Effects of different electrolytes on the electrochemical and dynamic behavior of electric double layer capacitors based on a porous silicon carbide electrode

Abstract

Controlling the structure and morphology of porous electrode materials is an effective strategy for realizing a high surface area and efficient paths for ion diffusion. Moreover, excellent electrical conductivity can significantly decrease the internal resistance of an electrode by the formation of a conductive network and facilitate the application of electrostatic charges, which favors the accumulation of an electrical double layer. In light of these facts, we demonstrate the fabrication of β-polytype porous silicon carbide spheres (PSiCS) with a hierarchical pore structure in which micro- and mesopores are interconnected with a mesoporous network. Further, to investigate the effects of the electrolyte on the electrochemical and dynamic behavior, two-electrode symmetrical supercapacitors based on the PSiCS electrode with an aqueous electrolyte (1 M potassium chloride, KCl) or an organic electrolyte (1 M tetraethylammonium tetrafluoroborate in acetonitrile, TEABF₄/AN) were assembled. The symmetrical supercapacitor based on the PSiCS electrode with the aqueous electrolyte exhibited a high charge-storage capacity with a specific capacitance of 82.9 F g⁻¹ at a scan rate of 5 mV s⁻¹, which is much higher than that obtained using the organic electrolyte (60.3 F g⁻¹ at a scan rate of 5 mV s⁻¹). However, the energy density of the organic electrolyte system was 102.59 W h kg⁻¹ at a scan rate of 5 mV s⁻¹, which is greatly superior to that of the aqueous electrolyte system (energy density: 29.47 W h kg⁻¹) owing to the wide cell operating voltage range.