Electrothermal Coupling Enables Defect-Targeted Topological Repair for Rapid Graphite Upcycling

Spent graphite (SG) from end-of-life lithium-ion batteries suffers from persistent structural disorder, yet the defect chemistry governing its regeneration remains poorly understood. Here, we identify carbon vacancies and quasi-sp³ topological defects as the dominant degradation motifs and leverage this insight to devise a defect-targeted regeneration strategy. Under electrothermal coupling enabled by flash Joule heating in a CoCl₂ molten-salt medium, cobalt species are selectively directed to defect sites, where strong Co-defect interactions reduce the energy barrier for topological reconstruction. The resulting Co-induced charge redistribution activates quasi-sp³ -carbon via population of π^* antibonding states, while thermally assisted and field-directed carbon migration promotes its conversion into a more ordered sp²-rich lattice. Concurrently, residual interphases and impurities are eliminated, lattice stress is relieved, and the cobalt catalyst is efficiently recovered. The regenerated graphite (RG) delivers a capacity of 257 mAh g⁻¹ after 1000 cycles at 1 A g⁻¹, corresponding to 83% retention relative to the post-activation capacity, and outperforms commercial graphite under identical conditions. This work establishes a chemically informed route for the rapid upcycling of SG through defect-selective topological repair.