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 Na 3 Zr 2 Si 2 PO 12 ceramic with an ionic conductivity of 1.3 × 10 −3 S⋅cm −1 at 25°C and a porous electrode containing Mn 3 O 4 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⋅cm −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.