Effects of plasticizer and nanofiller on the dielectric dispersion and relaxation behaviour of polymer blend based solid polymer electrolytes

Solid polymer electrolytes consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend (50:50 wt/wt%) with lithium triflate (LiCF₃SO₃) as a dopant ionic salt at stoichiometric ratio [EO + (CO)]:Li⁺ = 9:1, poly(ethylene glycol) (PEG) as plasticizer (10 wt%) and montmorillonite (MMT) clay as nanofiller (3 wt%) have been prepared by solution cast followed by melt–pressing method. The X–ray diffraction study infers that the (PEO–PMMA)–LiCF₃SO₃ electrolyte is predominantly amorphous, but (PEO–PMMA)–LiCF₃SO₃–10 wt% PEG electrolyte has some PEO crystalline cluster, whereas (PEO–PMMA)–LiCF₃SO₃–10 wt% PEG–3 wt% MMT electrolyte is an amorphous with intercalated and exfoliated MMT structures. The complex dielectric function, ac electrical conductivity, electric modulus and impedance spectra of these electrolytes have been investigated over the frequency range 20 Hz to 1 MHz. These spectra have been analysed in terms of the contribution of electrode polarization phenomenon in the low frequency region and the dynamics of cations coordinated polymer chain segments in the high frequency region, and also their variation on the addition of PEG and MMT in the electrolytes. The temperature dependent dc ionic conductivity, dielectric relaxation time and dielectric strength of the plasticized nanocomposite electrolyte obey the Arrhenius behaviour. The mechanism of ions transportation and the dependence of ionic conductivity on the segmental motion of polymer chain, dielectric strength, and amorphicity of these electrolytes have been explored. The room temperature ionic conductivity values of the electrolytes are found ∼10⁻⁵ S cm⁻¹, confirming their use in preparation of all-solid-state ion conducting devices.     

Structural, conductivity, and dielectric characterization of PEO–PEG blend composite polymer electrolyte dispersed with TiO2 nanoparticles

A solid polymer electrolyte (SPE) composites consisting blend of poly(ethylene oxide) (PEO) and poly(ethylene glycol) (PEG) as the polymer host with LiCF₃SO₃ as a Li⁺ cation salt and TiO₂ nanoparticle which acts as a filler were prepared using solution-casting technique. The SPE films were characterized by X-ray diffraction and Fourier transform infrared analysis to ensure complexation of the polymer composites. Frequency-dependent impedance spectroscopy observation was used to determine ionic conductivity and dielectric parameters. Ionic conductivity was found to vary with increasing salt and filler particle concentrations in the polymer blend complexes. The optimum ambient temperature conductivity achieved was 2.66?×?10^?4?S?cm^?1 for PEO (65 %), PEG (15 %), LiCF₃SO₃ (15 %), ethylene carbonate (5 %), and TiO₂ (3 %) using weight percentage. The dielectric relaxation time obtained from a loss tangent plot is fairly consistent with the conductivity studies. Both Arrhenius and VTF behaviors of all the composites confirm that the conductivity mechanism of the solid polymer electrolyte is thermally activated.     

AC impedance, FTIR and XRD investigations of poly acrylonitrile complexed with LiCF3SO3

Solid polymer electrolytes of high ionic conductivity are prepared using poly acrylonitrile (PAN), propylene carbonate (PC), ethylene carbonate (EC) and LiCF₃SO₃. The polymer films are characterised by X-ray diffraction, FTIR and a.c. impedance spectroscopic techniques. The conductivity studies of PAN-LiCF₃SO₃-PC-EC polymer electrolyte systems are carried out in the temperature range 301–373 K. The temperature dependence of the conductivity of the polymer films obeys the VTF relation. The conductivity values are presented and the results are discussed.     

Structural, thermal, and conductivity studies of high molecular weight poly(vinylchloride)-lithium triflate polymer electrolyte plasticized by dibutyl phthalate

Poly(vinylchloride) (PVC) is an insulator and acts as a host in polymer electrolyte systems where addition of inorganic salt lithium trifluoromethanesulfonate (LiCF₃SO₃) and dibutyl phthalate (DBP) converts the system to become conductor. The conductivity of polymer electrolytes is explained on the basis of ionic mobility. Thirty-five weight percent DBP plasticized polymer electrolyte has the highest conductivity value (3.30?×?10^?9 S cm^?1) at 303 K. Temperature dependence of the conductivity of polymer films obeys the Arrhenius rule. X-ray diffraction (XRD) proves that addition of DBP will increase the amorphous nature of the system and lead to enhancement in ionic conductivity. Complexation between high molecular weight PVC, LiCF₃SO₃, and DBP is confirmed by the shifting of peaks, decreasing of peaks intensity, and broadening of peaks in XRD. Thermogravimetric analysis reveals that addition of DBP to PVC–LiCF₃SO₃ system reduces the stability of the film. Subsequently, thermal stability decreases with the increase in DBP content in the polymer electrolytes.     

Synthesis and characterization of novel urethane cross-linked ormolytes for solid-state lithium batteries

A novel family of Li⁺-based organic/inorganic materials obtained by the sol–gel process is proposed. The compounds, named urethanesils, are obtained as thin, transparent, elastomeric and amorphous monolithic films. They incorporate solvating pendant methyl end-capped short poly(oxyethylene) chains which are covalently bonded to the silica backbone by means of urethane cross-links. The urethane linkages are formed by reacting 3-isocyanatepropyltriethoxysilane with hepta(ethylene glycol) methyl ether (HEGME). Li⁺ has been introduced in the urethanesils as lithium triflate (LiCF₃SO₃). Two compositions of salt have been considered: n=100 and 8, where n represents the molar ratio of (OCH₂CH₂) units per lithium ion. Infrared spectroscopy provides conclusive evidence that, although the oligopolyether chains of HEGME become less disordered upon formation of the inorganic network, the addition of salt induces disorder. The FTIR spectrum of the most concentrated urethanesil strongly suggests that the triflate ions are essentially coordinated in the material. The thermal and mechanical properties of the undoped and doped urethanesils have been investigated by DSC and DMTA. At 90°C, the highest ionic conductivity (approximately 10⁻⁶ Ω⁻¹ cm⁻¹) is observed for composition n=8. The electrochemical stability domain of the least concentrated urethanesil spans 5 V.     

Studies on the structure and transport properties of hexanoyl chitosan-based polymer electrolytes

Polymer electrolytes composed of hexanoyl chitosan as the host polymer, lithium trifluoromethanesulfonate (LiCF₃SO₃) as the salt, diethyl carbonate (DEC)/ethylene carbonate (EC) as the plasticizers were prepared and characterized by X-ray diffraction and impedance spectroscopy. The X-ray diffraction results reveal the variation in conductivity from structural aspect. This is reflected in terms of amorphous content. Sample with higher amorphous content exhibits higher conductivity. In order to further understand the source of the conductivity variation with varying plasticizers compositions as well as temperatures, the ionic charge carrier concentration and their mobility in polymer electrolyte were determined. The Rice and Roth model was proposed to be used to estimate the ionic charge carrier concentration, n. Knowing n and combining the result with dc conductivity, the mobility of the ionic charge carrier can be calculated. It is found that the conductivity change with DEC/EC composition is due mainly to the change in ionic charge carrier concentration while the conductivity change with temperature is due primarily to the change in mobility.     

Investigation on the effects of addition of SiO<Subscript>2</Subscript> nanoparticles on ionic conductivity,FTIR, and thermal properties of nanocomposite PMMA–LiCF<Subscript>3</Subscript>SO<Subscript>3</Subscript>–SiO<Subscript>2</Subscript>

Composite polymer electrolyte systems composed of poly(methyl methacrylate) (PMMA) as the host polymer, lithium trifluoromethanesulphonate (also known as lithium triflate; LiCF₃SO₃) as dopant salt, and a variety of different concentrations of nano-sized fumed silica (SiO₂) as inorganic filler were studied. The effect upon addition of SiO₂ on the ionic conductivity of the composite polymer electrolytes was investigated, and it was proven that the ionic conductivity had been enhanced. In addition, the interfacial stability also showed improvement. Maximum conductivity was obtained upon addition of 2 wt.% SiO₂. The complexation of PMMA and LiCF₃SO₃ was verified through Fourier transform infrared studies. The thermal stability of the polymer electrolytes was also found to improve after dispersion of inorganic filler. This was proven in the thermogravimetric studies.     

Electrochemical studies on polymer electrolytes based on poly(methyl methacrylate)-grafted natural rubber for lithium polymer battery

MG30 is natural rubber grafted with 30% poly(methyl methacrylate). Gel polymer electrolytes containing MG30–LiCF₃SO₃–X (X = propylene carbonate, ethylene carbonate) are prepared by solution casting technique. The polymer–salt complexes were investigated using Fourier-transformed infrared. The ionic conductivity of the electrolytes are determined by the ac impedance studies over the temperature range of 303–383 K and is observed to obey the Vogel–Tamman–Fulcher (VTF) rule. The Li⁺ transference number obtained using the Bruce and Vincent method is <0.3. The Li/Li⁺ interface stability is established and the electrolytes were found to be able to withstand a voltage of more than 4.2 V.     

A comparative study of lithium and sodium salts in PAN-based ion conducting polymer electrolytes

The conducting polymer electrolyte films consisting of polyacrylonitrile (PAN) as the host polymer, lithium triflate (LiCF₃SO₃) and sodium triflate (NaCF₃SO₃) as inorganic salts were prepared by the solution-cast technique. The pure PAN film was prepared as a reference. The ionic conductivity for the films is characterized using impedance spectroscopy. The room temperature conductivity for the PAN + 26 wt.% LiCF₃SO₃ film and the PAN + 24 wt.% NaCF₃SO₃ film is 3.04 × 10⁻⁴ S cm⁻¹ and 7.13 × 10⁻⁴ S cm⁻¹, respectively. XRD studies show that the complexation that has occurred in the PAN containing salt films and complexes formed are amorphous. The FTIR spectra results confirmed the complexation has taken place between the salt and the polymer. These results correspond with surface morphology images obtained from SEM analysis. The conductivity–temperature dependence of the highest conducting film from PAN + LiCF₃SO₃ and PAN + NaCF₃SO₃ systems follows Arrhenius equation in the temperature range of 303 to 353 K. The PAN containing 24 wt.% LiCF₃SO₃ film has a higher ionic conductivity and lower activation energy compared to the PAN containing 26 wt.%LiCF₃SO₃ film. These results can be explained based on the Lewis acidity of the alkali ions, i.e., the interaction between Li⁺ ion and the nitrogen atom of PAN is stronger than that of Na⁺ ion.     

PVDF-Based Nanocomposite Solid Polymer Electrolytes; the Effect of Affinity Between PVDF and Filler on Ionic Conductivity

Nanocomposite solid polymer electrolytes (NSPEs) based on poly(vinylidene fluoride) (PVDF) were prepared by dispersing two kinds of organoclay (Cloisite^® 30B, Cloisite^® 15A) consisting of silicate layers in the polymer matrix. The effect of affinity between PVDF and organoclay as the filler on ionic conductivity was investigated in relation to its content, dispersed condition of organoclay, and structural changes of nanocomposites. The characterizations of PVDF-based nanocomposites with various organoclay contents were carried out by XRD, TEM, DSC, and DMA. In order to confirm the ion conduction properties of NSPEs with LiCF₃SO₃ at room temperature, ac impedance analyzer and FT-IR spectrometer were used. As a result, a higher ionic conductivity appeared in the case of NSPE with C15A than that with C30B and the maximum conductivity was 1.04 × 10^–3 S/cm for the NSPE containing 5 wt% of C15A and 40 wt% of LiCF₃SO₃.     

Effect of the surface treatment of the TiO2 fillers on the properties of hexanoyl chitosan/polystyrene blend-based composite polymer electrolytes

Surface treatment of TiO₂ was done by immersing filler particles in 2 and 4 % sulphuric acid (H₂SO₄) aqueous solutions. Untreated, 2 and 4 % H₂SO₄-treated TiO₂ were referred as neutral, weakly acidic, and acidic TiO₂, respectively. Composite polymer electrolytes (CPEs) based on hexanoyl chitosan–polystyrene blend were prepared by using lithium trifluromethanesulfonate (LiCF₃SO₃) as the doping salt and three different types of the TiO₂ fillers. X-ray diffraction (XRD) results showed that the addition of TiO₂ reduced the crystalline fraction of the electrolytes. The conductivity performance of the CPEs varied in the order: acidic?<?weakly acidic?<?TiO₂ free?<?neutral TiO₂. A model based on the interaction between Lewis acid–base sites of TiO₂ with ionic species of LiCF₃SO₃ has been proposed to understand the conductivity mechanism brought about by the different types of fillers. The conductivity enhancement by neutral TiO₂ is attributed to the increase in the mobility of Li⁺ cations. Acidic TiO₂ decreased the conductivity by decreasing the anionic contribution. The conductivity variation with filler content was discussed on the basis of the number of free ions.     

Conductivity studies of plasticized proton conducting PVA–PVIM blend doped with NH4BF4

The proton conducting solid-state polymer electrolyte comprising blend of poly(vinyl alcohol) (PVA) and poly(N-vinylimidazole) (PVIM), ammonium tetrafluoroborate (NH₄BF₄) as salt, and polyethylene glycol (PEG) (molecular weight 300 and 600) as plasticizer is prepared at various compositions by solution cast technique. The prepared films are characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy analysis. The conductivity–temperature plots are found to follow an Arrhenius nature. The conductivity of solid polymer electrolytes is found to depend on salt and plasticizer content and also on the dielectric constant value and molecular weight of the plasticizer. Maximum ionic conductivity values of 2.20?×?10^?4 and 1.28?×?10^?4?S?cm^?1 at 30 °C are obtained for the system (PVA–PVIM)?+?20 wt.% NH₄BF₄?+?150 wt.% PEG300 and (PVA–PVIM)?+?20 wt.% NH₄BF₄?+?150 wt.% PEG300, respectively. The blended polymer, complexed with salt and plasticizer, is shown to be a predominantly ionic conductor. The proton transport in the system may be expected to follow Grotthuss-type mechanism.     

Role of polyvinyl alcohol in the conductivity behaviour of polyethylene glycol-based composite gel electrolytes

An attempt has been made in the present work to combine gel and composite polymer electrolyte routes together to form a composite polymeric gel electrolyte that is expected to possess high ionic conductivity with good mechanical integrity. Polyethylene glycol (PEG) based composite gel electrolytes using polyvinyl alcohol (PVA) as guest polymer have been synthesized with 1 molar solution of ammonium thiocyanate (NH₄SCN) in dimethyl sulphoxide (DMSO) and electrically characterized. The ionic conductivity measurements indicate that PEG:PVA:NH₄SCN-based composite gel electrolytes are superior (σ _max = 5.7 × 10⁻² S cm⁻¹) to pristine electrolytes (PEG:NH₄SCN system) and conductivity variation with filler concentration remains within an order of magnitude. The observed conductivity maxima have been correlated to PEG:PVA:NH₄SCN-and PVA:NH₄SCN-type complexes. Temperature dependence of conductivity profiles exhibits Arrhenius behaviour in low temperature regime followed by VTF character at higher temperature.      

Investigation on compositional effect of PEG:BaTiO<Subscript>3</Subscript> in plasticized PVC–LiBETi polymer composite electrolytes

The blend-based polymer electrolyte comprising poly(vinyl chloride) (PVC) and poly(ethylene glycol) (PEG) as host polymer and lithium bis(perfluoroethanesulfonyl)imide as complexing salt have been prepared. Ethylene carbonate and dimethyl carbonate (50:50 v/v) are used as plasticizer for the system. The barium titanate is used as a filler, and the ratio of (PEG:BaTiO₃) is varied to study its effect on the conductivity behavior of the electrolyte. XRD and ac impedance studies are carried out on the prepared samples. The ac impedance measurements show that the conductivity of the prepared samples depends on the (PEG:BaTiO₃) ratio, and its value is higher for (15:5) wt.% of (PEG:BaTiO₃)-incorporated film. The temperature dependence of the conductivity of the polymer films obeys VTF relation. The role of ferroelectric filler in enhancing the conductivity is studied. The thermal stability of the film is ascertained from TG/DTA studies. The phase morphological study reveals that the porous nature of the polymer electrolyte membranes depends on the (PEG:BaTiO₃) ratio.     

Effect of anion of lithium salt on the property of lithium salt-epoxidized natural rubber polymer electrolytes

Lithium salt, LiX (where X = BF ₄ ^? , I^?, CF₃SO ₃ ^? , COOCF ₃ ^? or ClO ₄ ^? ), was incorporated into epoxidized natural rubber (ENR). Thin films of LiX-ENR polymer electrolytes (PEs) were obtained via solvent casting method. These electrolytes were characterized using SEM/X-mapping, FTIR, differential scanning calorimeter, thermogravimetry analysis, and impedance spectroscopy. The trend in thermal stability and ionic conductivity of LiX-ENR PEs follow LiBF₄ > > LiCF₃SO₃ ~ LiCOOCF₃ > LiI > > LiClO₄. The LiClO₄ hardly dissociates and formed LiClO₄ aggregates within the polymer matrix that resulted in a PE with low thermal stability and low ionic conductivity. The LiCF₃SO₃, LiCOOCF₃, and LiI, however, exert moderate interactions with the ENR, and their respective PEs exhibit moderate ionic conductivity and thermal property. The occurrence of epoxide ring opening and complexation or cross-linking reactions in and between the ENR chains that involve BF ₄ ^? ions have produced a LiBF₄-ENR PE with superior thermal property and ionic conductivity as compared to other PEs studied in this work.     

Morphology,chemical interaction,and conductivity of a PEO-ENR50 based on solid polymer electrolyte

A solid polymer electrolytes (SPE) comprising blend of poly(ethylene oxide; PEO) and epoxidized natural rubber as a polymer host and LiCF₃SO₃ as a dopant were prepared by solution-casting technique. The SPE films were characterized by field emission scanning electron microscopy to determine the surface morphology, X-ray diffraction, and differential scanning calorimeter to determine the crystallinity and thermogravimetric analysis to confirm the mass decrease caused by loss of the solvent. While the presence of the complexes was investigated by reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Electrochemical impedance spectroscopy was conducted to obtain ionic conductivity. Scanning electron microscopy analysis showed that a rough surface morphology of SPE became smoother with addition of salt, while ATR-FTIR spectroscopy analysis confirmed the polymer salt complex formation. The interaction occurred between the salt, and ether group of polymer host where the triple peaks of ether group in PEO merged and formed one strong peak at 1,096 cm⁻¹. Ionic conductivity was found to increase with the increase of salt concentration in the polymer blend complexes. The highest conductivity achieved was 1.4 × 10⁻⁴ Scm⁻¹ at 20 wt.% of LiCF₃SO₃, and this composition exhibited an Arrhenius-like behavior with the activation energy of 0.42 eV and the preexponential factor of 1.6 × 10³ Scm⁻¹.     

Microscopic investigation of ionic conductivity in alkali metal salts-poly(ethylene oxide) adducts

We present conductivity, N.M.R. and D.S.C. measurements in two P(EO) complexes : P(EO) ₈LiCF₃SO₃ and P(EO) ₁₀NaI. From N.M.R. experiments, we deduce the respective amount of crystalline and elastomeric phases at all temperatures, as well as the salt concentration in these various phases. The elastomeric phase is shown to be responsible of the ionic conductivity at all temperatures, and to be very dilute (n ? 25 just above the pure P(EO) melting point. The high melting salt-rich complexes are found surstoechiometric (n ? 3.5). The various factors affecting the temperature dependence of the conductivity are discussed, as well as the kinetics problems.     

Combined effect of nanochitosan and succinonitrile on structural, mechanical, thermal, and electrochemical properties of plasticized nanocomposite polymer electrolytes (PNCPE) for lithium batteries

A sequence of novel plasticized polymer nanocomposite electrolyte systems based on polyethylene oxide (PEO) as polymer host, LiCF₃SO₃ as salt, and a variety of concentrations of nanochitosan as inert filler, succinonitrile as a solid non-ionic plasticizer has been prepared. The prepared membranes were subjected to X-ray diffraction, FT-IR, tensile strength, morphological studies, thermal analysis, AC ionic conductivity measurement, and interfacial analyses. The combined effect of succinonitrile and nanochitosan on the electrochemical properties of polymer electrolytes has been studied, and it was confirmed that the ionic conductivity is significantly increased. The maximum ionic conductivity of the plasticized nanocomposite polymer electrolytes are found to be in the range of 10^?2.8?S/cm. Besides, the interfacial stability also shows a significant improvement. The tensile measurement and thermal analysis results illustrate that the electrolytes based on that polymer host possess good mechanical and thermal stabilities.     

Effects of Al2O3 nanofiller and EC plasticizer on the ionic conductivity enhancement of solid PEO-LiCF3SO3 solid polymer electrolyte

A solid polymer electrolyte (SPE) is synthesized by solution casting technique. The SPE uses poly(ethylene oxide) PEO as a host matrix doped with lithium triflate (LiCF₃SO₃), ethylene carbonate (EC) as plasticizer and nano alumina (Al₂O₃) as filler. The polymer electrolytes are characterized by Impedance Spectroscopy (IS) to determine the composition of the additive which gives the highest conductivity for each system. At room temperature, the highest conductivity is obtained for the composition PEO-LiCF₃SO₃-EC-15%Al₂O₃ with a value of 5.07 10^− 4 S/cm. The ionic conductivity of the polymer electrolytes increases with temperature and obeys the Arrhenius law. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) studies indicate that the conductivity increase is due to an increase in amorphous content which enhances the segmental flexibility of polymeric chains and the disordered structure of the electrolyte. Fourier transform infrared spectroscopy (FTIR) spectra show the occurrence of complexation and interaction among the components. Scanning electron microscopy (SEM) images show the changes morphology of solid polymer electrolyte.     

Ionic transport, thermal, XRD, and phase morphological studies on LiCF3SO3-based PVC–PVdF gel electrolytes

The plasticized polymer electrolyte composed of polyvinylchloride (PVC) and polyvinylidene fluoride (PVdF) as host polymer, the mixture of ethylene carbonate and propylene carbonate as plasticizer, and LiCF₃SO₃ as a salt was studied. The effect of the PVC-to-PVdF blend ratio with the fixed plasticizer and salt content on the ionic conduction was investigated. The electrolyte films reveal a phase-separated morphology due to immiscibility of the PVC with plasticizer. Among the three blend ratios studied, 3:7 PVC–PVdF blend ratio has shown enhanced ionic conductivity of 1.47 × 10⁻⁵ S cm⁻¹ at ambient temperature, i.e., the ionic conductivity decreased with increasing PVC-to-PVdF ratio and increased with increasing temperature. A temperature dependency on ionic conductivity obeys the Arrhenius behavior. The melting endotherms corresponding to vinylidene (VdF) crystalline phases are observed in thermal analysis. Thermal study reveals the different levels of uptake of plasticizer by VdF crystallites. The decrease in amorphousity with increase in PVC in X-ray diffraction studies and larger pore size appearance for higher content of PVC in scanning electron microscopy images support the ionic conductivity variations with increase in blend ratios.