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.