For electric vehicles (EV) having a 500km range between charges, there is a need to develop smaller and lower-cost batteries. Lithium-air has the potential to deliver a step change in the specific energy of rechargeable lithium batteries. In order to develop a practical, safe, smaller and lower-cost lithium and sodium-air rechargeable EV battery it is necessary to eliminate the formation of dendritic deposits (on charge), increase the current density up to 100mAcm−2 (or reducing cell DC resistance to less than 10Ωcm2) and change the oxygen-discharge product from peroxide to oxide. We suggest here a novel concept, namely to replace the metallic lithium anode by liquid sodium and to operate the sodium–oxygen cell above the sodium melting point (97.8°C). In this report we studied the deposition–dissolution process of sodium in polymer electrolytes at 105°C and we present, for the first time, preliminary results that demonstrate the feasibility of running a liquid-sodium–oxygen cell with polymer electrolytes at above 100°C.