NOVELTY - Electrolyte solution comprises aqueous bromide, and a liquid complex comprising at least one 1-alkyl-3-alkyl-pyridinium halide combined with one or more bromine molecules.    USE - The electrolyte solution is useful for a bromine-generating electrochemical cell such as a zinc/bromine cell (all claimed).    ADVANTAGE - The electrolyte solution can be prepared with good yield and purity in an eco-friendly manner without involving the formation, isolation and purification of 1-alkyl-3-methyl-pyridinium bromide in a solid form.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a method-I for operating a bromine-generating electrochemical cell, comprising adding to the electrolyte of the cell at least one 1-alkyl-3-alkyl-pyridinium halide, and charging and/or discharging the cell;    (2) a method-II for preparing an aqueous solution of one or more 1-alkyl-3-methyl-pyridinium bromide, where the alkyl at position 1 is 3-10C alkyl group, which is straight-chain or branched, comprising reacting 3-picoline and one or more bromoalkanes in a reaction vessel at a temperature above the melting point of the reaction mixture, in the absence of a solvent, combining the reaction product comprising essentially of 1-alkyl-3-methyl-pyridinium bromide in a liquid form with water, and recovering the aqueous solution;    (3) 1-alkyl-3-methyl-pyridinium bromide comprising 1-methyl-3-methyl-pyridinium bromide, 1-n-propyl-3-methyl-pyridinium bromide, 1-n-pentyl-3-methylpyridinium bromide, 1-iso-butyl-3-methyl-pyridinium bromide or 1-iso-octyl-3-methyl-pyridinium bromide; and    (4) use of a 1-methylpyrrolidin-1-ium bromide compound of formula (IIA) as an as an additive for electrochemical cells which are based on the generation of elemental bromine.    R2 = 4-8C-straight chain or branched alkyl.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a membrane-containing zinc-bromine cell    Anode (1a)    Cathode (1c)    Separator positioned between the electrodes (2)    Anolyte (3a)    Reservoir. (3c)