Preparation and performance of plastic-bonded-carbon bromine electrodes

Abstract

A range of carbon blacks has been used in conjunction with a polypropylene binder to form electrodes for zinc/bromine cells. The resistivity of each of these carbon/plastic materials has been measured on hot-pressed pellets. The respective electrochemical activity has been determined from polarization tests using 2 cm 2 electrodes. These tests have shown that a two-layer electrode structure, with a surface layer containing a high fraction of carbon black, is necessary to obtain satisfactory activity. Best results have been achieved when this surface layer has been composed of blacks with a low bulk density and a high surface area. The best of the carbon/plastic compositions has been used to prepare 16 cm 2 bromine electrodes for testing in zinc/bromine cells. It has been possible to make electrodes with an initial polarization resistance of 0.3 ohm cm 2 and an initial ohmic resistance of 0.8 ohm cm 2. These values increase when the electrodes are left in contact with bromine-containing solutions, regardless of whether the electrodes have been charge/discharge cycled or not.