Powder electrolysis for direct selective lithium recovery from spent LiFePO4 materials

Abstract

This work employs an innovative powder-electrolysis method to selectively extract lithium from a mixed powder of spent LiFePO4 and graphite. The mixed powders were fixed on an anode carrier, enabling the powders to undergo electrolysis as a whole porous anode to selectively leach Li+ from the LiFePO4 into the solution. The effects of cell voltage, electrolyte flow rate, and electrolysis time were investigated. Results show the LiFePO4 undergoes a phase transformation to FePO4 after electrolytic delithiation. Under optimized conditions, the lithium extraction rate reached 92.72 wt.%. Heating the solution serves as an electrolyte purification technique, removing phosphorus to obtain high-purity Li3PO4 (99.21 %). The purified solution is recycled as an electrolyte for lithium enrichment, reducing reagents and water consumption. When the lithium concentration in the electrolyte reaches a certain level, such as more than 20 g/L, Li2CO3 product could be obtained with the addition of saturated Na2CO3 solution via precipitation.