PURPOSE: To unify electrodeposition of zinc on an electrode at the early stage of charging by adding a -SO3H radical having minus ions to a carbon plastic electrode.

CONSTITUTION: Polyolefin system synthetic resin such as the high density polyethylene or the like is made into a matrix while either of carbon black and graphite or their mixture and ion-exchange material pulverized powder having a -SO3H radical are blended therewith while being kneaded and molded for making it into a zinc electrode of a zinc/bromine cell. The desirable blending ratio of ion-exchange material pulverized powder is 5∼50wt% while the particle diameter is desirably 1∼5μm. Since the electrode surface is to have a sulfon radical, overvoltage at the early stage of charging is heightened and as a result uniform electro-deposition at the early stage of zinc electrodeposition can be achieved. Since it is not overvoltage rise only from an electrolytic liquid, there is no lowering of cell efficiency.