Composite super-capacitor/Na-ion battery with self-healing Fe–Cr alloy electrodes

Abstract

In this study, we synthesize a novel self-healing supercapacitor (SC) by combining a thermally and alkali-activated carbon interface with a unique chromium–iron alloy. Detailed device electrochemistry is presented, complemented by characterizations through XRD, SEM, and EDS analyses of electrode surfaces. We introduce rapid cyclic voltammetric measurements to illuminate electrical performance and charge storage of fabricated SCs. SEM measurements demonstrate heightened cycling efficiency, indicating reduced electrolyte degradation and dormant sodium metal formation. XRD measurements support SCs’ self-enhancement, evidenced by sodium metal formation and improved crystalline properties on electrode surfaces. SEM micrographs reveal distinct nanostructures—nanoneedles, nanoflowers, carbon nanotubes, and graphene—formed during charge–discharge cycles. EDS confirms reversible Na metal formation, while increased Cr peaks, acting as corrosion inhibitors, highlight self-healing, extending SC lifespan. Attaining a capacitance of around 30 mF and capacity of 55.6 mWh/kg, the material offers at least 1500 μF/g. Initial results showcase a composite SC/Na-ion battery with favorable and scalable SC characteristics.