A Low-Cost Zn-Based Aqueous Supercapacitor with High Energy Density

Low-cost supercapacitors with high energy densities have attracted great research attention, since it would broaden the application of capacitors. Increasing the capacitance is one principle to obtain a high energy density of a supercapacitor. In this study, a low cost aqueous Zn-based hybrid supercapacitor (AZHS) with high energy density is achieved using an actived carbon derived from corncob (denoted as ACC) as the positive electrode, zinc metal as the negative electrode, and the 2 M ZnSO₄ electrolyte. The actived carbon is prepared with a facile calcination-activation process, and it exhibits high specific surface area (2619 m² g^-1). Though without extra heteroatom doping, ACC demonstrates a superb specific capacitance in acidic, alkaline and neutral electrolytes. The assembled AZHS exhibits a high energy density of 94 W h kg^-1 at 68 W kg^-1 in a potential window of 0.2-1.8 V, and an excellent cycle stability with only 1.8% capacitance decay is obtained after 10 000 cycles at 5 A g^-1. These results suggest that a low cost supercapacitor with high energy density can be achieved by a hybrid system design using electrodes with high capacitance.