Direct regeneration of cathode materials in spent lithium-ion batteries toward closed-loop recycling and sustainability

The transformation of energy structure is deemed as a paramount strategy in accomplishing the ambition of carbon neutrality. Lithium-ion batteries (LIBs), as one of the most exceptional energy storage and conversion devices available, play a pivotal role in this energy revolution. However, due to the extensive production and limited lifespan of LIBs, the retirements of LIBs are set to boom in the coming years. The proper and timely recycling of these batteries are of paramount importance, from both environmental and economic perspectives. Direct cathode regeneration technology is the most promising solution for the treatment of these waste cathodes, as it enables the healing of spent cathodes with minimal energy and chemical consumption, without compromising the original structure of the cathode. Herein, we analyzed the degraded mechanisms of spent LIBs and found that relithiation and defect reparation are crucial steps for the regeneration of spent cathode materials. Various direct regeneration methods previously reported have been summarized, and their respective advantages and limitations as well as technical challenges when implemented into practical industrial applications are discussed. In addition, possible solutions to these problems are proposed, which guide the future direction for the sustainable development of the battery recycling industry.