Mg batteries are a promising battery technology that could lead to safer and significantly less expensive non-aqueous batteries with energy densities comparable or even better than state-of-the-art Li-ion batteries. Although the first prototype Mg battery using stable Mo6S8 as cathode was introduced over fifteen years ago, major challenges remain to be solved. In particular, the design of high energy cathode materials and the development of non-corrosive electrolytes with high oxidative stability are issues that need to be tackled. Herein, we present a new, general, and robust approach towards achieving stable cycling of Mg batteries. The core of our approach is the use of stable polymer cathode and Mg powder anode coupled with non-nucleophilic electrolytes. Our systems exhibit an excellent rate capability and significant improvement in electrochemical stability.
Magnesium−sulfur batteries are considered as attractive energystorage devices due to the abundance of electrochemically active materials and high theoretical energy density. Here we report the mechanism of a Mg−S battery operation, which was studied in the presence of simple and commercially available salts dissolved in a mixture of glymes. The electrolyte offers high sulfur conversion into MgS in the first discharge with low polarization. The electrochemical conversion of sulfur with magnesium proceeds through two well-defined plateaus, which correspond to the equilibrium between sulfur and polysulfides (high-voltage plateau) and polysulfides and MgS (low-voltage plateau). As shown by XANES, RIXS (resonant inelastic X-ray scattering), and NMR studies, the end discharge phase involves MgS with Mg atoms in a tetrahedral environment resembling the wurtzite structure, while chemically synthesized MgS crystallizes in the rock-salt structure with octahedral coordination of magnesium.
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