Characteristics of Magnesium-Sulfur Batteries Based on a Sulfurized Poly(acrylonitrile) Composite and a Fluorinated Electrolyte

Abstract A magnesium-sulfur (Mg-S) battery system based on a sulfurized poly(acrylonitrile) (“SPAN”) composite as cathode material is presented. Using magnesium tetrakis(hexafluoroisopropyloxy) borate, Mg[B(hfip)4]2, as conductive salt in the electrolyte, the cycle performance of Mg-S batteries based on SPAN and different types of Mg anodes, i.e. Mg foil and pressed Mg powder, respectively, were compared. A cell composed of Mg foil and SPAN delivered a discharge capacity around 300 mAh/gsulfur at C/30 while a cell based on SPAN and pressed Mg powder delivered ca. 500 mAh/gsulfur (energy density of ca. 422 mWh/gsulfur) at C/30 and also possessed good rate capability. The higher discharge capacities of Mg-S cells based on pressed anodes are attributed to the substantially higher specific surface area of the pressed cells. Post-mortem analysis of aged cells based on SPAN and a pressed Mg anode indicates the formation of MgF2 on both the cathode and the anode along with magnesium polysulfide species.