Hybrid Surface Modification and Bulk Doping Enable Spent LiCoO Cathodes for High-Voltage Operation.

The emerging market demand for high-energy-density of energy storage devices is pushing the disposal of end-of-life LiCoO (LCO) to shift toward sustainable upgrading into structurally stable high-voltage cathode materials. Herein, an integrated bulk and surface commodification strategy is proposed to render spent LCO (S-LCO) to operate at high voltages, involving bulk Mn doping, near surface P gradient doping, and LiPO/CoP (LPO/CP) coating on the LCO surface to yield upcycled LCO (defined as MP-LCO@LPO/CP). Benefiting from hybrid surface coating with Li-conductive LiPO (LPO) and electron conductive CoP (CP) coupled with Mn and P co-doping, the optimized MP-LCO@LPO/CP cathode exhibits enhanced high-voltage performance, delivering an initial discharge capacity of 218.8 mAh g at 0.2 C with excellent capacity retention of 80.9% (0.5 C) after 200 cycles at a cut-off voltage of 4.6 V, along with 96.3% of capacity retention over 100 cycles at 4.5 V. These findings may afford meaningful construction for the upcycling of commercial S-LCO into next-generation upmarket cathode materials through the elaborate surface and bulk modification design.