Researchers at Karlsruhe Institute of Technology have developed a new concept for rechargeable batteries, based on a fluoride shuttle – the transfer of fluoride anions between electrodes – which could allow high energy densities up to ten times as high as those of conventional lithium-ion batteries. Operational safety is also increased, as it can be done without lithium.

Metal fluorides may be applied as conversion materials in lithium-ion batteries. They may also allow for lithium-free batteries with a fluoride-containing electrolyte, a metal anode, and metal fluoride cathode, which reach a much better storage capacity and possess improved safety properties. Instead of the lithium cation, the fluoride anion takes over charge transfer. At the cathode and anode, a metal fluoride is formed or reduced.

The KIT researchers are now working on the further development of material design and battery architecture to improve the initial capacity and cyclic stability of the fluoride-ion battery. Another challenge lies in the further development of the electrolyte; the solid electrolyte applied is so far only suited for applications at elevated temperatures. Researchers are working to find a liquid electrolyte that is suitable for use at room temperature.

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Also: A low-cost approach to stabilization of Li metal anodes for high-performance rechargeable batteries was developed.