Optimization of magnesium-sulfur batteries through innovative materials and chemicals development

Due to the growing demand for energy storage materials, which is currently dominated by lithium-ion batteries. Nonetheless, considering the safety issues and the high costs of lithium batteries, rechargeable magnesium batteries have gained increased attention as an alternative thanks to their improved safety, high theoretical volumetric energy density (3832 mAh/cm3), as well as high earth-abundance and low costs. Sulfur, which possesses a high theoretical capacity (1672 mAh/g), non-toxicity and also earth abundance, is attractive as the cathode material to be coupled with the magnesium anodes. However, research on magnesium-sulfur (Mg-S) batteries is still very limited, compared to the developments in lithium batteries, mainly due to the lack of efficient and suitable electrolyte systems and compatible cathodes. Studies on pouch cell production and upscaling are and realization of the upscaling of particularly lacking. This thesis mainly consists of two chapters. The main objectives of the first chapter is the prodution of sulfur containing cathodes (Sulfur/Ketjen Black Composite,Sulfurized polyacrylonitrile (SPAN) and Aerogel) and the preparation of magnesium anodes (Gelion, PVDF/Aquivion and Mg/SnOx), together with the cathodes for cell assembly. In the second part of the thesis, the polysulfide shuttle mechanism was investigated and mitigated. For this process, Fraunhofer ISIT's patented LATP (Lithium Aluminum Titanium Phosphate) thin film separator technology was further developed and modified with metal oxide materials. Through the modification free sulfur molecules, that are in the electrolyte, are reduced by metal oxides to thiosulfates and retained on the separator surface. The new separators that produced with this mechanism are called ´´Sandwich Separator Technology´´ which is quite effective to minimize the polysulfide-shuttle in the cell.

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