(737e) Novel O2/H2O-Selective Membrane for Metal/Air Batteries

This presentation will describe new membrane materials and structures that can be used to encapsulate the cathode of a metal/air battery for its operation under ambient air conditions. The membrane barrier is needed to allow transport of oxygen from air into the cathode for the electrochemical reaction and to block permeation of water vapor that can degrade the battery. In this work, two kinds of membranes are found effective for selective permeation of oxygen over water vapor: immobilized oil membrane, supported dense polymer thin-film membrane. The immobilized oil membrane is prepared by loading silicone oil into the pores of a thin (~50µm), porous support sheet of suitable pore sizes and surface property for retaining of the oil by capillary force. The supported thin-film membrane was prepared by coating a dense layer of PTFE (polytetrafluoroethylene) material (<10mm thick) on a thin porous metal sheet support (~50µm). Both membranes enable stable operation of a lithium/air battery in ambient air (~20% RH) in a much longer time than the conventional porous diffusion membrane. With attachment of a quality membrane on the cathode, the battery operated in ambient air even shows better performance than the same battery housed in a dry box. Systematic membrane preparation, characterization, and battery testing results will be presented. The membrane has large potential for other metal/air battery systems.