Hybrid Anionic Electrolytes for the High Performance of Aqueous Zinc-Ion Hybrid Supercapacitors

Aqueous zinc-ion hybrid supercapacitors (AZHSs) are promising candidates for powering mobile devices due to their intrinsically high safety, the high theoretical capacity of zinc anodes, and the wide range of sources of raw materials for activated carbon (AC) cathodes. Here, we report that there is a synergistic effect between the anions of an AZHS electrolyte, which can significantly improve the specific capacity and rate capability of an AC cathode. The results showed that the specific capacities of the AC cathode//2 M ZnSO 4 (aq)//Zn anode energy storage system were 115 and 41 mAh g −1 at 0.1 and 5 A g −1 current densities, respectively. The specific capacity at a 0.1 A g −1 current density was enhanced to 136 mAh g −1 by doping 0.5% ZnCl 2 and 0.5% Zn(CF 3 SO 3 ) 2 in the 2 M ZnSO 4 electrolyte. The specific capacity at a 5 Ag −1 current density was enhanced to 69 mAh g −1 by doping 1% ZnCl 2 and 0.5% Zn(CF 3 SO 3 ) 2 in the 2 M ZnSO 4 electrolyte. In addition, the co-doped electrolyte increased the energy consumption of the binding of the AC surface groups with H + and inhibited the precipitation of Zn 4 SO 4 (OH) 6 ·5H 2 O. This provides an important perspective for improving the performance of AZHSs.