Recovery of Lithium, Iron, and Phosphorus from Spent LiFePO₄ Batteries Using Stoichiometric Sulfuric Acid Leaching System

Abstract

A selective leaching process is proposed to recover Li, Fe, and P from the cathode materials of spent lithium iron phosphate (LiFePO4) batteries. It was found that using stoichiometric H2SO4 at a low concentration as a leachant and H2O2 as an oxidant, Li could be selectively leached into solution while Fe and P could remain in leaching residue as FePO4, which is different from the traditional process of using excess mineral acid to leach all the elements into solution. Under the optimized conditions (0.3 M H2SO4, H2O2/Li molar ratio 2.07, H2SO4/Li molar ratio 0.57, 60 °C, and 120 min), the leaching rates of 96.85% for Li, 0.027% for Fe, and 1.95% for P were recorded. The Li contained in solution was then recovered by introducing Na3PO4 as a precipitant. Around 95.56% Li was precipitated and recovered in the form of Li3PO4 under the experimental conditions. In addition, the FePO4 in the leaching residue was directly recovered by burning at 600 °C for 4 h to remove carbon slag. This study illustrates an effective process for the recycling of spent LiFePO4 batteries in a simple, efficient, and cost-effective way, which give it potential to be industrially applied.