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