Direct regeneration of cathode materials from spent lithium-ion batteries using ternary lithium molten salt

Abstract

The recycling of spent lithium-ion batteries (LIBs) is critical for alleviating resource scarcity and mitigating environmental pollution. While the current industrial approaches primarily rely on pyrometallurgy and hydrometallurgy, these methods exhibit inherent limitations. In recent years, new ideas for direct repair and regeneration of spent LiNi_xCo_yMn_zO₂ (SNCM) cathode materials have emerged. Through innovative processes, the lithium ion (Li⁺) is added to SNCM cathode materials, so that the performance of SNCM cathode materials were restored and the “secondary life” of SNCM cathode materials were realized. In this work, we propose a new method for SNCM cathode materials based on a ternary lithium molten salt (TLMS) system. Combined with FactSage software, the phase diagrams of Li₂CO₃-LiNO₃, Li₂SO₄-LiNO₃ and Li₂SO₄-Li₂CO₃ systems were constructed to reveal the synergistic effect of lithium salts at high temperature, and the optimal repair temperature and ternary molten salt ratio were determined. The characterization showed that MR-NCM-60 % showed a single lattice fringe after repair, the I ₍₀₀₃₎/I₍₁₀₄₎ ratio reached the peak and the Mn³⁺ content decreased significantly, confirming the reverse transformation of the rock salt/spinel phase to the layered structure. Electrochemical tests show that MR-NCM-60 % retained a discharge capacity of 93.78 mAh g^-1 after 200 cycles at 0.2 C, and the rate performance is the best, which is attributed to the inhibition of Li/Ni cation mixing and the improvement of structural stability. This study provides a new idea for the repair and regeneration of SNCM cathode materials.