Repairability and Active Defect Utilization in Direct Regeneration of Lithium-Ion Battery Cathodes

Direct regeneration of spent lithium-ion battery (LIB) cathodes has emerged as a promising route toward closed-loop battery recycling. Yet most current approaches are fundamentally based on passive defect repair, focusing on restoring degraded materials to their original state. This review argues that degradation-induced defects should not be viewed solely as damage elimination, but also as structural resources that can be actively exploited to facilitate regeneration and enable materials upgrading. To support this perspective, the concept of repairability is introduced as a descriptor linking failure mechanisms with regeneration feasibility and strategy selection. Multiscale cathode degradation processes are analyzed from the standpoint of repairability, revealing distinct kinetic barriers and regeneration potentials among different chemistries. Regeneration strategies are subsequently reclassified into relithiation, structural restoration, and surface reconstruction, and interpreted within a barrier-engineering framework where the dominant degradation barrier dictates the optimal regeneration pathway. Beyond conventional restoration, emerging approaches that integrate regeneration with structural enhancement-including defect-mediated heteroepitaxy, single-crystal reconstruction, and bulk doping-are highlighted as routes toward cathodes that outperform their pristine counterparts. By shifting the defect repair to defect utilization, this review provides a new framework for understanding, designing, and advancing direct regeneration technologies, ultimately supporting the transition toward a sustainable battery economy.