Photovoltaic-Coupled Electrocatalysis System for On-Site Persulfate Generation and Sustainable Lithium Extraction.

The ever-increasing global demand for lithium-based energy storage requires green, economically viable strategies for the recovery of critical metals. Here, we report a photovoltaic-coupled electrocatalytic (PV-EC) system for efficient lithium recovery from spent LiFePO4 (LFP) cathodes by on-site electrochemical generation of persulfate (S2O82-) at a Ti/SnO2/PbO2 anode. Under optimal conditions, we achieved 100% lithium leaching efficiency in the two-electrode system in the laboratory. Mechanistic analysis reveals a tripartite, synergistic oxidation pathway: the electrocatalytically generated sulfate (SO4•-) and hydroxyl (•OH) radicals work in concert with direct electrode oxidation to facilitate a rapid LiFePO4-to-FePO4 phase transition, thereby ensuring preferential lithium leaching. Furthermore, we construct a PV-driven PV-EC system under outdoor conditions, and the system achieves a lithium leaching efficiency of 99.34% in 160 min with minimal iron dissolution, yielding recovered Li3PO4 product with a purity of 95.64%. A techno-economic assessment based on experimental conditions indicates a potential net profit of 1219.66 USD per ton of processed LFP material. The PV-EC system developed here for on-site persulfate generation and lithium leaching offers a feasible, green-chemistry approach for effective critical metal recovery from spent LFP cathodes, with potential extension to other urban mines and mineral tailings.