Studies on electrical conductivity and dielectric behaviour of PVdF–HFP–PMMA–NaI polymer blend electrolyte

Polymer blend electrolytes composed of poly(vinylidene fluoride-co-hexafluoro-propylene), poly(methyl methacrylate) and 1·0 M NaI as salt have been synthesized using solution caste technique by varying the PVdF(HFP)–PMMA blend concentration ratio systematically. A.c. impedance studies were performed to evaluate the ionic conductivity of the polymer electrolyte films. The highest ionic conductivity at room temperature for [PVdF(HFP)–PMMA(4:1)](20 wt%) – [NaI(1·0 M)](80 wt%) system is found to be 1·67 × 10^???2 S cm^???1. XRD studies reveal complete complexation of the salt in the polymeric blend systems. The temperature dependence conductivity has been performed in the range of 303–373 K and it is observed that it obeys the Arrhenius behaviour. It has been observed that the dielectric constant, ε _r and dielectric loss, ε _i, increases with temperature in the lower frequency region and is almost negligible in the higher frequency region. This behaviour can be explained on the basis of electrode polarization effects. Plot of real part, M _r and imaginary part, M _i vs frequency indicates that the systems are predominantly ionic conductors. The phenomenon suggests a plurality of relaxation mechanism.     

Characterization of carboxy methylcellulose doped with DTAB as new types of biopolymer electrolytes

The investigation of new solid biopolymer electrolyte (BEs) system based on carboxy methylcellulose (CMC) is creating opportunity for new types of electrochemical devices, which may themselves, in turn, revolutionize many industrial areas. Biodegradable carboxy methylcellulose (CMC) doped with dodecyltrimethyl ammonium bromide (DTAB) as BEs were prepared via solution-casting method. Upon addition of 35 wt. % of DTAB, highest ionic conductivity of 7·72 × 10^???4 Scm^???1 was achieved due to its higher amorphous region compared to other samples prepared. This result had been further proven in FTIR study. Temperature dependence relationship obeys the Arrhenius rule from which the activation energy, E _a, for ionic conductivity and activation energy for relaxation process, E _τ , were evaluated. The divergent values between E _a for ionic conductivity and relaxation process E _τ shows that the ions hop by jumping over a potential barrier.     

Synthesis and optimization of P(MMA-BA-MAA)/PEG-based polymer gel electrolytes

A polymer gel electrolyte based on poly(methyl methacrylate-butyl acrylate-methacrylic acid)/polyethylene glycol 400 blend (P(MMA-BA-MAA)/PEG400) was successfully prepared by a simple and efficient procedure. The optimal ionic conductivity was achieved to be 3.12 mS cm^?1 at the temperature of 30 °C when the electrolyte has the composition of 20 wt% P(MMA-BA-MAA)/PEG400 blend, 0.6 M NaI, and 0.06 M I₂ in the solvent γ-butyrolactone (GBL). For tuning the ionic conductivity, various additives were introduced into the polymer gel electrolytes. The measured values of open circuit voltage, short circuit current, and total photovoltaic efficiency indicates that the adding of pyridine (PY) leads to better performance of the final dye-sensitized solar cells (DSSCs), while the adding of Guanidine thiocyante (GuSCN) leads to a worse one. 4-Tert-butylpyridine (TBP) additive takes a more complex effect on the performance of the final DSSCs. For polymer gel electrolyte with 0.5 M pyridine, the final fabricated dye-sensitized solar cell has overall energy conversion efficiency (η) of 3.63 % (0.16 cm² active area) under AM 1.5 at irradiation of 100 mW cm^?2, which reached the level of the liquid electrolyte based device (η = 3.83 % at 0.16 cm² active area). Meanwhile, this gel electrolyte exhibits well long-term stability. The mechanism analysis revealed the dependences of ionic conductivity on the concentration of polymer and NaI and the temperatures.     

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.     

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.     

Studies on structural,electrical and dielectric properties of nickel ion conducting polyvinyl alcohol based polymer electrolyte films

Polyvinyl alcohol (PVA) complexed with different weight percent ratios of Nickel Bromide (NiBr₂) salt were prepared by using solution cast technique. X-ray diffraction analysis confirmed the complexation of the salt with the polymer. Differential scanning calorimetry was used to determine the glass transition and melting temperatures of pure PVA and PVA:NiBr₂ complexed films. Electrical conductivity was measured using ac impedance analyzer in the frequency and temperature range 1 Hz–1 MHz and 303–373 K respectively. It was observed that the magnitude of electrical conductivity increases with NiBr₂ salt concentration as well as temperature. Frequency dependence electrical conductivity of the complexed polymer electrolyte films follows the Jonscher’s equation. The dielectric behavior was analyzed using dielectric permittivity\(\left( {{\varepsilon ^\prime}} \right)\) and loss tangent \(\left( {\tan \delta } \right)\) of the samples. Relaxation time was determined from the variation of loss tangent with frequency at different temperatures. The modulus spectra indicated the non-Debye nature of the material.     

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.     

Studies on electrical double layer capacitor with a low-viscosity ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate as electrolyte

The performance of an electrical double layer capacitor (EDLC) composed of high surface area activated carbon electrodes and a new ionic liquid, 1-ethyl-3-methylimidazolium tetracyanoborate, [EMIm]TCB, as the electrolyte has been investigated by impedance spectroscopy, cyclic voltammetry and galvanostatic charge–discharge studies. The high ionic conductivity (~1·3 × 10^???2 S cm^???1 at 20 °C) and low viscosity (~22 cP) of the ionic liquid, [EMIm]TCB, make it attractive as electrolyte for its use in EDLCs. The optimum capacitance value of 195·5 F g^???1 of activated carbon has been achieved with stable cyclic performance.     

Preparation of PVDF/PMMA blend microporous membranes for lithium ion batteries via thermally induced phase separation process

Thermally induced phase separation (TIPS) process was employed to prepare microporous poly (vinylidene fluoride)/poly (methyl methacrylate) (PVDF/PMMA) blend membranes using sulfolane as the diluent. Then they were immersed in liquid electrolyte to form polymer electrolytes. The effect of PMMA on the morphology and the crystallinity of blend membranes was studied. It was found that phase separation between PVDF and PMMA occurred when PMMA content was 40 wt.%. The addition of PMMA increased porosity and decreased the crystallinity, which in turn enhanced electrolyte uptake of blend membrane and the ionic conductivity of corresponding polymer electrolyte. The maximum ionic conductivity was 2.45 × 10^− 3Scm^− 1 at 20 °C.     

The effect of titanium dioxide nano-filler on the conductivity,morphology and thermal stability of poly(methyl methacrylate)—poly(styrene-<Emphasis Type="Italic">co</Emphasis>-acrylonitrile) based composite solid polymer electrolytes

The composite solid polymer electrolyte (CSPE) samples, comprising of poly(methylmethacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN)/ethylene carbonate (EC)/propylene carbonate (PC)/lithium trifluoromethanesulfonate (LiCF₃SO₃)/anatase-TiO₂ as nano-filler (0, 5, 6, 7, 8 and 9 wt% for samples T0, T1, T2, T3, T4 and T5 respectively) were prepared by solution casting technique. Fourier transform infrared (FT-IR) spectral studies indicate the interaction of PMMA and plasticizers (EC, PC) with Lithium ion and nano-filler TiO₂ in samples. From AC impedance studies ionic conductivity, dielectric constant increase with increase in the concentration of nano-filler TiO₂ up to 9 wt%. The sample T5 shows lowest activation energy (E_a) of 0.14 eV, very short relaxation time (τ) of 1.49?×?10^?7 s and exhibits maximum ionic conductivity of 1.05?×?10^?4 S cm^?1 at room temperature. The conductivity-temperature dependence studies showed that the conductivity of all samples depict Arrhenius behaviour suggesting ion-hopping mechanism. Dielectric studies reveal ion conducting nature of CSPE samples. Thermogravimetric analysis indicate the thermal stability of CSPE sample T5 up to 333 °C with maximum degradation at 388 °C. DSC studies reveal absence of glass transition temperature (T_g) of atactic component of PMMA in CSPE sample T5 indicating amorphous nature. X-ray diffraction patterns shows shift in the position of peaks confirming the complex formation of the PMMA-SAN-EC-PC-LiCF₃SO₃-TiO₂ system. SEM analysis indicates that the presence of lithium salt and filler TiO₂ on polymer host does not lead to heterogenous polymer blend thus retaining its amorphous nature.     

A soluble-lead redox flow battery with corrugated graphite sheet and reticulated vitreous carbon as positive and negative current collectors

A soluble-lead redox flow battery with corrugated-graphite sheet and reticulated-vitreous carbon as positive and negative current collectors is assembled and performance tested. In the cell, electrolyte comprising of 1·5 M lead (II) methanesulfonate and 0·9 M methanesulfonic acid with sodium salt of lignosulfonic acid as additive is circulated through the reaction chamber at a flow rate of 50 ml min^???1. During the charge cycle, pure lead (Pb) and lead dioxide (PbO₂) from the soluble lead (II) species are electrodeposited onto the surface of the negative and positive current collectors, respectively. Both the electrodeposited materials are characterized by XRD, XPS and SEM. Phase purity of synthesized lead (II) methanesulfonate is unequivocally established by single crystal X-ray diffraction followed by profile refinements using high resolution powder data. During the discharge cycle, electrodeposited Pb and PbO₂ are dissolved back into the electrolyte. Since lead ions are produced during oxidation and reduction at the negative and positive plates, respectively there is no risk of crossover during discharge cycle, preventing the possibility of lowering the overall efficiency of the cell. As the cell employs a common electrolyte, the need of employing a membrane is averted. It has been possible to achieve a capacity value of 114 mAh g^???1 at a load current-density of 20 mA cm^???2 with the cell at a faradaic efficiency of 95%. The cell is tested for 200 cycles with little loss in its capacity and efficiency.     

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.     

α-Fe2O3 /(PVA + PEG) Nanocomposite films; synthesis,optical, and dielectric characterizations

Hematite (α-Fe₂O₃) nanorods with an average diameter of 40 nm were prepared using a template-free sol–gel method. These nanorods then mixed with polyvinyl alcohol (PVA)/polyethylene glycol (PEG) blend at concentrations of 0.0, 0.5, and 1.0 wt.%. The transmittance percentage (T%) of the films showed a decrease from 80.26 to 33.24 %. The direct optical band gap also decreased from 5.28 to 4.83 eV whereas the refractive index significantly increased with increasing the hematite content. The dielectric measurements were performed in the temperature range 303–413 K and frequency range 30 kHz–3.0 MHz. According to the temperature dependence of the dielectric constant (ε’), α _a -relaxation peaks observed in all films and assigned to the micro-Brownian motion of the polymer blend chains. The behavior of the ac conductivity, σ _ac (f), of the nanocomposite films indicated that the homogenous distribution of α-Fe₂O₃ nanorods allows the formation of conductive three-dimensional networks throughout the nanocomposite film. Also, indicated that the correlated barrier hopping is the most suitable conduction mechanism.     

AC impedance and dielectric spectroscopic studies of Mg<Superscript>2 + </Superscript> ion conducting PVA–PEG blended polymer electrolytes

Polyvinyl alcohol (PVA)–polyethylene glycol (PEG) based solid polymer blend electrolytes with magnesium nitrate have been prepared by the solution cast technique. Impedance spectroscopic technique has been used, to characterize these polymer electrolytes. Complex impedance analysis was used to calculate bulk resistance of the polymer electrolytes. The a.c.-impedance data reveal that the ionic conductivity of PVA–PEG–Mg(NO₃)₂ system is changed with the concentration of magnesium nitrate, maximum conductivity of 9·63 × 10^− 5 S/cm at room temperature was observed for the system of PVA–PEG–Mg(NO₃)₂ (35–35–30). However, ionic conductivity of the above system increased with the increase of temperature, and the highest conductivity of 1·71 × 10^− 3 S/cm was observed at 100°C. The effect of ionic conductivity of polymer blend electrolytes was measured by varying the temperature ranging from 303 to 373 K. The variation of imaginary and real parts of dielectric constant with frequency was studied.     

Morphology, thermal, electrical and electrochemical stability of nano aluminium-oxide-filled polyvinyl alcohol composite gel electrolyte

In the present work, an attempt has been made to develop nano aluminium oxide (Al₂O₃)-filled polyvinyl alcohol (PVA) composite gel electrolytes. Surface morphological studies, thermal behaviour, electrochemical stability and electrical characterization of these composite gel electrolytes have been performed. An increase in the concentration of Al₂O₃ in composite gel electrolytes increases the amorphous characteristics of pure PVA. Bulk conductivity of composite gel electrolytes increases by an order of magnitude on addition of a nano filler. Maximum conductivity of 5·81 × 10^?2 S/cm is observed for 6 wt% Al₂O₃-filled polymer gel composite electrolytes. Temperature dependence of electrical conductivity shows a combination of Arrhenius and Vogel-Tamman-Fulcher (VTF) nature. Maximum current stability during oxidation and reduction cycle is noticed for 6 wt% Al₂O₃-filled PVA composite electrolyte, viz. ±1·65 V.     

Fast response time alcohol gas sensor using nanocrystalline F-doped SnO2 films derived via sol–gel method

Pure and fluorine-modified tin oxide (SnO₂) thin films (250–300 nm) were uniformly deposited on corning glass substrate using sol–gel technique to fabricate SnO₂-based resistive sensors for ethanol detection. The characteristic properties of the multicoatings have been investigated, including their electrical conductivity and optical transparency in visible IR range. Pure SnO₂ films exhibited a visible transmission of 90% compared with F-doped films (80% for low doping and 60% for high doping). F-doped SnO₂ films exhibited lower resistivity (0· 12 × 10^???4 Ω  cm) compared with the pure (14·16 × 10^???4 Ω  cm) one. X-ray diffraction and scanning electron microscopy techniques were used to analyse the structure and surface morphology of the prepared films. Resistance change was studied at different temperatures (523–623 K) with metallic contacts of silver in air and in presence of different ethanol vapour concentrations. Comparative gas-sensing results revealed that the prepared F-doped SnO₂ sensor exhibited the lowest response and recovery times of 10 and 13 s, respectively whereas that of pure SnO₂ gas sensor, 32 and 65 s, respectively. The maximum sensitivities of both gas sensors were obtained at 623 K.     

Solution blown aligned carbon nanofiber yarn as supercapacitor electrode

Carbon materials with various microtextures and wide availabilities represent very attractive electrode materials for supercapacitors. In this paper, a modified solution blowing process, using a pair of parallel rods as collector, was reported to fabricate carbon nanofiber yarn (CNFY) with polyacrylonitrile (PAN) as precursor polymer. The morphology and structure of the nanofibers were investigated. The PAN precursor and carbon nanofibers were well-aligned and their average diameter was 280 nm and 187 nm, respectively. The performance of CNFY as supercapacitor electrode was evaluated. The CNFY possessed high conductivity of 608.7 Scm^?1 and mass specific capacitance of 70 Fg^?1 at the current density of 500 mAg^?1, and the reduction of capacitance is 29.14 % of the initial value at the current density range from 0.5 to 8 Ag^?1. The superior performance of the CNFY electrode was attributed to the well-aligned structure and high electrical conductivity which afforded the potential application as a novel electrode for supercapacitors.     

Novel in situ crosslinked polymer electrolyte for solid-state dye-sensitized solar cells

A novel poly(citric acid-ethylene glycol)/LiI/I₂ (PCE/LiI/I₂) solid polymer electrolyte (SPE) based on the biodegradable PCE matrix has been prepared in situ, by penetrating of the PCE prepolymer sol into mesoporous TiO₂ photoanode, followed by curing. The PCE prepolymer can easily penetrate into the mesoporous photoanode, which could induce good interfacial contact between the SPE and photoanode. Assembled with the SPE, highly efficient and stable solid-state dye-sensitized solar cells (DSSCs) have been gained due to the good interfacial contact of SPE/TiO₂ photoanode as well as the favorable ionic conductivity of the SPE. The results show that the contents of CA determine the aggregation structure such as the inter-segmental distance and free volume of the PCE matrix, which consequently affects the ionic diffusion coefficient and conductivity of the PCE/LiI/I₂ electrolyte, and accordingly the photoelectric performance of the DSSCs. With CA content of 32.4 wt%, the SPE reaches the optimal ionic conductivity of 5.43 × 10^?5 S cm^?1 and the solid-state DSSCs obtain the best overall photoelectric conversion efficiency of 1.22 % at 60 mW cm^?2.     

Parallel spinnerets electrospinning construct and properties of electrical-luminescent bifunctional bistrand-aligned nanobundles

A structure of electrical-luminescent bifunctional bistrand-aligned nanobundles has been successfully fabricated by specially designed parallel spinnerets electrospinning technology. Eu(BA)₃phen (BA = benzoic acid, phen = 1,10-phenanthroline) and polyaniline (PANI) were respectively incorporated into polyvinyl pyrrolidone (PVP) and electrospun into bistrand-aligned nanobundles with PANI/PVP as one strand nanofiber and Eu(BA)₃phen/PVP as another strand nanofiber. The morphologies and properties of the final products were investigated in detail by scanning electron microscopy, transmission electron microscopy, fluorescence spectroscopy, Hall effect measurement system, and UV–Vis-NIR spectrophotometer. It is found that the as-prepared samples exhibit the nanostructures of bistrand-aligned nanobundles. The mean diameter for individual nanofiber of the bistrand-aligned nanobundles is 180 nm. The [PANI/PVP]//[Eu(BA)₃phen/PVP] bistrand-aligned nanobundles possess excellent electrical conduction and luminescent properties. Fluorescence emission peaks of Eu³⁺ are observed in the [PANI/PVP]//[Eu(BA)₃phen/PVP] electrical-luminescent bifunctional bistrand-aligned nanobundles and assigned to ⁵D₀ → ⁷F₀ (581 nm), ⁵D₀ → ⁷F₁ (592 nm), ⁵D₀ → ⁷F₂ (615 nm) energy levels transitions of Eu³⁺ ions, and the ⁵D₀ → ⁷F₂ hypersensitive transition at 615 nm is the predominant emission peak. The electrical conductivity reaches up to the order of 10^?3 S/cm. The electrical conductivity and luminescent intensity of the bistrand-aligned nanobundles can be tunable by adding various amounts of PANI and rare earth complex. The novel [PANI/PVP]//[Eu(BA)₃phen/PVP] electrical-luminescent bifunctional bistrand-aligned nanobundles have potential applications in display devices and nanomechanics, etc. owing to their excellent electrical conduction and fluorescence.     

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.