US Patent 7414825 Electrochemical device

An electrochemical device includes a pair of electrodes at least containing activated carbon powder, a separator interposed between the pair of electrodes, and an electrolytic solution impregnated into the pair of electrodes and the separator. The electrodes and the separator are stacked on a collector. Each of the electrodes includes at least two layers arranged in a thickness direction, and the two layers are made of the activated carbon powder having mutually different average grain sizes. The average grain size of the activated carbon powder in the layer contacting the separator is greater than the average grain size of the activated carbon powder in the layer located on the collector side.