One-step synthesis of porous carbon derived from starch for all-carbon binder-free high-rate supercapacitor

Fast charge–discharge capability even at high current densities is desired for supercapacitors. One-step simple synthesis using sol-gel method is used to fabricate binder-free activated carbon electrode, where KOH was used to tune the porosity of electrode. The gravimetric capacitance of the optimized electrode is up to 272 F g−1 at a current density of 1 A g−1. More importantly, 75.9% gravimetric capacitance retention is kept at an ultrahigh current density of 50 A g−1. Furthermore, a symmetrical supercapacitor device is assembled in 1 M Et4NBF4 in acetonitrile, which delivers an energy density of 18–25 W h kg−1. Apparently, the carbon material with open rich pores provides short ion diffusion pathways for energy storage and the binder-free method guarantees high conductivity of the whole system, leading to high-rate performance. The porous carbon structure as well as the low-cost and simple design paves the way for fabricating supercapacitors with enhanced rate capability.