Vanadium redox-flow batteries are a technology that can be used to store fluctuating energies from solar and wind power. In order to reduce the manufacturing costs of the batteries, e.g., cheaper raw materials can be used. By using polystyrene-based polymers for membrane production, conductivities comparable to perfluorosulfonic acid membranes can be achieved. A way to produce these heterogeneous membranes consisting of disperse and continuous phase is shown.