Preparation and performance analysis of barium titanate incorporated in corn starch‐based polymer electrolytes for electric double layer capacitor application

Polymer electrolyte membranes composing of corn starch as host polymer, lithium perchlorate (LiClO₄) as salt, and barium titanate (BaTiO₃) as composite filler are prepared using solution casting technique. Ionic conductivity is enhanced on addition of BaTiO₃ by reducing the crystallinity and increasing the amorphous phase content of the polymer electrolyte. The highest ionic conductivity of 1.28 × 10^?2 S cm^?1 is obtained for 10 wt % BaTiO₃ filler in corn starch‐LiClO₄ polymer electrolytes at 75°C. Glass transition temperature (T_g) of polymer electrolytes decreases as the amount of BaTiO₃ filler is increased, as observed in differential scanning calorimetry analysis. Scanning electron microscopy and thermogravimetric analysis are employed to characterize surface morphological and thermal properties of BaTiO₃‐based composite polymer electrolytes. The electrochemical properties of the electric double‐layer capacitor fabricating using the highest ionic conductivity polymer electrolytes is investigated using cyclic voltammetry and charge‐discharge analysis. The discharge capacitance obtained is 16.22 F g^?1. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43275.     

Solid polymer electrolytes. VII. Preparation and ionic conductivity of gelled polymer electrolytes based on poly(ethylene glycol) diglycidyl ether cured with α,ω‐diamino poly(propylene oxide)

Crosslinked polymer electrolyte networks were prepared from poly(ethylene glycol) diglycidyl ether blended with an epoxy resin (diglycidyl ether of bisphenol A) in different ratios and then cured with α,ω‐diamino poly(propylene oxide) in the presence of lithium perchlorate (LiClO₄) as a lithium salt. The ionic conductivities of these polymer electrolytes were determined by alternating current (AC) impedance spectroscopy. Propylene carbonate (PC) was used as a plasticizer to form gelled polymer electrolyte networks. The conductivities of the polymer electrolytes containing 46 wt % PC plasticizer were approximately 5 × 10^?4 S cm^?1 at 25°C and approximately 10^?3 S cm^?1 at 85°C. These polymer electrolytes were homogeneous and exhibited good mechanical properties. The effects of the polymer composition, plasticizer content, salt concentration, and temperature on the ionic conductivities of the polymer electrolytes were examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1264–1270, 2004     

Synthesis and characterization of SrBi4Ti4O15ferroelectric filler based composite polymer electrolytes for lithium ion batteries

Composite polymer electrolytes (CPEs) based on poly (ethylene oxide) (PEO) (Mol.Wt ∼6×10⁵) complexed with LiN(CF₃SO₂)₂ lithium salt and SrBi₄Ti₄O₁₅ ferroelectric ceramic filler have been prepared as films. Citrate gel technique and conventional solid state technique were employed for the synthesis of the ferroelectric fillers in order to study the effect of particle size of the filler on ionic conductivity of the polymer electrolyte. Characterization techniques such as X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) and temperature dependant DC conductivity studies were taken for the prepared polymer composite electrolytes. The broadening of DTA endotherms on addition of ceramic fillers to the polymer salt complex indicated the reduction in crystallinity. An enhancement in conductivity was observed with the addition of SrBi₄Ti₄O₁₅ as filler to the (PEO)₈-LiN(CF₃SO₂)₂ polymer salt complexes. Among the investigated samples (PEO)₈-LiN(CF₃SO₂)₂ +10 wt% SrBi₄Ti₄O₁₅ (citrate gel) polymer composite exhibits a maximum conductivity.     

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     

Effect of surface modified porous inorganic-organic hybrid polyphosphazene nanotubes on the properties of polyethylene oxide based solid polymer electrolytes

2-(2-methyloxyethoxy)ethanol modified poly (cyclotriphosphazene-co-4,4′-sufonyldiphenol) (PZS) nanotubes were synthesized and solid composite polymer electrolytes based on the surface modified polyphosphazene nanotubes added to PEO/LiClO₄ model system were prepared. Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM) were used to investigate the characteristics of the composite polymer electrolytes (CPE). The ionic conductivity, lithium ion transference number and electrochemical stability window can be enhanced after the addition of surface modified PZS nanotubes. The electrochemical investigation shows that the solid composite polymer electrolytes incorporated with PZS nanotubes have higher ionic conductivity and lithium ion transference number than the filler SiO₂. Maximum ionic conductivity values of 4.95 × 10⁻⁵ S cm⁻¹ at ambient temperature and 1.64 × 10⁻³ S cm⁻¹ at 80 °C with 10 wt % content of surface modified PZS nanotubes were obtained and the lithium ion transference number was 0.41. The good chemical properties of the solid state composite polymer electrolytes suggested that the inorganic-organic hybrid polyphosphazene nanotubes had a promising use as fillers in solid composite polymer electrolytes and the PEO₁₀-LiClO₄-PZS nanotubes solid composite polymer electrolyte can be used as a candidate material for lithium polymer batteries.     

Composite polymer electrolytes based on the low crosslinked copolymer of linear and hyperbranched polyurethanes

Low crosslinked copolymer of linear and hyperbranched polyurethane (CHPU) was prepared, and the ionic conductivities and thermal properties of the composite polymer electrolytes composed of CHPU and LiClO₄ were investigated. The FTIR and Raman spectra analysis indicated that the polyurethane copolymer could dissolve more lithium salt than the corresponding polymer electrolytes of the non crosslinked hyperbranched polyurethane, and showed higher conductivities. At salt concentration EO/Li = 4, the electrolyte CHPU30‐LiClO₄ reached its maximum conductivity, 1.51 × 10^?5 S cm^?1 at 25°C. DSC measurement was also used for the analysis of the thermal properties of polymer electrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3607–3613, 2007     

Metallic-lithium, LiFePO4-based polymer battery using PEO—ZrO2 nanocomposite polymer electrolyte

A study of the electrochemical properties of a PEO-based polymer electrolyte with nanometric ZrO₂ as ceramic filler has been carried out in order to confirm an earlier reported model dealing with the role of ceramic fillers within PEO-based polymer electrolytes as components that enhance such properties as conductivity, lithium transference number, compatibility with lithium metal electrodes and cyclability. A prototype of a lithium polymer battery, based on a membrane made from a nanocomposite polymer electrolyte doped with ZrO₂, utilizing LiFePO₄ + 1%Ag as cathode, has been assembled and galvanostatically cycled, resulting in excellent performance at temperatures ranging from 100 °C to 60 °C (close to the crystallization temperature of PEO).     

Novel polymeric systems for lithium ion batteries gel electrolytes: II. Hybrid cross-linked poly(fluorosilicone-ethyleneoxide)

Cross-linked, self-supporting, membranes for lithium ion battery gel electrolytes were obtained by cross-linking a mixture of polyfluorosilicone (PFSi) and polysilicone containing ethylene oxide (EO) units [P(Si-EO)]. The membranes were also reinforced with nanosized silica. The two polymer precursors were synthesized with functional groups capable to form inter-molecular cross-linking, thus obtaining three-dimensional, polymer matrices. The precursors were dissolved in a common solvent and cross-linked to obtain free-standing PFSi/P(Si-EO):SiO₂ composite films. The latter were undergone to swelling processes in (non-aqueous, aprotic, lithium salt containing) electrolytic solutions to obtain gel-type polymer electrolytes. The properties of the swelled PFSi/P(Si-EO):SiO₂ samples were evaluated as a function of the electrolytic solutions and the dipping time. The PFSi/P(Si-EO):SiO₂ membranes exhibited large swelling properties, high ionic conductivity and good electrochemical stability.     

Ionic conductivity and spectroscopic characterisation of γ-LiAlO2-filled polymer electrolytes

Spectroscopic characterisation of γ-LiAlO₂ composite polymeric electrolytes based on poly-(ethylene oxide)(PEO)/perfluorinated polyphosphazene blends and LiPF₆ as electrolyte was studied by means of FTIR and X-ray spectroscopy. Ionic conductivity was analysed by using complex impedance. A parallel study was made on samples containing propylene carbonate as plasticizer instead of γ-LiAlO₂. The results obtained indicate, in a first approximation, that there is a drastic change in PEO morphology resulting from the co-ordination with the lithium salt and, at the same time, that the morphology of the composite polymer electrolytes is dependent on the nature of the polymer host. Complex impedance data show that the incorporation of γ-LiAlO₂ enhances the ionic conductivity of the composite polymer electrolyte, a reverse behaviour is found for the composite systems plasticized with PC.     

Spectroscopic and electrochemical studies on block‐polymer/PMMA blend based composite polymer electrolytes

Poly(methylmethacrylate)(PMMA)/oxymethylene‐linked polyoxyethylene multi‐block polymer(Om‐POE_n, where n represents number of unit  CH₂CH₂O ) blend based composite electrolyte films containing different lithium salt concentration and nanofillers' content are prepared using solvent evaporation technique. The interaction of polymer–salt complex has been confirmed using FTIR spectral studies. The figuration of CPE was studied by XRD. Ionic conductivity and thermal behavior of the CPEs were studied with various salt concentrations, temperature, and nanofillers' content. The surface structure of the CPE is also investigated using scanning electron microscopy. The high room temperature ionic conductivity, transmittivity in the visible region, and thermal stability make these CPEs potential candidates as solid‐like electrolytes for electrochemical devices. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Poly(methyl methacrylate) based nanocomposite gel polymer electrolytes with enhanced safety and performance

The study presents preparation of poly methyl methacrylate (PMMA) based nanocomposite gel polymer electrolytes consisting of, salt lithium perchlorate (LiClO₄), plasticizer PC/DEC and different proportions of SiO₂ nanofiber by solution casting process. The effect of the composition of the electrolytes on their ionic, mechanical and thermal characteristics was investigated. Morphology of the nanocomposite electrolyte films has been observed by scanning and transmission electron microscopes. Interactions among the constituents of the composite and structural changes of the base polymer were investigated by Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. The maximum conductivity i.e. 10^?3 Scm^?1 at room temperature is obtained with the electrolyte composition of 0.6(PMMA)-0.15(PC + DEC)-0.1LiClO₄ (wt%) containing 10 wt% SiO₂ nanofiber and the temperature dependent conductivity data of the electrolyte follows Vogel-Tamman-Fulcher (VTF) behavior.     

Effect of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanofiller on ion conductivity,transmittance, and glass transition temperature of PEI:LiTFSI:PC:EC polymer electrolytes

In the present study, ion conductivity, optical properties, and glass transition temperatures are characterized for polymer electrolytes composed of poly(ethyleneimine) (PEI), lithium bis(trifluoromethane)sulfonylimide (LiTFSI) salt, propylene carbonate (PC), and ethylene carbonate (EC). It was doped with nanoceramic particles in different ratio (0–15 wt.%) to see the effect of ceramic particles. The salt concentration was fixed as 1.04 mol.kg^?1. Although valuable improvement in ion conductivity could not be achieved due to nano-Al₂O₃ fillers, ion conductivity results are placed between 10^?2 and 10^?4 S/cm. Differential scanning calorimetry (DSC) measurements and optical measurements of all electrolytes were performed between ?80 and 140 °C, in the wavelength range between 400 and 700 nm for sample with 80 μm thickness, respectively. The results showed that transmittance of electrolytes decreased monotonically for increasing Al₂O₃ contents. In particular, its transmittance value at 550 nm where human sight is at its greatest sensitivity went from 100% without nanoparticles to 50% for 15 wt% of Al₂O₃.     

Dielectric,Mechanical, and Thermal Properties of Low-Permittivity Polymer–Ceramic Composites for Microelectronic Applications

A new low-permittivity polymer–ceramic composite for packaging applications has been developed. The ceramic-reinforced polyethylene and polystyrene composites were prepared by melt mixing and hot molding techniques. Low-loss, low-permittivity Li₂MgSiO₄ (LMS) ceramics prepared by the solid-state ceramic route were used as the filler to improve the dielectric properties of the composites. The relative permittivity and dielectric loss were increased with the increase in the ceramic loading at radio and microwave frequencies. The mechanical properties and thermal conductivity of the Li₂MgSiO₄-reinforced polymer–ceramic composite were also investigated. The stability of the relative permittivity of polymer–ceramic composites with temperature and frequency was investigated. The experimentally observed relative permittivity, thermal expansion, and thermal conductivity were compared with theoretical models.     

Polystyrene-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite solid polymer electrolyte for lithium secondary battery

In a common salt-in-polymer electrolyte, a polymer which has polar groups in the molecular chain is necessary because the polar groups dissolve lithium salt and coordinate cations. Based on the above point of view, polystyrene [PS] that has nonpolar groups is not suitable for the polymer matrix. However, in this PS-based composite polymer-in-salt system, the transport of cations is not by segmental motion but by ion-hopping through a lithium percolation path made of high content lithium salt. Moreover, Al₂O₃ can dissolve salt, instead of polar groups of polymer matrix, by the Lewis acid-base interactions between the surface group of Al₂O₃ and salt. Notably, the maximum enhancement of ionic conductivity is found in acidic Al₂O₃ compared with neutral and basic Al₂O₃ arising from the increase of free ion fraction by dissociation of salt. It was revealed that PS-Al₂O₃ composite solid polymer electrolyte containing 70 wt.% salt and 10 wt.% acidic Al₂O₃ showed the highest ionic conductivity of 9.78 × 10^-5 Scm^-1 at room temperature.     

Poly(ethylene oxide)/clay nanocomposites for solid polymer electrolyte applications

Poly(ethylene oxide) (PEO)/clay nanocomposites were prepared using a solution intercalation method. The organoclay (Nanocore I30E) used for nanocomposite synthesis was basically an octadecylammonium salt of montmorillonite clay prepared using an ion exchange method. Nanocomposite‐based solid polymer electrolytes were prepared using LiBF₄. The nanocomposite structures were characterised using wide‐angle X‐ray diffraction. The crystallisation behaviour and thermal properties were studied using differential scanning calorimetry. It was found that the crystallinity of the composite electrolytes decreases with increasing clay concentration up to 7.5 wt% and then increases with a further increase in clay concentration. The trend is different from that observed in PEO/clay nanocomposites without lithium salt where the crystallinity gradually decreases with increasing clay concentration. The solid polymer electrolyte samples were evaluated using an alternating current impedance analyser. A considerable increase in room temperature conductivity was observed at the optimum clay concentration. The conductivity decreases beyond the optimum clay concentration. Copyright © 2007 Society of Chemical Industry     

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.     

Polymer electrolytes based on poly(ethylene glycol) and cyanoresin

Polymer electrolytes based on a mixed polymer matrix consisting of poly(ethylene glycol) (PEG) and cyanoresins with lithium salt and plasticizer were prepared with an in situ blending process to improve both the mechanical properties and the ionic conductivity (σ). The PEG/lithium perchlorate (LiClO₄) complexes, including blends of cyanoethyl pullulan (CRS) and cyanoethyl poly(vinyl alcohol) (CRV), exhibited higher σ's than a simple PEG/LiClO₄ complex when the blend compositions of CRS/CRV were 5 : 5 or 3 : 7 or than CRV alone. When the CRS/CRV blend was compared with a copolymer of cyanoethyl pullulan and cyanoethyl poly(vinyl alcohol) (CRM) in the same molar ratio, the σ values of the polymer electrolytes containing the CRM copolymer series were slightly higher than those of the CRS/CRV blends containing PEG/LiClO₄ complexes. Moreover, the addition of cyanoresin to PEG/LiClO₄/(ethylene carbonate–propylene carbonate) polymer electrolytes provided better thermal stability and dynamic mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2402–2408, 2007     

New solid polymer electrolytes based on PEO/PAN hybrids

Hybrid polymer dry electrolytes comprised of poly(ethylene oxide) (PEO), polyacrylonitrile (PAN), and LiClO₄ were investigated. The impedance spectroscopy showed that the effect of PAN on the ion conductivity of PEO‐based electrolytes depends on the concentration of lithium salt. When the mole ratio of lithium to oxygen is 0.062 (15%LiClO₄‐PEO), adding PAN will increase the ionic conductivity. Differential scanning calorimetry, NMR, and IR data suggested that the enhanced conductivity was due to both the decreasing of the PEO crystallinity and increasing of the degree of ionization of lithium salt. There was obviously no interaction between PAN and lithium ions, and PAN acts as a reinforcing filler, and hence contributes to the mechanical strength besides reducing the crystallinity of the polymer electrolytes. When the LiClO₄‐PEO‐PAN hybrid polymer electrolyte was heated at 200°C under N₂, PAN crosslinked partially, which further decreased the crystallinity of PEO and increased the ionic conductivity, and at the same time prevented the recrystallization of PEO upon sitting at ambient environment. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1530–1540, 2006     

Characterization of Lithium Ion-Conducting Blend Biopolymer Electrolyte Based on CH–MC Doped with LiBF<Subscript>4</Subscript>

Lithium ion-conducting polymer blend electrolytes based on chitosan and methylcellulose complexed with lithium tetrafluoroborate (LiBF₄) were prepared by a solution-casting method. The features of complexation of the solid polymer electrolytes were studied using X-ray diffraction techniques. Electrical conductivity of the prepared films was measured as a function of frequency at a different temperature. The increased trend of the electrical conductivity with increasing temperature and salt concentration can be attributed to increasing the mobility and number of lithium ions, respectively. The polymer electrolyte system exhibited Arrhenius-type, temperature-dependence ion conductivity behavior. Optical properties such as optical band gap, tail due to localized states and complex refractive index were estimated for present polymer electrolyte system from optical absorption measurement in the wavelength region 190–1100 nm. It was found that the optical direct band gap values shifted to lower energies upon addition of LiBF₄ salt up to 40 wt% dopant concentration, and showed an increasing tendency for a further increase in dopant concentration. The high refractive index for this composition (2.44–2.63) at visible wavelengths eminently suitable for optical applications.     

1H NMR,thermal, and conductivity studies on PVAc based gel polymer electrolytes

The lithium‐ion conducting gel polymer electrolytes (GPE), PVAc‐DMF‐LiClO₄ of various compositions have been prepared by solution casting technique. ¹H NMR results reveal the existence of DMF in the gel polymer electrolytes at ambient temperature. Structure and surface morphology characterization have been studied by X‐ray diffraction analysis (XRD) and scanning electron microscopy (SEM) measurements. Thermal and conductivity behavior of polymer‐ and plasticizer‐salt complexes have been studied by differential scanning calorimetry (DSC), TG/DTA, and impedance spectroscopy results. XRD and SEM analyses indicate the amorphous nature of the gel polymer‐salt complex. DSC measurements show a decrease in T_g with the increase in DMF concentrations. The thermal stability of the PVAc : DMF : LiClO₄ gel polymer electrolytes has been found to be in the range of (30–60°C). The dc conductivity of gel polymer electrolytes, obtained from impedance spectra, has been found to vary between 7.6 × 10^?7 and 4.1 × 10^?4 S cm^?1 at 303 K depending on the concentration of DMF (10–20 wt %) in the polymer electrolytes. The temperature dependence of conductivity of the polymer electrolyte complexes appears to obey the VTF behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008