Selective recovery of Li and FePO4 from spent LiFePO4 cathode scraps by organic acids and the properties of the regenerated LiFePO4

Abstract

To recycle the sharply growing spent lithium-ion batteries and alleviate concerns over shortages of resources, particularly Li, is still an urgent issue. In this work, an organic acids based leaching approach at room temperature is proposed to recover Li and FePO4 from spent LiFePO4 cathode powder. The coexistent metal ions, Cu and Al, have also been investigated. Citrus fruit juices, rich in organic acids, such as citric acid and malic acid, have been used as leaching agents in this work. Among lemon, orange and apple, lemon juice shows the best leaching effect based on its suitable pH of the reaction system. Under the optimized conditions, the leaching rates of Li, Cu and Al can reach up to 94.83%, 96.92% and 47.24%, while Fe and P remain as low as 4.05% and 0.84%, respectively. Li2CO3 and FePO4 can be recovered from the leachate and the leaching residue, respectively. The recovered FePO4 was used to prepare new cathode material LiFePO4. The crystalline carbon, present in the spent LiFePO4 cathode scraps, has a significant effect on the electrochemical performances of the regenerated LiFePO4. The regenerated LiFePO4 cathode material delivered a comparable discharge capacity of 155.3 mAh g−1 at 0.1C and rate capacity to the fresh LiFePO4. For the cycling stability, it displays capacity retention of 98.30% over 100 cycles at 1 C with a fading rate of 0.017% per cycle. The proposed organic acids-based recycling strategy is much benign for recycling the spent LiFePO4 cathode materials.