Non-etching and controllable fabrication of hollow carbon spheres for high-performance supercapacitor

Due to their unique hollow sphere structure and good graded porous framework, hollow carbon spheres have potential applications in energy conversion and storage. In this study, hollow polymer spheres with regular morphology, uniform size and good dispersion were prepared by one-step hydrothermal reaction without complicated etching process. The formation process of hollow polymer spheres was also studied, and hollow carbon spheres of different sizes were prepared. HCSs20 possessed the largest specific surface area of 1603.28 m2·g−1. The HCSs20 electrode exhibited a high specific capacitance of 261 F·g−1 at a current density of 0.5 A·g−1. Moreover, the symmetric supercapacitor assembled with HCSs20, as the active material, possessed an energy density of 13.34 Wh·kg−1at a power density of 1 kW·kg−1 in a 3 M KOH electrolyte. It exhibited a good performance in the cycle life test at low current density (91 % specific capacitance retention after 9000 cycles).