A high-energy-density mixed-aprotic-aqueous sodium-air cell with a ceramic separator and a porous carbon electrode

A mixed aqueous/aprotic Na-air cell that works at room temperature has been fabricated and its discharge properties have been examined experimentally as a primary cell. A dense Na₃Zr₂Si₂PO₁₂ ceramic with an ionic conductivity of 1.3 × 10^-3 S·Ecm^-1 at 25°C and a porous electrode containing Mn₃O₄ catalyzed carbon are used as a solid electrolyte separator and an air electrode, respectively. This cell gives a maximum output power density of 21 mW·Ecm^-2 at 25°C, which is one of the best results among alkali metal-air cells reported to date. Electrochemical impedance spectroscopy reveals that a reduction in ohmic resistivity of the ceramic separator is now crucial for a further increase in power density.