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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.Carbon-based materials have been playing a significant role in the development of high energy supercapacitors.High-surface area activated carbon remains the electrode material of choice for commercial systems due to the inherently lower cost relative to the more exotic alternatives such as graphene,carbon nanotubes,or their hybrids.However,activated carbon possesses an inferior electrochemical performance relative to these more open and electrically conductive structures.This limits its feasibility as electrodes for future high-performance devices.We created unique 3D carbon-based nanomaterials by using biomass precursors.These 3D carbon-based nanomaterials with open structures achieve superior electrochemical performance.In particular,high energy superpcapacitors,including asymmetric aqueous-based capacitor,Li-ion capacitor,Na-ion capacitor,and ionic liquid-based symmetric supercapacitors,were successfully designed by using nanostructured carbon-based materials.These results give deep insight into the material science and electrochemical fields,and high energy supercapacitors can be obtained from both materials design and system construction.