Recycling of cobalt from spent Li-ion batteries as β-Co(OH)2 and the application of Co3O4 as a pseudocapacitor

• Published in: Journal of power sources 2014-12, Vol.270, p.158-165
• Main Authors: Barbieri, E.M.S., Lima, E.P.C., Lelis, M.F.F., Freitas, M.B.J.G.
• Format: Article
• Language: English
• Subjects: Applied sciences; Capacitors. Resistors. Filters; Cobalt hydroxide; Cobalt oxide; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Li-ion batteries; Pseudocapacitor; Recycling; Various equipment and components
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2014.07.108

This work has investigated recycling cobalt from the cathodes of spent Li-ion batteries as β-Co(OH)2, obtaining Co3O4. β-Co(OH)2 with a hexagonal structure by using chemical precipitation (CP) or electrochemical precipitation (EP). In addition, the study has investigated whether the charge density applied directly affects the β-Co(OH)2 morphology. Co3O4 is formed by heat-treating β-Co(OH)2 at 450 °C for 3 h (h) in an air atmosphere. After calcining, the Co3O4 shows a cubic structure and satisfactory purity grade, regardless of the route used for preparation via which it was obtained. Cyclic voltammetry (CV) is then used for electrochemical characterization of the Co3O4 composite electrodes. In the cathodic process, CoO2 undergoes reduction to CoOOH, which undergoes further reduction to Co3O4. In the anodic process, Co3O4 undergoes oxidation to CoOOH, which simultaneously undergoes further oxidation to CoO2. The composite electrodes containing Co3O4, carbon black, and epoxy resin show great reversibility, charge efficiency, and a specific capacitance of 13.0 F g−1 (1.0 mV s−1). The synthesis method of Co(OH)2 influences the charge efficiency of Co3O4 composite electrodes at a scan rate of 10.0 mV s−1. Therefore, in addition to presenting an alternative use for exhausted batteries, Co3O4 composites exhibit favorable characteristics for use as pseudocapacitors. •Recycling cobalt from spent Li-ion batteries as Co(OH)2 and Co3O4.•Morphological and structural characterization of recycled Co(OH)2 and Co3O4.•Electrochemical characterization of Co3O4 composite electrodes.•Co3O4 composites as promising pseudocapacitors.