Magnesium Sulfur Battery with a Porous Magnesium Powder Anode

Kurzfassung

Magnesium sulfur (MgS) secondary batteries show many advantages including a high theoretical volumetric density of 3200 Wh*L-1 compared to 2700 Wh*L-1 for lithium sulfur batteries. Furthermore, sulfur and magnesium are abundant and non-toxic materials. Another advantage compared to lithium is that magnesium is less susceptible to dendrite formation during deposition and less reactive thus enhances the safety of those batteries and facilitates handling of magnesium anodes. Unfortunately magnesium offers slower diffusion and reaction kinetics compared to lithium due to the divalent magnesium ion. High capacity loss during the first cycles can be observed [1]. Common electrolyte salts form a passivation layer on the magnesium anode which is non-permeable for magnesium ions [2, 3]. The development of components and processes applicable to large-scale production and low cost fabrication is a great challenge for the commercialization of metal sulfur batteries. Magnesium powder anodes provide excellent benefits compared to magnesium foil anodes in terms of lower overpotential and impedance, higher cycle stability, freedom of design and lower costs. Herein we report a magnesium powder anode with medium capacity retention and recovery of potential plateaus over reversible cycling. Furthermore powder anodes showed an optimized behavior during charging leading to an improved coulomb efficiency compared to magnesium foil anodes. Battery cells with a powder anode showed pronounced voltage plateaus and no problem to reach a 2.8 V cut-off voltage. Within the compaction pressure range investigated a magnesium powder anode prepared by relatively low pressures showed advantageous properties and was further investigated by electrochemical impedance spectroscopy. References 1. Sievert, B., Häcker, J., Bienen, F., Wagner, N and Friedrich, A. K. 77, 413–424 (2017). 2. Z. Lu, A. Schechter, M. Moshkovich, and D. Aurbach, J. Electroanal. Chem., 466, 203, (1999). 3. R. Mohtadi and F. Mizuno, Beilstein J. Nanotechnol., 5, 1291, (2014).