Comparison of the origin of high capacitance at nickel and/or carbon aqueous electrolyte interfaces and its uses in the development of potassium ion intercalation based super capacitor

This paper deals with the origin of high capacitance at nickel/aqueous alkaline carbonate and carbon/aqueous alkaline carbonate electrolyte interfaces and the consequent success achieved in the development of nickel and carbon super capacitors. Aminoguanidine bicarbonate (AGBC) has been used as an addition agent in the electrolyte to enhance the capacity. The basic mechanism of charge storage in these capacitors is the intercalation and deintercalation of K⁺ ion at both nickel/nickel oxide and carbon electrodes. The electrolyte being aqueous potassium carbonate solution. Intercalation-deintercalation phenomenon at these electrodes has been confirmed by XRD studies, which proves the decrease in “2θ” values with an attendant increase in “d” values and also by transmission electron microscopy (TEM). Further the capacity values calculated from cyclic voltammetry (CV) are found to be high, the values ranging from 3400 to 6800 μF.cm^-2 for nickel and from 14700 to 32900 μF.cm ^-2 for carbon. Dissolved oxygen and AGBC content are found to have effect on the capacity values. Individual capacitors and capacitor banks fabricated using the nickel and carbon electrodes, and the aqueous alkaline carbonate solution have been tested for their performance. The most important characteristic of these capacitors is that their voltage windows are greater than 1.2 V. This comparative study confirms that both nickel and carbon are prospective candidates for electrodes in alkaline media. For use in electrical double layer (EDL)/super capacitors in the presence or absence of oxygen and/or AGBC