Determination of Cell Potential Stability Limits by Floating

Determination of Cell Potential Stability Limits by Floating 

The SOH of an EC is evaluated by monitoring capacitance and ESR at various lifetimes of the system. An EC is usually considered by manufacturers as out of service when the ESR is increased by 100% or the initial capacitance is reduced by 20% [99]. Generally, it is typical that the ESR reaches the end-of-life limit earlier than capacitance [98]. The failures which can appear during the working time of a capacitor may be 

Opening of the system due to gas evolution and internal overpressure A capacitance loss of the carbon electrode caused by (i) reduced accessible surface area due to oxidation of the carbon surface or pore blockage by electrolyte decomposition products and (ii) electrolyte decomposition leading to ionic starvation in the electrode [100] 

An increase in ESR due to weakening of the adhesion between the active mass and the current collector (it is often caused by gas evolution or corrosion of the current collector) or to the formation of decomposition products on the electrode. 

4 Attractive Electrochemical Capacitors in Aqueous Solutions 301 5th discharge 

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