Mechanochemical-assisted carbothermal reduction for recycling spent lithium-ion batteries: a green and economical recycling strategy

Abstract

This work improves the traditional carbothermal reduction reaction (CTR) for recovering spent LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523). The traditional CTR was investigated, revealing that during calcination, graphite reacts starting from its outer surface and gradually moving towards the interior. This requires higher temperatures and sufficient graphite to achieve complete reaction, leading to unnecessary energy consumption and greenhouse gas emissions. To address these two drawbacks, we perform a mechanochemical reaction (MC) prior to calcination, using mechanochemical force to disrupt the NCM523 structure and ensure thorough mixing with graphite. Under the action of H₂O₂, high-valent metals are reduced to low-valent states. This improved process enables full reaction at lower temperatures and with reduced graphite requirements. The optimal conditions are identified through single-factor experiments and response surface experiments, achieving a Li leaching rate of 97.48%. Finally, the feasibility of the process for battery regeneration technology is verified, and the regenerated battery (R-NCM) is restored in all aspects of electrochemical performance compared to the spent battery (S-NCM). Compared to traditional hydrometallurgy and pyrometallurgy, this process is ¥6.942 ($0.9756) per kg cheaper than pyrometallurgy and ¥4.817 ($0.6769) per kg cheaper than hydrometallurgy. This work proposes an environmentally friendly and cost-effective recycling pathway, offering a promising solution for recovering cathode materials from spent lithium-ion batteries.