The in-house project pushed the development of Lithium-sulphur batteries using new cathodes, electrolytes, and anodes that could attractively replace today's Lithium-ion batteries in electromobility applications. Lithium-sulphur distinguishes itself with its very low material cost and high energy density up to 400 Wh/kg, which the researchers hope could be further optimized up to 500 Wh/kg. These cells already achieve up to 40% higher energy densities than the best lithium ion cells today.
Li-S cells designed with metallic lithium anodes come with their own challenge though, they have a poor cycling ability, and can only be discharged and re-charged 50 to 100 times. This is due to a chemical reaction whereby the electrolyte attacks the anode surface.
Hence, Fraunhofer's scientists developed a novel cell design based around an anode made of a silicon alloy as a substitute for metallic lithium. What's more, the new cell design replaces the expensive cathode material of Li-ion cells by the abundant and cost-effective non-toxic sulphur.
Besides their involvement with materials development, the four participating Fraunhofer Institutes – the Institute for Material and Beam Technology IWS (Dresden), Institute for Organic Electronics, Electron Beam and Plasma Technology FEP (Dresden), Institute for Transportation and Infrastructure Systems IVI (Dresden), and Institute for Chemical Technology ICT (Pfinztal) –also worked on the scalability of the fabrication processes for anodes and cathodes in the form of roll-to-roll foils and on the construction of battery modules.
This new anode and cell design has been implemented and demonstrated in Li-S and Li-ion prototype cells at the Fraunhofer IWS and the researchers were also able to efficiently produce the sulphur cathodes.