Improving electrochemical performance of rechargeable magnesium batteries with conditioning-free Mg-Cl complex electrolyte

The scheme shows the synthesis process of electrolyte MAT by the method of dividing Mg powders into TEG solution which contains 0.012 mol/L TiCl4 and 0.4 mol/L AlCl3. [Display omitted] •The electrolyte with high Mg/Al ratio is synthesized by TiCl4-initiated reaction.•The electrochemically active species in the electrolyte is [MgCl∙TEG]+.•The Mg powders act as magnesium ion precursor and moisture scavenger for electrolyte.•The discharge specific capacity of Mg-S battery is 834 mAh/g after 100 cycles.•The conversion kinetics of sulfur cathode is enhanced by lithium bromide electrolyte additive. Electrolyte plays an important role in development of rechargeable magnesium batteries with high energy density and safety. Here, a novel electrolyte is synthesized by the reaction between magnesium powder, AlCl3 and TiCl4 in tetraethylene glycol dimethyl ether. It shows promising electrochemical properties among the current inorganic Mg2+ electrolytes in terms of excellent reversibility and good stability, which can support magnesium deposition and stripping for 1000 cycles with a relatively low overpotential at 0.1 mA/cm2. The non-nucleophilic characteristics makes it well-suited for sulfur cathode of rechargeable Mg batteries. The rechargeable Mg battery coupled with KB/S electrode using copper current collector and Mg anode delivers a high discharge specific capacity of nearly 1000 mAh/g and an impressive prolonged cycle life for 100 cycles, and also shows the excellent rate capability when using lithium bromide as electrolyte additive.