Upcycling of Cathode Materials from Spent Lithium-Ion Batteries: Progress, Challenges, and Outlook

With the growing popularity of electronic devices and electric vehicles, the number of spent lithium-ion batteries (LIBs) is increasing dramatically. It is a promising and sustainable strategy to recycle transition metal resources from cathodes of spent LIBs to prepare functional materials for energy storage and conversion systems. This review summarizes the recycling and upcycling of cathode materials from spent LIBs, especially the upcycling, an alternative route to direct regeneration. Multicomponent transition metal-based materials are reported to be promising effective catalysts with the merits of good electrochemical reactivity and excellent stability. The regeneration of metal-based materials from spent cathodes for catalysts are summarized, with an emphasis on oxygen evolution reaction (OER) catalysts for water-splitting and oxygen reduction reaction (ORR)/OER bifunctional catalysts for Zn-air batteries. Subsequently, we review in detail the upcycling of valuable components from spent cathodes to prepare electrode materials for supercapacitors. Finally, it concludes with challenges and an outlook to ensure long-term sustainability of battery industry.