An EDL can be formed on the surface of an electrode, cell membrane or nanoparticles by adsorption of ions from an electrolyte solution, dissociation of the surface compound, or redistribution of the electron density. Also, an EDL is always formed at the surface of bodies bordering with plasma due to flows of ions and electrons to and from the plasma.

Most often electrical double layers are observed on the interface between a solid body and an electrolyte. In this case the adsorption of ions of a certain type and, consequently, of a certain sign turns out to be more beneficial; such ions bonded directly to the surface and determining its charge are called “potential determining ions”. Ions of opposite signs, which stay close to the adsorbed ions due to the electrostatic attraction forces, are called “counterions”. On the solution side the EDL is bordered with a diffuse layer formed due to thermal motion of the counterions (see Fig.).

As the spatial separation of charges is always accompanied by formation of an electric potential difference, the EDL can be considered as a kind of micro-capacitor, in which the distance between the plates is determined by molecular dimensions (see supercapacitor).

The electric double layer has a strong influence on the rate of electrode processes in electrolytes, plasma treatment of surfaces, spreading of electrical impulses along nerve and muscle fibres, and stability of disperse systems, because the surface charge of the particles prevents their coagulation.