Researchers have developed new polymer electrolytes for redox flow batteries that are flexible, efficient, and environmentally friendly.
In redox flow batteries, the energy-storing components are dissolved in a solvent, and can therefore, be stored at a decentralized location, which allows the battery to be scaled as required, from a few milliliters to several cubic meters of electrolyte solution.
Thanks to this flexibility, redox flow batteries could become an important means of energy storage; however, until now, they suffered from two weaknesses that have prevented their widespread use. The first is the frequent use of environmentally hazardous and toxic heavy metal salts, such as vanadium dissolved in sulfuric acid, as electrolytes. The other problem is the restriction of the batteries to a maximum working temperature of 40 °C, which necessitates the use of an elaborate cooling system. With the help of the new material, these two problems were solved.
The new type of polymer is soluble in water — which makes it suitable for use in an aqueous electrolyte — and that contains iron, which provides the ability to store electricity. At the same time, the polymer can cope with a significantly higher temperature of up to 60 °C, so that the additional expense for sensitive temperature management is eliminated. In addition, during their tests with the new system, the researchers discovered that it also works more efficiently than its predecessors.
This means that electricity can be stored in a non-hazardous, water-based solution that is then stored temporarily in tanks and the electricity in the battery can be used again the next day without significant losses or additional effort. Systems of this kind can also be used in warmer regions.