Solid-State Proton Battery Operated at Ultralow Temperature

Most rechargeable batteries suffer from severe capacity loss at low temperature, which limits their applications in cold environments. Herein, we propose an original proton battery, which involves a MnO₂@graphite felt cathode and a MoO₃ anode in an acid electrolyte containing Mn²⁺. Its operation depends on the MnO₂/Mn²⁺ conversion in the cathode and H₃O⁺ insertion/extraction in the anode. This battery exhibits a promising energy density (177.4 Wh kg^–1) and a supercapacitor-like power density (66.6 kW kg^–1) at room temperature. We demonstrate that the electrolyte shows high conductivities even after freezing at low temperatures. As a result, a solid-state proton battery is formed at −70 °C, which maintains 81.5% of the room temperature capacity and shows an unprecedented cycle stability (a negligible capacity fading over 100 cycles). Furthermore, even at −78 °C, it can still deliver sufficient energy to power an electric device.