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Kurzfassung

A solvent-free liquid electrolyte with excellent charge/discharge performance and without the need for additional supporting salts

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Hintergrund

To integrate high shares of solar and wind renewables into the global electricity grids, efficient battery storage systems are needed. In this context, redox flow batteries are among the most promising candidates for large-scale energy storage, as they offer a flexible and scalable modular design and an exceptionally long lifetime. However, the limited energy density of redox flow batteries is an obstacle to their widespread market introduction and is the subject of intensive scientific research.

The most common solution so far is a vanadium-based electrolyte. But this metal is rare, compared to the demand, and therefore expensive. Alternatively organic redox-active materials in particular have attracted a lot of attention due to their low cost, large abundance and structural tunability. However used as an aqueous solution their handicap is a limited stability window of water and restricted solubility of redox-active organic materials and thus a lower energy density.

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Lösung

Inventors of Saarland University were able to develop solvent-free liquid electrolytes that contain much higher concentrations of redox-active organic compounds and enable a wider working potential and thus a much higher energy density than the usual aqueous solutions. With regard to this aspect, the electrolytes according to the invention can easily compete with the usual vanadium-based systems but furthermore offer a favourable cost and environmental balance.

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Vorteile

• High energy density
• Low cost organic compounds as redox-active agents
• High tunability
• Excellent charge/discharge performance
• Free of solvents like water (=> higher operating voltage, higher concentration of redox-active compounds)
• No additional supporting salts needed
• Liquid over a wide temperature range of at least -70 to +80 degrees Celcius
• Good safety characteristics