Abstract: A battery cell comprising a flexible housing, a first and second electrode, an electrolyte and at least one seal region. The flexible housing includes a perimeter seal at which the housing is sealed around its perimeter. The first and second electrode each comprise a first region and a second region protruding from the first region, wherein the first and second regions of the first and second electrodes are situated within the flexible housing. The electrolyte is situated between the first region of the first electrode and the first region of the second electrode. The first regions of the first and second electrodes and the electrolyte are arranged to define an electrochemical zone housed within the flexible housing. The second regions of the first and second electrodes protrude from the electrochemical zone. The at least one seal region comprises a region in which internal surfaces of the flexible housing are sealed together.