High Rate Performance of Single-Crystalline NCM Upcycled from Spent Lithium-Ion Batteries Via Direct Recovery and Modification

The global expansion of spent lithium-ion batteries (LIBs) presents both an urgent environmental issue and a significant economic opportunity, driving the development of diverse recycling processes worldwide. Direct regeneration is a promising method for recovering materials from spent LIBs. However, most existing direct regeneration methods focus solely on recovering cathodes without addressing further improvements in their performance. Herein, a direct regeneration method is reported to upcycle single-crystalline lithium nickel manganese cobalt oxides (NCM) from spent polycrystalline NCM based on a facile phosphoric acid etching approach. Moreover, the Li3PO4 coating and PO43- polyanion doping are simultaneously achieved on the surface of single-crystal NCM during the upcycling single-crystalline process. The enlarged lattice spacing and fast ionic conductor coating layer enhance Li+ diffusion and mitigate phase transformations during delithiation/lithiation. Benefiting from the synergistic effect of single crystal structure and surface modification, the upcycled single-crystalline LiNi0.65Co0.2Mn0.15O2 demonstrates excellent electrochemical performances, including large reversible capacity (approximate to 186 mAh g-1 at 0.1C), high-rate capability (approximate to 142 mAh g-1 at 10C), and excellent cycling stability (approximate to 99% retention for 100 cycles). This approach provides a novel and effective upcycling pathway to transform the spent LIBs into value-added cathode materials, achieving a win-win situation for environmental protection and resource conservation.