DIAGNOSTIC ANALYSES FOR MECHANISMS OF SELF-DISCHARGE OF ELECTROCHEMICAL CAPACITORS AND BATTERIES

In the charged condition, electrochemical capacitors, like batteries, are in a state of high energy relative to that of the system in the di scharged state. Hence there is a 'driving force', corresponding to the free energy of discharge, tending to spontaneously diminish the charg e if some mechanism(s) of self-discharge exist. An ideally polarizable (chargeable) capacitor has no self-discharge or current-leakage pathw ay and hence can remain charged indefinitely. However, practical capac itors, like batteries, suffer appreciable self-discharge over periods of days or months so that this phenomenon is of major interest in eval uation of capacitor performance and choice of materials to minimize se ll-discharge Several mechanisms of self-discharge are distinguished an d the resulting forms of the change of potential on open-circuit with time or log time provide a means of identifying the type of self-disch arge process that occurs. With RuO2, some remarkable potential-recover y effects arise following discharge.