Advanced Solid-State Electrolysis for Green and Efficient Spent LiFePO4 Cathode Material Recycling: Prototype Reactor Tests

Spent lithium iron phosphate (LFP) battery recycling has to avoid excessive reagent cost and secondary pollution, such as waste acid. This research proposed a solid-state electrolysis method to reduce reagent cost and wastewater amount. This method was similar to the discharge mechanism of the lithium-ion battery, which innovatively adopted solid-state electrode reactions to leach Li and Fe into the phosphoric acid electrolyte. Meanwhile, several key performance indicators of such electrolyzers were evaluated. The time-space yield of the solid-state electrodes reached 108.17 g m(-2) h(-1). The leaching efficiency of Li and Fe reached 98.23 and 96.06%, respectively, with electric energy consumption of only 578.15 kW h per ton spent LFP cathode materials. The apparent leaching kinetics analysis determined the control step of the Li and Fe leaching process. The recovery rates of Li and Fe were 93.51 and 97.96%, respectively. Battery-grade FePO4 and Li3PO4 products were derived, which were directly employed for LiFePO4 reproduction. With further evaporation to prepare NH4H2PO4, there was no waste water in all processes of this novel recycling method. This study demonstrates the possibility of green and efficient spent LFP recovery and contributes to environmental protection and sustainable development of resources.