Batteries based on Mg anodes are safe, show high volumetric capacity, and inexpensive, but the lack of compatible electrolytes and suitable cathodes has restricted the development of rechargeable Mg batteries. A group at CAS Qingdao Institute of Bioenergy has developed to this end a new type of organic magnesium borate based electrolyte which was synthesized via a facile in-situ reaction of tris(hexafluoroisopropyl)borate [B(HFP)3], MgCl2 and Mg powders in 1,2-dimethoxyethane (DME). It features high Mg plating/stripping performance, such as high anodic stability up to 3.3 V (vs. Mg/Mg2+), high ionic conductivity of 5.58 mS·cm–1, low overpotential of 0.11 V for plating process and above 98% Coulombic efficiency. The electrolyte is well compatible with sulfur positive electrodes. Magnesium sulfur batteries using this electrolyte were demonstrated to endure more than 100 cycles without obvious capacity decay and to enable fast conversion process, even at the charging current density up to 500 mA·g–1.

CAS news release, December 19, 2017