Improving the reversibility of the H2-H3 phase transitions for layered Ni-rich oxide cathode towards retarded structural transition and enhanced cycle stability

Although the layered Ni-rich LiNi _x Co _y Mn _1-x-y O ₂ (0.7 < x < 1, 0 < y < 0.3) cathode materials are expected to deliver high capacity, their moderate cycle lifetime and thermal stability still hinder practical applications. There's often a tradeoff between high capacity and structure stability since more Li ⁺ ions delithiated during charging will leave the structure of the layered Ni-rich materials more vulnerable. Herein, we propose that improving the reversibility of H2-H3 phase transition for Ni-rich materials is effective to tackle this challenge. It has been confirmed that the generation of microcracks and structural transformations have been suppressed since the H2-H3 phase transition becomes reversible, while which shows little effect on capacity delivery. Consequently, using Ni-rich LiNi _0.9 Co _0.1 O ₂ as the cathode material, the 100 ^th capacity retention cycling at 38 mA g ⁻¹ has been improved remarkably from 69.7% to 97.9% by adopting this strategy. Hence, it should be a novel solution to realize both high capacity and stable cyclability for the Ni-rich cathodes.