Insight into the Supercapacitive Behavior of Activated Hollow Porous Carbon Spheres in Different Electrolytes

Supercapacitive behaviors of the porous carbon electrode principally depend on the properties of electrolyte. In this paper, activated hollow porous carbon spheres (AHPCSs) with large specific areas were prepared by the hydrothermal method and subsequent one-step KOH activation treatment. The electrochemical performances and supercapacitive characteristics of the AHPCS supercapacitors were evaluated in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) ionic liquid electrolyte, 1 mol L–1 LiPF6 organic electrolyte, and 6 mol L–1 KOH aqueous electrolyte. It has been found that the supercapacitors with AHPCS electrode have definitely good supercapacitive behaviors in the three electrolytes. Especially, the AHPCS supercapacitor in the EMIMBF4 ionic liquid electrolyte that has a wide operating voltage of 0–3.0 V exhibits an excellent rate performance with capacitance retention of 72.3% from 0.5 to 10 A g–1 and a good cycle performance with a high capacitance retention of 94.2% after 4000 consecutive cycles. Moreover, it obtains a high energy density of 80.5 Wh kg–1 at 750 W kg–1, which transcends most of the currently reported carbon-based supercapacitors. Therefore, the supercapacitors with EMIMBF4 ionic liquid as electrolyte and AHPCSs as active electrode materials show tremendous potential in terms of boosting comprehensively electrochemical performance.