VO2: from negative electrode material to symmetric electrochemical capacitor

Abstract

A novel negative electrode material of 3D irregular ellipsoidal VO₂ with excellent pseudocapacitive properties is synthesized via a simple heat treatment method. The structural analysis and morphological features show the stable morphological basis of this material, which can favor electron transportation and electroactive species diffusion. The VO₂ displays an excellent specific capacitance of 548 F g⁻¹ at a current density of 0.5 A g⁻¹, a wide potential window of −1.0 V to 1.0 V, an excellent energy density of 194.8 W h kg⁻¹ at a power density of 400.5 W kg⁻¹, and a rapidly reversible redox Faraday response. In addition, a VO₂//VO₂ symmetric supercapacitor has been assembled with a high potential window of 1.6 V, higher than traditional carbon-based cells. As a result, the VO₂//VO₂ symmetric supercapacitor can deliver a specific capacitance of 60 F g⁻¹ at a current density of 0.25 A g⁻¹ with a good energy density (21.3 W h kg⁻¹ at a power density of 207.2 W kg⁻¹) and stable power characteristics, which demonstrate the excellent performance of the VO₂//VO₂ symmetric supercapacitor and the great potential of using a VO₂ electrode as the negative and/or positive electrodes for supercapacitors with a high comprehensive performance.