Lithium and cobalt recovery for lithium-ion battery recycle using an improved oxalate process with hydrogen peroxide

Abstract

Lithium cobalt oxide (LiCoO2) is the first and most commercially successful form of layered transition metal oxide cathode used in lithium-ion batteries (LIBs). Recycling LiCoO2 cathodes is critical for stabilizing the Li and Co economy. In this work, a kinetic investigation of a closed-loop oxalate-based process for recovery and separation of Li and Co from LiCoO2 has been developed. Metal extraction from LiCoO2 is a non-catalytic solid-liquid reaction with both solid and aqueous products. To understand the kinetics and identify the rate-limiting mechanism, a combined shrinking core model (cSCM) was used for LiCoO2 digestions. LiCoO2 in the presence of aqueous oxalic acid (H2C2O4) at the optimum concentration of 0.46 M and 100 °C results in efficient extraction and separation of Li and Co. Diffusion of H2C2O4 into LiCoO2 occurs through a product layer of cobalt oxalate dihydrate (CoC2O4·2H2O) that forms on the surface and this process was identified as rate-limiting. The CoC2O4·2H2O was precipitated in a micro-rod morphology when 0.46 M hydrogen peroxide (H2O2) was added along with 0.23 M H2C2O4, and the reaction was carried out at a temperature of 55–75 °C. In this case, the chemical reaction at the LiCoO2 surface was identified as the rate-limiting step. Addition of H2O2 resulted in a 33% reduction in the overall activation energy, a 50% reduction in energy consumption, and a 13% reduction in the cost of reagents. This work signifies the importance of a cost-effective, environmentally-friendly, and energy-efficient process for recovering critical metals such as Li and Co from spent LIB cathodes.