Recovery of LiCl and Co3O4 from the cathode material contained in spent lithium-ion batteries using chlorination roasting with MgCl2·6H2O

Abstract

Highly demanded lithium and cobalt are considered critical metals because their reserves in the earth’s crust are relatively low in abundance, and they are found in a few countries. Thus, the extraction of these metals from spent lithium-ion batteries (LIBs) has gained much attention since they are present in relatively high concentrations in the cathode of the battery. Chlorination roasting is an attractive technique of metal extraction because of its salient features: short reaction times and moderate reaction temperatures, selectivity to the extraction of certain metals and in many cases implies the use of low-cost chlorinating reactants. However, there are few studies concerning the recycling of metals through chlorination roasting. This research paper evaluates the chlorination roasting using MgCl2⋅6H2O as chlorinating reactant followed by water-leaching to recycle lithium and cobalt from the cathode material of spent LIBs. First, a non-isothermal chlorination test between 20 and 900 ◦C was performed to evaluate how temperature affects the chlorination of the metals and the presence of impurities. Then, isothermal chlorination tests at 420, 440 and 470 ◦C for times between 60 and 350 min were performed to evaluate the effect of time on the purity of the product. It was found that the chlorination treatment is selective to lithium. HCl(g) generated during the decomposition of MgCl2⋅6H2O reacts with lithium to produce LiCl. Cobalt is extracted as Co3O4, as it is another product of the chlorination reaction. The product of LiCl impurified with Mg(OH)Cl, formed during the extraction process, was purified by a heat treatment in air at 570 ◦C for 60 min followed by water-leaching. This treatment also generates MgO as a by-product. The optimum conditions of the extractive process were the followings: 440 ◦C and 210 min. The extraction yields of lithium and cobalt were 83.29% and 89.66%, respectively. The recycling process proposed here proved to be efficient. Moreover, the magnesium chloride generated as waste from the lithium extraction process from brines could be applied in the process from a circular economy point of view.