An electrochemical strategy to fabricate MnOx thin film from spent batteries for pseudocapacitive applications

Highlights: • Fabrication of MnO_x thin film from spent batteries. • Thermal isolation of manganese from batteries and the utilization of the recovered manganese for electrodeposition. • Modifying the surface and the enhancement of the adherence of MnO_x thin film to the surface of ITO. • Enhanced specific capacitance of 411 F g⁻¹ (at 1 mV s⁻¹) with a retention rate of 92% after 2500 cycles. -- Abstract: This paper details a sustainable procedure to fabricate MnO_x thin film electrode with enhanced pseudocapacitance property from end-of-life batteries. Manganese (Mn) in form of metal was thermally isolated from spent batteries and then used as a precursor for electrodeposition. MnO_x was electrodeposited on an ITO current collector at ambient temperature using cyclic voltammetery (CV) at potential in the range between −1.5 V and 1.5 V vs. SCE at a scan rate of 50 mV s⁻¹. At potential of −1.2 V, Mn was deposited in metallic form on the surface of ITO which then converted to MnO_x. The initial deposition of Mn acted as a surface modifier which significantly improved the adherence of MnO_x thin film to the surface of ITO. The physicochemical properties of the as-prepared manganese oxide thin film were examined using HR-XPS, FE-SEM, HR-TEM, and TOF-SIMS. From TEM and SIMS analysis, the thickness of the film was revealed to be between 110 and 120 nm. XPS analysis also indicated that oxidation state of Mn across the depth of the film was a combination of (III) and (IV), which intensify the electron transfer capabilities. The electrochemical performance of MnO_x thin film as a supercapacitor was also comprehensively investigated. The result showed that the MnO_x thin film exhibited an enhanced specific capacitance of 411 F g⁻¹ (at 1 mV s⁻¹) with a retention rate of 92% after 2500 cycles. The outcome of this paper can be potentially used to help to tackle the problem associated with the tremendous growth in the demand for the metals used in fabrication of energy storage devices while simultaneously help in recovery of valuable metals embedded within end-of-life batteries.