Electrical Double Layer Capacitor: Principle And Operation

Electrical Double Layer Capacitors, or supercapacitors as they are often called, are high capacity devices that offer much higher capacitance than other capacitors.

These are in high demand, because of the recent boom in electric vehicles. Their structure as well as principle of function is much different, resulting in improved performance. Furthermore, several organic and ionic electrolytes are being investigated to increase capacitance.

Let’s examine the structure and principle of function of supercapacitors.

Principle of EDL Capacitor

Aluminum electrolytic capacitors and ceramic capacitors have a conventional dielectric. Supercapacitors, in contrast, lack the dielectric constant as a solid or liquid electrolyte is filled between its two electrodes.

An electric double layer is formed in these capacitors between the electrodes and the electrolyte. This works as the dielectric. The capacitance is thus proportional to the layer’s surface area.

Activated carbon helps achieve higher capacitance due to the large surface area available for electrodes.


Charge and discharge of the capacitor depends on ion absorption and desorption mechanism of electrical double layer.

The capacitor is charged when ions are drawn over the electrical double layer by applying voltage to the electrodes. In contrast, they move away from the layer when discharging the capacitor.

This is how the process of charging and discharging takes place in supercapacitors.

Structure of supercapacitors

The capacitor consists of following three components:

  1. Electrodes
  2. Electrolyte (plus the electrolyte salt)
  3. Separator

The separator prevents the two facing electrodes from bridging a contact with each other. Application of activated carbon powder to the electrodes’ electricity collector helps generate an electrical double layer on the surface, where powder connects with the electrolyte.

The activated electrodes have a variety of powders with holes on the surface. Hence, the layer is generated at points where these powders come in contact with the electrolyte.

As a result, the equivalent circuit electrode resistance (Re) as well as the resistance caused by ion moving (Rs) represents a complicated equivalent circuit with various resistances connected in series to capacitors.

Of course, the specific details of EDC vary from manufacturer to manufacturer, but its capacitance largely depends on the electrolyte and electrolyte salt being used. As such, several car manufacturers and other companies are looking to find the most efficient combinations.

Research indicates Tetraethylammonium tetrafluoroborate TEABF4 and other similar solutions perform better than Lithium solutions. This may pave a way for battery-free cars, using supercapacitors with highly efficient electrolyte composition.

If you’re interested in researching organic and ionic electrolytes for supercapacitors, you’ve come to the right place. We have a list of solutions that you can order today. As fine chemical distributors, we mainly deal with the following electrolyte solutions:

Visit the associated links to find information about their individual chemical and physical properties. Feel free to contact us for orders or queries.