Supercapacitors are attracting intense scientific attention as they can be used for next-generation portable and flexible electronics.Supercapacitors have higher energy density than dielectric capacitors,greater power density and longer cycle life than batteries.The main challenge for supercapacitors is to increase their energy density that is close to that of batteries,while maintaining their high power and long cycling ability.Extensive research work has been devoted to improve the electrochemical performance of supercapacitors by increasing the specific capacitance and optimizing the cell voltage.