 In 1836, he invented the Daniell cell, which consists of a copper pot filled with a copper sulfate solution, in which is immersed an unglazed earthenware container filled with sulfuric acid and a zinc electrode.The earthenware barrier is porous, which allows ions to pass through but keeps the solutions from mixing.The Daniell cell was a great improvement over the existing technology used in the early days of battery development and was the first practical source of electricity.