Effect of ion size and charge on carbon based electrodes.

Electrochemical supercapacitors are one of the most reliable power sources with high power density. Among various types, activated carbon based supercapacitors store the charge through formation of double layer of ions at the electrode and electrolyte interfaces. However, the extent of double layer formation and thereby the total charge stored in these capacitors is quite dependent on the ion size as well as charge of the ions. In this research, we investigated the effect of ion size and the ion charge on the capacitance of activated carbon based supercapacitors in two electrode configuration. We employed a commercial microporous activated carbon (pore size \textless 2 nm, area \textgreater 1000 m$^{\mathrm{2}}$/g) cloth for these investigations, and the electrolytes were LiNO$_{\mathrm{3}}$, Mg(NO$_{\mathrm{3}})_{\mathrm{2}}$ and Al(NO3)3.$_{\mathrm{\thinspace }}$ We conducted impedance and cyclic voltammetry measurements. The capacitance values decreased in the following order 1m Mg(NO$_{\mathrm{3}})_{\mathrm{2}}$\textgreater 1/3m Al(NO$_{\mathrm{3}})_{\mathrm{3}}$ \textasciitilde 1m Al(NO$_{\mathrm{3}})_{\mathrm{3}}$\textgreater 0.5m Mg(NO$_{\mathrm{3}})_{\mathrm{2}}$ \textasciitilde 1m LiNO$_{\mathrm{3.\thinspace }}$The electrolyte solution with Mg(NO$_{\mathrm{3}})_{\mathrm{2}}$ showed the largest capacitance of 240 F/g, while Al(NO$_{\mathrm{3}})_{\mathrm{3}}$ showed 140 F/g and scan rate employed was 2 mV/s, and further in-depth analysis on ion size and charge effects will be conducted with respect to the type of the electrolytes used and presented.