A green and effective room-temperature recycling process of LiFePO₄ cathode materials for lithium-ion batteries

Nowadays LiFePO₄ cathode develops rapidly for its advantages of long life span, low cost and non-toxicity, especially in electrical vehicle markets. Because of its stable olivine structure, LiFePO₄ is difficult to be recycled by the conventional hydrometallurgical processes as for LiCoO₂ or LiNi_xCo_yMn_zO₂. Pyrometallurgical processes consume much energy and release toxic gases. Herein, an effective room-temperature process based on the mechanochemical treatment is proposed to extract metals from LiFePO₄. Spent LiFePO₄ is co-grinded with low-cost citric acid agent in a ball mill. After grinding, the mixture is dissolved in deionized water and filtrated. With addition of H₂O₂, the extraction efficiency of Li reaches as high as 99.35%. Conversely, Fe is hardly extracted with a low extraction efficiency of only 3.86%, indicating a selective recovery of valuable Li element. In addition, when H₂O is used instead of H₂O₂, the mechanochemical reaction changes and the extraction efficiencies of Li and Fe at optimal conditions reach 97.82% and 95.62%, respectively. The Fe impurity is removed as Fe(OH)₃ precipitation by adding NaOH, and Li is recycled as Li₂CO₃ after reaction with saturated Na₂CO₃ at 95 °C. This simple and easily-operated process has little negative impact on the environment and has great potential in industrial applications.