Sustainable Hydrochloric–Phosphate Acid Leaching Strategy for Selective Lithium Extraction and Direct Recovery of FePO₄·2H₂O from Spent LiFePO₄ Materials

Hydrometallurgy is currently the dominant industrial process for recycling lithium iron phosphate (LFP) batteries. However, this method faces significant challenges, including long processing steps, high reagent consumption, and secondary pollution, which are the primary factors hindering its economic feasibility and large-scale application. This study proposes a novel hydrochloric–phosphate mixed acid leaching system for LFP battery recycling, enabling the simultaneous selective extraction of lithium and the synthesis of battery-grade iron phosphate during the leaching step. Under the optimal conditions, the leaching rate of lithium was 100%, the loss rate of iron was 4.47%, the purity of iron phosphate was 99.96%, and the purity of lithium carbonate was more than 99.5%. The recycled iron phosphate served as an effective precursor for synthesizing high-performance LFP cathode materials, providing a discharge capacity of 169.2 mAh/g at 105 °C and retaining 90.21% capacity after 300 cycles. This innovative process achieves full-element recovery from LFP batteries, eliminates secondary pollution, and greatly simplifies the process steps. We anticipate that this method will advance the sustainable recycling of LFP batteries and contribute to the development of a closed-loop, ecofriendly battery industry.