Lithium Molten Salt Battery at Near Room Temperature Using Low-Melting Alkali Metal Melts

Low-melting alkali metal salts containing the asymmetric amide anion, such as fluorosulfonyl(trifluoromethylsulfonyl) amide, has the possibility to be a molten salt electrolyte for a lithium secondary battery. The alkali metal molten salt containing lithium and the cesium cation can be compared to a conventional organic electrolyte and room temperature electrolyte at the same temperature due to its reduced melting point. The alkali metal molten salt has a much higher viscosity and lower ionic conductivity than the ionic liquid with the same mole composition of the lithium cation. The alkali metal molten salt also has a higher charge transfer resistance of the lithium metal. However, it shows a higher capacity for the LiFePO4 half-cell than an ionic liquid electrolyte. This superiority is remarkable when using a thick LiFePO4 composite sheet. This indicates that the alkali metal molten salt would have specific transport behavior for the lithium cation in the LiFePO4 composite electrode.