PEO:KIO3 Polymer electrolyte system- its application to solid state electrochemical cell

In search of polymer electrolyte based on PEO- salt complexes other than the extensively studied lithium-based polymer electrolytes, we report the new polymer electrolyte based on PEO complexed with KIO₃ salt. Several experimental techniques such as differential scanning calorimetry (DSC), composition dependence conductivity, temperature dependence conductivity and transport number measurements have been performed to characterize the polymer electrolyte. DSC study reveals that the melting temperature of pure PEO is shifting towards lower temperatures by complexing with the KIO₃ salt. The conductivity-temperature plots show two regions below and above the melting point (T_m). Transport numbers data suggest that the charge transport in this polymer electrolyte system is mainly due to ions. Using the polymer electrolyte films solid-state electrochemical cells have been fabricated and the discharge characteristics studied. The open circuit voltage (OCV) and short circuit current (SCC) are found to be 2.69 V and 346µA respectively.     

Ion transport and electrochemical cell characteristic studies of a new (PVP 1 NaNO3) polymer electrolyte system

Polymer electrolyte films based on poly (vinyl pyrrolidone) (PVP) complexed with NaNO₃ salt have been prepared by solution—cast technique. Several experimental techniques such as X-ray diffraction, Infrared (IR), DC—electrical conductivity, transference number measurements have been employed to characterize the polymer electrolyte. The conductivity of the (PVP + NaNO₃) electrolyte is about 10⁴ times larger than that of pure PVP at room temperature. The transference number measurements show that the charge transport in this polymer electrolyte system is predominantly due to ions. Using this polymer electrolyte, an electrochemical cell with the configuration Na/(PVP + NaNO₃)/(I₂ + C + electrolyte) has been fabricated and its discharge characteristics studied. The open circuit voltage (OCV) and short circuit current (SCC) observed for the cell are 2.65 V and 1.1 mA respectively. A number of other cell parameters evaluated are also reported.     

Effect of complexing salt on conductivity of PVC/PEO polymer blend electrolytes

Solid polymer electrolyte membrane comprising poly(vinyl chloride) (PVC), poly(ehylene oxide) (PEO) and different lithium salts (LiClO₄, LiBF₄ and LiCF₃SO₃) were prepared by the solution casting technique. The effect of complexing salt on the ionic conductivity of the PVC/PEO host polymer is discussed. Solid polymer electrolyte films were characterized by X-ray diffraction, FTIR spectroscopy, TG/DTA and ac impedance spectroscopic studies. The conductivity studies of these solid polymer electrolyte (SPE) films are carried out as a function of frequency at various temperatures ranging from 302 K to 353 K. The maximum room temperature ionic conductivity is found to be 0·079 × 10^?4 S cm^?1 for the film containing LiBF₄ as the complexing salt. The temperature dependence of the conductivity of polymer electrolyte films seems to obey the Vogel-Tamman-Fulcher (VTF) relation.     

Influence of 1-ethyl-3-methylimidazolium bis (trifluoromethyl sulfonyl) imide plasticization on zinc-ion conducting PEO/PVdF blend gel polymer electrolyte

The influence in terms of plasticizer on zinc-ion conducting polymer blend electrolyte system, [PEO (90 wt%)/PVdF (10 wt%)]-15 wt% Zn (CF₃SO₃)₂] with various concentrations of 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (EMIMTFSI) was investigated. The freshly-prepared thin films of [PEO (90 wt%)/PVdF (10 wt%)]-15 wt% Zn (CF₃SO₃)₂)?+?x wt% EMIMTFSI, where x?=?1, 3, 5, 7, and 10 wt%] were characterized by means of X-ray diffraction (XRD), Fourier transformed infrared (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and impedance analysis techniques. The room temperature XRD patterns tend to support the enhanced amorphous phase as a result of deducing the degree of crystallinity of the polymer blend–salt system by the addition of 7 wt% EMIMTFSI. The relevant SEM images of 7 wt% EMIMTFSI incorporated gel polymer electrolyte exhibit a minimised spheurilite structure when compared to that of the polymer blend–salt system. Unusually, the highest ionic conductivity realized in the case of the typical gel polymer electrolyte system, [PEO/PVdF-Zn (CF₃SO₃)₂ + 7 wt% EMIMTFSI] is found to be 1.63?×?10^?4 S cm^?1 at room temperature. The temperature dependence of conductivity has been examined based on the Vogel–Tammann–Fulcher (VTF) equation, thereby suggesting the segmental chain motion and free volume changes. The occurrence of ion dynamics and dielectric relaxation behaviour in the chosen system has been analysed in a detailed fashion at room temperature using frequency response impedance formalisms involving electric modulus and dielectric permittivity features.     

Structural,electrical and electrochemical parameters of PEO–NaClO3 composite for battery applications

Polyethylene oxide–NaClO₃ composite have been prepared by solution casting technique with different weight percentages as a polymer electrolyte for battery application. The prepared composites were characterized by various tools like XRD, FTIR and SEM. The X-ray diffraction analysis shows the complexation of polymer with salt and existence of both crystalline and amorphous phases. From FTIR spectra confirms the formation of PEO–NaClO₃ composites. SEM images shows the grains are highly agglomerated and its average size increases with increase in salt ratio. Frequency dependence of dielectric property and ac electrical conductivity of polymer electrolytes were studied within the frequency range of 50 Hz to 5 MHz using complex impedance analysis technique. Ionic conductivity follows Arrhenius type behavior as a function of temperature. The fabricated cell of 25 wt.% of PEO–NaClO₃ composites generated high current of 1.79 A.     

Lithium ion conducting solid polymer blend electrolyte based on bio-degradable polymers

Lithium ion conducting polymer blend electrolyte films based on poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) with different Mwt% of lithium nitrate (LiNO₃) salt, using a solution cast technique, have been prepared. The polymer blend electrolyte has been characterized by XRD, FTIR, DSC and impedance analyses. The XRD study reveals the amorphous nature of the polymer electrolyte. The FTIR study confirms the complex formation between the polymer and salt. The shifts in T _g values of 70 PVA–30 PVP blend and 70 PVA–30 PVP with different Mwt% of LiNO₃ electrolytes shown by DSC thermograms indicate an interaction between the polymer and the salt. The dependence of T _g and conductivity upon salt concentration has been discussed. The ion conductivity of the prepared polymer electrolyte has been found by a.c. impedance spectroscopic analysis. The PVA–PVP blend system with a composition of 70 wt% PVA: 30 wt% PVP exhibits the highest conductivity of 1·58 × 10^???6 Scm^???1 at room temperature. Polymer samples of 70 wt% PVA–30 wt% PVP blend with different molecular weight percentage of lithium nitrate with DMSO as solvent have been prepared and studied. High conductivity of 6·828 × 10^???4 Scm^???1 has been observed for the composition of 70 PVA:30 PVP:25 Mwt% of LiNO₃ with low activation energy 0·2673 eV. The conductivity is found to increase with increase in temperature. The temperature dependent conductivity of the polymer electrolyte follows the Arrhenius relationship which shows hopping of ions in the polymer matrix. The relaxation parameters (ω) and (τ) of the complexes have been calculated by using loss tangent spectra. The mechanical properties of polymer blend electrolyte such as tensile strength, elongation and degree of swelling have been measured and the results are presented.     

Synthesis and characterization of polyethylene oxide based nano composite electrolyte

Polyethylene oxide (PEO) – montmorillonite (MMT) composite electrolytes were synthesised by solution casting technique. The salt used for the study is Lithium perchlorate (LiClO₄). The morphology and percentage of crystallinity data were obtained through X-ray Diffraction and Differential Scanning Caloriemetry. The ionic conductivity of the polymer electrolytes was studied by impedance spectroscopy. The addition of MMT resulted in an increase in conductivity over the temperature range of 25–60^°C. The ionic conductivity of a composite polymer electrolyte containing 1.2 wt% MMT was 1 × 10^?5 S cm^?1 at 25^°C, which is at least one order of magnitude higher than that of the polymer electrolyte (4 × 10^?7S cm^?1). The increase in ionic conductivity is explained on the basis of crystallinity of the polymer electrolyte.     

Effect of ZnO nanoparticles on the structure and ionic relaxation of poly(ethylene oxide)-LiI polymer electrolyte nanocomposites

The effect of ZnO nanoparticles on the structure and ionic relaxation of LiI salt doped poly(ethylene oxide) (PEO) polymer electrolytes has been investigated. X-ray diffraction, high resolution transmission electron microscopy and field emission scanning electron microscopy show that ZnO nanoparticles dispersed in the PEO-LiI polymer electrolyte reduce the crystallinity of PEO and increase relative smoothness of the surface morphology of the nanocomposite electrolyte. The electrical conductivity of the nanocomposites is found to increase due to incorporation of ZnO nanoparticles. We have shown that the structural modification due to insertion of ZnO nanoparticles results in the enhancement of the mobility i.e., the hopping rate of mobile Li+ ions and hence the ionic conductivity of PEO-LiI-ZnO nanocomposite electrolyte.     

Study of effect of composition, irradiation and quenching on ionic conductivity in (PEG) x : NH4NO3 solid polymer electrolyte

We have prepared, characterized and investigated a new PEG-2000 based solid polymer electrolyte (PEG) _x : NH₄NO₃. Ionic conductivity measurements have been made as a function of salt concentration as well as temperature in the range 265–330 K. Selected compositions of the electrolyte are exposed to a beam of 8 MeV electrons and ⁶⁰Co γ-rays to an accumulated dose of 10 kGy to study the effect on ionic conductivity. The electrolyte samples are also quenched at liquid nitrogen temperature and conductivity measurements are carried out. The ionic conductivity at room temperature exhibits a characteristic peak for the composition, x = 46. Electron beam irradiation results in an increase in conductivity for all compositions by a factor of 2–3. Exposure to γ-rays enhances the conductivity by one order of magnitude. Quenching at low temperature has resulted in an increase in conductivity by 1–2 orders of magnitude. The enhancement of conductivity upon irradiation and quenching is interpreted as due to an increase in amorphous region and decrease in crystallinity of the electrolyte. DSC and NMR measurements also support this conclusion.     

Enhancement of ionic conductivity of PEO based polymer electrolyte by the addition of nanosize ceramic powders

The ionic conductivity of polyethylene oxide (PEO) based solid polymer electrolytes (SPEs) has been improved by the addition of nanosize ceramic powders (TiO2 and AL2O3). The PEO based solid polymer electrolytes were prepared by the solution-casting method. Electrochemical measurement shows that the 10 wt% TiO2 PEO-LiClO4 polymer electrolyte has the best ionic conductivity (about 10(-4) S cm(-1) at 40-60 degrees C). The lithium transference number of the 10 wt% TiO2 PEO-LiClO4 polymer electrolyte was measured to be 0.47, which is much higher than that of bare PEO polymer electrolyte. Ac impedance testing shows that the interface resistance of ceramic-added PEO polymer electrolyte is stable. Linear sweep voltammetry measurement shows that the PEO polymer electrolytes are electrochemically stable in the voltage range of 2.0-5.0 V versus a Li/Li+ reference electrode.     

SAXS/WAXS/DSC study of temperature evolution in nanopolymer electrolyte

Soft matter polymer electrolytes as nanostructured materials are very attractive components for batteries and for opto-electronic devices as a new generation of dye-sensitized solar cells. (PEO)₈ZnCl₂ polymer electrolytes were prepared from PEO and ZnCl₂. The nanocomposites (PEO)₈ZnCl₂/TiO₂ themselves contained TiO₂ nanograins. In this work, the influence of TiO₂ nanograins or the morphology and ionic conductivity of the nanocomposite was systematically studied by small-angle X-ray scattering (SAXS) simultaneously recorded with wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) at the synchrotron ELETTRA. Shown by previous impedance spectroscopy measurements (IS), the room temperature conductivity of nanocomposite polymer electrolyte increased more than two times above 65 °C, relative to pure composites of PEO and salts. The SAXS/DSC measurements yielded insight into the temperature-dependent changes of the grains of the electrolyte as well as into the effects of heating and cooling rates. The crystal structure and temperatures of melting and crystallization of the nanosize grains was revealed by the simultaneous WAXS measurements.     

Enhancement of the ionic conductivity of poly(ethylene oxide) electrolyte film by polyaniline addition

To improve the electrical conductivity of LiClO₄–poly(ethylene oxide) (PEO) complex, nonconductive polyaniline (NPANI) was employed as an additive. The electrical conductivity of the PEO–LiClO₄–NPANI electrolyte was at least ten times that of the original PEO–LiClO₄ electrolyte. The amine and/or imine nitrogen atoms in the NPANI polymer chain as well as the oxygen atoms in the PEO poly-merchain attracted the Li⁺ ions, and ion-dipole interaction occurred. The interaction enhanced the mobility of the ClO₄ ^– ions. The positively charged nitrogens were electronically stabilized in the entire polymer chain because NPANI had conjugated electrons. The mechanism is unique and different from those of other polymer additives. It is the very first example in which NPANI was employed as the additive for the PEO solid electrolyte and in which NPANI was found to be an effective additive. In addition, the NPANI addition hardly affected the physical properties of the PEO matrix such as the glass transition temperature and the melting temperature.     

Conductivity studies of plasticized PEO-Lithium chlorate–FIC filler composite polymer electrolytes

A new report of the synthesis of (PEO/plasticizer)LiClO₄–Li_1.3Al_0.3Ti_1.7(PO₄)₃ polymer electrolyte films prepared by the solution-cast technique is represented in this work. DSC trace revealed that T_g decreased with the increase of plasticizer content in the polymer electrolyte films. SEM morphology showed that the surface morphology of films was relatively smooth and homogeneous. Conductivity studies by EIS measurement indicated that the temperature dependence of ionic conductivity of films followed Vogel–Tamman–Fulcher (VTF) equation. The pre-exponential factor (A) and the pseudo activation energy (E_a) increased with the increase of plasticizer content in the polymer electrolyte films. At the 40 wt.% plasticizer content, A and E_a respectively had a maximum.     

Ionic transport in P(VdF-HFP)-PEO based novel microporous polymer electrolytes

A novel microporous polymer electrolyte (MPE) comprising blends of poly(vinylidene fluoride-cohexafluoropropylene) [P(VdF-HFP)] and polyethylene oxide (PEO) was prepared by phase inversion technique. It was observed that addition of PEO improved the pore configuration, such as pore size, pore connectivity and porosity of P(VdF-HFP) based membranes. The room temperature ionic conductivity was significantly enhanced. The highest porosity of about 65% and ionic conductivity of about 7 × 10⁻⁴ S cm⁻¹ was obtained when the weight ratio of PEO was 40%. The liquid electrolyte uptake was found to increase with increase in porosity and pore size. However, at higher weight ratio of PEO (> 40%) porosity, pore size and ionic conductivity was decreased. This descending trend with further increase of PEO weight ratio was attributed to conglomeration effect of PEO at the pores.     

Highly conductive non aqueous polymer gel electrolytes containing ammonium hexafluorophosphate (NH4PF6)

Non aqueous polymer gel electrolytes based on polyethylene oxide (PEO) and ammonium hexafluorophosphate (NH₄PF₆) show high conductivity above 10⁻² S/cm at 25°C. The addition of PEO to liquid electrolytes has been found to result in an increase in free ion concentration by dissociating ion aggregates present in these electrolytes at higher concentrations (≥0.4 M) of NH₄PF₆ alongwith an increase in viscosity. The free ion concentration and viscosity play a dominant role on the conductivity behaviour of these polymer gel electrolytes at low and high concentrations of PEO respectively. The presence of ion aggregates and their dissociation with the addition of PEO has also been checked by FTIR and the results are in agreement with the conductivity behaviour.     

Ionic conductivity and diffusion coefficient of barium-chloride-based polymer electrolyte with poly(vinyl alcohol)–poly(4-styrenesulphonic acid) polymer complex

A composite polymer electrolyte comprising poly(vinyl alcohol)–poly(4-styrenesulphonic acid) with barium chloride dihydrate (\(\hbox {BaCl}_{2}{\cdot } 2\hbox {H}_{2}\hbox {O}\)) salt complex has been synthesized following the usual solution casting. The ionic conductivity of polymer electrolyte was analysed by impedance spectroscopy. The highest room temperature (at 30\({^{\circ }}\)C) conductivity evaluated was 9.38 \(\times \) 10\(^{-6}\) S cm\(^{-1}\) for 20 wt% loading of \(\hbox {BaCl}_{2}\) in the polymer electrolyte. This has been referred to as the optimum conducting composition. The temperature-dependent ionic conductivity of the polymer electrolyte exhibits the Arrhenius relationship, which represents the hopping of ions in polymer composites. Cation and anion diffusion coefficients are evaluated using the Trukhan model. The transference number and enhanced conductivity imply that the charge transportation is due to ions. Therefore this polymer electrolyte can be further studied for the development of electrochemical device applications.     

The effects of salt concentration on ion state and conductivity in comb cross-linked polymer electrolytes

A new type of comb cross-linked polyurethane/acrylate polymer was designed. The polymer has sparse network structure with many long comb molecule chains. A new solid polymer electrolyte (SPE) was prepared based on the polymer. The salt in the solid polymer electrolytes has different existent states with different salt contents. With increase of salt concentration, the ion pairing gradually becomes important existent form of salt, and T _g value of the SPE increases. At the same time, ionic conductivity increases rapidly. It is possible to design novel solid polymer electrolytes with high ionic conductivity to meet practical application by comb cross-linked polymer with high salt content.     

Dielectric relaxation studies on [PEO–SiO<Subscript>2</Subscript>]:NH<Subscript>4</Subscript>SCN nanocomposite polymer electrolyte films

Present work deals with findings on dielectric relaxation behaviour and a.c. conduction in a SiO₂-doped polymer nanocomposite electrolyte system, namely, [(100 − x)PEO + xSiO₂]:yNH₄SCN. The formation of nanocomposite has been ascertained by XRD measurements. The effect of salt and filler (SiO₂) on conductivity response of PEO-based nanocomposite polymer electrolyte has been investigated by impedance spectroscopy. The variation of dielectric permittivity, dielectric loss and modulus spectra with frequency and temperature was carried out from impedance spectroscopy data. The a.c. conductivity seems to follow the universal power law.     

Performance characteristics of guanine incorporated PVDF-HFP/PEO polymer blend electrolytes with binary iodide salts for dye-sensitized solar cells

In this work, we have investigated the influence of guanine as an organic dopant in dye-sensitized solar cell (DSSC) based on poly(vinylidinefluoride-co-hexafluoropropylene) (PVDF-HFP)/polyethylene oxide (PEO) polymer blend electrolyte along with binary iodide salts (potassium iodide (KI) and tetrabutylammonium iodide (TBAI)) and iodine (I₂). The PVDF-HFP/KI + TBAI/I₂, PVDF-HFP/PEO/KI + TBAI/I₂ and guanine incorporated PVDF-HFP/PEO/KI + TBAI/I₂ electrolytes were prepared by solution casting technique using DMF as solvent. The PVDF-HFP/KI + TBAI/I₂ electrolyte showed an ionic conductivity value of 9.99 × 10⁻⁵ Scm⁻¹, whereas, it was found to be increased to 4.53 × 10⁻⁵ Scm⁻¹ when PEO was blended with PVDF-HFP/KI + TBAI/I₂ electrolyte. However, a maximum ionic conductivity value of 3.67 × 10⁻⁴ Scm⁻¹ was obtained for guanine incorporated PVDF-HFP/PEO/KI + TBAI/I₂ blend electrolyte. The photovoltaic properties of all these polymer electrolytes in DSSCs were characterized. As a consequence, the power conversion efficiency of the guanine incorporated PVDF-HFP/PEO/KI + TBAI/I₂ electrolyte based DSSC was significantly improved to 4.98% compared with PVDF-HFP/PEO/KI + TBAI/I₂ electrolyte based DSSC (2.46%). These results revealed that the guanine can be an effective organic dopant to enhance the performance of DSSCs.