Huiping Yang, Zhefei Sun, Yonghui Zhao, Ying Zhang, Zhiyi Sun, Hongling Yi, Huiqun Wang, Yi Mao, Jiayu Li, Wenxing Chen, Jiexi Wang, Shijie Feng, Qinghe Zhao, Yang Cao, Jiajia Han, Qiaobao Zhang, Li Zhang
High-nickel layered positive electrodes suffer from progressive structural degradation arising from lattice oxygen loss and inherent lattice strain. Although surface coatings are widely used to stabilize lattice-oxygen redox and mitigate electro-chemo-mechanical degradation, achieving coatings with full continuity, robust interfacial bonding, and fast Li+ conductivity remains challenging. Herein, we present a fundamentally different approach to shell formation via a self-derived subtractive strategy, departing from the conventional additive-based coating methods. By accurately applying transient thermal pulses, surface lithium is selectively extracted from layered LiNixCoyMn1-x-yO2 (x = 0.8 ~ 0.9), directly converting the outer region into a coherent spinel-phase shell with tunable thickness. This nanoscale spinel-phase skin forms a robust mortise-and-tenon-like interconnection with the layered bulk, enabling isotropic, high-rate Li+ extraction/insertion while maintaining electronic conductivity throughout cycling. It effectively confines active oxygen intermediates, and suppresses interfacial side reactions and strain evolution under high-potential operation. Therefore, the spinel-phase skin-encapsulated LiNi0.8Co0.1Mn0.1O2 achieves an initial Coulombic efficiency of 95.3% and enables pouch cells with 80.1% capacity retention after 2000 cycles at 180 mA g-1. This strategy is extendable to LiNi0.9Co0.05Mn0.05O2, may open new avenues for advancing nickel-rich positive electrode technologies. High-nickel layered positive electrodes suffer from lattice oxygen loss and inherent lattice strain. Here, authors report a self-derived subtractive strategy to form a coherent spinel-phase shell with tunable thickness to confine active oxygen intermediates and suppresses interfacial side reactions.