Abstract
In recent years, lithium iron phosphate (LFP) batteries have been widely used in the electric vehicle industry. The recycling of spent LFP will be propitious to conserving resources and alleviating the environmental risks it poses. In this study, a selective extraction method for lithium from spent LFP was proposed using nitric acid. Lithium leached into the liquid phase, while P and Fe remained in the leaching residue. Under the conditions of 120°C, HNO3/Li molar ratio of 2, and time of 2 h, the leaching efficiency of lithium reached 99.5 %, with a selectivity reaching 82.1 %. Initially, LFP was decomposed to liberate Li, Fe, and P in the liquid phase. Subsequently, ferrous ions were oxidized to trivalent, high-valent iron ions re-precipitated as FePO4·2 H2O. Thermodynamic calculations indicate that the temperature and pH value of the extraction system have significant influence on both the oxidation and reprecipitation steps. An imbalance of Fe/P ratio (<1) in the raw material hinders the selectivity of lithium extraction, and supplementing this portion of Fe can enhance the selectivity to over 90 %. Additionally, LiCO3 and anhydrous FePO4 were effectively regenerated from the leachate and residue. This study provides a novel approach for the recycling of spent LFP and probably contributes to the sustainability of the lithium ion battery industry.
Published Version
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