A stacked battery has at least two cell segments arranged in a stack. Each cell segment may have a first electrode unit having a first active material electrode, a second electrode unit having a second active material electrode, and an electrolyte layer between the active material electrodes. One or more gaskets may be included in each cell segment to seal the electrolyte within the cell segment. The electrode units may be ''dish shaped'' and may contain a pressure equalization valve to reduce electrode unit deflection and improve pressure equalization between cell segments. The pressure equalization valve may allow a gas to diffuse through adjacent cell segments and may substantially prevent electrolyte from diffusing through.