Lithium-Sulfur High Energy Accumulators

The successful design of Li-S batteries with high energy density has the challenging perspective to significantly boost the development of environmently friendly automotive technology. Li-S batteries will triple the energy density of existing Li-oxide batteries combined with high reversibility of fast charging-discharging cycles and lifetime of thouthands of cycles. Based on detailed investigations of novel cathode materials with nanocontainers for electrochemical active materials, we plan to develop hierarchically structured carbon electrodes on micro- and nano-scale leading to high-energy density Li-S batteries. In our multidisciplinary consortium polymer engineers will develop the new polymer-based cathode materials, electro-chemists will optimise the electrochemical performance and physicists try to understand basic principles both from experimental as well as from theoretical viewpoint. Application aspects will be introduced by close contact with a leading battery producing company. New materials development routes will be combined with dedicated instrumentation to reveal structural and electro- chemical aspects at different levels, absolute elemental composition, depth profiling and electronic oxidation states as well as simulation of charging and discharging.

Realizing a future in which electric driven vehicles dominate the picture of calm cities, small and light weighted batteries capable of providing a high and stable amount of energy over many charge/discharge cycles are necessary. Lithium Sulfur Batteries are a promising candidate for overcoming the existing technological restrictions of state of the art Lithium Ion batteries in terms of energy density. However, lots of research has to be done to overcome technological challenges within this system and paving the way for its public use.In this collaborative research project Varta Micro Innovation (VMI) GmbH worked together with a multidisciplinary consortium of researches aiming at different issues. The knowhow of chemical engineers from the Leibniz Institut für Polymerforschung (IPF) in Dresden on synthesizing nano structured carbon materials (which are an important ingredient in sulfur containing electrodes) was combined with VMIs knowhow on testing electrochemical power sources resulting in a novel approach for the fabrication of carbon sulfur material which showed high initial capacities, however the cycling stability of the batteries has still to be improved. Therefore physicists from Physikalisch Technische Bundesanstalt (PTB) Berlin and Universität Ulm investigated the principles inside the battery, which is crucial for understanding the performance limiting factors in a battery. Theoretical simulations and an advanced analytical method (Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy) were combined, trying to identify chemical species at different states of charge of the battery. The analytical method was proven to be applicable for the specific issue and has now to be taken to the next level by applying in situ investigations.