Epitaxially Grown Lattice‐Coherent Surface Enabling Superior Mechanical Integrity for High‐Voltage LiCoO2 Cathode

The growing demand for high‐energy‐density cathode is pushing LiCoO2 towards 4.6 V operation. However, the structural and interfacial instability of high‐voltage LiCoO2 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 LiCoO2 surface, which enhances the intrinsic mechanical integrity of high‐voltage LiCoO2. Through establishing the lattice‐coherent Li‐rich surface, adverse side reactions, irreversible phase transition and lattice oxygen loss are significantly inhibited in high‐voltage LiCoO2, thereby alleviating cracks formation and maintaining the structural integrity. The presence of the Li‐rich phase endows LiCoO2 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 LiCoO2.