Novel zinc-ion hybrid supercapacitors with enhanced specific capacity by redox-active ions

Zinc-ion hybrid supercapacitors (ZHSCs) have been widely reported for its prominent electrochemical performance, promising safety and low cost. However, the limited energy density has long hindered its application in various fields. Herein, novel redox-active ions enhanced aqueous ZHSCs are proposed, in which VOSO4 served as the additive in electrolytes to promote the specific capacity through redox pairs. In these supercapacitors, redox-active ions (VO2+) were introduced into 1 M ZnSO4 electrolyte and occurred redox reactions during the charge/discharge cycles, which provided additional capacity. Combined with the reversible ion adsorption on the surfaces of activated carbon, the prepared ZHSCs exhibit an ultra-high specific capacity of 9.09 mAh/cm2 at 0.8 mA/cm2, which surprisingly exceeds that of ZHSCs without redox-active ions by about 10 times.