CaCl₂-assisted roasting for high-efficiency lithium extraction and fluorine stabilization in LFP battery recycling

Sustainable recycling of spent lithium iron phosphate (LFP) batteries is essential for securing the lithium supply and reducing environmental impact. This study introduces a single-step calcium chloride (CaCl₂) roasting protocol that simultaneously removes the poly(vinylidene fluoride) (PVDF) binder, immobilizes fluorine, and converts LiFePO₄ into water-soluble LiCl. Roasting at 600 °C for 1 h immobilizes fluorine as fluorapatite (Ca₅(PO₄)₃F_0.875Cl_0.125), preventing HF emissions. Density functional theory (DFT) confirms that forming fluorapatite and LiCl under these conditions is thermodynamically favored, and a subsequent water rinse recovers 99.83 % of the lithium, yielding battery-grade Li₂CO₃ at 99.81 % purity. Electrochemical testing of regenerated LFP demonstrates performance comparable to literature values, confirming the suitability of the recovered Li₂CO₃ for re-synthesis. Unlike conventional approaches that rely on organic solvents, high-temperature combustion for PVDF removal, or strong mineral acids for lithium dissolution, our method eliminates the need for such harsh conditions, dramatically reducing both reagent use and energy consumption. Phase evolution and fluorine capture, elucidated by multiple characterizations, verify a three-stage mechanism governed by CaCl₂ decomposition and gaseous chloride transfer. Material and energy balance assessments predict favorable techno-economic and life-cycle metrics, and the 600 °C operating temperature aligns with existing PVDF combustion lines, facilitating industrial adoption. The proposed route thus offers a scalable, environmentally benign pathway for high-purity lithium recovery from LFP waste.