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

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 2V 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 0.5Ag(-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.