High volumetric supercapacitor with a long life span based on polymer dots and graphene sheets

A series of polymer dots/graphene sheets composites with high densities are prepared and tested for supercapacitors . Polymer dots (PDs) are synthesized by one-step method at room temperature . They can effectively increase surface areas of the composites (almost 10 times), and the functional groups from PDs produce high pseudocapacitance , so that the samples exhibit high specific capacitances (e. g., 364.2 F cm −3 at 1 A g −1 ) and high cycling stability (e. g., more than 95% of the initial capacity retention over 10 000 cycles at different current densities). The optimal sample is employed to fabricate a symmetric supercapacitor , which exhibits an energy density up to 8 Wh L −1 and a power density up to 11 800 W L −1 , respectively.