An electrochemical cell assembly (500) includes a first cell and a second cell. The first cell can include a first anode (503) and a first cathode (504), wound in a first jellyroll assembly (501) with a first jellyroll assembly exterior defined by the first cathode. The second cell can include a second anode (512) and a second cathode (513), wound in a second jellyroll assembly (502) with a second jellyroll assembly exterior defined by the second anode. The first cell and the second cell can be arranged in a housing with the first jellyroll assembly exterior adjacent to the second jellyroll assembly exterior to improve energy density. The first cell assembly and the second cell assembly can have different widths to create differently shaped cell assemblies.