Dual‐Phase Engineering Coupled With Valence Gradient and Entropy Assistance Unlocking 4.9 V‐Tolerant Co‐Free High‐Ni Cathodes

ABSTRACT Layered high‐Ni (Ni ≥ 0.9) cathodes are being developed to endure high‐voltage operations above 4.5 V for unlocking unprecedented energy density, but they still suffer from exacerbated chemomechanical and electrochemical degradation primarily due to excessive lattice strain, oxygen loss, and phase distortion during prolonged cycling. Herein, we design a high‐Ni, Co‐free cathode, which features an entropy‐assisted core–shell layered/spinel dual‐phase, coupled with a Ni‐valence gradient framework, via a multi‐component complex doping involved co‐precipitation strategy. The coherent structural ordering from surface spinel phase to bulk layered phase, driven by the Ni‐enriched core/Mn‐enriched shell arrangement, and the entropy‐assistance and valence‐gradient layout, hugely prevents mechanical degradation, surface side‐reactions, and oxygen loss, delivering a pseudo strain‐free cathode. Thanks to these appealing merits, the cathode breaks through current voltage limitations while maintaining an optimal balance between capacity and sustainability, enabling the stable high‐voltage operation up to 4.9 V. Moreover, an exceptional cyclability under strenuous conditions is achieved in practical Ah‐level pouch‐type cells employing graphite and metallic Li anodes, operating at ultrahigh voltages of 4.65 and 4.8 V, respectively. Besides, the oxygen loss‐triggered phase transitions upon heating are markedly delayed. More significantly, our contribution here propels the tremendous advancement of high‐Ni, Co‐free cathodes to the commercializable levels.