October 21, 2015

Synthetic Batteries for the Energy Revolution

The research team and its new battery (from left to right): Prof. Dr. Ulrich S. Schubert,
Tobias Janoschka und Dr. Martin Hager. Foto: Anne Günther/FSU

(October 21, 2015) Chemists of Jena University present an innovative redox-flow battery based on organic polymers and water

Sun and wind are important sources of renewable energy, but they suffer from natural fluctuations: In stormy weather or bright sunshine electricity produced exceeds demand, whereas clouds or a lull in the wind inevitably cause a power shortage. For continuity in electricity supply and stable power grids, energy storage devices will become essential. So-called redox-flow batteries are the most promising technology to solve this problem. However, they still have one crucial disadvantage: They require expensive materials and aggressive acids.

A team of researchers at the Friedrich Schiller University Jena (FSU Jena), in the Center for Energy and Environmental Chemistry (CEEC Jena) and the JenaBatteries GmbH (a spin-off of the University Jena), made a decisive step towards a redox-flow battery which is simple to handle, safe and economical at the same time: They developed a system on the basis of organic polymers and a harmless saline solution. "What's new and innovative about our battery is that it can be produced at much less cost, while nearly reaching the capacity of traditional metal and acid containing systems," Dr. Martin Hager says. The scientists present their battery technology in the current edition of the renowned scientific journal 'Nature' (DOI:10.1038/nature15746).

In contrast to conventional batteries, the electrodes of a redox-flow battery are not made of solid materials (e.g., metals or metal salts) but they come in a dissolved form: The electrolyte solutions are stored in two tanks, which form the positive and negative terminal of the battery. With the help of pumps the polymer solutions are transferred to an electrochemical cell, in which the polymers are electrochemically reduced or oxidized, thereby charging or discharging the battery. To prevent the electrolytes from intermixing, the cell is divided into two compartments by a membrane. "In these systems the amount of energy stored as well as the power rating can be individually adjusted. Moreover, hardly any self-discharge occurs," Martin Hager explains.

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