Narges Ataollahi

Preparation and characterization of PVDF-MG49-NH4CF3SO3 based solid polymer electrolyte

Abstract The ionic conductivity of ammonium-based solid polymer films of poly(vinylidene fluoride) (PVDF) blended with MG49, a graft of natural rubber and poly(methyl methacrylate), with various compositions of ammonium triflate NH4CF3SO3, was investigated. As a result, 30 wt.% of NH4CF3SO3-doped polymer electrolyte exhibits the highest ionic conductivity at 6.32×10-4 S/cm at room temperature. The conductivity enhancement can be attributed to the increase in the number of NH4+ as charge carriers. The significance of the blend is the increase of one order in ionic conductivity as compared with pure PVDF electrolyte. The temperature dependence of conductivity of the electrolyte does not obey the Arrhenius law. However, the conductivity increases with temperature and it reached 1.56×10-3 S/cm at 363 K. X-ray diffraction reveals a decrease in crystallinity of the electrolyte upon the addition of NH4CF3SO3 salt. This result is supported by scanning electron microscopy. Linear sweep voltammetry demonstrates that the anodic stability of the electrolyte is up to 4 V. Therefore, the electrolyte shows good compatibility with high-voltage electrode. Hence, this electrolyte system can be a prospective candidate as lithium-ion conducting electrolyte for lithium batteries.

Comparative study of the properties of plasticized (PVDF-HFP)-MG49-LiBF 4 blend polymer electrolytes

Poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) blended with poly (methyl methacrylate) grafted natural rubber (MG49) and lithium tetrafluoroborate (LiBF4) as charge carriers based polymer electrolyte was prepared by solution casting technique. The effect of propylene carbonate (PC) and ethylene carbonate (EC) plasticizers on the properties of the polymer electrolyte films was investigated. Electrochemical impedance spectroscopy (EIS) showed that ionic conductivity increases as the concentration of plasticizer increases and the highest room temperature conductivities obtained are 1.51 × 10−3 S cm−1 and 7.39 × 10−4 S cm−1 at 80 wt % PC and 40 wt % EC, respectively. The addition of PC resulted in ionic conductivity enhancement in contrast with EC plasticizer. The temperature dependence conductivity for 80 wt % PC reached 6.52 × 10−2 S cm−1 at 373 K. Scanning electron microscopy (SEM) indicated the compatibility of PC with (PVDF-HFP)-MG49-LiBF4 whereas EC shows immiscibility with (PVDF-HFP)-MG49-LiBF4 complex. X-Ray Diffraction (XRD) studies show high degree of amorphous nature of the plasticized polymer electrolytes as indicated by reduction in the intensity of crystalline peaks. Thermogravimetric analysis (TGA) illustrates that the addition of plasticizer decreases the thermal stability of polymer electrolyte. However, linear sweep voltammetry (LSV) shows the electrochemical stability is up to 4 V.

Ionic Conductivity of PVDF-HFP/MG49 Based Solid Polymer Electrolyte

Blend-based polymer electrolytes composed of PVDF-HFP/MG-49 (70/30) and LiClO4 as lithium salt has been studied. Solution casting method was applied to prepare the polymer electrolyte. Electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the electrolyte films. The maximum value of 2.51×10ˉ6 S cm-1 was obtained at ambient temperature for the 30 wt. % of LiClO4 and the conductivity increased to 1.10×10ˉ3 S cm-1 by increasing the temperature up to 383 K. FTIR spectra demonstrated that complexation occurred between the polymers and lithium salt.

Effects of LiCF3SO3 on PVDF-HFP/MG49 (70/30) Based Blend Polymer Electrolyte

Poly (vinylidene fluoride-hexafluoro propylene) (PVDF-HFP), Poly (methyl methacrylate)-grafted natural rubber (MG49) (70/30) complexed with different compositions of lithium trifluoromethane sulfonate (LiCF3SO3) based solid polymer electrolyte has been prepared using solution casting method. This work has demonstrated that conductivity values were found to depend upon the concentration of LiCF3SO3. The highest ionic conductivity was 1.97×10ˉ4 S cm-1at 25 wt. % of LiCF3SO3 at room temperature. X-ray diffraction (XRD) indicates decrease in the degree of crystallinity by increasing of salt concentration.