OptimizingAnnealing Strategy to Achieve EffectiveGrain Boundary Modification with Aluminum Oxide for Stable CyclingNi-Rich Cathodes

Grain boundary engineering, achieved by combining annealing and surface coating, is an effective strategy for modifying high-nickel-layered oxide cathode materials. However, high-temperature annealing can induce irreversible phase transformations in high-nickel materials, which significantly hinder lithiation/delithiation and degrade their electrochemical performance. In this study, we propose a grain boundary engineering approach for LiNi_0.83Mn_0.05Co_0.12O₂, combining rapid heating to the annealing temperature with atomic layer deposition (ALD) to enhance its electrochemical properties. Compared to conventional heating, the rapid heating process minimizes Li/O loss and prevents the formation of a disordered phase. More importantly, grain boundary modification and bulk gradient doping effectively reduce large cracks and the erosion of the cathode, which slows down the capacity decay during long cycles. The direct heating sample exhibits a significant improvement in capacity retention, and after stable cycling for 300 times at C/3, the capacity retention rate remained at 84.7%. This approach offers a promising low-cost strategy for the development of advanced cathode materials with enhanced cycling stability.