Polymer electrolytes based on magnesium triflate for quasi-solid-state magnesium-sulfur batteries

Abstract

Abstract Herein, magnesium-ion conducting polymer electrolytes (PE) based on polyvinylidene fluoride (PVDF), tetraethylene glycol dimethyl ether (TEGDME), succinonitrile (SN), and different concentrations of magnesium triflate salt ((CF 3 SO 3 ) 2 Mg) were fabricated. The structural, optical, electrical, and electrochemical properties were investigated. The conductivity increases to about 10 −5 S.cm −1 with increasing the concentration of (CF 3 SO 3 ) 2 Mg up to 33 wt%, at room temperature. The ionic transference number for the matrix containing 33 wt% of (CF 3 SO 3 ) 2 Mg increases from ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>m</mml:mi> <mml:msup> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:msub> </mml:math> = 0.4) to ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>M</mml:mi> <mml:msup> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.8</mml:mn> </mml:math> ) with increasing the temperature comparatively from room temperature to 55 °C. Also, the cell with 33 wt% of (CF 3 SO 3 ) 2 Mg shows low overpotential and steady Mg stripping/plating during the initial cycles at 55 °C. Polymer and dual electrolytes, as well as bare and modified Mg surface electrodes, are used to create Mg/S cells. The cell with a modified Mg surface electrode and dual electrolyte exhibit lower interfacial impedance, higher energy density, and charge-discharge capacity than the cell with a bare Mg electrode and polymer electrolyte.