An electrochromic (EC) cell having improved dielectric tunability and lower dielectric losses is disclosed. A multi-layer structure includes at least one electrochromic layer of a transition metal oxide between electrode layers. Two electrolyte layers are located on either side of the at least one electrochromic layer and next to the electrode layers. An ion storage film layer of a transition metal oxide may be provided between the electrochromic layer and one of the electrolyte layers. This structure prevents the shortening of the channel height when a voltage is applied therefore reducing dielectric losses.