Capacitor tech talk Spring 2008

 If the popular symmetric electrochemical capacitors are nonpolar, why do they have polarity markings?
Several factors can make double-layer capacitors, nonpolar in principle, polar in actual practice. To begin with, the materials commonly used for current collectors to improve their performance often render the devices incapable of reverse polarity operation. Also, the amount of material in each electrode may be slightly different to increase the stored energy in the device (to compensate for the fact that the rest potential of the electrode material is often not centered in the window of voltage stability). Adding a . . .