The present disclosure is directed towards the design of electrochemical cells for use in high pressure or high differential pressure operations. The electrochemical cells of the present disclosure have non-circular external pressure boundaries, i.e., the cells have non-circular profiles. In such cells, the internal fluid pressure during operation is balanced by the axial tensile forces developed in the bipolar plates, which prevent the external pressure boundaries of the cells from flexing or deforming. That is, the bipolar plates are configured to function as tension members during operation of the cells. To function as an effective tension member, the thickness of a particular bipolar plate is determined based on the yield strength of the material selected for fabricating the bipolar plate, the internal fluid pressure in the flow structure adjacent to the bipolar plate, and the thickness of the adjacent flow structure.