Selective recovery of lithium from spent LiFePO4 powders with electrochemical method

Abstract

In recent years, with the flourishing of new energy vehicles, the lithium iron phosphate (LFP) batteries are vigorously developed due to their low cost and high stability. Meanwhile, it leads to an increase in large-scale retirement of batteries. Therefore, it is crucial to develop a green and efficient recycling method. In this work, an indirect electrochemical oxidation has been proposed for selective leaching of Li ions. An electrochemical system using boron-doped diamond electrode (BDD) with high oxygen evolution potential as anode and RuO2/Ti as cathode has been built to generate oxidizing species and enhance the oxidative reaction contact for an indirect oxidation of LFP. The operating conditions were optimized to a current density of 110 mA/cm2, Na2SO4 electrolyte concentration of 0.225 M, pH of 1.7, solid–liquid ratio of 16 g/L. The leaching efficiency of Li ions reached up to 95.53 % and the leaching efficiency of Fe ions was less than 0.01 % at room temperature. A purity of lithium carbonate product of 99.93 % was obtained after precipitation of the leaching solution. This proposed method could realize efficient and rapid selective leaching of Li and Fe ions by indirect oxidation, realizing selective leaching and significantly reducing the usage of acid.