History of electrochemistry
In 1789, Franz Aepinus developed a device with the properties of a "condenser" (now known as a capacitor.) The Aepinus condenser was the first capacitor developed after the Leyden jar, and was used to demonstrate conduction and induction. The device was constructed so that the space between two plates could be adjusted, and the glass dielectric separating the two plates could be removed or replaced with other materials.
Electrolytic capacitor
Charles Pollak (born Karol Pollak), a producer of accumulators, found out that the oxide layer on an aluminum anode remained stable in a neutral or alkaline electrolyte, even when the power was switched off. In 1896 he filed a patent for an "Electric liquid capacitor with aluminum electrodes" (de: "Elektrischer Flüssigkeitskondensator mit Aluminiumelektroden") based on his idea of using the oxide layer in a polarized capacitor in combination with a neutral or slightly alkaline electrolyte.