(i) At high frequencies, the supercapacitor behaves as a pure resistor and a semi-circular response is seen. The radius of the semi-circle and its initial intercept with the real axis primarily depend on the electrode and bulk electrolyte resistances, although some authors state that charge-transfer resistance can also contribute to domain. The intermediate frequency domain is characterised by a linear line at ca. 45 ° relative to the Re(Z) axis, which has been assigned to the penetration of the electrolyte into the pore network of the electrode and the corresponding transition to diffusion-limited electrolyte transport. A shift of this domain to lower frequencies and higher real impedances suggests more limited ionic mass transport and slower electric double-layer formation. (iii) At low frequencies, a linear response is observed, attributed to the capacitive behaviour of the electric double-layer formed at the electrode/electrolyte interface. An ideal supercapacitor displays a vertical line in this domain, and the extent of variation from this theoretical response indicates non-ideal capacitive behaviour due to poor ionic accessibility and movement. Curvature of the response in this domain can indicate a high resistance to ion movement within the electrode pores.