The Jena research team and its innovative battery (from left to right) are: Prof. Dr. Ulrich S. Schubert, Tobias Janoschka und Dr. Martin Hager. Credit: Anne Guenther/FSU
It is simple to handle, safe and economical at the same time. The new redox-flow battery can withstand up to 10,000 charging cycles without losing a crucial amount of capacity. Jena (Germany) 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. Redox-flow batteries are the most promising technology to solve this problem but require expensive materials and aggressive acids.
A team at FSU Jena developed a new system. “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 electrodes of a redox-flow battery are not made of solid materials (e.g., metals or metal salts) but are in a dissolved form: The electrolyte solutions are stored in 2 tanks ie + and – 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 2 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.
Traditional redox-flow systems mostly use the heavy metal vanadium, dissolved in sulphuric acid as electrolyte ~extremely expensive, highly corrosive and life-span is limited. In the redox-flow battery novel synthetic materials are used: In their core structure they resemble Plexiglas and Styrofoam (polystyrene), but functional groups have been added enabling the material to accept or donate electrons. No aggressive acids are necessary anymore; the polymers rather ‘swim’ in an aqueous solution. “Thus we are able to use a simple and low-cost cellulose membrane and avoid poisonous and expensive materials,” Tobias Janoschka explains.
“This polymer-based redox-flow battery is ideally suited as energy storage for large wind farms and photovoltaic power stations,” Prof. Dr. Ulrich S. Schubert says. The energy density of the system presented in the study is 10 watt-hrs/L. The scientists are working on larger, more efficient systems. http://www.uni-jena.de/en/Research+News/FM151021_Batterie_en.html
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