Electrolyte‐Driven Redox Enhancement in Electrospun ZnCo 2 O 4 Nanofibers for High‐Energy Flexible Symmetric Supercapacitors

Abstract

The development of highly efficient and long‐lasting supercapacitor electrodes based on earth‐abundant transition‐metal oxides is important for renewable energy storage. Herein, one‐dimensional ZnCo 2 O 4 (1D ZC) nanofibers were synthesized by electrospinning and evaluated as electrode materials for supercapacitor applications. Among the prepared samples, 1D ZC‐400 exhibited a specific surface area of 52.4 m 2 /g and a contact angle of 45°. These properties indicate favorable electrolyte wettability and ion accessibility. The electrochemical performance was evaluated in KCl, NaOH, and KOH electrolytes. ZC‐400 showed the best performance in 1 M KOH, delivering a specific capacitance of 675 F/g at 3 mA/cm 2 . This enhanced performance is attributed to favourable ion transport and OH − ion accessibility, which facilitate Faradaic charge‐storage reactions. The electrode showed good cycling stability, retaining 95.16% of its initial capacitance after 5000 charge‐discharge cycles. X‐ray photoelectron spectroscopy confirmed the retention of the Zn, Co, and O chemical states after cycling. A ZC‐400//ZC‐400 symmetric supercapacitor delivered a specific capacitance of 545.5 F/g, an energy density of 91.60 Wh/kg, and a power density of 4.12 kW/kg. The device showed capacitance loss of 5.35% at 180° bending compared with the flat state, demonstrating good flexibility and potential for flexible energy‐storage applications.