularly at highly delithiated state by irreversible phase transition, initiation/propagation of cracks, and extensive reactions with electrolyte. Herein, a tungsten boride (WB)‐doped single‐crystalline LiNi 0.83 Co 0.07 Mn 0.1 O 2 (SNCM) cathode is reported that affectively addresses these drawbacks. In situ/ex situ microscopic and spectroscopic evidence that B 3+ enters the bulk of the SNCM, enlarging the interlayer spacing, thus facilitating Li + diffusion, while W 3+ forms an amorphous surface layer consisting of Li x W y O z (LWO) and Li x B y O z (LBO), which aids the construction of a robust cathode‐electrolyte interphase (CEI) film, are shown. It is also shown that WB doping is effective in controlling the degree of the c‐axis contraction and release of oxygen‐containing gases at high voltages. The best doping concentration of WB is 0.6 wt.%, at which the capacity retention rate of the SNCM reaches 93.2% after 200 cycles at 2.7–4.3 V, while the morphology and structure of the material remain largely unchanged. The presented modification strategy offers a new way for the design of new stable SNCM cathodes for high‐energy‐density LIBs.