Breaking the Cycle of Heterogeneous Degradation: Surface-Targeted Protection for Ni-Rich Cathodes in Practical High-Energy Batteries

There is a growing awareness of degradation heterogeneity in batteries, but improvement strategies are rarely explored. Here we show that the heterogeneous degradations in high-energy Ni-rich layered oxide batteries are closely related to the initial mechanical damage of the cathode particles induced by the electrode calendering process. We further present a surface-targeted healing (TH) strategy through atomic layer deposition of Al₂O₃ on the most vulnerable near-surface cathode particles. Despite the localized coating, this approach mitigates particle fracture propagation, suppresses layered-to-rock-salt phase transitions, and reduces the level of transition-metal dissolution across the entire electrode. Practical pouch cells with TH-modified cathodes exhibited 78.6% capacity retention after 400 cycles at 55 °C under zero external pressure, outperforming their conventional counterparts (70.6% after 200 cycles). The work demonstrates that electrode-scale postsynthesis modifications, rather than exhaustive particle-level coatings, can effectively address degradation heterogeneity. This strategy opens avenues for designing durable high-energy batteries under aggressive operating conditions.