Easy Scalable High-Energy-Magnesium-Sulfur (Mg/S)-Batteries

Kurzfassung

Demands in energy storage require a significant improvement in the energy density of battery systems. Therefore innovative systems with a substantially higher specific energy and improved cycle life have to be developed. The combination of Magnesium and Sulfur addresses several advantages, such as natural abundance, operational safety and a high volumetric capacity. However the research so far was hindered because a stable electrolyte for Mg-S-Batteries was missing [1]. Muldoon et. al. developed a stable and reversibly working nonnucleophilic electrolyte based on a recrystallized Mg2+ salt complex [Mg(μ- Cl)3(THF)6][HMDSAlCl3] (HMDS=hexamethyldisilazid) [2]. This crystalline electrolyte salt though could only be obtained in THF, revealing several disadvantages [2]. A break-through in Mg/S battery performance was obtained by Fichtner et. al. They at first synthesized a one-step routine between [(HMDS)2Mg]=magnesium bis(hexamethyldisilazid) and AlCl3 in different ethers, enhancing solvent choice and possibility of neglecting aforementioned disadvantages [3]. Furthermore a magnesium-anode enhances safety of Mg-S-battery, due to the missing tendency of dendrite formation [4]. Safety as well as capacity and scalability of fabrication of a battery are important factors to assess market opportunities of these secondary cells. Therefore the German Aerospace Center, located in Stuttgart, is focusing its development on the performance of “easy-to-fabric” high-energy-sulfur-electrodes with a realistic active material loading. Based on the multiannual experience in the development of lithium-sulfur batteries, we extend our activities to the field of magnesium sulfur-battery-development. In a first attempt two different S-C-Cathodes were evaluated with a 0.6m Mg2+-salt electrolyte solved in a mixture of 2:1 by volume of bis(2-methoxyethyl)ether and an ionic liquid. Furthermore different approaches for a working Mg-graphite-compositeanode are presented. Additionally a method for electrolyte viscosity measurement in an argon filled glovebox is applied.