DOUBLE-LAYER IMPEDANCE OF A NICKEL-OXIDE ELECTRODE AT LOW STATES-OF-CHARGE

The double-layer impedance of a porous electrode is generally modelled by a transmission-line model or by invoking fractal geometry. In a ni ckel oxide electrode at low state-of-charge, however, the porosity doe s not affect significantly the impedance of the electrode below 100 Hz . Even then, the double-layer impedance cannot be represented by a pur e capacitor. The reasons for this are to be found in the physical natu re of the impregnated active material. Based on a phenomenological the ory, the double-layer impedance can be modelled by a set of resistor/c apacitor elements connected in parallel.