Development of carbon coated membrane for zinc/bromine flow battery with high power density

► A carbon coated membrane (CCM) is first developed and employed for the zinc/bromine flow battery. ► A distinguished improvement of the activity of the positive electrode is achieved. ► The internal resistance of the cell decreases obviously attributed to CCM. ► High energy efficiency of 75% is achieved which increases by 68% at 40 mA cm−2. ► A nearly two-fold increase in the power density is achieved.