Influence of plasticizer contents on the properties of HEC-based solid polymeric electrolytes

Solid polymeric electrolytes were obtained by the plasticization process of hydroxyethylcellulose (HEC) with different quantities of glycerol and addition of lithium trifluoromethane sulfonate (LiCF₃SO₃) salt. The samples were prepared in the form of transparent films with very good adhesion properties. These films were characterized by X-ray diffraction, thermal analysis (DSC) and UV-NIR spectroscopy. The ionic conductivity measurements were obtained by impedance complex spectroscopy as a function of both salt contents and temperature. The best conductivity values of 1.07 × 10⁻⁵ S/cm at 30 °C and 1.06 × 10⁻⁴ S/cm at 83 °C were obtained for the samples of HEC plasticized with 48% of glycerol and containing [O]/[Li] = 6. These results show that plasticized HEC is a very good material to be used for the preparation of new solid polymeric electrolytes.     

Preparation and electrochemical performance of gel polymer electrolytes with a novel star network

Well-defined star shaped polymers with α-Cyclodextrin (α-CD) core linking PMMA-block arms were synthesized by atom transfer radical polymerization (ATRP). Gel polymer electrolytes (GPEs) were prepared by encapsulating electrolyte solution of 1 mol L⁻¹ of LiClO₄/EC-PC (volume 1:1) into the obtained star shaped polymer host. The ionic conductivity of the GPEs and the cycling characteristics of LiCoO₂/GPEs/Graphite cell were studied by electrochemical impedance spectroscopy and charge-discharge testing, respectively. The results indicate that the GPEs have a high ionic conductivity up to 1.63 × 10⁻³ S cm⁻¹ at room temperature and exhibit a high electrochemical stability potential of 4.5 V (vs. Li/Li⁺). The discharge capacity of LiCoO₂/GPEs/Graphite cell is about 98% of its initial discharge capacity after 20 cycles at 0.1 C rate. Discharge capacity of the model cell with GPEs is stable with charge-discharge cycling.     

Effects of polymer matrix and salt concentration on the ionic conductivity of plasticized polymer electrolytes

Two polar polymers with different dielectric constants, poly(vinylidene fluoride) (PVDF) and poly(ethylene oxide) (PEO), were each blended with a chlorine-terminated poly(ethylene ether) (PEC) and one of the two salts, LiBF₄ and LiCF₃CO₂, to form PEC plasticized polymer electrolytes. The room-temperature ionic conductivity of the PEC plasticized polymer electrolytes reached a value as high as 10^?4 S/cm. The room-temperature ionic conductivity of the PVDF-based polymer electrolytes displayed a stronger dependence on the PEC content than did the PEO-based polymer electrolytes. In PVDF/PEC/LiBF₄ polymer electrolytes, the dynamic ionic conductivity was less dependent on temperature and more dependent on the PEC content than it was in PEO/PEC/LiBF₄ polymer electrolytes. The highly plasticized PVDF-based polymer electrolyte film with a PEC content greater than CF4 (CF4 defined as the molar ratio of the repeat units of PEC to those of PVDF equal to 4) was self-supported and nonsticky, while the corresponding PEO-based polymer electrolyte film was sticky. In these highly plasticized PVDF-based polymer electrolytes, the curves of the room-temperature ionic conductivity vs. the salt concentration were convex because the number of carrier ions and the chain rigidity both increased with increase of the salt content. The maximum ionic conductivity at 30°C was independent of the PEC content, but it depended on the anion species of the lithium salts in these highly plasticized polymer electrolytes. © 1995 John Wiley & Sons, Inc.     

Performance of PVDF-HFP-based gel polymer electrolytes with different pore forming agents

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolytes (GPEs) with polyvinylpyrrolidone (PVP) and urea as a pore forming agent, respectively, were fabricated by phase inversion method. Physicochemical properties of the as-prepared polymer electrolytes were characterized by SEM, XRD, TG, electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). The results showed that the GPE membranes using urea as pore forming agent present a uniform surface with abundant interconnected micro-pores and possess upto 330?°C decomposition temperature; the XRD patterns indicate that adding urea into the polymer matrix can attain more amorphous areas than adding PVP; the reciprocal temperature dependence of ionic conductivity of as-prepared GPEs follows Vogel-Tamman-Fulcher relation and the ionic conductivity at room temperature is 2.212?mS cm^?1 for PVP pore forming GPEs and 2.823?mS cm^?1 for urea pore forming GPEs, respectively; the interfacial resistance of the Li/GPEs/Li cell using urea as pore forming agent can achieve a quick steady value of about 660??? cm^?1 lower than that of PVP of about 760??? cm^?1 during the same storage conditions; the electrochemical stability window of the GPEs with urea can be stable upto 5.0?V (vs. Li⁺/Li) at room temperature. The battery performance of the assembled Li/GPEs/LiCoO₂ coin cell also showed that the cell using urea as pore forming agent in GPEs demonstrated excellent first charge/discharge rate and cycle performances. These excellent physicochemical and battery properties indicated that urea can be used as a kind of excellent pore forming agent for polymer electrolytes in the lithium-ion polymer battery.     

Enhanced mechanical strength and conductivity of PVFM based membrane and its supporting polymer electrolytes

Polyvinyl formal based polymer electrolyte membranes are prepared via the optimized phase inversion method with poly(ethylene oxide) (PEO) blending. The physical properties of blend membranes and the electrochemical properties of corresponding gel polymer electrolytes (GPEs) are characterized by field emission scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, mechanical strength test, electrolyte uptake test, AC impedance spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge test. The comparative study shows that the appearance of PEO obviously enhances the tensile strength of membranes and the ionic conductivity of corresponding GPEs. When the weight ratio of PEO is 30%, the tensile strength of membrane achieves 12.81 MPa, and its GPE shows high ionic conductivity of 2.20 × 10⁻³ S cm⁻¹, wide electrochemical stable window of 1.9–5.7 V (vs. Li/Li⁺), and good compatibility with LiFePO₄ electrode. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41839.     

Plasticized pectin-based gel electrolytes

Pectin is a natural polymer present in plants and, as all natural polymers has biodegradation properties. Chemically, pectin is a polysaccharide composed of a linear chain of 1→4 linked galacturonic acids, which is esterified with methanol at 80%. The pectin-based gel electrolytes in a transparent film form were obtained by a plasticization process with glycerol and addition of LiClO₄. The films showed good ionic conductivity results, which increased from 10⁻⁵ S/cm for the samples with 37 wt.% of glycerol to 4.7 × 10⁻⁴ S/cm at room temperature for the sample with 68 wt.% of glycerol. The electrochemical behaviors of the samples were studied by electrochemical impedance spectroscopy (EIS), and Nyquist graphs are showed and discussed. The obtained pectin-based samples also presented good adherence to the glass, flexibility, homogeneity (SEM) and transparency (about 70% in the vis) properties. They are good candidates to be applied as gel electrolytes in electrochromic devices.     

Effect of calixpyrrole in PEO-LiBF4 polymer electrolytes

It is shown that the addition of calix[6]pyrrole to polyether based electrolytes doped with LiBF₄ results in an considerable increase in the cation transport number tLi+ as confirmed by dc-ac current techniques as well as by PFG NMR studies. The value of tLi+ in composite electrolytes beyond a certain minimum value weakly depends on the concentration of added calix[6]pyrrole. The increase in lithium transference number is associated with a decrease in ionic conductivity of composite polymeric electrolytes compared to the pure PEO-LiBF₄ systems.     

Effective influences of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIMTFSI) ionic liquid on the ion transport properties of micro-porous zinc-ion conducting poly (vinyl chloride) /poly (ethyl methacrylate) blend-based polymer electrolytes

A series of new gel polymer electrolytes (GPEs) based on different concentrations of a hydrophobic ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIMTFSI) entrapped in an optimized typical composition of polymer blend-salt matrix [poly(vinyl chloride) (PVC) (30 wt%) / poly(ethyl methacrylate) (PEMA) (70 wt%) : 30 wt% zinc triflate Zn(CF₃SO₃)₂] has been prepared using facile solution casting technique. The AC impedance analysis has revealed the occurrence of the maximum ionic conductivity of 1.10 × 10^?4 Scm^?1 at room temperature (301 K) exhibited by the PVC/PEMA- Zn(OTf)₂ system containing 80 wt% ionic liquid. The addition of EMIMTFSI into the optimized PVC/PEMA- Zn(OTf)₂ system in different weight percentages enhances the number of free zinc ions thereby leading to enrichment of ionic conductivity. The structural and complexation behaviour of the as prepared polymer gel electrolytes was substantiated by subjecting these electrolyte films to X-ray diffraction (XRD) and Attenuated total reflectance - Fourier transformed infrared (ATR-FTIR) investigations. The wider electrochemical stability window ~ 3.23 V and a reasonable cationic transference number (t_Zn ²⁺) of 0.63 have been attained for the polymer gel electrolyte film containing higher loading of (80 wt%) ionic liquid. The development of the amorphous phase of these gel polymer electrolyte membranes with increasing ionic liquid content was observed from scanning electron microscopic (SEM) analysis. The results of the current work divulge the assurance of developing GPEs based on ionic liquids for prospective application in zinc battery systems.     

Flexible and Conductive 3D Printable Polyvinylidene Fluoride and Poly(N,N‐dimethylacrylamide) Based Gel Polymer Electrolytes

In this work, 3D printable gel polymer electrolytes (GPEs) based on N,N‐dimethylacrylamide (DMAAm) and polyvinylidene fluoride (PVDF) in lithium chloride containing ethylene glycol solution are synthesized and their physicochemical properties are investigated. 3D printing is carried out with a customized stereolithography type 3D gel printer named “Soft and Wet Intelligent Matter‐Easy Realizer” and free forming GPE samples having variable shapes and sizes are obtained. Printed PVDF/PDMAAm‐based GPEs exhibit tunable mechanical properties and favorable thermal stability. Electrochemical proprieties of the printed GPEs are carried out via impedance spectroscopy in the temperature range of 25–90 °C by varying PVDF content. Ionic conductivity as high as 6.5 × 10^?4 S cm^?1 is achieved at room temperature for GPE containing low PVDF content (5 wt%) and conductivity of the GPEs is increased as temperature rises.     

Dielectric and electrical characterization of (PEO–PMMA)–LiBF<Subscript>4</Subscript>–EC plasticized solid polymer electrolyte films

Plasticized solid polymer electrolytes (PSPEs) consisting of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend (50/50 wt%) based matrix with lithium tetrafluoroborate (LiBF₄) as dopant ionic salt (10 wt%) and varied concentrations (x = 0, 5, 10 and 15 wt%) of ethylene carbonate (EC) as plasticizer have been prepared. Classical solution-cast (SC) and the ultrasonic assisted followed by microwave irradiated (US–MW) solution-cast methods have been used for the preparation of (PEO–PMMA)–LiBF₄–x wt% EC films, and the same have been hot–pressed to get their smooth surfaces. Dielectric relaxation spectroscopy (DRS) and X–ray diffraction (XRD) techniques have been employed to characterize the dielectric and electrical dispersions and the structural properties of the PSPE films, respectively. It has been observed that the ionic conductivity of these semicrystalline ion-dipolar complexes is governed by their dielectric permittivity and polymers chain segmental dynamics. The increase in ionic conductivity values with the increase of plasticizer concentration in the PSPEs also varies with the films’ preparation methods. The US–MW method prepared PSPE film containing 15 wt% EC has a maximum ionic conductivity (1.86 × 10^?5 S cm^?1) at room temperature, whereas, the films having low concentrations of EC exhibit the conductivity of the order of 10^?6 S cm^?1.     

Effects of the surface treatment of the Al2O3 filler on the lithium electrode/solid polymer electrolyte interface properties

The lithium deposition-dissolution process in solid polymer electrolytes containing Al₂O₃ filler treated under different conditions has been investigated comparing with the ionic conduction behavior of the electrolyte. The composite electrolytes were prepared from poly(ethylene oxide) (PEO), LiBF₄ and α-Al₂O₃ filler by using a dry process, where the surface of α-Al₂O₃ was beforehand modified by a wet process. The exchange current densities, i₀, of the lithium electrode process in P(EO)₂₀LiBF₄ with and without Al₂O₃ filler were determined by a micro-polarization method. The temperature dependence of i₀ provided similar values for activation energy, ca. 25 and 70 kJ mol⁻¹ in both temperature regions above and below 60 °C, respectively. The effect of the surface treatment of the filler on the lithium electrode process gave a different tendency from that on the ionic conductivity. The Al₂O₃ surface treated by alkali solution enhanced the electrode process to the largest extent among the fillers used here, while it led to rather poor cycling stability in voltammetry. The enhanced reaction rate at the lithium electrode/solid polymer electrolyte interface has probably resulted in the improved ion dissociation by the surface groups of the Al₂O₃ filler.     

The Effect of Incorporation of Multi-Walled Carbon Nanotube into Poly(Ethylene Oxide) Gel Electrolyte on the Photovoltaic Performance of Dye-Sensitized Solar Cell

Gel polymer electrolytes (GPEs) consist of poly(ethylene oxide) (PEO), sodium iodide (NaI) and different amount of multi-walled carbon nanotubes (MWCNT) were prepared. The conductivity study revealed that the highest ionic conductivity of GPE was 7.02 × 10^?3 S cm^?1. The structural and complexation between the materials are authenticated via X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Under the exposure of AM 1.5, the fabricated DSSCs exhibited the highest photoenergy conversion efficiency of 7.23% with a short circuit current density (J_SC) of 18.64 mA cm^?2, open circuit voltage (V_OC) of 0.590 mV and fill factor (FF) of 65.7%.     

Morphology,crystallinity, and electrochemical properties of in situ formed poly(ethylene oxide)/TiO2 nanocomposite polymer electrolytes

A method to produce nanocomposite polymer electrolytes consisting of poly(ethylene oxide) (PEO) as the polymer matrix, lithium tetrafluoroborate (LiBF₄) as the lithium salt, and TiO₂ as the inert ceramic filler is described. The ceramic filler, TiO₂, was synthesized in situ by a sol–gel process. The morphology and crystallinity of the nanocomposite polymer electrolytes were examined by scanning electron microscopy and differential scanning calorimetry, respectively. The electrochemical properties of interest to battery applications, such as ionic conductivity, Li⁺ transference number, and stability window were investigated. The room‐temperature ionic conductivity of these polymer electrolytes was an order of magnitude higher than that of the TiO₂ free sample. A high Li⁺ transference number of 0.51 was recorded, and the nanocomposite electrolyte was found to be electrochemically stable up to 4.5 V versus Li⁺/Li. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2815–2822, 2003     

Preparation and electrochemical properties of composite polymer electrolytes containing 1-ethyl-3-methylimidazolium tetrafluoroborate salts

The effects of room-temperature molten salt addition on the micro-structure and electrochemical properties of composite electrolytes (CEs) based on poly(ethylene oxide) (PEO)/ethylene carbonate (EC)/LiBF₄ were studied. Additional salt, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF₄), was found to influence the crystalline structure and heterogeneous morphology, resulting in changes to the ionic conductivity of the CE. The CE containing 0.2 mol of EMIBF₄ showed a small crystallinity, 27.9%. These CEs showed the highest ion conductivity, 3.1 × 10⁻⁴ S/cm, five times higher than that of the pristine PEO/EC/LiBF₄. This enhanced conductivity originated from the decreased crystallinity and improved ion transference due to a Lewis acid-base interaction. The CE containing 0.3 mol of EMIBF₄ showed decreased conductivity due to the lower mobility, reflecting the high viscosity of the molten salt.     

Effect of modified montmorillonites on the ionic conductivity of (PEO)16LiClO4 electrolytes

Three kinds of modified montmorillonites were prepared by ion exchange method, and added into (PEO)₁₆LiClO₄ matrix to study the effect on the ionic conductivity of (PEO)₁₆LiClO₄ electrolytes. The structure of the modified montmorillonites and polymer composites were characterized by wide-angle X-ray diffraction. HP 4192A was used to measure the ionic conductivity of the polymer electrolytes. The results show that the addition of optimum content of 250-Li-mont enhances the ionic conductivity of the PEO based electrolyte by nearly 30 times more than the plain system and that is much higher than the other two modified montmorillonites. The difference of enhancement in conductivity caused by adding these three montmorillonites can be attributed to the difference in structure of the samples as characterized by wide-angle X-ray diffraction.     

Fabrication and characterization of PEO/PPC polymer electrolyte for lithium‐ion battery

A new poly(propylene carbonate)/poly(ethylene oxide) (PEO/PPC) polymer electrolytes (PEs) have been developed by solution‐casting technique using biodegradable PPC and PEO. The morphology, structure, and thermal properties of the PEO/PPC polymer electrolytes were investigated by scanning electron microscopy, X‐ray diffraction, and differential scanning calorimetry methods. The ionic conductivity and the electrochemical stability window of the PEO/PPC polymer electrolytes were also measured. The results showed that the T_g and the crystallinity of PEO decrease, and consequently, the ionic conductivity increases because of the addition of amorphous PPC. The PEO/50%PPC/10%LiClO₄ polymer electrolyte possesses good properties such as 6.83 × 10^?5 S cm^?1 of ionic conductivity at room temperature and 4.5 V of the electrochemical stability window. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of LiBO2 addition on the microstructure and lithium-ion conductivity of Li1+xAlxTi2−x(PO4)3(x = 0.3) ceramic electrolyte

Concerning the safety problems of conventional Li-ion batteries with liquid electrolytes, it is crucial to develop reliable solid-state electrolytes with high ionic conductivity. Li_1+xAl_xTi_2?x(PO₄)₃ (LATP, x = 0.3) is regarded as one of the most promising solid electrolytes due to its high ionic conductivity and excellent chemical stability to humidity.Herein, a new strategy is proposed for improving the sintering behavior and enhancing the ionic conductivity of LATP by using LiBO₂ as the sintering aid via liquid phase sintering. The as-prepared sample LATP with homogeneous microstructure and high relative density of 97.1% was successfully synthesized, yielding high total ionic conductivity of 3.5 × 10^?4 S cm^?1 and low activation energy of 0.39 eV at room temperature. It was found that the addition of LiBO₂ could effectively enhance the densification and increase the ionic conductivity of LATP electrolyte, proving an effective way to synthesis LATP ceramics by a simple and reliable route.     

Conductivity study of a gelatin-based polymer electrolyte

Natural polymers are particularly interesting due to their richness in nature, very low cost and principally biodegradation properties. For these reasons different solid polymeric electrolytes (SPE) have been obtained using cellulose derivatives, starch, chitosan and rubber. This work presents the results of gelatin-based protonic SPEs, which were characterized by impedance spectroscopy, X-ray diffraction, UV-vis-NIR spectroscopy and scanning electron microscopy (SEM). The ionic conductivity results obtained for these SPEs were 4.5 × 10⁻⁵ S/cm and 3.6 × 10⁻⁴ S/cm at room temperature and 80 °C, respectively. Temperature-dependent ionic conductivity measurements were taken to analyze the mechanism of ionic conduction in polymer electrolytes. Good conductivity results combined with transparency and good adhesion to the electrodes have shown that gelatin-based SPEs are very promising materials to be used as solid electrolyte in electrochromic devices.     

Electrochemical investigations on the effect of dispersoid in PVA based solid polymer electrolytes

Various compositions of TiO₂ dispersed PVA‐PMMA‐LiBF₄‐EC based electrolytes were prepared using solution casting technique. The prepared electrolytes were characterized using AC impedance, XRD, SEM, FTIR, etc. The ionic conductivity value is increased with the increase in filler content (up to 8 wt %) and then decreased with the increase in filler content. The results are described using Vogel–Tamman–Fulcher theory. The thermal and transport properties of the electrolyte exhibiting maximum conductivity have also been studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3950–3956, 2007     

Synthesis and characterization of novel crosslinked polyurethane–acrylate electrolyte

Flexible, transparent, and crosslinked polymer films were synthesized by polymerization of PEG‐modified urethane acrylate using a simple method. A series of novel solid polymer electrolytes and gel electrolytes were prepared based on this type of polymer film. To understand the interactions among salt, solvent, and polymer, the swelling behaviors of the crosslinked polymer in pure propylene carbonate (PC) and liquid electrolyte solutions (LiClO₄/PC) were investigated. The results showed that the swelling rate in the electrolyte solution containing moderate LiClO₄ was greater than that in pure PC. Thermogravimetric analysis (TGA) also supported the interaction between the solvent and polymer. The morphology and crystallinity of the crosslinked polymer and polymer electrolytes were studied using atomic force microscopy (AFM) and wide‐angle X‐ray diffraction (WAXD) spectroscopy. The effects of the content of the electrolyte solution on the ionic conductivity of gel electrolytes were explored. The dependence of the conductivity on the amount of the electrolyte solution was nonlinear. With a different content of the plasticizer, the ionic conduction pathway of the polymer electrolytes would be changed. The best ionic conductivity of the gel electrolytes, which should have good mechanical properties, was 4 × 10^r?3 S cm^?1 at 25°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 340–348, 2003