Especially in the application of stationary energy storage devices, redox flow batteries have significant advantages over Lithium-based systems. These advantages include the ability to scale energy and power independently, the use of non-flammable materials and the potential of more cost-effective scaling. In the field of redox-flow batteries, the primary focus is on vanadium-based systems. However, vanadium-based systems have some drawbacks due to the low gravimetric energy densities, the high price of vanadium, as well as the short life span of the membrane separating the half-cells.
In light of these drawbacks alternative systems have been identified as a potential solution. Among these bromine-based systems has several advantages. It consists of cheap and highly abundant material and electrolyte with high concentrations can be used which increases the theoretical energy density. However, it should be noted that bromine is highly corrosive and reacts with the cell components especially the membrane. In this regard bromine complexing agents (BCA) are a possible solution for minimising the destructive effects of bromine in the cell.
In our work, we analysed different BCAs with regard to their influence on the kinetic and reversibility of the bromine reaction. Our research has identified two distinct types of BCA: the first type showed strong complexation abilities for bromine and inhibited bromine diffusion through the membrane, but limited cell discharge; the second type showed weak complexation abilities and enabled cycling of bromine, but did not prevent bromine diffusion.