A facile route for the efficient leaching, recovery, and regeneration of lithium and iron from waste lithium iron phosphate cathode materials

Abstract

The recycling of lithium iron phosphate power batteries that have exploded in retirement is urgent, but the focus and difficulty of the recycling is the effective recovery of lithium and iron elements in the cathode active material. In this study, the cathode sheets and other components of the lithium-ion batteries were obtained by pretreatment, and the cathode active material and the Al foil of the collector were recovered by stirring with dilute alkali solution (optimized conditions of alkali solution concentration 0.075 mol L-1, liquid–solid ratio 20 mL g−1, and stirring time 40 min). The H2SO4-H2O2 system was used to leach used lithium iron phosphate cathode powder, the leaching process conditions were optimized and the leaching mechanism was revealed. The leaching rates of Li and Fe elements reached 98.79 % and 94.97 %, respectively, at a H2SO4 concentration of 2.5 mol L-1, a H2O2 dosage of 6 mL, a liquid–solid ratio of 25 mL g−1, a leaching temperature of 60 °C and a leaching time of 60 min. The pH value was precisely adjusted in the chemical precipitation method to recover lithium and iron elements from cathode active material. The recovered products FePO4 and Li2CO3 were used as the precursors for the regeneration of LiFePO4 cathode material. The electrochemical performance of LiFePO4/C materials regenerated at 700 °C from the raw material with a lithium to iron molar ratio of 1.03:1 was relatively good, with a first discharge specific capacity of 160.1 mAh g-1 at 0.1 C, and a charge/discharge efficiency of 96.70 % for the first cycle. The good electrochemical performance was still maintained at a higher rate, with a capacity retention of 99.7 % after 100 cycles at 1 C.