Preparation of FePO4 and LiH2PO4 from cathode mixture materials of scrapped LiFePO4 batteries

Abstract

Typically, LiFePO4 batteries (LFPBs) contain a shell, cathode mixture materials, anode mixture materials, current collector, electrolyte, separator, and other components. Cathode mixture materials are composed of a binder, conductive additive, and LiFePO4/C. After LFPBs are scrapped, their appropriate disposal is necessary to avoid pollution. This study investigated the recovery of Li, Fe, and P by hydrometallurgy from scrapped LFPBs. To remove the binder, conductive additive, and carbon coating layer, recycled cathode mixture materials are oxidized to Li3Fe2(PO4)3 and Fe2O3 at 600 °C. Using H3PO4 as a leaching agent, the optimal leaching efficiencies, i.e., 99.2% and 97.68% for Li and Fe, respectively, can be achieved when the reaction time, temperature, Li in the Li3Fe2(PO4)3 and Fe2O3 mixture materials to the H3PO4 molar ratio (L/P ratio), and H3PO4 concentration are 12 h, 95 °C, 1:5, and 0.5 mol/L, respectively. Moreover, Li can be leached into a solution efficiently and recovered as LiH2PO4, while Fe and P can be selectively precipitated as FePO4·xH2O. FePO4 is prepared by a heat treatment. Furthermore, LiFePO4/C is re-synthesized by FePO4, LiH2PO4, Fe2O3, LiOH, and sucrose.