Investigation of the electrochemical performance of Mg-ion batteries based on PVDF-HFP thin polymer electrolyte films

Abstract

In the present work, poly(vinylidene fluoride-hexafluoropropylene):magnesium trifluoromethanesulfonate (PVDF-HFP:MgTf) polymer electrolytic films with a porous structure were developed using the solution-casting method. With its high performance and versatility, PVDF-HFP has been widely employed in the development of solid polymer electrolyte films (SPEFs). In this study, metal salt particles are successfully included as an inorganic filler into solid PVDF-HFP films, reducing pore size and boosting the amorphous character of the films. Fourier transform infrared spectroscopy is used to examine the chemical structure of the produced SPEFs, and scanning electron microscopy is used to evaluate the surface morphology and locate pores in the SPEFs. The surface nature of the PVDF-HFP films and the PVDF-HFP:MgTf is confirmed by X-ray diffraction. The electrochemical stability of PVDF-HFP and PVDF-HFP:MgTf films is studied through a differential scanning calorimetry experiment. Results revealed that PVDF-HFP:MgT films could be stabilized when filled with electrolytes and electrodes and made less porous by adding inorganic salt particles. Further, electrochemical impedance spectroscopy is used to measure electrical conductivity between 303 and 423 K. At room temperature, PVDF-HFP and PVDF-HFP/Mg2+ SPEFs have optimal ionic conductivities of 3.38 × 10−7 and 1.08 × 10−6 SS ccmm−1−1 respectively. Ionic conductivity was found to increase with temperature. The modulus of the imaginary part of the loss tangent (M′ and M″) was found to be related to dielectric and conductivity relaxation.