Optimized mesopores enabling enhanced rate performance in novel ultrahigh surface area meso-/microporous carbon for supercapacitors

Highlights: • A new class of hierarchically mesoporous/microporous carbon is reported. • The new carbon material is derived from silicone using alkaline activation. • The new carbon material has an ultrahigh surface area with majority of mesopores. • The new carbon material exhibited excellent rate performance in EDLCs. • The new carbon material achieved very high energy density in EDLCs. Increasing both the energy density and the power density of supercapacitors is an important but challenging research subject. Porous carbon with extremely high surface, such as activated carbon, is a key engineering material for current supercapacitor technology. Here we report optimized mesopores enabling significantly enhanced rate performance in hierarchically meso-/microporous carbon with a ultrahigh surface area for supercapacitors, which is prepared by a new in-situ template method to exhibit a high mesopore volume proportion (66.0%), as well as a large pore volume up to 2.47 cm³ g⁻¹, and an ultrahigh specific surface area of 3122 m² g⁻¹. Polysiloxane was used as a precursor to produce nonporous SiOC, and sequentially NaOH was used to activate SiOC to produce highly porous carbon by removing silica and activating carbon. Hierarchically porous carbon C800 exhibited a high energy density up to 42 Wh kg⁻¹ at a power density of 374 W kg⁻¹, and still retained an energy density of 21 Wh kg⁻¹ at a high power density of 30 kW kg⁻¹. The superior rate performance of the supercapacitor is attributed to that C800 contains a majority proportion of mesopores which facilitate fast ion migration during high power charging/discharging.