Abstract
The future need to recycle enormous quantities of Li-ion batteries is a consequence of the rapid rise in electric vehicles required to decarbonise the transport sector. Cobalt is a critical element in many Li-ion battery cathode chemistries. Herein, an electrochemical reduction and recovery process of Co from LiCoO2 is demonstrated that uses a molten salt fluidised cathode technique. For the Li-Co-O-Cl system, specific to the experimental process, a predominance diagram was developed to aid in understanding the reduction pathway. The voltammograms indicate two 2-electron transfer reactions and the reduction of CoO to Co at −2.4 V vs. Ag/Ag+. Chronoamperometry revealed a Faradaic current efficiency estimated between 70-80% for the commercially-obtained LiCoO2 and upwards of 80% for the spent Li-ion battery. The molten salt electrochemical process route for the recycling of spent Li-ion batteries could prove to be a simple, green and high-throughput route for the efficient recovery of critical materials.
Highlights
Lithium-ion batteries (LiBs) have found varied use in portable energy storage devices [1,2], power tools and electric vehicles, and have the potential for larger-scale stationary electric storage [3]
Predominance diagrams are analogous to Pourbaix diagrams; the former compare the standard electrode potential to the negative logarithm of O2− ion activity, pO2− rather than pH
All thermodynamic data used in producing the diagram has been obtained from HSC Chemistry 6.0 database
Summary
Lithium-ion batteries (LiBs) have found varied use in portable energy storage devices [1,2], power tools and electric vehicles, and have the potential for larger-scale stationary electric storage [3]. Compared with alternative battery chemistries, they possess high energy and power densities, long cycle lifespans and flexible operating conditions [4,5]. The growth of the energy storage market is a positive development for society, it brings with it a number of challenges; such as, the scarcity of raw materials like cobalt [7,8,9], and the environmental footprint of production, towards which the extraction of these materials is a large contributor [10,11]. The recycling of LiBs, and the recovery of valuable materials, would provide a solution to this, and is an essential part of the future life cycle of energy storage devices. There are currently five main recycling methods: pyrometallurgical recovery, physical materials separation, hydrometallurgical metals reclamation, direct recycling and biological metals recla-
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