Epitaxially Grown Lattice‐Coherent Surface Enabling Superior Mechanical Integrity for High‐Voltage LiCoO 2 Cathode

Abstract The growing demand for high‐energy‐density cathode is pushing LiCoO 2 towards 4.6 V operation. However, the structural and interfacial instability of high‐voltage LiCoO 2 is exacerbated when the charging cut‐off voltage exceeds 4.55 V, resulting in severe mechanical failure and subsequent dramatic capacity decay. Herein, through thermally driven element interdiffusion, a highly durable Co‐containing Li‐rich phase with the lattice coherence has been epitaxially grown along LiCoO 2 surface, which enhances the intrinsic mechanical integrity of high‐voltage LiCoO 2 . Through establishing the lattice‐coherent Li‐rich surface, adverse side reactions, irreversible phase transition and lattice oxygen loss are significantly inhibited in high‐voltage LiCoO 2 , thereby alleviating cracks formation and maintaining the structural integrity. The presence of the Li‐rich phase endows LiCoO 2 with the additional capacity and the excellent cycling stability at 4.6 V and even at 4.7 V. This work taps into a new avenue of surface engineering on high‐voltage LiCoO 2 .