An Overview of the Polysulfide/Bromine Flow Battery

The Polysulfide/Bromine flow battery (FB) meets the requirements to enable high market penetration of energy storage onto electricity grids, and support the drive towards decarbonized global electricity markets. It decouples power from energy, and has high energy and power densities. Regenesys Technologies developed a low-cost 100 kW module tailored to the Polysulfide/Bromine couple that achieved resistivity measurements of 5.5 Ω cm², delivering efficiencies of 62% at 60 mA cm⁻². Options to reducing the resistivity to 3 Ω cm²were explored and showed promise, but have yet to be validated. The couple has a weakness in the migration of sulfide through the membrane, which results in a self-discharge reaction that limits electrolyte lifetime. However, this can be addressed through a novel electrolyte management system. Finally, the technology was advanced to a 15 MW 120 MWh⁻¹commercial-scale plant that was built, but its operations halted before commissioning was completed.