Alkali cation incorporated MnO2 cathode and carbon cloth anode for flexible aqueous supercapacitor with high wide-voltage and power density

Aqueous supercapacitor with the character of cost-effective and environmental-friendly has been regarded as the promising energy storage device. However, the operating voltage of aqueous supercapacitor is usually limited by the electrochemical stability of water, which greatly hinders their application and development. Such a limitation may be surpassed by increasing the over-potential of oxygen evolution reaction and hydrogen evolution reaction. Herein, metal cation inserted MnO 2 nanosheets supported on carbon cloth substrate were prepared via electrochemical activation, which can stably work as cathode in an expended positive potential window of 0–1.3 V (vs SCE). To complement this wide potential positive electrode, K + was adsorbed onto an activated carbon cloth via electrochemical reduction method. As anode, K + adsorbed activated carbon cloth displayed extended negative potential window of −1.2-0 V (vs SCE) due to the adsorption of K + effectively prevented the hydrogen evolution reaction. A 2.5 V aqueous asymmetric supercapacitor was assemble based on Na–MnO 2 @CC cathode and KACC anode, delivering the maximum energy density of 475.7 μWh/cm 2 and power density 5 mW/cm 2 as well as exceptional cycling performance and excellent flexibility.