Recovery of high-purity metallic cobalt from lithium nickel manganese cobalt oxide (NMC)-type Li-ion battery

A process for the recovery of high-purity metallic cobalt from NMC-type Li-ion battery, which uses lithium nickel manganese cobalt oxide as the cathode material, is reported in this manuscript. First, leaching experiments of the cathode material were done with different types of acid and base solutions to compare the leaching efficiency of cobalt and the other metals. Complete leaching of cobalt is required for the recovering process and was eventually achieved when using a reductive leaching method. Second, extraction experiments were done by using different extractants to extract different metals from the leachate solution. It was found that a consecutive and selective separation of manganese first and cobalt second could result in the highest yield and selectivity of cobalt. P-204 (di(2-ethylhexyl)phosphoric acid) was used for extracting manganese, and P-507 (2-ethyl(hexyl)phosphonic acid mono-2-ethylhexyl ester) was used for extracting cobalt. Last, electrowinning was applied using the cobalt solution after back-extraction to recover cobalt into its metallic form. The overall recovery ratio for cobalt was calculated to be about 93% with a high purity of 98.8%.