Effect of lithium salt concentration in PVAc/PMMA-based gel polymer electrolytes

Hybrid solid polymer electrolyte films comprising of poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA), LiClO₄, and propylene carbonate are prepared by solution casting technique by varying the salt concentration. In this study, PVAc/PMMA polymer blend ratio is fixed as 25:75 on the basis of conductivity and mechanical stability of the film. X-ray diffraction, Fourier transform infrared impedance, thermogravimetry/differential thermal analysis and scanning electron microscopy studies are carried out for the polymer electrolytes. The maximum ionic conductivity is found to be 4.511 × 10⁻⁴ S cm⁻¹ at 303 K for the plasticized polymer electrolyte with 8 wt.% of LiClO₄. The ionic conductivity is found to decrease with an increase of LiClO₄ concentration.     

Electrical properties of a solid polymeric electrolyte of PVC–ZnO–LiClO4

The ZnO filler has been introduced into a solid polymeric electrolyte of polyvinyl chloride (PVC)–ZnO–LiClO₄, replacing costly organic filler for conductivity improvement. Ionic conductivity of PVC–ZnO–LiClO₄ as a function of ZnO concentration and temperature has been studied. The electrolyte samples were prepared by solution casting technique. The ionic conductivity was measured using impedance spectroscopy technique. It was observed that the conductivity of the electrolyte varies with ZnO concentration and temperature. The temperature dependence on the conductivity of electrolyte was modelled by Arrhenius and Vogel–Tammann–Fulcher equations, respectively. The temperature dependence on the conductivity does not fit in both models. The highest room temperature conductivity of the electrolyte of 3.7 × 10⁻⁷ Scm⁻¹ was obtained at 20% by weight of ZnO and that without ZnO filler was found to be 8.8 × 10⁻¹⁰ Scm⁻¹. The conductivity has been improved by 420 times when the ZnO filler was introduced into the PVC–LiClO₄ electrolyte system. It was also found that the glass transition temperature of the electrolyte PVC–ZnO–LiClO₄ is about the same as PVC–LiClO₄. The increase in conductivity of the electrolyte with the ZnO filler was explained in terms of its surface morphology.     

Solid polymeric electrolyte of PVC–ENR–LiClO<Subscript>4</Subscript>

The ionic conductivity of PVC–ENR–LiClO₄ (PVC, polyvinyl chloride; ENR, epoxidized natural rubber) as a function of LiClO₄ concentration, ENR concentration, temperature, and radiation dose of electron beam cross-linking has been studied. The electrolyte samples were prepared by solution casting technique. Their ionic conductivities were measured using the impedance spectroscopy technique. It was observed that the relationship between the concentration of salt, as well as temperature, and conductivity were linear. The electrolyte conductivity increases with ENR concentration. This relationship was discussed using the number of charge carrier theory. The conductivity–temperature behaviour of the electrolyte is Arrhenian. The conductivity also varies with the radiation dose of the electron beam cross-linking. The highest room temperature conductivity of the electrolyte of 8.5 × 10⁻⁷ S/cm was obtained at 30% by weight of LiClO₄. The activation energy, E _a and pre-exponential factor, σ _o, are 1.4 × 10⁻² eV and 1.5 × 10⁻¹¹ S/cm, respectively.     

Preparation and characterization of PVAc–PMMA-based solid polymer blend electrolytes

In the present work, a novel blend polymer electrolyte membrane using poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA), and lithium per chlorate (LiClO₄) in different compositions has been prepared by the solution-casting technique. Their chemical, structural characters, thermal behavior, surface morphology, and ionic conductivity were studied using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric/differential thermal analyzer, scanning electron microscopy, and AC impedance analyzer, respectively. A maximum ionic conductivity value of 1.67 × 10⁻⁴ S/cm at 303 K is obtained for PVAc–PMMA–LiClO₄ complexes in the ratio of 25 × 75, keeping LiClO₄ constant as 10 wt.% among all the compositions studied.     

Ionic conduction behavior in PVC–PEG blend polymer electrolytes upon the addition of TiO2

The blend-based polymer electrolyte consisting of poly (vinyl chloride) (PVC) and poly (ethylene glycol) (PEG) as host polymers and lithium perchlorate (LiClO₄) as the complexing salt was studied. An attempt was made to investigate the effect of TiO₂ concentration in the unplasticized PVC–PEG polymer electrolyte system. The XRD and FTIR studies confirm the formation of a polymer–salt complex. The conductivity results indicate that the incorporation of ceramic filler up to a certain concentration (15 wt.%) increases the ionic conductivity and upon further addition the conductivity decreases. The maximum ionic conductivity 0.012 × 10⁻⁴ S cm⁻¹ is obtained for PVC–PEG–LiClO₄–TiO₂ (75–25–5–15) system. Thermal stability of the polymer electrolyte is ascertained from TG/DTA studies.     

Structural and ionic conductivity studies on P(ECH-EO):γ-BL:LiClO<Subscript>4</Subscript> plasticized polymer electrolyte

The plasticized polymer electrolyte consisting of poly(epichlorohydrin-ethyleneoxide) [P(ECH-EO)], lithium perchlorate (LiClO₄) and γ-butyrolactone (γ-BL) have been prepared by simple solution casting technique. The polymer–salt–plasticizer complex has been confirmed by XRD analysis. The ionic conductivity studies have been carried out using AC impedance technique. The effect of plasticizer (γ-BL) on ionic conductivity has been discussed with respect to different temperatures. The maximum value of ionic conductivity is found to be 1.3 × 10⁻⁴ Scm⁻¹ for 70P(ECH-EO):15γ-BL:15LiClO₄ at 303 K. The temperature dependence of the plasticized polymer electrolyte follows the Vogel–Tamman–Fulcher formalism. The activation energy is found to decrease with the increase in plasticizer.     

Effect of ethylene carbonate plasticizer and TiO<Subscript>2</Subscript> nanoparticles on 49% poly(methyl methacrylate) grafted natural rubber-based polymer electrolyte

The effect of plasticizer and TiO₂ nanoparticles on the conductivity, chemical interaction and surface morphology of polymer electrolyte of MG49–EC–LiClO₄–TiO₂ has been investigated. The electrolyte films were successfully prepared by solution casting technique. The ceramic filler, TiO₂, was synthesized in situ by sol-gel process and was added into the MG49–EC–LiClO₄ electrolyte system. Alternating current electrochemical impedance spectroscopy was employed to investigate the ionic conductivity of the electrolyte films at 25 °C, and the analysis showed that the addition of TiO₂ filler and ethylene carbonate (EC) plasticizer has increased the ionic conductivity of the electrolyte up to its optimum level. The highest conductivity of 1.1 × 10⁻³ Scm⁻¹ was obtained at 30 wt.% of EC. Fourier transform infrared spectroscopy measurement was employed to study the interactions between lithium ions and oxygen atoms that occurred at carbonyl (C=O) and ether (C-O-C) groups. The scanning electron microscopy micrograph shows that the electrolyte with 30 wt.% EC posses the smoothest surface for which the highest conductivity was obtained.     

Influence of NaY on the morphology and conductivity characteristics of poly(ethylene oxide)-LiClO4 electrolyte with plasticizer EC

A novel solid-state composite polymer electrolyte (CPE), based on a polymer, poly(ethylene oxide) (PEO), alkali metal salts, and NaY molecular sieve powders with a small amount of low molecular weight plasticizer, ethylene carbonate (EC) is investigated. (PEO)₁₆LiClO₄ polymer metal salt complexes with 5 wt% EC, and different content of NaY are prepared by the solution casting technology. The crystallization characteristic, surface morphology, and ionic conductivity of the CPE systems are studied using X-ray diffractometer (XRD) analysis, scanning electron microscopy (SEM), energy dispersive spectrometer, and impedance spectroscopy. It is found that NaY incorporation has a beneficial effect on the enhancement of ionic conductivity, increasing two orders of magnitude. XRD spectra show that the NaY has a major influence on the crystallization process of polymer matrix. By incorporating NaY, the crystallinity degree of PEO matrix obviously decreases. SEM images show a dramatic modification of surface morphology, the surface spherulites of polymer matrix disappear, and ultra-branched and cross-linked framework structure forms, which play an important role in ion transport and enhancing the tensile strength (TS). The TS is achieved 2.12 MPa with the content of 35 wt% NaY, far higher than the 0.17 MPa with (PEO)₁₆LiClO₄–5 wt% EC. In addition, it is demonstrated for the first time that EC affects the network structure of the molecular sieve and leads to exhibit enhanced ionic conductivity of electrolyte maintaining for a long time.     

Solid polymer electrolytes based on squaric acid structure

Poly(squarate)s (PPS-1 and PPS-2) were synthesized by the reaction of squaryl dichloride with hydroquinone for PPS-1 and with 2,5-diethoxy-1,4-bis(trimethylsilyloxy)benzene for PPS-2, and the ionic conductivities, thermal properties, and electrochemical and thermal properties of their polymer electrolytes with LiN(CF₃SO₂)₂ were investigated. The ionic conductivity increased with increasing the lithium salt concentration for the PPS-1–LiN(CF₃SO₂)₂ electrolyte, and the highest ionic conductivities of 8.60 × 10⁻⁵ S/cm at 100 °C and 9.57 × 10⁻⁸ S/cm at 30 °C were found at the [Li] to [O] ratio of 2:1. And also, the ionic conductivity for the PPS-1–LiN(CF₃SO₂)₂ electrolyte increased with an increase in the lithium salt concentration, reached a maximum value at the [Li] to [O] ratio of 1:2, and then decreased. The highest ionic conductivity was to be 1.04 × 10⁻⁵ S/cm at 100 °C and 1.71 × 10⁻⁸ S/cm at 30 °C, respectively. Both polymer electrolytes exhibited relatively better electrochemical and thermal stabilities. Addition of the PPS-1 as a plasticizer into the poly(ethylene oxide) (PEO)–LiN(CF₃SO₂)₂ electrolyte system suppressed the crystallization of PEO, and improved the ionic conductivity at room temperature. Invited paper dedicated to Professor W. Weppner on his 65th birthday.     

Structural,thermal and ion transport studies on nanocomposite polymer electrolyte-{(PEO + SiO<Subscript>2</Subscript>):NH<Subscript>4</Subscript>SCN} system

Development and characterisation of polyethylene oxide (PEO)-based nanocomposite polymer electrolytes comprising of (PEO-SiO₂): NH₄SCN is reported. For synthesis of the said electrolyte, polyethylene oxide has been taken as polymer host and NH₄SCN as an ionic charge supplier. Sol–gel-derived silica powder of nano dimension has been used as ceramic filler for development of nanocomposite electrolytes. The maximum conductivity of electrolyte ∼2.0 × 10⁻⁶ S/cm is observed for samples containing 30 wt.% silica. The temperature dependence of conductivity seems to follow an Arrhenius-type, thermally activated process over a limited temperature range.     

Fabrication of a nanoparticle TiO<Subscript>2</Subscript> photoelectrochemical cell utilizing a solid polymeric electrolyte of PAN–PC–LiClO<Subscript>4</Subscript>

A nanoparticle TiO₂ solid-state photoelectrochemical cell utilizing as a solid electrolyte of poly(acrylonitrile)–propylene–carbonate–lithium perchlorate (PAN–PC–LiClO₄) has been fabricated. The performance of the device has been tested in the dark and under illumination of 100-mW cm⁻² light. A nanoparticle TiO₂ film was deposited onto indium tin oxide-covered glass substrate by controlled hydrolysis technique assisted with spin-coating technique. The average grain size for the TiO₂ film is 76 nm. LiClO₄ salt was used as a redox couple. The room temperature conductivity of the electrolyte is 4.2 × 10⁻⁴ S cm⁻¹. A graphite electrode was prepared onto a glass slide by electron beam evaporation technique. The device shows the rectification property in the dark and shows the photovoltaic effect under illumination. The best J _sc and V _oc of the device were 2.82 μA cm⁻² and V _oc of 0.58 V, respectively, obtained at the conductivity of 4.2 × 10⁻⁴ S cm⁻¹ and intensity of 100 mW cm⁻². The J _sc was improved by about three times by introducing nanoparticle TiO₂ and by using a solid electrolyte of PAN–PC–LiClO₄ replacing PVC–PC–LiClO₄ in the device. The current transport mechanism of the cell is also presented in this paper.     

Preparation and characterizations of PVAc/P(VdF-HFP)-based polymer blend electrolytes

A novel group of polymer blend electrolytes based on the mixture of poly(vinyl acetate) (PVAc), poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP), and the lithium salt (LiClO₄) are prepared by solvent casting technique. Ionic conductivity of the polymer blend electrolytes has been investigated by varying the PVAc and PVdF-HFP content in the polymer matrix. The maximum ionic conductivity has been obtained as 0.527 × 10⁻⁴ Scm⁻¹ at 303 K for PVAc/PVdF-HFP ((25/75) wt.%)/LiClO₄ (8 wt.%). The complex formations ascertained from XRD and FTIR spectroscopic techniques and the thermal behavior of the prepared samples has been performed by DSC analysis. The surface morphology and the surface roughness are studied using SEM and AFM scanning techniques respectively.     

Conductivity studies of plasticized anhydrous PEO-KOH alkaline solid polymer electrolyte

Polyethylene oxide (PEO)–potassium hydroxide (KOH)-based alkaline solid polymer electrolyte films have been prepared by using methanol as solvent. The highest room temperature ionic conductivity of (2.1 ± 0.5) × 10⁻⁸ S cm⁻¹ was achieved for the composition of 70 wt% PEO:30 wt% KOH. The addition of plasticizer, ethylene carbonate, propylene carbonate, or polyethylene glycol to the highest conductivity of PEO–KOH system helps to increase the ambient ionic conductivity to the order of 10⁻⁶–10⁻⁴ S cm⁻¹. The log σ vs 1/T plot of PEO–KOH showed a small conductivity decrease at 50–60 °C range. The small decrease and the hysteresis that occur during the heating–cooling cycle was overcome by the presence of the plasticizer. X-ray diffraction observation supports the conductivity results.     

Structural and ionic conductivity studies on proton conducting polymer electrolyte based on polyvinyl alcohol

An attempt has been made to prepare a new proton conducting polymer electrolyte based on polyvinyl alcohol (PVA) doped with NH₄NO₃ by solution casting technique. The complex formation between polymer and dissociated salt has been confirmed by X-ray diffraction analysis. The ionic conductivity of the prepared polymer electrolyte has been found by ac impedance spectroscopic analysis. The highest ionic conductivity has been found to be 7.5 × 10⁻³ Scm⁻¹ at ambient temperature for 20 mol% NH₄NO₃-doped PVA with low activation energy (~0.19 eV). The temperature-dependent conductivity of the polymer electrolyte follows an Arrhenius relationship, which shows hopping of ions in the polymer matrix.     

Electrochemical study of P(VDF-HFP)/PMMA blended polymer electrolyte with high-temperature stability for polymer lithium secondary batteries

In the present study, a kind of solid polymer electrolyte (SPE) based on poly(vinylidene difluoride-co-hexafluoropropylene)/poly(methyl methacrylate) blends was prepared by a casting method to solve the safety problem of lithium secondary batteries. Owing to being plasticized with a room temperature ionic liquid, N-butyl-N′-methyl-imidiazolium hexafluorophosphate, the obtained SPE shows a thermal decomposition temperature over 300°C and an ionic conductivity close to 10⁻³ S cm⁻¹. The SPE-3 sample, in which the weight of two polymers is equivalent, possesses an ionic conductivity of 0.45 × 10⁻³ S cm⁻¹ at 25°C and presents an electrochemical window of 4.43 V. The ionic conductivity of the SPE-3 is as high as 1.73 × 10⁻³ S cm⁻¹ at 75°C approaching to that of liquid electrolyte. The electrochemical performances of the Li/LiFePO₄ cells confirmed its feasibility in lithium secondary batteries.     

Electrical and structural properties of poly (ethylene oxide)/silver triflate polymer electrolyte system dispersed with MgO nanofillers

Solvent-free films of poly (ethylene oxide)–silver triflate (PEO–AgCF₃SO₃)/MgO-based nanocomposite polymer electrolytes (PEO)₅₀AgCF₃SO₃–x wt.% MgO (x = 1, 3, 5, 7, and 10) obtained using solution casting technique were found to exhibit an appreciably good complexation of MgO nanofiller within the polymer electrolyte system and non-Debye type of relaxation as revealed by Fourier transform infrared and complex impedance analyses. Optimized filler (5 wt.% MgO) when incorporated into the polymer electrolyte resulted in a maximum electrical conductivity of 2 × 10⁻⁶ S cm⁻¹ in conjunction with a silver ionic transference number (t _Ag+) of 0.23 at room temperature (298 K). Detailed structural, thermal, and surface morphological investigation indicated a slight reduction in the degree of crystallinity owing to the addition of MgO nanofiller.     

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.     

Preparation and characterization of polyindole–ZnO composite polymer electrolyte with LiClO<Subscript>4</Subscript>

This paper describes the preparation and conductivity studies of polyindole–ZnO composite polymer electrolyte (CPE) with LiClO₄. Polyindole–ZnO-based polymer nanocomposites were prepared by chemical method and characterized by XRD, infrared (IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The IR spectrum confirms the intermolecular interaction between polyindole and ZnO. The significant spectral changes of polyindole and ZnO nancomposites reveal the strong interaction between polyindole and ZnO nanoparticles. The structural morphologies of the ZnO, polyindole, and polyindole–ZnO are obtained from SEM. The TEM image of polyindole nanocomposite shows that ZnO is embedded in polyindole matrix. An enhanced conductivity of 4.405 × 10⁻⁷ S cm⁻¹ at 50 °C for the CPE was determined from impedance studies.     

Impedance and FTIR studies on plasticized PMMA–LiN(CF<Subscript>3</Subscript>SO<Subscript>2</Subscript>)<Subscript>2</Subscript> nanocomposite polymer electrolytes

Plasticized polymer electrolytes composed of poly(methyl methacrylate) (PMMA) as the host polymer and lithium bis(trifluoromethanesulfonyl)imide LiN(CF₃SO₂)₂ as a salt were prepared by solution casting technique at different ratios. The ionic conductivity varied slightly and exhibited a maximum value of 3.65 × 10⁻⁵ S cm⁻¹ at 85% PMMA and 15% LiN(CF₃SO₂)₂. The complexation effect of salt was investigated using FTIR. It showed some simple overlapping and shift in peaks between PMMA and LiN(CF₃SO₂)₂ salt in the polymer electrolyte. Ethylene carbonate (EC) and propylene carbonate (PC) were added to the PMMA–LiN(CF₃SO₂)₂ polymer electrolyte as plasticizer to enhance the conductivity. The highest conductivities obtained were 1.28 × 10⁻⁴ S cm⁻¹ and 2.00 × 10⁻⁴ S cm⁻¹ for EC and PC mixture system, respectively. In addition, to improve the handling of films, 1% to 5% fumed silica was added to the PMMA–LiN(CF₃SO₂)₂–EC–PC solid polymer electrolyte which showed a maximum value at 6.11 × 10⁻⁵ S cm⁻¹ for 2% SiO₂.     

Investigation on PVDF-HFP microporous membranes prepared by TIPS process and their application as polymer electrolytes for lithium ion batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) microporous membranes were prepared via thermally induced phase separation (TIPS) process. Then they were immersed in a liquid electrolyte to form polymer electrolytes. The effects of polymer content in casting solution on the morphology, crystallinity, and porosity of the membranes were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and a mercury porosimeter, respectively. Ionic conductivity, lithium-ion transference number, and electrochemical stability window of corresponding polymer electrolytes were characterized by AC impedance spectroscopy, DC polarization/AC impedance combination method, and linear sweep voltammetry, respectively. The results showed that spherulites and “net-shaped” structure coexisted for the membranes. Polymer content had no effect on crystal structure of the membranes. The maximum transference number was 0.55. The temperature dependence of ionic conductivity followed the Vogel–Tammann–Fulcher (VTF) relation. The maximum ionic conductivity was 2.93 × 10⁻³ Scm⁻¹ at 20 °C. Electrochemical stability window was stable up to 4.7 V (vs. Li⁺/Li).