Modified chalcogens with a tuned nano-architecture for high energy density and long life hybrid super capacitors

Abstract

A novel in situ vanadium-modified NiCo₂S₄ wrapped with graphene sheets was synthesized using a simple solvothermal technique. The vanadium-modified sample (VNCS) demonstrated superior electrochemical performance over graphene-wrapped NiCo₂S₄ (GNCS) and pure NiCo₂S₄ (NCS) samples, with a specific capacitance of 1340 F g⁻¹ at a current density of 2 A g⁻¹. The VNCS sample also showed outstanding capacitance retention at 50 A g⁻¹ (1024 F g⁻¹), which is 430% higher than that of the NCS sample. The cycling stability of VNCS was significantly improved by more than 140% compared to the NCS sample with less than 10⁻³ F per cycle loss in capacitance after 10 000 cycles. We also report the fabrication of hybrid supercapacitors (HSCs) using three different materials for the faradaic electrode. The VNCS-HSCs showed significant improvements in all electrochemical performance measurements compared to NCS-HSCs. The capacitance retention at 50 A g⁻¹ was improved by more than 260% and the long cycling stability was improved by more than 180% after 10 000 cycles. The VNCS-HSC delivered an energy density of 45.9 W h kg⁻¹ at 0.87 kW kg⁻¹ and maintained a superior energy density of 33.6 W h kg⁻¹ at 9 kW kg⁻¹ indicating the excellent potential of this material in hybrid super capacitor applications.