Highly efficient selective extraction of Li from spent LiNi_xCo_yMn_zO₂ assisted with activated pyrite in a subcritical water system

As the strategic importance of Li in the energy sector increases, selective Li extraction technology from spent lithium-ion batteries (LIBs) is attracting increasing attention. Current Li extraction processes typically suffer from lengthy procedures, high costs, and low efficiency. To improve the efficiency of Li extraction, a novel approach to achieve efficient Li recovery is proposed in this study, namely, reacting pyrite (FeS₂) with LiNi_xCo_yMn_zO₂ (NCM) powder in a subcritical water reduction (SWR) system. The reducing solvent environment created by the enhanced reaction of FeS₂ with subcritical water converts the high−valent metals in NCM to a low-valent state, causing the collapse of the stable laminar structure and allowing Li⁺ to be released smoothly. After dual activation through mechanochemical and roasting processes, more than 99 % of Li is preferentially extracted under optimal conditions. Furthermore, Li⁺ in solution is converted into highly pure Li₂CO₃, while other metallic elements remain in the residue. Using inexpensive FeS₂ for efficient Li extraction without adding additional chemical reagents is a promising approach for recovering spent LIBs.