Electric double layer capacitance on hierarchical porous carbons in an organic electrolyte

Nanoporous carbons were prepared by using colloidal crystal as a template. Nitrogen adsorption/desorption isotherms and transmission electron microscope images revealed that the porous carbons exhibit hierarchical porous structures with meso/macropores and micropores. Electric double layer capacitor performance of the porous carbons was investigated in an organic electrolyte of 1 M LiClO₄ in propylene carbonate and dimethoxy ethane. The hierarchical porous carbons exhibited large specific double layer capacitance of ca. 120 F g⁻¹ due to their large surface areas. In addition, the large capacitance was still obtained at a large current density up to 10 A g⁻¹, which satisfies demands from the high power application such as hybrid electric vehicles. Capacitance analysis of the hierarchical porous structures revealed the contribution of meso/macropores and micropore to the electric double layer capacitance to be 8.4 and 8.1 μF cm⁻², respectively. The results indicated electric double layer is formed even when solvated ions are larger than pore diameters.