Dielectric properties and conductivity of PVdF-co-HFP/LiClO₄polymer electrolytes

Abstract

In this study, it was aimed to prepare a series of PVdF-co-HFP based electrolytes with different LiClO4 loadings and to investigate their chemical and electrical properties in detail. For this purpose, PVdF-co-HFP based electrolytes with different LiClO4 loadings (1–20 weight %) were prepared using solution casting method. X-ray diffraction (XRD), differential scanning calorimetry, and thermogravimetric (TGA) –differential thermal and dielectric spectroscopy analysis of PVdF-co-HFP/LiClO4 were performed to characterize their structural, thermal, and dielectric properties, respectively. XRD results showed that the diffraction peaks of PVdF-co-HFP/LiClO4 electrolytes broadened and decreased with LiClO4. TGA patterns exhibited that PVdF-co-HFP/LiClO4 electrolytes with 20 wt % of LiClO4 had the lowest thermal stability and it degraded above 473 K, which is highly applicable for solid polymer electrolytes. Dielectric constant, dielectric loss, and conductivities were calculated by measuring capacitance and dielectric loss factor of PVdF-co-HFP/LiClO4 in the range from 10 mHz to 20 MHz frequencies at room temperature. In consequence, conductivities of PVdF-co-HFP/LiClO4 increased significantly with frequency for low loading of LiClO4 while they only slightly changed with higher LiClO4 addition. On the other hand, dielectric constant values of PVdF-co-HFP/LiClO4 films decreased with frequency whereas they rose with LiClO4 addition. The dielectric studies showed an increase in dielectric constant and dielectric loss with decreasing frequency. This result was attributed to high contribution of charge accumulation at the electrode–electrolyte interface. The electrolyte showed the maximum conductivity of 8 × 10−2 S/cm at room temperature.

Enhanced electroactive β‐phase and dielectric properties in P(VDF‐HFP) composite flexible films through doping with three calcium chloride salts: CaCl2, CaCl2·2H2O, and CaCl2·6H2O

“…This is attributed to the fact that the porosity and β ‐phase fraction of this composite film reached their maximum, as confirmed in Figure 3 and Table 3, resulting in a significantly higher relative dielectric constant in the composite film. It is also shown that the dielectric loss is only 0.49 at frequency of 10 Hz, which is much smaller than most of the data reported in literature at the same level of dielectric constant 45,75 . Therefore, the enhancement of net dipole moment is beneficial to the improvement of polarization and dielectric constant of P(VDF‐HFP)/CaCl 2 ·6H 2 O composite films.…”

“…The capacitance (C) of each sample was determined as a function of frequency ranging from 1 Hz to 100 kHz at room temperature. The dielectric constant $$$ \left({\varepsilon}_r^{\prime}\right) $$$ or real part of the relative permittivity, dielectric loss tangent (tan δ ), and ionic conductivity ( σ ) of all samples could be derived from the following relationships 45–47 : $$$$ {\varepsilon}_r^{\prime }=\frac{C\kern0.1em t}{\varepsilon_0A},\tan \delta =\frac{{\varepsilon^{\prime}}_r^{\prime }}{\varepsilon_r^{\prime }},\sigma =\frac{t}{R_bA}, $$$$ where ε 0 represents the vacuum permittivity (8.854 × 10 −12 Fm −1 ), and t and A denote the film thickness (m) and the area of the electrode contact (m 2 ), respectively. $$$ {\varepsilon^{\prime}}_r^{\prime } $$$ represents the imaginary component of the relative permittivity.…”

“…It is also shown that the dielectric loss is only 0.49 at frequency of 10 Hz, which is much smaller than most of the data reported in literature at the same level of dielectric constant. 45,75 Therefore, the enhancement of net dipole moment is benefi- Consequently, these findings indicate that the addition of hydrated salt plays a crucial role in making them well-suited for dielectric applications.…”

“…The capacitance (C) of each sample was determined as a function of frequency ranging from 1 Hz to 100 kHz at room temperature. The dielectric constant ε 0 r À Á or real part of the relative permittivity, dielectric loss tangent (tan δ), and ionic conductivity (σ) of all samples could be derived from the following relationships [45][46][47] :…”