Synthesis and characterization of polyvinylidene fluoride/magnesium bromide polymer electrolyte for magnesium battery application

The development of a magnesium ion conducting electrolyte is essential for designing rechargeable magnesium batteries. Herein, we report magnesium-ion conducting polymer electrolytes (PE) based on polyvinylidene fluoride (PVDF) and tetraethylene glycol dimethyl ether (TEGDME) with magnesium bromide salt processed by solution casting method. Fourier-transform infrared spectroscopy (FTIR) shows a composite between the polymer and the MgBr2 salt forms. X-ray diffraction (XRD) data reveals that the broad reflections of the PVDF polymer are reduced with the addition of TEGDME and MgBr2, with scanning electron microscopy (SEM) illustrating changes in the morphology. The ionic conductivity and the relaxation time are found to be 1.2 × 10−6 S cm−1 and 5.7 × 10−5 s−1 at room temperature, respectively. This polymer electrolyte exhibits initial cycles with low overpotential, reversible Mg plating/stripping, and an excellent Mg-ion transfer number (tMg2+) = 0.55. The assembled Mg/graphite and Mg/graphene nanoplatlets (GNP) prototype cells with this polymer electrolyte (PE) demonstrate the interaction of the magnesium ions with the electrodes.