Easily synthesized fluorinated magnesium alkoxyborates with non-corrosive and chemically stable features show high electrochemical performance as magnesium ion conducting salts.

Rechargeable calcium (Ca) batteries have the prospect of high-energy and low-cost. However, the development of Ca batteries is hindered due to the lack of efficient electrolytes. Herein, we report novel calcium tetrakis(hexafluoroisopropyloxy)borate Ca[B(hfip)₄]₂ based electrolytes exhibiting reversible Ca deposition at room temperature, a high oxidative stability up to 4.5 V and high ionic conductivity >8 mS cm⁻¹. This finding opens a new approach towards room-temperature rechargeable calcium batteries.

Non-nucleophilic electrolytes with outstanding electrochemical performances for magnesium batteries have been synthesized through the reaction between a bisamide magnesium and a Lewis acid in an aprotic solvent. High anodic stability, good ionic conductivity, excellent cycling efficiency and the feasibility of the preparation make the in situ generated electrolyte very promising for the potential application in rechargeable magnesium batteries.