Recovery of iron phosphate and lithium carbonate from sulfuric acid leaching solutions of spent LiFePO4 batteries by chemical precipitation

Abstract

The recycling of lithium and iron from spent lithium iron phosphate (LiFePO<sub>4</sub>) batteries has gained attention due to the explosive growth of the electric vehicle market. To recover both of these metal ions from the sulfuric acid leaching solution of spent LiFePO<sub>4</sub> batteries, a process based on precipitation was proposed in this study. Since ferric and ferrous ions coexisted in the leaching solution, all the ferrous ions were first oxidized to ferric ions by adding H<sub>2</sub>O<sub>2</sub> to the leaching solution. About 99% iron(III) was recovered as iron phosphate by adjusting the solution pH to 2 at 25 <sup>o</sup>C for 30 mins. After the precipitation of iron phosphate, the remaining Li(I) in the filtrate was recovered as lithium carbonate by precipitation with Na<sub>2</sub>CO<sub>3</sub> as a precipitant. Addition of acetone to the filtrate at room temperature greatly enhanced the precipitation percentage of Li(I). Moreover, solid Na<sub>2</sub>CO<sub>3</sub> was better than Na<sub>2</sub>CO<sub>3</sub> solution in precipitating Li(I). About 95% of lithium ions was recovered as carbonate precipitates under the optimum conditions: solution pH = 11, 3.0 molar ratio of solid Na<sub>2</sub>CO<sub>3</sub> to Li(I), 7/5(v/v) volume ratio of acetone to the filtrate, 25 <sup>o</sup>C, 300 rpm for 2 hrs.