Thermal, vibrational, and dielectric studies on PVP/LiBF4+ionic liquid [EMIM][BF4]-based polymer electrolyte films

• Free-standing polymer electrolyte film-based (PVP)/salt (LiBF4)+IL [EMIM][BF4] were prepared.
• TGA and dielectric results give evidence of the presence of uncomplexed PVP, PVP/salt, and PVP/IL complexes.
• Complexation of PVP with salt and IL has been confirmed by FT-IR studies.
• Temperature dependence of conductivity exhibits VTF behavior.
• Plasticization effect of IL introduces large shifts in Tm of PVP.

Free-standing polymer electrolyte membranes based on poly(vinyl) pyrrolidone (PVP)/salt(LiBF4) having different amounts of ionic liquid (IL) [EMIM][BF4] were prepared and characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and alternating current (AC) impedance spectroscopic techniques. The DSC results show a shift in Tm of PVP with salt/or IL content. TGA and DTGA (first derivative of TGA) results give evidence of the presence of uncomplexed PVP, PVP/salt, and PVP/IL complexes. Signatures of these entities are also present in the dielectric spectra. Complexation of PVP with salt and IL has been confirmed by FT-IR analysis. Electrical conductivity as a function of temperature has been studied for PVP/LiBF4/IL [EMIM][BF4]. Role of IL in changing phase transition, conductivity, and dielectric relaxation frequency has been discussed.

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