Recycling spent lithium-ion batteries (LIBs) is crucial for environmental protection and sustainability. Currently, the main methods for recycling spent LIBs include element extraction and material regeneration. Materials upcycling is a complementary strategy aimed at transforming existing materials into next-generation high-performance materials. This review summarizes recent advancements in upcycling cathode materials from spent LIBs into high-performance cathode. We begin by outlining the development of cathode materials and exploiting how material upcycling can meet the needs of future battery technologies. Next, we introduce the concept and historical evolution of cathode material upcycling and provide a detailed summary of strategies such as doping, coating, and the transformation between different cathode materials. Finally, we discuss the challenges of cathode upcycling and offer guidance for future research directions.

Sodium-ion batteries (SIBs) have been commercialized in 2023 and are expected to capture a substantial market share in the future. However, the material systems in SIBs are very similar to those in lithium-ion batteries (LIBs), which necessitate consideration of recycling in terms of safety issues, environmental concerns, and economic values. In this study, we present the first evaluations of the disassembly of spent commercialized SIBs and the leaching and regeneration of their cathode material (NaNi_1/3Fe_1/3Mn_1/3O₂). We find that pretreatment of SIBs recycling offers advantages, particularly in separating the cathode and removing impurities from the material surface. The primary challenge in recycling is that failed cathode materials are difficult to dissolve in traditional inorganic acids, with an extraction rate of only 57.4% even when a reducing agent is added. Fortunately, there is a possibility for the failed NaNi_1/3Fe_1/3Mn_1/3O₂ regeneration. By replenishing sodium and repairing the structure through thermal treatment, the capacity can be restored to 109.4 mAh g⁻¹, with potential practical applications. Economic analysis indicates that the recycling of spent SIBs through cathode material regeneration results in a profit of ＄3.76 kg⁻¹ battery, even surpassing the ＄2.64 kg⁻¹ battery profit from LIB recycling. We hope that this research will provide a foundation for SIB recycling.