The tremendous consumption of lithium-ion batteries (LIBs) raises concern about sustainable resources especially for the valuable metals. Recycling valuable metals from spent LIBs is expected to meet the demand growth of LIBs. Herein, a novel approach combined with oxalic acid leaching, calcination relithiation, and annealing is proposed to regenerate spent LiNi0.5Co0.2Mn0.3O2 (NCM523) cathodes. This approach can reduce the recycling cost, accompanied with small energy consumption. Moreover, almost 98% of the valuable metals (Ni, Co, Mn) can be directly regenerated. The regenerated NCM523 cathode exhibits an initial capacity of 146.1 mAh g–1, with ∼85% capacity retention after 100 cycles. This work not only provides an efficient and simple method for recycling spent cathodes but also gives a new perspective of sustainable manufacturing of energy materials.

The conventional lithium-ion battery technology relies on the liquid carbonate-based electrolyte solution, which causes excessive side reactions, serious risk of electrolyte leakage, high flammability, and significant safety hazards. In this work, phosphonate-functionalized imidazolium ionic liquid (PFIL) is synthesized and used as a gel polymer electrolyte (GPE) to replace the organic carbonate-based electrolyte solution. The as-prepared ionic liquid-based gel polymer electrolyte (IL-GPE) shows low crystallinity, flame retardance, and excellent electrochemical performance. Thanks to the fast double channel transport of lithium ions in the IL-GPE electrolyte, a high ionic conductivity of 0.48 mS cm −1 and a lithium-ion transference number of 0.37 are exhibited. Symmetrical lithium cells with IL-GPE retain stable cycling even after 3000 h under 0.1 mA cm −2 . IL-GPE exhibits good compatibility toward lithium metal, yielding excellent long-term electrochemical kinetic stability. IL-GPE induces the formation of a uniform and robust SEI layer, inhibiting the growth of lithium dendrites and improving the rate performance and cycle stability. Furthermore, Li/LiFePO 4 cells exhibit a specific capacity of 63 mA h g −1 after 150 cycles at 5.0 C, with a capacity retention of 90.2%. It is foreseen that this GPE is a promising candidate to enhance the safety of high-performance lithium metal batteries.