Ag+ ion transport studies in a polyvinyl alcohol-based polymer electrolyte system

Thick films of pure polyvinyl alcohol and polyvinyl alcohol doped with silver nitrate with different compositions have been prepared by solution cast technique. The FT-IR spectrum confirms the complexation process. The conductivity of the pure polyvinyl alcohol is of the order of 10⁻⁷ Sm⁻¹ at 90 °C, and its value increases by two orders of magnitude when doped with 20 wt% of AgNO₃. The activation energy, calculated from the Arrhenius plot for all compositions of the poly vinyl alcohol doped with silver nitrate, is between 0.24 and 0.35 eV. The migration energy for the ion in polymer electrolyte has been calculated from the modulus spectrum, and is in good agreement with the activation energy calculated from the Arrhenius plot. The modulus spectra indicate the non-Debye nature of the material.     

Structural,dielectric, and conductivity studies of yttrium-doped LiNiPO<Subscript>4</Subscript> cathode materials

Olivine-structured pure LiNiPO₄ and yttrium-doped LiNiPO₄ have been synthesized by a Pechini-type polymerizable precursor method. Compound formation temperature is confirmed from thermogravimetry to differential thermal analysis. Powder X-ray diffraction pattern confirmed the formation of phase pure LiNiPO₄ compound with an orthorhombic structure with fine crystallite size. Presence of preferred local cation environment is understood from Fourier transform infrared spectroscopy (FTIR) studies. XRD and FTIR studies show that doped yttrium ion entered in the lattice of LiNiPO_4. It has been found that the ionic conductivity of LiNiPO₄ is enhanced by around two orders of magnitude by doping yttrium. Dielectric spectra show the decrease in dielectric constant with increase in frequency. Dielectric loss spectra reveal that dc conduction contribution predominates in the sample.     

Dielectric and conductivity relaxations in PVAc based polymer electrolytes

The polymer electrolytes composed of a blend of poly (vinyl acetate) (PVAc) and poly (methylmethacrylate) (PMMA) as a host polymer and LiClO₄ as a salt are prepared by a solution casting technique. The formation of blend polymer- salt complex has been confirmed by FT-IR spectral studies. The conductivity- temperature plots are found to follow an Arrhenius nature. Arrhenius plot shows the decrease in activation energy with the increase in salt concentration. The dielectric behaviour of the sample is analysed using dielectric permittivity (ε′), dielectric loss (ε″) and electric modulus (M″) of the samples. The impedance cole- cole plot shows the high frequency semi- circle is due to the bulk effect of the material and the depression in the semicircle shows the non-Debye nature of the material. The bulk conductivity is found to vary between 2.5×10⁻⁵ Scm⁻¹ to 1.7×10⁻³ Scm⁻¹ with the increase of salt concentration of blend polymer samples. The migration energy derived from the dissipation factor is almost equal to the activation energy calculated from conductivity. The modulus spectrum of the samples shows the non-Debye behaviour of the polymer electrolyte films. The low frequency dispersion of the dielectric constant implies the space charge effects arising from the electrodes. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Vibrational,electrical, and ion transport properties of PVA-LiClO<Subscript>4</Subscript>-sulfolane electrolyte with high cationic conductivity

Novel solid polymer electrolytes, poly(vinylalcohol)-lithium perchlorate (PVA-LiClO₄) and PVA-LiClO₄-sulfolane are prepared by solvent casting method. The experimental results show that sulfolane addition enhances the ionic conductivity of PVA-LiClO₄ complex by three orders. The maximum ionic conductivity of 1.14 ± 0.20 × 10^?2 S cm^?1 is achieved for 10 mol% sulfolane-added electrolyte at ambient temperature. Polymer-salt-plasticizer interactions are analyzed through attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Lithium ion transference number is found by AC impedance spectroscopy combined with DC potentiostatic measurements. The results confirm that sulfolane improves the Li⁺ transference number of PVA-LiClO₄ complex to 0.77 from 0.40. The electrochemical stability window of electrolytes is determined by cyclic voltammetry (CV). The broad electrochemical stability window of 5.45 V vs. lithium is obtained for maximum conducting electrolyte. All-solid-state cell is fabricated using maximum conducting electrolyte, and electrochemical impedance study is carried out. It reveals that electrolyte interfacial resistance with Li electrode is very low. The use of PVA-LiClO₄-sulfolane as a viable electrolyte material for high-voltage lithium ion batteries is ensured.     

Ionic conductivity studies on LiSmO<Subscript>2</Subscript> by impedance spectroscopy

Lithium samarium oxide has been prepared by solid-state reaction method and characterized by X-ray diffraction (XRD) and impedance spectroscopy. XRD pattern of the sample reveals the formation of the sample. The conductivity studies, dielectric studies, and modulus analysis of the samples have been carried out for different temperatures. The bulk conductivity of the sample has been found to be 1.21 × 10⁻⁵ Scm⁻¹ at 420 °C. The temperature variation of the direct current conductivity obeys the Arrhenius relation. The modulus analysis of the sample indicates the non-Debye nature of the sample which corresponds to long-time slow polarization and relaxation of hopping charges.     

Ionic conductivity studies on Sr stabilized zirconia by impedance spectroscopy

Sr stabilized zirconia has been prepared by the co-precipitation method and electrically characterized by using impedance spectroscopy in the frequency range from 42 Hz to 5 MHz. The charge carrier concentration of the material has been calculated from the conductance spectra and it is found to be of the order of 10²⁵ cm⁻³. The conductance spectra show a dc plateau and a dispersive region suggesting correlated hopping motion of the ions. The impedance analysis shows a depressed semicircle indicating non-Debye nature of the material as well as the broad nature of modulus peaks indicates non-Debye behaviour. The bulk resistance of the material has been extracted from the impedance spectra and it is found to be 3.5×10⁷ Ω·cm⁻¹ at 673 K. The low frequency dispersion of the dielectric constant implies the space charge effects arising from the electrodes. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28 – 30, 2003.     

Influences of LiCF3SO3 and TiO2 nanofiller on ionic conductivity and mechanical properties of PVA:PVdF blend polymer electrolyte

In recent years, solid polymer electrolytes have been extensively studied due to its flexibility, electrochemical stability, safety, and long life for its applications in various electrochemical devices. Interaction of LiCF₃SO₃ and TiO₂ nanofiller in the optimized composition of PVA:PVdF (80:20—system-A possessing σ ~ 2.8 × 10⁻⁷ Scm⁻¹ at 303 K) blend polymer electrolyte have been analyzed in the present study. LiCF₃SO₃ has been doped in system-A, and the optimized LiCF₃SO₃ doped sample (80:20:15-system-B possessing σ ~ 2.7 × 10⁻³ Scm⁻¹ at 303 K) has been identified. The effect of different concentration of TiO₂ in system-B has been analyzed and the optimized system is considered as system-C (σ ~ 3.7 × 10⁻³ Scm⁻¹ at 303 K). The cost effective, solution casting technique has been used for the preparation of the above polymer electrolytes. Vibrational, structural, mechanical, conductivity, thermal, and electrochemical properties have been studied using FTIR, XRD, stress-strain, AC impedance spectroscopic technique, DSC and TGA, LSV, and CV respectively to find out the optimized system. System-C possessing the highest ionic conductivity, higher tensile strength, low crystallinity, high thermal stability, and high electrochemical stability (greater than 5 V vs Li/Li⁺) is well suitable for lithium ion battery application.

     

Investigation on dielectric relaxations of PVP-NH4SCN polymer electrolyte

Poly (N-vinyl pyrrolidone) (PVP) and ammonium thiocyanate (NH₄SCN) based polymer films with different compositions have been prepared by solution casting technique. The amorphous nature of the polymer electrolytes has been confirmed by XRD analysis. The FTIR analysis confirms the complex formation of the polymer with the salt. The conductivity analysis shows that the 20 mol% ammonium thiocyanate doped polymer electrolyte has high ionic conductivity and it has been found to be 1.7 × 10⁻⁴ S cm⁻¹, at room temperature. From the admittance plot, the activation energy has been found to be low for 20 mol% salt doped polymer electrolyte. The dielectric behavior has been analyzed using dielectric permittivity (ε^∗), dissipation factor (tan δ) and electric modulus (M^∗) of the samples.     

Structural, vibrational, thermal, and conductivity studies on proton-conducting polymer electrolyte based on poly (N-vinylpyrrolidone)

The proton-conducting polymer electrolytes based on poly (N-vinylpyrrolidone) (PVP), doped with ammonium chloride (NH₄Cl) in different molar ratios, have been prepared by solution-casting technique using distilled water as solvent. The increase in amorphous nature of the polymer electrolytes has been confirmed by XRD analysis. The FTIR analysis confirms the complex formation of the polymer with the salt. A shift in glass transition temperature (T _g) of the PVP/NH₄Cl electrolytes has been observed from the DSC thermograms which indicates the interaction between the polymer and the salt. From the AC impedance spectroscopic analysis, the ionic conductivity of 15?mol% NH₄Cl-doped PVP polymer complex has been found to be maximum of the order of 2.51?×?10^?5?Scm^?1 at room temperature. The dependence of T _g and conductivity upon salt concentration has been discussed. The linear variation of the proton conductivity of the polymer electrolytes with increasing temperature suggests the Arrhenius type thermally activated process. The activation energy calculated from the Arrhenius plot for all compositions of PVP doped with NH₄Cl has been found to vary from 0.49 to 0.92?eV. The dielectric loss curves for the sample 85?mol% PVP:15?mol% NH₄Cl reveal the low-frequency ?? relaxation peak pronounced at high temperature, and it may be caused by side group dipoles. The relaxation parameters of the electrolytes have been obtained by the study of Tan?? as a function of frequency.     

Electrical,dielectric and electrochemical studies on new Li ion conducting solid polymer electrolytes based on polyethylene glycol <Emphasis Type="Italic">p-tert</Emphasis>-octylphenyl ether

The aim of this work is to study the effect of non-ionic short chain liquid polymer on the conductivity of PVA-LiClO₄ membrane. Polyethylene glycol p-tert-octylphenyl ether (Triton X-100) is used as an additive with different concentrations in PVA-LiClO₄ matrix. The conductivity of additive incorporated polymer electrolyte increases to two orders of magnitude than the pristine polymer electrolyte. The maximum conductivity is measured to be 1.92 mS/cm at ambient temperature. The conductivity enhancement is correlated with the availability of free ions as well as segmental motion of polymer chain with the aid of FTIR and Dielectric relaxation tools. DC polarization and cyclic voltammetry techniques are also carried out to check the suitability of prepared polymer electrolytes as electrolyte material for batteries.