You might be tempted to think that these back to back dielectric coated metal sheets shouldn't have a polarity.

But take a look at Tecate, for example: https://www.tecategroup.com/products/ultracapacitors/ultracapacitor-FAQ.php.

"Ultracapacitors, by contrast, generally do not have any dielectrics but rather utilize a thin coating on the metal plates to keep the positive and negative charges in place. The porous nature of the carbon coating used in this "electric double layer" gives the plates a larger surface area, which allows for a higher number of charges to be stored on them...To charge them, ultracapacitors are submerged in an electrolyte consisting of positive and negative ions dissolved in a solvent. There are two types of electrolytes used by ultracapacitor manufacturers: One is water-soluble, and the other is non-water-soluble. The non-water-soluble electrolyte increases the withstand voltage per cell compared to that of a water-soluble electrolyte, producing a higher energy density. Tecate Group cells are made with non-water-soluble electrolytes."

When you buy these EDLC capacitors, their leads have polarity markings on them. You must also be careful to operate within much lower voltages: typically 2.7V or 2.5V.

@michael magaree

Thank you. You mean polarity in EDLC ultracapacitors relates to electrolye-electrode matching and if they are connected to reverse polarity they dont damage; only they work less performance.

but in electrolytic capacitors (not EDLC named) reverse polarity damages the capacitor..

Yes EDCL super capacitors have polarity.

They're composed of two (2) electrodes having different materials and characteristics.

Commercial Electric Double-Layer Capacitors (EDLC) supercapacitors have polarity because they consist of two electrodes with opposite charges: a positive electrode and a negative electrode. When the supercapacitor is charged, ions in the electrolyte accumulate at the interface between the electrodes, creating an electric double layer. This results in a potential difference between the electrodes, giving the supercapacitor its polarity.

EDLC supercapacitors are typically symmetric, meaning both electrodes are made of the same material (usually activated carbon). However, there are also asymmetric supercapacitors, which use different materials for the positive and negative electrodes to enhance performance. Asymmetric supercapacitors can achieve a wider operational voltage window and higher energy density compared to symmetric ones

Yes, asymmetric EDLC supercapacitors have polarity due to different electrode materials, which create an uneven voltage distribution. Reversing polarity can cause degradation or failure, so they must be used with the correct orientation.