Direct Recycling of High-Nickel Cathodes from Spent EV Lithium-Ion Batteries: Impact of Pre-treatment Methods

With the rapid increase in the size of the electric vehicle (EV) market, the environmental impact and recyclability of end-of-life lithium-ion batteries (LIBs) have become a serious concern. This has led to a greater focus on the direct recycling of LIB electrodes, which, unlike conventional pyrometallurgical and hydrometallurgical processes used to recover elemental metals, preserves the electrode structure while regenerating degraded active materials. This study systematically investigates the effect of pre-treatment conditions on the regeneration performance of high-nickel Li(Ni_0.82Co_0.12Mn_0.05Al_0.007)O₂ cathode materials recovered from spent EV batteries. Two pre-treatment routes are compared: (1) N-methyl-2-pyrrolidone (NMP) solvent dissolution only and (2) NMP solvent dissolution followed by thermal treatment at 500 ℃. Scanning electron microscopy and X-ray diffraction reveal that thermal treatment effectively removes surface impurities but also induces partial structural degradation and reduces the crystallinity. After solid-state sintering, the regenerated cathode (R-SD-NCM) obtained via NMP solvent dissolution delivers an initial discharge capacity of 186.89 mAh g^{− 1} and superior capacity retention (86.64% after 50 cycles). Furthermore, R-SD-NCM exhibits a lower charge-transfer resistance and maintains a stable layered structure, leading to an enhanced high-rate performance. These results highlight the potential of the proposed eco-friendly and energy-efficient direct recycling-based regeneration process, which minimizes the need for chemical treatment and high-temperature thermal treatment.