Research progress on green recycling technologies for lithium-ion batteries based on molten salt methods

Abstract

The rapid increase in spent lithium-ion batteries (LIBs) has created an urgent demand for recycling technologies that can achieve efficient resource recovery, material regeneration, and reduced environmental impacts. Molten salt methods have attracted increasing attention because of their high ionic conductivity, favorable thermal stability, dissolution capability, and tunable chemical reactivity. This review summarizes the classification and physicochemical characteristics of molten salt systems and systematically examines their applications in spent LIB recycling, including pretreatment, cathode regeneration, anode graphite recovery, molten salt electrochemical recovery, and high-value material conversion. Particular attention is given to the relationships among material degradation characteristics, molten salt functions, and regeneration behavior in representative cathode systems, including LiCoO 2 (LCO), LiFePO 4 (LFP), LiNi x Co y Mn z O 2 (NCM), and LiNi x Co y Al z O 2 (NCA). The roles of molten salts in lithium replenishment, ion transport, redox regulation, defect repair, structural reconstruction, and selective component recovery are comparatively discussed. In addition, techno-economic performance and environmental impacts are evaluated to examine the practical feasibility of different recycling routes. Overall, molten salt methods provide a versatile platform that connects material separation, direct regeneration, selective recovery, and value-added reutilization; however, their broader application is still constrained by molten salt recycling and purification, complex-feedstock adaptability, equipment corrosion, process integration, and limited scale-up validation.