Co-recovery of spent LiCoO2 and LiFePO4 by paired electrolysis

Abstract

Recycling critical elements from spent batteries has always placed an emphasis on green chemistry. However, the reduction or minimization of the input of chemicals, secondary waste and energy consumption still needs to explore new technologies. In this work, we propose a paired electrolysis process to concurrently treat lithium cobalt oxide (LiCoO₂, as a cathode) and lithium iron phosphorate (LiFePO₄, as an anode) in sulfuric acid solution. In this process, LiCoO₂ is reduced to release Co²⁺ and Li⁺ into the electrolyte through a surface chemical reaction control process. The activation energies of Li and Co are 23.38 and 28.70 kJ mol⁻¹. LiFePO₄ is oxidized to FePO₄ while releasing Li⁺ through a surface chemical reaction control process with an activation energy of 14.95 kJ mol⁻¹. Through this approach, both leaching efficiencies of Li and Co reach above 98%. Since two electrode reactions simultaneously proceed in one electrolytic cell, the paired electrolysis has the benefit of maximizing energy efficiency, as well as reducing the amount of chemicals and secondary waste.