Enhancement of Zn-ion hybrid supercapacitors by using dual redox-active ions electrolytes

Aqueous Zn-ion hybrid supercapacitors are promising, competitive, environmentally friendly, and safe energy storage systems. However, the low capacity of such supercapacitors cannot satisfy current technological requirements for economic and social development. In this study, novel aqueous Zn-ion hybrid supercapacitors are proposed. In these supercapacitors, the dual redox-active ions enhanced electrolytes, porous sheet carbons, and Zn foils were used as the electrolytes, positive electrodes, and negative electrodes, respectively. Dual redox-active ions in the electrolytes can participate in electrochemical energy storage, which considerably increases the specific capacity of such devices. A high specific capacity of 1.25 mAh/cm2 (312.2 mAh/g) is achieved at 0.8 mA/cm2 for dual redox-active ions (Mn2+ and Br−). This capacity is 2.66 times higher than those of Zn-ion hybrid supercapacitors without redox-active ions and exceeded most reported values in literature.