Synthesis and characterisation of novel additives for use in the hybrid ZnBr₂ flow battery

Zinc-bromine redox flow batteries (RFB) are energy storage devices capable of integrating with renewable generators and so improve energy management from these intermittent sources. However, this system is susceptible to self-discharge via the electrogenerated bromine transferring through the separator and reacting with the plated zinc. Here we examine the use of novel quaternary ammonium complexes to capture the electrogenerated bromine but keep it in the aqueous phase (as opposed to the immiscible phase formed with Af-methyl-A'-ethylpyrrolidinium, MEP). Electrochemical analysis indicates that these complexes do not impact on the electrode kinetics and exhibit similar physical properties as to the MEP. However, the latter still shows an enhanced ability to complex the bromine to higher polybromide states (i.e. Brf).