Enhancement on the selective flotation separation of carbon coated LiFePO4 and graphite electrode materials

Abstract

With the rapid development of lithium-ion batteries, the recycling of spent lithium-ion batteries will be a big challenge in the future, among which the recycling of spent positive and negative electrode materials powder is a difficult point. Flotation has been able to separate triplet materials from graphite to some extent, but there are still many problems to be solved in the separation of LiFePO4 from graphite. In this study, a novel flotation reagent regime was proposed to enhance the flotation separation performance of LiFePO4 and graphite electrode materials by carbonaceous surface selective inhibition, which were achieved by H acid as a depressor. The flotation results showed that under the flotation conditions of pH value 9.3 ± 0.1, 10.0 mg/L n-dodecane, 7.5 mg/L MIBC, and 250 mg/L H acid, the recovery of LiFePO4 and graphite were 11.95 % and 94.28 %, respectively. The adsorption kinetic model showed that the adsorption speed of LiFePO4 electrode material is higher than graphite, the adsorption isothermal model showed that the adsorption capacity of LiFePO4 electrode material is significantly higher than graphite. The results of X-ray photoelectron spectroscopy showed that the interaction between H acid and LiFePO4 or graphite electrode material is mainly π-π interaction. Raman spectroscopy analysis showed that the carbon disorder degree and skeleton form of the graphite and LiFePO4 are significantly different, which makes H acid more easily adsorbed on the surface of LiFePO4. This study provided a new method for the efficient separation and recovery of LiFePO4 and graphite electrode materials from spent lithium iron phosphate batteries.