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Ca metal anode rechargeable batteries are seen as a sustainable high-energy density and high-voltage alternative to the current Li-ion battery technology due to the low redox potential of Ca metal and abundance of Ca. Electrolytes are key enablers on the path towards next-generation battery systems. Within this work, we synthesize a new calcium tetrakis(hexafluoroisopropyloxy) aluminate salt, Ca[Al(hfip)4]2, and benchmark it versus the state-of-the-art boron analogue Ca[B(hfip)4]2. The newly developed aluminate-based electrolyte exhibits improved performance in terms of conductivity, Ca plating/stripping efficiency, and oxidative stability as well as Ca battery cell performance. A marked improvement of 0.5 V higher oxidative stability can pave the path towards high-voltage Ca batteries. A critical issue of solvent quality during salt synthesis is identified as well as solvent decomposition at the Ca metal/electrolyte interface, which leads to passivation of the Ca metal anode. However, the new aluminate salt with preferable electrochemical properties over the existing boron analogue opens up a new area for future Ca battery research based on aluminium compounds. [ABSTRACT FROM AUTHOR]

Sedimentation is a naturally occurring process of allowing particles in water bodies to settle out of the suspension under a gravity effect. In this study, the sediments of the Drava River were fully investigated to determine the heavy metal concentrations along the river and their potential reuse in the construction sector. Naturally dehydrated sediments from the Drava River were tested as an additive for the production of fired bricks. The dredged sediments were used as a substitute for natural brick clay in amounts up to 50% by weight, and it was confirmed that up to 20% by weight of the added sediment could be used directly in the process without critically affecting performance. Finally, the naturally dehydrated sediments were also evaluated for their use as a filling material in the construction of levees. The natural moisture content of the dehydrated sediment was too high for it to be used without additives, so quicklime was added as an inorganic binder. The test results showed an improvement in the geotechnical properties of the material to such an extent that it is suitable as a filling material for levees. [ABSTRACT FROM AUTHOR]

Magnesium-sulfur batteries are considered as attractive energy-storage 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. [ABSTRACT FROM AUTHOR]

Commercial LiMn2O4 powder was used as the base material for probing magnesiation, cycling behavior, and structural stability/changes in (MgxLi1-x)Mn2O4 spinel cathodes in aqueous Mg(NO3)2 and non-aqueous Mg(TFSI)2/diglyme and Mg(Mg(HFIP)2 − 2Al(HFIP)3/diglyme electrolytes. Each of the samples was delithiated and, then, magnesiated electrochemically in the corresponding electrolyte. The electrochemical activity of the cathode cycled in aqueous electrolyte showed high reversibility during the oxidation process; however, large polarization and a relatively fast capacity fading were the culprits of the system. Cycling in Mg(TFSI)2/diglyme electrolyte solution resulted in much lower initial specific capacity compared to an aqueous counterpart, as well as a much faster failure. On the other hand, cycling in Mg(HFIP)2 − 2Al(HFIP)3/diglyme electrolyte solution demonstrated excellent cycling performance with very low polarization in the first cycles. The observed voltages for this system were near theoretical values for the Mg insertion. Although the electrochemical measurements suggest reversible magnesiation, detailed structural and analytical STEM investigation revealed the differences in the atomic structure and Mn valence of all three cathode samples upon cycling. The electrolytes' influence on the structural rearrangement during Mg insertion is discussed for each of the three systems. [ABSTRACT FROM AUTHOR]

Development of magnesium sulfur battery is accompanied with all known difficulties present in Li–S batteries, however with even more limited choice of electrolytes. In the present work, the influence of current collector on electrochemical mechanism was investigated in light of different reports where improved behavior was ascribed to electrolyte. Notable differences in cycling behavior are reported when Al current collector is replaced by Cu current collector independent of electrolyte. The initial reduction of sulfur follows similar reaction path no mater of current collector, but formation of MgS can be in competition with formation of CuS in the presence of Cu cations. With the subsequent cycling cells prepared from cathodes deposited on Cu current collector show decrease in the voltage and formation of single plateau during cycling. The change corresponds to the involvement of Cu into the reaction and formation of redox couple Mg/CuS as determined by Cu K-edge XANES measurements. Corrosion of Cu foil is identified by SEM and serves as a source of Cu cations for the chemical reaction between Cu and polysulfides. Mg/CuS redox couple shows improved cycling stability, but theoretical energy density is severely reduced due to substitution of S with CuS as cathode active material. Image 1 • Influence of current collectors on electrochemistry of Mg–S battery is shown. • Increased stability and rate capability can be achieved with Cu current collector. • Formation of CuS was confirmed when using Cu current collector. • Severe degradation of Cu current collector was observed in different electrolytes. • Cu current collectors can not be used in combination with sulfur cathode. [ABSTRACT FROM AUTHOR]