Preparation and Recovery Behavior of Lithium Chloride (LiCl) from Lithium Iron Phosphate (LiFePO4) Cathode Active Materials via Hydrogen Reduction and CaCl2-Assisted Thermal Chlorination

In this study, lithium was recovered from LiFePO4 (LFP) cathode active materials through a two-step thermal process combining hydrogen reduction and chlorination roasting. Hydrogen reduction was conducted while varying temperature and holding time to promote oxygen removal from LFP and induce phase separation into Li3PO4 and iron phosphides (FeP and Fe2P). Based on stoichiometric assessment using the degree of LFP decomposition and the reduction in oxygen moles, the optimal hydrogen-reduction condition was determined to be 900 °C for 1 h. Subsequently, CaCl2 was selected as an appropriate chlorination agent using thermodynamic considerations, and the hydrogen-reduced product was reacted with CaCl2 to convert Li3PO4 into water-soluble LiCl. The mass of LiCl produced was quantified as a function of reaction temperature. Water leaching enabled the separation of LiCl from the insoluble residues, resulting in an overall lithium recovery of 71.7%.