A sustainable process for selective recovery of lithium as lithium phosphate from spent LiFePO4 batteries

This work demonstrates a novel, systematic and sustainable route for the treatment of cathode powder of spent LiFePO4 batteries. First time, lithium was selectively leached using formic acid as lixiviant with H2O2 as an oxidant. Effect of different parameters i.e., formic acid and H2O2 concentration, pulp density, temperature and time have been studied. The optimised leaching conditions were used for the selective leaching of Li and Li was precipitated as Li3PO4 in two steps, i.e., firstly, in situ precipitation at pH = 12.5, 60 °C and then at pH = 12.5, 90 °C using saturated Na3PO4 solution from the pregnant leach solution. The products were recovered with high purity (>99.5%) and X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM) techniques were used for characterization. The overall study confirmed the suitability of the developed scheme for industrial application to provide economic and environmental benefits. Green chemistry metrics and the revenue generated from the developed process were calculated which revealed that the process is indeed green, sustainable, and economic.