The non-faradaic current associated with the charging of the electrical double layer at an electrode-solution interface, given by: $$i_{\mathrm{DL}}=\frac{\mathrm{d}(\sigma A)}{\mathrm{d}t}$$ where $\sigma$ = surface charge density of the double layer, $A$ = area of the electrode-solution interface and $t$ = time. Capital letters should be used as subscripts to avoid the possibility of confusing this symbol with that for the limiting diffusion current.