Fig. 1: Schematic of recycling strategy.

Schematic of the additive strategy for the direct recycling (A− to A)/upcycling (A− to A+) of spent cathode materials and the subtractive strategy for transforming different spent cathode materials to high-performance cathode materials (A & B to X). The working principle of the additive strategy relies on the lithium supplementation reaction during a high-temperature process, delivering a single type of regenerated cathode material. In contrast, the subtractive strategy makes the upcycling of complex solid waste towards a next-generation low-Co 5 V-class cathode material, an alternative idea for the sustainable use of resources.