The first device to store electricity was a glass jar filled with water

The Leyden jar was the first practical capacitor, developed independently by Ewald Georg von Kleist and Pieter van Musschenbroek in the mid-18th century. The device consisted of a glass jar filled with water, with a metal rod inserted through a cork. When the rod was touched to a static electricity generator, the glass acted as a dielectric insulator, allowing a massive charge to build up and be stored on the surface of the water.