Low-Voltage Suspension Electrolysis Enables Redox Coupled Synergistic Leaching for Closed Loop Recycling of Mixed NCM-LFP Cathodes

Abstract

The rapid growth of spent lithium-ion batteries (LIBs) has created an urgent need for efficient and environmentally safe recycling technologies, particularly for mixed cathode materials. In this study, a low voltage suspension electrolysis enhanced synergistic leaching process was developed to overcome the low synergy efficiency and limited throughput that restrict conventional electrochemical leaching methods for spent LIBs. Under mild conditions of 40 ℃ and 1.2 V, the process achieves a high throughput of 40 g·L-1 (25 mL·g-1) without gas evolution side reactions, and the leaching efficiencies of Li, Ni, Co, Mn, and Fe all exceed 98% without the use of reductants. Kinetic analysis demonstrates that the leaching follows a shrinking core model, with Li dissolution controlled by surface reactions, Ni and Co by mixed control, and Mn and Fe by chemical reactions. Mechanism studies reveal that Fe ion mediated electron transfer is the primary driver of redox coupling, that 1.2 V lies near the critical transition region of competing electrode processes, and that Mn undergoes unique intra-crystalline migration during NCM leaching, which accelerates particle dissipation. High purity FePO4, NCM precursor, and Li2CO3 were recovered from the leachate, and regenerated NCM and LFP exhibited good electrochemical performance. Full reagent recovery, the absence of secondary pollution, an estimated profit of of 3.1 $/kg and the DC electrolysis power consumption of 0.006 kW·h·kg-1black powder, demonstrate strong industrial feasibility. This work provides an efficient, low cost, and environmentally responsible route for the resource closed-loop recovery of spent lithium-ion batteries and advances the mechanistic understanding of leaching systems.