Spent LiFePO4 to High-Value LiF: Enhanced Mechanical Chlorination Coupled with a Fluorination Reaction Mechanism

LiFePO4(LFP) batteries are among the earliest commercialized and most discarded lithium-ion batteries. Although existing recovery technologies focus on the conversion of LiFePO4to Li2CO3, challenges associated with achieving near-full recovery and high-value products remain. This study proposes a strategy for the conversion of spent LiFePO4to LiF by mechanical chlorination coupled with a fluorination reaction. The optimum conditions were determined to be a ball-to-powder ratio (BPR) = 15, NH4Cl:LFP = 3, H2O2= 2.0 mL, rotation speed = 600 rpm, and grinding time = 12 h. Results showed that 97.14% Li was converted into LiCl by H2O2–NH4Cl mechanical chlorination. When chlorinated intermediates were immersed in water, FePO4could be harvested, and 96.79% Li could be recovered as LiF with a purity of 99.50% after adding NH4F. When Cl-functionalized renewable resin was used to exchange 99.89% F−, 0.63 g NH4Cl per litre of LiF conversion residual liquid was derived. The favourable results were attributed to the1O2generated by H2O2, which had a strong electron affinity to break Li–O bonds and provided superior conditions for the combination of Li and Cl. During fluorination, the formation of LiF reduced the ion concentration, and the entropy decreased, contributing to the spontaneous reaction. Therefore, the proposed method paves the way for near-full recovery and high-value products of spent LiFePO4.