Highly conductive polyaniline (PANI) membranes synthesized by a proton doping method are used as waterproof barriers for lithium air batteries. When the membrane is attached to the air cathode, it promotes lithium ion transport into the electrode and blocks the moisture entrance, which can protect the lithium anode from erosion. Electrolyte evaporation from the battery is also greatly reduced. Electrochemical tests show that lithium air cells with this design deliver a much higher specific capacity, 3241mAhg−1 (referring to carbon), under high relative humidity (RH>20%) conditions; the cells also have an excellent rate capability.