Zinc–bromine battery
| Specific energy | 34.4–54 W·h/kg (124–190 J/g) |
|---|---|
| Energy density | 15.7–39 W·h/L (56.5–140 kJ/L) |
| Charge/discharge efficiency | 75.9% |
| Energy/consumer-price | US$400/kW·h (US$0.11/kJ) |
| Cycle durability | >2,000 cycles |
| Nominal cell voltage | 1.8 V |
The zinc–bromine flow battery is a type of hybrid flow battery. A solution of zinc bromide is stored in two tanks. When the battery is charged or discharged the solutions (electrolytes) are pumped through a reactor stack and back into the tanks. One tank is used to store the electrolyte for the positive electrode reactions and the other for the negative. Zinc bromine batteries from different manufacturers have energy densities ranging from 34.4–54 W·h/kg.
The predominantly aqueous electrolyte is composed of zinc bromide salt dissolved in water. During charge, metallic zinc is plated from the electrolyte solution onto the negative electrode surfaces in the cell stacks. Bromide is converted to bromine at the positive electrode surface and is stored in a safe, chemically complexed organic phase in the electrolyte tank. Each high-density polyethylene (HDPE) cell stack has up to 60 bipolar, plastic electrodes between a pair of anode and cathode end blocks.
The zinc–bromine battery can be regarded as an electroplating machine. During charging zinc is electroplated onto conductive electrodes, while at the same time bromine is formed. On discharge the reverse process occurs, the metallic zinc plated on the negative electrodes dissolves in the electrolyte and is available to be plated again at the next charge cycle. It can be left fully discharged indefinitely without damage.
A new type of Zinc Bromine battery, called a Zinc Bromine Gel battery, is currently being developed in Australia. It is lighter, safer, quicker to charge, and flexible.
The primary features of the zinc bromine battery are:
Drawbacks include:
Zinc–bromine flow battery providers include:
These battery systems compete to provide energy storage solutions at a lower overall cost than other energy storage systems such as lead-acid, vanadium redox, sodium–sulfur, lithium-ion and others.
At the negative electrode zinc is the electroactive species. Zinc has long been used as the negative electrode of primary cells. It is a widely available, relatively inexpensive metal which is electronegative, with a standard reduction potential, E° = −0.76 V vs SHE. However, it is rather stable in contact with neutral and alkaline aqueous solutions. For this reason it is used today in zinc–carbon and alkaline primaries.
...
Wikipedia