Reversible Plating and Stripping of Sodium at Inert Electrodes in Room Temperature Chloroaluminate Molten Salts

Sodium has been suggested as a possible anode in high energy‐density batteries using room temperature chloroaluminate molten salt electrolytes, but it cannot be used directly in typical melts because the reduction of Na + falls beyond the negative voltage limit. When a neutral melt of 1‐methyl‐3‐ethylimidazolium chloride and aluminum chloride is buffered with , and excess protons are added, the negative voltage limit is extended to −2.4 V ( vs. an melt reference electrode) and the reversible plating and stripping of sodium is observed. Compositional data from scanning electron microscopy and energy dispersive spectra (SEM/EDS) verify that a layer of sodium is deposited on the surface of Pt and W electrodes. MEI + appears to be reduced at nearly the same potential as sodium and probably forms a protective layer on top of the sodium. These plated species are fairly stable on the electrode surface as judged by a constant rest potential over several hours, but can easily be stripped off the electrode by a positive potential scan. These characteristics suggest that sodium is a good candidate for the anode in a rechargeable battery.