An optimal architecture for a polymer electrolyte battery, wherein one or more layers of electrolyte (e.g., solid block-copolymer) are situated between two electrodes, is disclosed. An anolyte layer, adjacent the anode, is chosen to be chemically and electrochemically stable against the anode active material. A catholyte layer, adjacent the cathode, is chosen to be chemically and electrochemically stable against the cathode active material.