Converting spent lithium cobalt oxide battery cathode materials into high-value products via a mechanochemical extraction and thermal reduction route

Abstract

This study innovatively combines mechanochemistry and high-temperature thermal reduction to achieve the recovery of valuable metals from spent LIBs. First, under the action of mechanical force, the crystal structure of lithium cobalt oxide (LiCoO2) found in the cathode materials of spent LIBs was destroyed and converted into lithium carbonate (Li2CO3) and Li-free residue (C/Co3O4) using dry ice as a co-grinding reagent. The optimum Li2CO3 recovery conditions were determined to be as follows: a ratio of dry ice: LiCoO2 powder mass of 20:1; a rotation speed of 700 rpm, and a reaction time of 1.5 h. With these conditions the maximum percentage of Li2CO3 recovered was 95.04 wt%. The Co3O4 in Li-free residue was reduced to a high-value Co0 product via a high-temperature (800 °C) heat treatment. Gibbs free energy analysis confirmed that the carbon in the Li-free residue could be used as a self-reducing reagent for the thermal reduction of Co3O4. The reactants and products of each step were characterized by XRD, FT-IR, XPS and SEM techniques. The green route for recycling spent LIBs that this study proposes realizes the green and cost-effective conversion of LiCoO2 to high-value products, which may become an outstanding example of recycling spent LIBs.