A novel Li/H2O primary battery is reported. The battery consists of a thin film lithium metal anode evaporated on hybrid inorganic/organic lithium ion conductive solid electrolyte, H2O as the electroactive cathode material, and a Pt mesh current collector. The hybrid electrolyte consists of a two-phase ceramic, lithium aluminum titanium phosphate/aluminum phosphate (LATP/AlPO4), sealed with polyvinylidene fluoride. These cells display an open cell potential of 0.90V, a current output range between 0.78 and 0.50 mu A under constant 1 M Omega load discharge, and specific energy of 2660 Wh/kg. Battery life is shown to be proportional to the mass of the Li metal anode employed and has been demonstrated for up to 37.5 h. (C) 2012 Elsevier Ltd. All rights reserved.