Rechargeable aqueous metal-halogen cell

A rechargeable aqueous metal-halogen cell comprising a casing, a pair of spaced apart porous electrode substrates in the casing, a micro-porous separator between the electrode substrates defining a positive and a negative electrode compartment, an aqueous electrolytic solution containing a zinc salt selected from the class consisting of zinc bromide, zinc iodide and mixtures thereof in both compartments, and an organic halogen complexing additive of nitrobenzene in the electrolytic solution of at least the positive electrode compartment, the additive present in an amount from 1 to 90 weight percent of the electrolytic solution.