Revitalizing Retired LiCoO2 Cathodes for High-Voltage Endurance via a One-Step Synergistic Upcycling

Current demands for recycling retired cathode materials and developing high-energy-density lithium-ion batteries inspire the possible conversion of end-of-life LiCoO2 (LCO) streams into next-generation high-voltage cathode materials. In this work, we demonstrate a one-step approach that upcycles degraded LCO materials by synergistically combining Mg/Al dual-doping with Li3PO4 surface engineering for stable high-voltage applications. The product demonstrates exceptional electrochemical performance up to 4.6 V, delivering 211.7 mAh g–1 at 0.1 C with outstanding cycling stability (98.56% and 80.21% capacity retention after 200 and 500 cycles at 1 C, respectively), far exceeding that of commercial LCO material (75.52% after 200 cycles); the superiority stems from the synergistic bulk-surface modification that simultaneously suppresses phase transitions and interfacial degradation during electrochemical operations. This work provides a transformative pathway for unlocking the high-voltage potential of LCO from degraded materials while demonstrating that rational material engineering well aligns environmental sustainability with enhanced electrochemical performance.