Process for recycle of spent lithium iron phosphate battery via a selective leaching-precipitation method

Abstract

Applying spent lithium iron phosphate battery as raw material, valuable metals in spent lithium ion battery were effectively recovered through separation of active material, selective leaching, and stepwise chemical precipitation. Using stoichiometric Na2S2O8 as an oxidant and adding low-concentration H2SO4 as a leaching agent was proposed. This route was totally different from the conventional methods of dissolving all of the elements into solution by using excess mineral acid. When experiments were done under optimal conditions (Na2S2O8-to-Li molar ratio 0.45, 0.30 mol/L H2SO4, 60 °C, 1.5 h), leaching efficiencies of 97.53% for Li+, 1.39% for Fe3+, and 2.58% for PO43− were recorded. FePO4 was then recovered by a precipitation method from the leachate while maintaining the pH at 2.0. The mother liquor was concentrated and maintained at a temperature of approximately 100 °C, and then a saturated sodium carbonate solution was added to precipitate Li2CO3. The lithium recovery yield was close to 80%.