Synergistic recycling of spent LiFePO4 batteries with chromium-plating wastewater: a self-sustained approach for selective lithium leaching and dual waste valorization

As the dominant cathode material for power and energy storage systems, lithium iron phosphate (LiFePO₄) batteries hold over 70 % of the market share in China, with spent LiFePO₄ (S-LFP) waste projected to exceed 2 million tons by 2030. However, recycling S-LFP remains challenging due to low economic viability and secondary pollution risks from conventional hydrometallurgical methods. This study introduces an innovative “waste-synergistic” strategy for dual waste valorization, utilizing Cr(VI)-laden electroplating wastewater as a self-sustained lixiviant to achieve selective lithium extraction (92.34 %) from S-LFP cathode and Cr(VI) detoxification (99.11 %). Redox-driven leaching via Fe(II)-Cr(VI) coupling shows low activation energy (17.62 kJ/mol). Resynthesized LiFePO₄ from recycled Li₂CO₃ and FePO₄ exhibits robust electrochemical performance, delivering an initial discharge capacity of 146 mA·h·g⁻¹ at 1C and retaining 95.4 % capacity after 100 cycles. Life-cycle assessment and economic analysis revealed significant reductions in environmental impact, alongside a net profit of US$1.34 per kilogram of processed S-LFP powder. This self-sustained closed-loop approach mitigates environmental hazards from both S-LFP and Cr(VI) effluents while advancing circular economy principles, establishing a scalable and sustainable paradigm for lithium battery recycling.