The present invention provides a separator for electrochemical cells, comprising a gas barrier having an electrically conducting pathway extending therethrough and a porous, electrically conducting member in electrical contact with each side of the electrically conducting pathway. In another aspect of the invention, a separator for electrochemical cells is provided comprising a porous, electrically conducting sheet and a gas impermeable material disposed within a portion of the sheet to form a gas barrier. In yet another aspect of the invention, a separator for electrochemical cells is provided comprising two porous, electrically conducting sheets and an electrically conducting gas barrier disposed in electrical contact between the sheets.