Suppressed Lattice Oxygen Release via Ni/Mn Doping from Spent LiNi0.5Mn0.3Co0.2O₂ toward High-Energy Layered-Oxide Cathodes

LiCoO 2 has suffered from poor stability under high voltage as a result of insufficient Co–O bonding that causes lattice oxygen release and lattice distortions. Herein, we fabricated a high-voltage LiCoO 2 at 4.6 V by doping with Ni/Mn atoms, which are obtained from spent LiNi 0.5 Mn 0.3 Co 0.2 O 2 cathode materials. The as-prepared high-voltage LiCoO 2 with Ni/Mn substitutional dopants in the Co layer enhances Co–O bonding that suppresses oxygen release and harmful phase transformation during delithiation, thus stabilizing the layered structure and leading to a superior electrochemical performance at 4.6 V. The pouch cell of modified LiCoO 2 exhibits a capacity retention of 85.1% over 100 cycles at 4.5 V (vs graphite). We found that our strategy is applicable for degraded LiCoO 2, and the regenerated LiCoO 2 using this strategy exhibits excellent capacity retention (84.1%, 100 cycles) at 4.6 V. Our strategy paves the way for the direct conversion of spent batteries into high-energy-density batteries.