Facile and efficient recovery of lithium from spent LiFePO4 batteries via air oxidation–water leaching at room temperature

Abstract

The economical recycling of the spent LiFePO₄ batteries in industry is challenging due to its low lithium recovery rate, and high reagent and wastewater treatment costs. Here, air oxidation–water leaching was directly employed to selectively recover lithium from the spent LFP material, in which the high leaching efficiency of lithium and the good separation effect of lithium and iron were achieved simultaneously. The thermodynamic analysis indicates that lithium can be selectively extracted under a weak acid and oxidizing atmosphere. XRD, AC-TEM, TOF-SIMS, etc. were employed to investigate the leaching mechanism, and it reveals that the oxidation of Fe and the de-intercalation of Li take place simultaneously and the ratio of the FePO₄ phase to LiFePO₄ phase gradually increases in the lithium leaching course, and the olivine structure remains essentially unchanged. 99.3% of Li is leached into solution, while only 0.02% Fe and P are dissolved. The kinetic study result suggests that selective leaching of Li is diffusion controlled. Eventually, a new LFP cathode material was prepared with Li₂CO₃ (obtained from the leachate) and the FePO₄ residue, exhibiting sound electrochemical performance. The proposed method enjoys the benefits of a high lithium recovery rate, low waste generation and high economic profit, which paves a promising way to recycle the spent LFP material.