Achievable Surface–Bulk Structure Dual Reinforced by Room-Temperature Al-Induced Engineering Enables Stable Battery Cycling of 4.6 V LiCoO₂

The LiCoO2 cathode cannot maintain stable battery cycling under high voltage, as the undesired release of lattice O and harmful surface side reactions compromise its structural stability, resulting in battery capacity degradation. Herein, inspired by architectural engineering, we proposed a surface–bulk structure dual-reinforced strategy to tackle the aforementioned challenges by room-temperature Al-induced engineering, which could achieve surface disordering and phosphating and bulk gradient Ni doping of the LiCoO2 cathode. Such a multifunctional structure could delay the detrimental transition, restrain lattice O loss, reduce harmful surface side reactions, and form a phosphate-rich CEI with high ionic conductivity and stability. The as-prepared modified LiCoO2 as the cathode in lithium-ion batteries displayed remarkably enhanced cycle stability than bare LiCoO2 (91.9% vs 45.3% after 100 cycles in 3.0–4.6 V at a current density of 1 C). Even at a 5 C high rate, the modified LiCoO2 cathode also displayed superb battery cycling (92% after 100 cycles at 3.0–4.6 V). This room-temperature Al-induced engineering is universal to other layered cathode materials.