Enhancing the direct regeneration of spent NCM523 with eutectic molten salt through mechanochemistry-mediated surface restructuring

The widespread use of lithium (Li)-ion batteries (LIBs) with ternary cathodes raises environmental and resource sustainability concerns. Direct regeneration of spent LIBs presents an eco-friendly solution by minimizing energy use, emissions, and waste. Although the molten salt method is highly effective for direct regeneration of spent LIBs, it requires prolonged high-temperature treatment. This study introduces a ball milling-induced surface reconstruction for the eutectic molten salt (LiOH/Na 2 SO 4 ) method to regenerate degraded LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523). High-energy ball milling plays a dual role: (1) improving regeneration efficiency of the spent NCM523 and eliminating defective phases while renewing surfaces through mechanical stress, which accelerates Li + replenishment to cut regeneration time to just 11 hours, (2) acting synergistically with eutectic molten salt as a front-end auxiliary process to restore the performance of spent NCM523. The ball-milled NCM523 exhibits commercial-level electrochemical performance (158.37 mAh/g initial capacity at 0.1C, 93.08% retention after 100 cycles at 0.5C), outperforming non-ball-milled counterparts (73.79% retention) and highlighting the critical role of mechanical pretreatment. This approach enhances surface reconstruction, enabling efficient direct regeneration with reduced energy, water consumption, emissions, and offers scalable, cost-effective LIB recycling, aligning with circular economic principles and advancing sustainable battery regeneration. Graphical abstract Schematic illustration of the underlying mechanism for ball milling-assisted direct regeneration of spent NCM523 cathode materials. • A novel method efficiently regenerates spent battery materials using low-temperature melting salts. • Mechanical pretreatment cuts regeneration time with low energy use while boosting performance. • The regenerated batteries show high capacity and excellent long-term cycling stability. • This eco-friendly process supports circular economy by reducing waste and emissions.