Figure 5. Electrochemical Impedance Spectroscopy (EIS) study.

(a) The equivalent circuit of Randle's model, where Rs is the equivalent series resistance (ESR), R_CT is the resistance of the electrode-electrolyte, R_L is the leakage resistance. CPE_DL is the constant phase element (CPE) of double layer, W0 is the Warburg element, CPE_L is the mass capacitance. Experimental and modeled Nyquist plots for complex impedance for RGM after (b) 1^st cycle and (c) 8100^th cycle. (d) Normalized real capacitance against frequency plot and (e) imaginary capacitance against frequency for RGM, and RGM after 8100 cycles.