Enhancing the overcharged performance of Li(Ni_0.8Co_0.15Al_0.05)O₂ electrodes by CeO₂-Al₂O₃ surface coating

The nickel-rich cathode materials (LiNi_0.8Co_0.15Al_0.05O₂, NCAs) in Lithium ion batteries often suffer from oxygen loss problems under partially overcharged conditions (>4.3 V), leading to capacity fading and safety problem. Herein, we utilize a facile ball-milling method to coat the NCAs with a shell of cerium aluminum composite oxide (CeO₂-Al₂O₃), which is commonly used as oxygen storage material. Proved by in situ X-ray diffraction results, the coating CeO₂-Al₂O₃ layer is capable to suppress the lattice volume change and irreversible phase transition of NCAs. The CeO₂-Al₂O₃ coating layer can adsorb released oxygen under overcharged conditions and replenish lattice oxygen of NCAs under oxygen-leaned conditions. The protective layer can also prevent dissolution of the transition metals caused by HF attack in electrolytes. As a result, the as prepared electrode presents high specific capacity of 186.4 mA h g⁻¹ and excellent cycle stability with capacity retention of 94.1% after 300 cycles at a rate of 0.5 C under overcharged conditions (3.0–4.5 V). Coating CeO₂-Al₂O₃ is an efficient strategy to solve capacity fading problem and safety problem caused by partially overcharge, and such strategy shows significant promise for practical applications.