In some GCD tests, after several hundred cycles, the specific capacity of the supercapacitor has increased. How is it possible? What happens chemically?
Ahmed Emad Fathy Abbas
Activation of electrode surface area - The active surface area of the electrodes (e.g. activated carbon or graphene) may become more accessible and ion-accessible after repeated charge-discharge cycling. This can expose more micropores and surface area over time and increase capacitance. Improved wetting - For supercapacitors with porous electrodes and liquid electrolytes, the electrolyte penetration into fine pores can improve gradually. Better electrolyte access to surface area enhances the capacitance. Redox reactions - Some pseudo-capacitance effects involve fast surface redox reactions, which could catalyze and improve in rate/yield with cycling. Products may also deposit onto surfaces, increasing reactive sites. Self-healing effects - Small amounts of decomposition products from the electrolyte can deposit within defects on porous carbon over cycles, essentially "healing" them and improving properties. Equilibration - The electrochemical and morphological changes occurring initially during cycling may simply take some time to equilibrate before reaching a maximum steady capacitance response.
here are a few possible reasons why the specific capacitance of a supercapacitor could increase after several hundred charge-discharge cycles:
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