Zinc instead of lithium: New battery stores green electricity and produces hydrogen

While energy generation from wind and sun is becoming increasingly economical, there is a lack of cost-effective and efficient storage facilities that could supply the country with green energy over a longer period of time. In addition, fluctuations in power generation caused by lulls and darkness (so-called ,Dunkelflauten’) can currently only be compensated for by using conventional power plants. As a result, a double infrastructure has to be maintained and fossil fuels continue to play an important role. This makes the switch to renewable energies more difficult.

Zinc - inexpensive, available, recyclable

In the Zn-H2 project, a consortium of research institutions and the companies Zn2H2 GmbH and Steel Pro Maschinenbau GmbH is focusing on innovative solutions to store green energy for a long time. To this end, the researchers are combining well-known processes in the battery sector with zinc anodes with alkaline water electrolysis and developing a new type of storage technology. 

Unlike lithium batteries, zinc storage systems are much cheaper, use readily available, recyclable raw materials such as steel, zinc as well as potassium hydroxide and also enable the production of hydrogen. The ultimate goal is to develop electrically rechargeable hydrogen storage systems that store energy in the form of metallic zinc and provide electricity and hydrogen on demand.

Project coordinator Robert Hahn from Fraunhofer IZM explains what happens in the battery: "During charging, water oxidises to oxygen, and at the same time zinc oxide is reduced to metallic zinc. When the storage cell is discharged as needed, the zinc is converted back into zinc oxide. The water is reduced again, so hydrogen is produced and released." Since the material costs are less than a tenth of the cost of a lithium battery, this opens up an economically attractive perspective for storing green energy.

First tests successful

In the laboratory, the researchers were able to prove the basic principle of the new system, and a demonstrator is to be created by the end of the year. Finally, eight cells with a capacity of approximately 12 volts and 50 ampere-hours are to be electrically connected. 

The first tests on single cells were successful: with realistic use in seasonal ,Dunkelflauten’, but also with daily use as solar storage, the inexpensive catalysts have a service life that would allow operation for more than ten years. The system still has to go through several stages of up-scaling before it is suitable for industrial use.