Recovery of Cobalt from Lithium-Ion Batteries Using Fluidised Cathode Molten Salt Electrolysis

Abstract

Within the next 30 years, the number of vehicles powered by electricity is predicted to rise to 1 billion representing an exponential increase from 7.9 million used in 2019 [1]. These electrified vehicles will rely on lithium-ion rechargeable batteries with projections augmented by the impending ban on new petrol and diesel car sales. Despite these batteries offering a green, carbon-free alternative they remain overshadowed by the sustainable use of raw materials. Thus, the future need to recycle enormous quantities of Li-ion batteries arises because of the projected increase in the electrified fleet of vehicles required to decarbonise the transport sector. Cobalt is an essential element in several Li-ion battery cathode chemistries (e.g. NMC, NCA and LCO). In this study, we present an electrochemical reduction process of LiCoO2 to Co using a molten salt fluidised cathode technique at 450 oC [2]. Using thermodynamic calculations, a predominance diagram was constructed in Figure 1 to aid in understanding the reduction pathway. Cyclic voltammograms indicate two 2-electron transfer steps, the first where Co3O4 is reduced to CoO at −0.55 V vs Ag/Ag+ followed by the second reduction step of CoO to Co at −2.4 V vs. Ag/Ag+. The reduction potential of Co was used to determine the input parameters in the current versus time profiles. The Faradaic current efficiencies for both the commercially obtained LiCoO2 and spent Li-ion battery yield values greater than 70%. Thus, the fluidised cathode technique could prove to be an energy-efficient and high-throughput route for the recovery of cobalt, in this work, as well as different materials found in other batteries. Gielen, R. Gorini, N. Wagner, R. Leme and G. Prakash. International Renewable Energy Agency (IRENA), Global Renewables Outlook: Energy Transformation 2050, Abu Dhabi, Edition: 2020.M. Mirza, R. Abdulaziz, W.C. Maskell, C. Tan, P.R. Shearing, D.J.L. Brett, Recovery of cobalt from lithium-ion batteries using fluidised cathode molten salt electrolysis, Electrochim. Acta. 391 (2021) 138846. Figure 1