Transference Numbers of Zinc in Zinc‐Chloride Battery Electrolytes

Migration of zinc‐ion species affects the local zinc chloride concentration and solution density in the electrolyte adjacent to the zinc electrode and thereby influences natural convection at this electrode during both charge and discharge. This work presents experimentally measured transference numbers for ionic‐zinc species in aqueous solutions containing at 30°C using the Hittorf method. Negative transference numbers for zinc are obtained in most mixed‐salt solutions with minima of −0.2 to −0.3 occurring in the chloride ion concentration range of 6–8m. The transference number of zinc depends generally on the total chloride content. The effect of the cations is small, noticeable only at higher concentration, and follows the order of their ionic mobilities. The data support the presence of anionic zinc complexes such as and , which account for the negative transference numbers.