High-Efficiency Recovery of Waste Graphite Anodes Using Molten Salts: Microstructural Evolution and Electrochemical Performance

Abstract

The rapid growth of lithium-ion battery (LIB) production has led to increasing volumes of end-of-life batteries containing hazardous electrolytes and metal residues, underscoring the urgent need for efficient recycling strategies. While cathode recovery has been widely studied, the regeneration of spent graphite anodes remains underexplored despite rising global demand for battery-grade graphite. In this work, two molten salt treatments, NaOH and a LiCl–KCl eutectic, were evaluated for their effectiveness in reactivating waste graphite (WG). Structural analyses revealed that both treatments increased the interlayer spacing from 3.3533 A˚ to 3.3632–3.3657 A˚ and reduced surface defects, with the LiCl–KCl melt achieving the highest degree of graphitization. Electrochemical testing demonstrated substantial performance enhancements. The regenerated samples delivered reversible capacities of 334.4 mAh g-1 and 423.6 mAh g-1, far exceeding that of 227.0 mAh g-1 for untreated WG, with capacity retention above 90% after 50 cycles. Impedance and cyclic voltammetry analyses further confirmed reduced charge transfer resistance, more stable solid electrolyte interphase formation, and accelerated lithium-ion transport in molten salt-treated graphite. Overall, molten salt regeneration, particularly with LiCl–KCl, offered a promising, high-efficiency route for restoring waste graphite to battery-grade quality, supporting sustainable LIBs recycling and circular material utilization.