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 fine-porous separator between the electrode substrates defining a positive and a negative electrode compartment, an 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 in the electrolytic solution of at least the positive compartment, the additive present in an amount from 10 to 50 weight percent of the electrolytic solution, the organic halogen complex additive selected from the class consisting of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycols having a molecular weight from about 200 to 6000, alkyl ethers and alkyl esters thereof, the alkyl having from one to four carbon atoms, and polypropylene glycol having a molecular weight from about 200 to 6000, alkyl ethers and alkyl esters thereof, the alkyl having from one to four carbon atoms.