Dependence of electric double layer capacitance on electrolyte ion for carbon electrolyte interface

Abstract

The effect of the kind of electrolyte ions and carbon surface on electric double layer capacitance was investigated using graphitized carbon black (GCB), multi-walled carbon nanotube (MWCNT), or activated carbon (ACF) as active material and (C₂H₅) ₄NBF₄, (C₄H₉) ₄NBF₄, (C₆H₁₃) ₄NBF₄, (C₂H₅) ₄NCF₃SO₃, or (C₂H₅) ₄N (CF₃SO₂) ₂N as electrolyte salt for propylene carbonate solution. The GCB and MWCNT, which have no or less microporosity, showed no dependence of the capacitance on the kinds of the electrolyte ions. This suggests that the capacitance is not related to the size of ions adsorbed on carbon surface in the absence of micropores. In the case of the ACF, the smaller capacitances were observed when bulkier ions adsorbing/desorbing. This tendency was more prominent for narrower micropore width, which can be explained by the ion sieving effect of micropores.