Cell development

Lithium sulfur batteries are characterized by high gravimetric energy densities and low material costs. A challenge for the application of these cells results from the volume or thickness changes over the charge state, which can be up to 10 %. Due to this volume increase, special adjustments would be necessary on system level.

The project aims at developing a new generation of cells with a significantly reduced total density change and full capacity utilization by adapting the electrode materials and integrating them into overall cell concepts. At Fraunhofer IWS the complete process chain for the prototyping of cells up to 25 Ah has been established and first Li-S cells achieve specific energies > 400 Wh/kg. New electrode and material concepts can thus be transferred into multilayer pouch cells and evaluated closely to the application.

Lithium-ion cells with graphite and oxide electrodes are state-of-the-art today. To further increase the energy density of future-oriented lithium-ion cells, innovative electrode concepts such as Li-metal, silicon, Ni-rich NCM or sulfur are being developed. These materials, however, show strong changes in volume during charging and discharging and thus pose great challenges not only for the electrode development but also for the entire cell design. The volume changes of the electrodes cause, among other things, changes in the thickness of pouch cells, which have to be extensively compensated in the battery modules.

At the EBZ Dresden new, innovative approaches to minimize volume changes at electrode level are therefore integrated and tested in cell concepts. By modeling multilayer pouch cells, the cell design will be improved to achieve high energy densities with minimal thickness changes over the charge state.