A major challenge to the development of the next-generation all-solid-state rechargeable battery technology is the inferior performance caused by insufficient ionic conductivity in the electrolyte and poor mixed ionic-electronic conductivity in the electrodes. Here we demonstrate the utility of elevated temperature as an advantageous means of enhancing the conductivity in the electrolyte and promoting the catalytic activity at electrodes in an all-ceramic rechargeable Na+-battery. The new Na+-battery consists of a 154-μm thick Na-β′′-Al2O3 electrolyte membrane, a 22-μm thick P2-Na2/3[Fe1/2Mn1/2]O2 cathode and 52-μm thick Na2Ti3O7-La0.8Sr0.2MnO3 composite anode. The battery is shown to be capable of producing a reversible and stable capacity of 152 mAhg−1 at 350 °C. While the battery's achievable capacity is limited by the electrode materials employed, it does exhibit unique low self-discharge rate, high tolerance to thermal cycling and an outstanding safety feature.