03 Fakultät Chemie

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Author: search.filters.author.Buchmeiser, Michael R.Subject: search.filters.subject.621.3

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    High‐performance magnesium‐sulfur batteries based on a sulfurated poly(acrylonitrile) cathode, a borohydride electrolyte, and a high‐surface area magnesium anode
    (2020) Wang, Peiwen; Trück, Janina; Niesen, Stefan; Kappler, Julian; Küster, Kathrin; Starke, Ulrich; Ziegler, Felix; Hintennach, Andreas; Buchmeiser, Michael R.
    Post‐lithium‐ion battery technology is considered a key element of future energy storage and management. Apart from high gravimetric and volumetric energy densities, economic, ecologic and safety issues become increasingly important. In that regards, both the anode and cathode materials must be easily available, recyclable, non‐toxic and safe, which renders magnesium‐sulfur (Mg-S) batteries a promising choice. Herein, we present Mg-S cells based on a sulfurated poly(acrylonitrile) composite cathode (SPAN), together with a halogen‐free electrolyte containing both Mg[BH4]2 and Li[BH4] in diglyme and a high‐specific surface area magnesium anode based on Rieke magnesium powder. These cells deliver discharge capacities of 1400 and 800 mAh/gsulfur with >99 % Coulombic efficiency at 0.1 C and 0.5 C, respectively, and are stable over at least 300 cycles. Energy densities are 470 and 400 Wh/kgsulfur at 0.1 C and 0.5 C, respectively. Rate tests carried out between 0.1 C and 2 C demonstrate good rate capability of the cells. Detailed mechanistic studies based on X‐ray photoelectron spectroscopy and electric impedance spectroscopy are presented.
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    Differences in electrochemistry between fibrous SPAN and fibrous S/C cathodes relevant to cycle stability and capacity
    (2017) Warneke, Sven; Eusterholz, Michael; Zenn, Roland K.; Hintennach, Andreas; Dinnebier, Robert E.; Buchmeiser, Michael R.
    Two different Li/S cathodes are compared in terms of capacity (mA.h.gsulfur-1) and intermediates during discharge and charge. One cathode material is based on fibrous SPAN, a sulfur-containing material obtained via the thermal conversion of poly(acrylonitrile), PAN, in the presence of sulfur. In this material, sulfur is covalently bound to the polymeric backbone. The second cathode material is based on porous activated carbon fibers (ACFs) with elemental sulfur embedded inside the ACFs’ micropores. Cyclic voltammetry clearly indicates different discharge and charge chemistry of the two materials. While S-containing ACFs show the expected redox-chemistry of sulfur, SPAN does not form long-chain polysulfides during discharge; instead, sulfide is chopped off the polymer-bound sulfur chains to directly form Li2S. The high reversibility of this process accounts for both the high cycle stability and capacity of SPAN-based cathode materials.