A hybrid supercapacitor based on flower-like Co(OH)2 and urchin-like VN electrode materials

Abstract

A series of hybrid electrochemical capacitors were fabricated by using the flower-like cobalt hydroxide (Co(OH)₂) and urchin-like vanadium nitride (VN) as the positive and negative electrode materials, respectively. Both Co(OH)₂ and VN electrode materials showed excellent electrochemical performance due to their unique structure and fast reversible Faradic reaction characteristics. With different operation voltage window (OVW) and negative/positive mass ratios, the impact on capacitance performance of the hybrid supercapacitor was investigated thoroughly, which demonstrated that both mass ratio and OVW played an important role in their capacitance performance. Furthermore, theoretical modeling was performed and the simulation result was found to be in agreement with the experimental result for the influence of the negative/positive mass ratio on capacitance performance of the hybrid supercapacitor. When an optimized negative/positive mass ratio was located, the Co(OH)₂//VN hybrid supercapacitor could be cycled reversibly in the high-voltage region of 0–1.6 V and delivered a high energy density of 22 W h kg⁻¹. Even at a large power density of 15.9 kW kg⁻¹, the hybrid supercapacitor still possessed a desirable specific energy density of 9 W h kg⁻¹. Such an impressive hybrid supercapacitor was expected to be a highly promising candidate for application in high-performance energy storage systems.