TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The aqueous bromide is an aqueous solution of zinc bromide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The electrolyte solution comprises 1-n-butyl-3-methyl-pyridinium bromide. The electrolyte solution further comprises: at least one of 1-n-propyl-3-methyl-pyridinium bromide, 1-n-pentyl-3-methyl-pyridinium bromide and 1-n-hexyl-3-methyl-pyridinium bromide; and one or more alkyl pyridinium bromide compounds of formula (I), N-alkyl pyridinium bromide compounds of formula (II), and 1-alkyl-3-methyl imidazolium bromide compounds of formula (III). (I) is preferably N-ethyl pyridinium bromide and 1-ethy1-2-methyl pyridinium bromide. (II) is preferably N-methyl-N-butyl pyrrolidinium bromide, N-methyl-N-hexyl pyrrolidinium bromide and N-methyl-N-isooctyl pyrrolidinium bromide. (III) 1-n-butyl-3-methyl imidazolium bromide. The aqueous solution is a concentrated aqueous solution, where the concentration of the solution is 60-90 wt%. Preferred Components: The 1-alkyl-3-alkyl-pyridinium halide is 1-alkyl-3-methyl-pyridinium bromide. The alkyl at position 1 is 3-10C alkyl group, which is straight-chain or branched. The 3-10C alkyl group comprises n-propyl, n-butyl, n-pentyl or n-hexyl. The concentrated aqueous solution comprises at least one 1-alkyl-3-methyl-pyridinium bromide comprising 1-n-propyl-3-methylpyridinium bromide, 1-n-butyl-3-methyl-pyridinium bromide, 1-npentyl-3-methyl-pyridinium bromide or 1-n-hexyl-3-methylpyridinium bromide, and further comprises 1-ethyl-3-methyl pyridinium bromide. The 1-alkyl-3-methyl-pyridinium bromide is isolated in a non-solid form. Preferred Method: The method-I comprises adding 1-alkyl-3-methyl-pyridinium bromide, and further comprises adding (I)-(III) to the electrolyte. The solvent-free reaction mixture is heated to a temperature of greater than 70 degrees C, maintaining the progressively formed 1-alkyl-3-methyl-pyridinium bromide in a liquid form and providing a stirrable reaction mass, and combining the liquid 1-alkyl-3-methyl-pyridinium bromide directly with water to form a clear aqueous solution.R3 = H or alkyl;R4 = alkyl;X = -CH2-, -O- or absent;R1, R2 = alkyl, where at least one of R1 and R2 is an alkyl comprising more than 3 carbon atoms; andR5, R6 = alkyl. EXAMPLE - Typical electrolyte solution comprised of 2.25 M of zinc bromide, 0.2 M of bromine, and 0.8 M of N-methyl-N-butyl-pyrrolidinium bromide.