A Novel Inorganic Low Melting Electrolyte for Secondary Aluminum‐Nickel Sulfide Batteries

A new, inorganic low melting electrolyte with the composition LiAlCl 4 ‐ NaAlCl 4 ‐ NaAlBr 4 ‐ KAlCl 4 (3:2:3:2) [or equivalently LiAlBr 4 ‐ NaAlCl 4 ‐ KAlCl 4 (3:5:2)] has been developed. The melting point for this neutral melt is 86°C; the decomposition potential is approximately 2.0V; the ionic conductivity is measured in the range 97°–401°C and is 0.142s cm −1 at 100°C, and the density is 2.07g cm −3 . The conductivity seems to be an almost linear combination of the conductivities of the four individual halo salts which form the melt. Other examined higher melting mixtures exhibit conductivities deviating less than ±10% from their combination expectations. The low melting electrolyte is employed in the rechargeable battery system Al / electrolyte / Ni 3 S 2 at 100°C. The open‐circuit voltage of this system is from 0.82 to 1.0V. Dendrite‐free aluminum deposits are obtained. The cycling behavior of the battery system is reported.