Direct regeneration and upcycling of spent lithium-ion battery cathodes: Mechanisms and prospects

The rapid increase in end-of-life lithium-ion batteries has made the development of efficient regeneration technologies with low environmental impact a critical challenge for sustainable resource utilization. While traditional pyrometallurgical and hydrometallurgical processes can recover metals, they suffer from high energy consumption, significant pollution, and severe lithium loss. In contrast, the direct regeneration technology avoids decomposing cathode materials and instead regenerates them through structural repair, offering a more environmentally friendly and resource-efficient pathway for battery reclamation. This review first clarifies the urgency of lithium-ion battery regeneration from resource, environmental, and economic perspectives. It then systematically analyzes the failure modes and degradation mechanisms of cathode materials, anode materials, and electrolytes, which has received less systematic attention in previous reviews. Furthermore, based on these failure mechanisms, the reaction principles, advantages, and limitations of various direct regeneration processes are summarized in detail. This review also summarizes recent progress in upcycling spent cathodes into other functional materials, highlighting potential new directions for battery regeneration. Finally, key challenges and future development trends for direct regeneration technologies are outlined. This review aims to provide technical insights and innovative ideas for researchers and industry professionals, helping advance lithium-ion battery regeneration toward a more efficient, low-carbon, and closed-loop system.