During discharge, Zn and Br combine into zinc bromide, generating 1.8 volts across each cell. This will increase the Zn2+ and Br- ion density in both electrolyte tanks. During charge, metallic zinc will be deposited (plated) as a thin film on one side of the carbon-plastic composite electrode. Meanwhile, bromine evolves as a dilute solution on the other side of the membrane, reacting with other agents (organic amines) to make thick bromine oil that sinks down to the bottom of the electrolytic tank. It is allowed to mix with the rest of the electrolyte during discharge. The net efficiency of this battery is about 75%.

Deployment Status:
The ZnBr battery was developed by Exxon in the early 1970's. Over the years, many multi-kWh ZnBr batteries have been built and tested. Meidisha demonstrated a 1MW/4MWh ZnBr battery in 1991 at Kyushu Electric Power company. Some multi-kWh units are now available pre-assembled, complete with plumbing and power electronics.

Developers / Suppliers:
ZBB Energy Corp
Premium Power Corporation