Supercapacitor is a new type of energy storage device between capacitor and battery. It has the characteristics of fast charging and discharging and energy storage function, but no chemical reaction occurs during the energy storage process.The device has unique characteristics such as high power charging and discharging, long cycling life, environment friendly, wide working temperature, maintenance-free and so on, so it has become a hot spot of research and application in new energy area. In China, the most widely used application for supercapacitor is on the braking energy recovery system of urban hybrid electrical buses.