Aqueous V2O5/activated carbon zinc-ion hybrid capacitors with high energy density and excellent cycling stability

Abstract

Hybrid metal-ion capacitors are designed to promote the energy density of supercapacitors with less sacrifice of power density. Zinc-ion hybrid supercapacitor, based on the multivalent ion storage principle, is a kind of energy storage device in which both the high energy density and power density can be achieved. Here, we propose a new configuration of zinc-ion hybrid supercapacitors composed of mild aqueous ZnSO4 electrolyte, activated carbon (AC) anode and V2O5 cathode. The operating voltage of the hybrid supercapacitor can reach to 2 V in the aqueous electrolyte when the mass ratio of AC to V2O5 is 1:1. The maximum energy density of zinc-ion hybrid capacitor is about 3.9 times higher than that of AC symmetric supercapacitor, while its maximum power density is 1.7 times higher than that of zinc-ion battery. The capacity retention of the hybrid supercapacitors is 97.3% over 6000 charge–discharge cycles at 0.5 A g−1. Compared with MnO2 zinc-ion hybrid supercapacitors system, the stable nature of V2O5 allows new zinc-ion hybrid supercapacitors system to achieve a better cycling performance. The unique electrochemical performance, low cost and high safety of the new zinc-ion hybrid supercapacitor endow it with a very wide range of applications in consumer electronics and stationary energy storage.