Preparation and ionic conductivity of composite polymer electrolytes based on hyperbranched star polymer

Hyperbranched star polymer HBPS-(PPEGMA) _x was synthesized by atom transfer radical polymerization (ATRP) using hyperbranched polystyrene (HBPS) as macroinitiator and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as monomer. The structure of the prepared hyperbranched star polymer was characterized by ¹H NMR, ATR-FTIR, and GPC. Polymer electrolytes based on HBPS-(PPEGMA) _x , lithium salt, and/or nano-TiO₂ were prepared. The influences of lithium salt concentration and type, nano-TiO₂ content, and size on ionic conductivity of the obtained polymer electrolytes were investigated. The results showed that the low crystallinity of the prepared polymer electrolyte was caused by the interaction between lithium salt and polymer. The addition of TiO₂ into HBPS-(PPEGMA) _x /LiTFSI improved the ionic conductivity at low temperature. The prepared composite polymer electrolyte showed the highest ionic conductivity of 9?×?10^?5 S cm^?1 at 30 °C when the content of TiO₂ was 15 wt% and the size of TiO₂ was 20 nm.     

Ionic conductivity studies in composite solid polymer electrolytes based on methylmethacrylate

The preparation and characterization of composite polymer electrolytes of PMMA-LiClO₄-DMP for different concentrations of CeO₂ have been investigated. FTIR studies indicate complex formation between the polymer, salt and plasticizer. The electrical conductivity values measured by a.c. impedance spectroscopy are found to depend upon the CeO₂ concentration. The temperature dependence of the conductivity of the polymer films seems to obey the VTF relation. The conductivity values are presented and the results are discussed.     

Ionic conductance of composite electrolytes based on network polymer with ceramic powder

Effects of ceramic fillers (α-Al₂O₃, γ-Al₂O₃ and BaTiO₃) have been investigated on the ionic conductance of polymeric complexes consisting of poly(ethylene oxide)-modified poly(methacrylate) (PEO-PMA) and lithium bis(trifluoromethylsulfonyl)imide, Li(CF₃SO₂)₂N, and ceramic powder. The addition of ceramic powder increased the ionic conductivity over an ambient temperature range. Conductivity of 4.9 × 10^− 5 S cm^− 1 at 333 K (60 °C) was obtained for the composite containing 15 wt.% α-Al₂O₃ prepared by photo-polymerization. The optimum content of Al₂O₃ was different among the methods of polymerization. The highest conductivity was obtained for the composite containing 5 wt.% of α-, or γ-Al₂O₃ prepared by thermal polymerization. The addition of the ceramic filler scarcely influenced the thermal properties of the polymer matrix. XRD and NMR experiments showed that the ionic mobility could be enhanced in the composites by addition of α-Al₂O₃. The addition of small amounts of ferroelectric BaTiO₃ also increased the ionic conductivity of the polymeric complex, but its extent was smaller than the case of the Al₂O₃ addition.     

PMMA based protonic polymer gel electrolytes

The paper reports the synthesis of protonic polymer gel electrolytes containing different hydroxy benzoic acids (ortho-, meta- and para-) and aliphatic dicarboxylic acids. Gel electrolytes were prepared by adding polymethylmethacrylate (PMMA) in different weight ratios to the 1M solution of above acids in a ternary solvent mixture of propylene carbonate (PC), ethylene carbonate (EC) and dimethylformamide (DMF) in equal volume ratio. The conductivity of these gel electrolytes has been found to depend upon the amount of PMMA added to the system. A “Breathing Polymeric Chain Model” has been proposed to explain the variation of conductivity with PMMA concentration in these gel electrolytes.     

An investigation on PAN-PVC-LiTFSI based polymer electrolytes system

Polymer-salt complex with poly(vinyl chloride) (PVC) and poly(acrylonitrile) (PAN) as host polymers blended with lithium bis-(trifluoro methanesulfonyl)imide, LiTFSI [LiN(CF₃SO₂)₂] as dopant salt were prepared in the form of thin film. Fourier transform infrared (FTIR) studies show the evidence of the complexation between PVC, PAN and LiTFSI. Ionic conductivity studies reveal that polymer electrolyte with 30 wt.% LiTFSI has the highest ionic conductivity of 4.39 × 10^− 4 S/cm at room temperature. The polymer electrolytes are also found to be stable up to 315 °C before they decompose. Thermal stability of the polymer electrolytes was also found to increase with increase in salt content. This was proven through thermogravimetric studies.     

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.     

Characterisation of plasticized PMMA based solid polymer electrolytes

Polymer electrolyte films prepared from poly (methyl methacrylate) and LiAsF₆ with different concentrations of plasticizer (DBP) are described. The formation of polymer-salt complexes has been confirmed by XRD and FTIR spectral studies. The temperature dependence of the conductivity of the polymer films obeys the VTF relation. Values of conductivities of the polymer complexes are presented and discussed.     

Nanocomposite polymer electrolytes

The present effort reviews the state-of-the-art trends in respect of composite polymer electrolytes (CPEs) which are nowadays revolutionizing the modern approach towards energy storage and power supply gadgets. This evaluation mainly encompasses a series of systems based on polymer hosts such as poly(ethylene oxide) (PEO), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), poly(vinylidene fluoride) (PVDF), poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA), and polyvinylchloride (PVC) developed and analyzed so far apart from certain nanofiller incorporated composite polymer electrolytes being used in conjunction with well-suited electrodes owing to their practical significance in several advanced types of power sources including hybrid electric vehicles. The emerging nanoscale techniques have by now led the market to appreciate the application potential of nanostructured inorganic and organic materials so as to realize enhanced efficiencies of batteries thereby providing one of the most promising energy storage devices as well.     

Ni-MH battery based on plasticized alkaline solid polymer electrolytes

Solid-state nickel metal hydride cells were fabricated using plasticized alkaline solid polymer electrolytes (ASPE) prepared from polyvinyl alcohol (PVA), potassium hydroxide (KOH), alumina (α-Al₂O₃), and propylene carbonate (PC). The ASPE film with PVA/KOH/α-Al₂O₃/PC/H₂O weight ratio of 1.00:0.67:0.09:2.64:1.32 and conductivity of (6.6 ± 1.7) × 10⁻⁴ S cm⁻¹ was used in fabrication of the electrochemical cells. To investigate the electrochemical properties of the plasticized ASPE, cells with the configuration Mg₂Ni/plasticized ASPE/Ni(OH)₂ were fabricated. At the eighth cycle with a current drain of 0.1 mA and plateau voltage of ∼1.1 V, the discharge lasted for 14 h before the cell was considered to have failed. The failure mode of the cell was due to the formation of thin Mg(OH)₂ insulating layers.     

Performance studies on composite gel polymer electrolytes for rechargeable magnesium battery application

Effect of micron-sized MgO particles dispersion on poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF–HFP) based magnesium-ion (Mg²⁺) conducting gel polymer electrolyte has been studied using various electrical and electrochemical techniques. The composite gel films are free-standing and flexible with enough mechanical strength. The optimized composition with 10 wt% MgO particles offers a maximum electrical conductivity of ∼6×10⁻³ S cm⁻¹ at room temperature (∼25°C). The Mg²⁺ ion conduction in gel film is confirmed from cyclic voltammetry, impedance spectroscopy and transport number measurements. The applicability of the composite gel electrolyte to a rechargeable battery system has been examined by fabricating a prototype cell consisting of Mg (or Mg–MWCNT composite) and V₂O₅ as negative and positive electrodes, respectively. The rechargeability of the cell has been improved, when Mg metal was substituted by Mg–MWCNT composite as negative electrode.     

Conductivity study of some polymer electrolytes based on polyacrylonitrile

The present paper deals with the room temperature conductivity study of some polymer electrolytes based on polyacrylonitrile, ammonium tetraflouroborate as dopant, and propylene carbonate (PC) and polyethylene glycols (PEG300 and PEG600) as plasticizers. The additions of plasticizers having different dielectric constant have been found to modify the conductivity of polymer electrolytes. The increase in room temperature conductivity with plasticizer addition has been found to depend upon (1) the amount of salt present and (2) amount of plasticizers added. The polymer electrolytes prepared were characterized by X-ray diffraction, scanning electron micrographs, infrared, thermogravimetric, and AC impedance measurements. The highest room temperature conductivity observed in case of these polymer electrolytes was ∼10–13 s/cm.     

Dielectric and conductivity relaxations in PVAc based polymer electrolytes

The polymer electrolytes composed of a blend of poly (vinyl acetate) (PVAc) and poly (methylmethacrylate) (PMMA) as a host polymer and LiClO₄ as a salt are prepared by a solution casting technique. The formation of blend polymer- salt complex has been confirmed by FT-IR spectral studies. The conductivity- temperature plots are found to follow an Arrhenius nature. Arrhenius plot shows the decrease in activation energy with the increase in salt concentration. The dielectric behaviour of the sample is analysed using dielectric permittivity (ε′), dielectric loss (ε″) and electric modulus (M″) of the samples. The impedance cole- cole plot shows the high frequency semi- circle is due to the bulk effect of the material and the depression in the semicircle shows the non-Debye nature of the material. The bulk conductivity is found to vary between 2.5×10⁻⁵ Scm⁻¹ to 1.7×10⁻³ Scm⁻¹ with the increase of salt concentration of blend polymer samples. The migration energy derived from the dissipation factor is almost equal to the activation energy calculated from conductivity. The modulus spectrum of the samples shows the non-Debye behaviour of the polymer electrolyte films. The low frequency dispersion of the dielectric constant implies the space charge effects arising from the electrodes. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Single-ion conductivity enhancement for the composite polymer electrolytes based on Li(PVAOB)/PPEGMA for lithium-ion batteries

In the present work, a series of single-ion conducting composite polymer electrolytes based on lithium polyvinyl alcohol oxalate borate (Li(PVAOB)) and poly(polyethylene glycol methacrylate) (PPEGMA) were produced. PEGMA was polymerized into PPEGMA, and the Li(PVAOB) was prepared from poly (vinyl alcohol) (PVA), oxalic acid, and boric acid. Li(PVAOB) was blended with PPEGMA at different stoichiometric ratios to obtain a single-ion conducting system. All the electrolytes were characterized by Fourier transformation infrared spectroscopy (FT-IR), thermogravimetry analysis (TGA), differential scanning calorimeter (DSC), and scanning electron microscopy (SEM) techniques. These results verified the interaction between host and guest polymers, sufficient thermal stability within the measured conductivity domain, and the homogeneity of the composite electrolytes. The effect of PPEGMA onto the ionic conductivity was investigated using impedance spectroscopy. The Li(PVAOB)-60PPEGMA is the optimum content, and this sample has a maximum ionic conductivity of 3 × 10^?4 S/cm at 100 °C which is approximately five orders of magnitude higher than neat Li(PVAOB). Activation energy (E _a ) of ionic transport decreased from 11.9 to 0.27 kJ/mol, suggesting a much faster ionic mobility for higher PPEGMA-containing samples.     

Experimental investigations on poly(ethylene oxide) based sodium ion conducting composite polymer electrolytes dispersed with SnO2

New Na⁺ ion conducting composite polymer electrolytes comprising of polyethylene oxide (PEO)-NaClO₄ and PEO-NaI complexes dispersed with SnO₂ are reported. The results of the studies based on optical microscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infra-red (FTIR) spectroscopy, impedance analysis and mechanical testing are presented and discussed. The electrical conductivity of ≈5·10⁻⁵ S·cm⁻¹ at 40 °C was achieved for the dispersion of ≈10 wt.% of SnO₂ in both systems. The composition dependence of the conductivity has been well correlated with the variation in glass transition temperature and degree of crystallinity. A substantial enhancement in the mechanical properties of the composite films was observed at the cost of slight decrease in the conductivity at higher concentration of SnO₂. The temperature dependence of the conductivity follows apparently the Arrhenius type thermally activated process below and above the melting temperature of PEO. The conductivity of the materials has been found to be strongly humidity dependent. The materials are shown to be ionic with t_ion>0.9. The electrochemical stability of the materials has been observed to be up to ≈3.2 V for (PEO)₂₅NaClO₄+x% SnO₂ and is limited to ≈1.9 V for (PEO)₂₅NaI+x% SnO₂.     

Blended lithium ion conducting polymer electrolytes based on boroxine polymers

A new series of blended polymer electrolytes based on a boroxine polymer (BP) with poly(ethylene oxide) (PEO), an ethylene oxide–propylene oxide copolymer or poly(methyl methacrylate) were prepared. Good room temperature mechanical properties were exhibited by electrolytes containing in excess of 30% PEO. Cationic transference number measurements indicated that a slight improvement in lithium ion conductivity could be achieved by using a mixture of LiCF₃SO₃ and LiN(CF₃SO₂)₂ as the electrolyte salt. Electrolytes incorporating significant proportions of BP exhibited reduced lithium–polymer electrolyte interfacial resistance.     

Effect of silane-functionalized mesoporous silica SBA-15 on performance of PEO-based composite polymer electrolytes

Silane-functionalized mesoporous silica SBA-15 particles with ultra-high specific surface area and large pore size were used as fillers in PEO-based solid electrolytes. FT-IR results confirmed the silane functionalization of SBA-15. Ionic conductivity and lithium ion transference number of the composite polymer electrolytes were found to simultaneously reach a high value of 5 wt.% silane-functionalized SBA-15 introduced in the matrix. It may be due to the combination effects of the unique structure of SBA-15 (i.e., ultra-high specific surface area and large pore size), the particularly functionalized surface of SBA-15 to promote fast ion transfer, and the good dispersion and compatibility of silane-functionalized SBA-15 in the composite polymer electrolytes. The results suggest an alternative way to improve the performance of solid polymer electrolytes.     

Solid polymer electrolytes based on poly(lithium carboxylate) salts

The ionic conductivity, lithium ion transference number, electrochemical stability, and thermal property of solid polymer electrolytes composed of poly(ethylene oxide) (PEO) and poly(lithium carboxylate)s, (poly(lithium acrylate) (Poly(Li-A)) or poly(lithium fumarate) (Poly(Li-F)), with and without BF₃·OEt₂ were investigated. The ionic conductivities of all solid polymer electrolytes were enhanced by one to two orders of magnitude with addition of BF₃·OEt₂ because the dissociation of lithium ion and carboxylate anion was promoted by the complexation with BF₃. The lithium ion transference number in the solid polymer electrolytes based on poly(lithium carboxylate)s showed relatively high values of 0.41–0.70, due to the suppression of the transport of counter anion by the use of a polymeric anion. The solid polymer electrolytes with addition of BF₃·OEt₂ showed good electrochemical stability.     

Ionic conductivity of polymer electrolytes based on phosphate and polyether copolymers

Linear polyphosphate random copolymers (LPC) composed of phosphate as a linking agent with poly(ethylene glycol) (PEG) and/or poly(tetramethylene glycol) (PTMG) were synthesized to increase local segmental motion for improved ion transport. Ionic conductivity and thermal behavior of LPC series–LiCF₃SO₃ complexes were investigated with various compositions, salt concentrations and temperatures. The PEG(70)/PTMG(30)/LiCF₃SO₃ electrolyte exhibited ionic conductivity of 8.04×10⁻⁵ S/cm at 25°C. Salt concentration with the highest ionic conductivity was considerably dependent on EO/TMO compositions in LPC series–salt systems. Relationship between solvating ability and chain flexibility with various compositions and salt concentrations was investigated through theoretical aspects of the Adam–Gibbs configurational entropy model. Temperature dependence on the ionic conductivity in LPC6 series–salt systems suggested the ion conduction follows the Williams–Landel–Ferry (WLF) mechanism, which is confirmed by Vogel–Tamman–Fulcher (VTF) plots. The ionic conductivity was affected by segmental motion of the polymer matrix. VTF parameters and apparent activation energy were evaluated by a non-linear least square minimization method. These results suggested that the solvating ability of the host polymer might be a dominant factor to improve the ionic conductivity rather than chain mobility.     

FTIR and thermal studies of modified natural rubber based polymer electrolytes

Chemical modification of natural rubber (NR) has frequently been attempted to improve the performance in specific application. 30% poly (methyl metacrylate) grafted NR (MG 30) has been explored as a potential candidate for polymer electrolytes. The complexation effect of LiCF₃SO₃, ethylene carbonate (EC) and Al₂SiO₅ in polymer host electrolytes has been investigated using FTIR ICP-OES spectrometry. Thermal studies of the systems have displayed a stable trend of glass temperature transition at elevated salt concentration whereas incorporation of EC and filler into the system results in the same pattern in their T_g values. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Impedance spectra of polymer electrolytes

The authors present a phenomenological view on dielectric relaxation in polymer electrolytes. Polymer electrolytes are seen as molecular mixtures of an organic polymer and an inorganic salt. The following is based on systems with high molar mass poly(ethylene oxide) (PEO) and epoxidized natural rubber with 25 mol% of epoxide content (ENR-25) filled with lithium perchlorate (LiClO₄). Dielectric properties of these systems have been studied as a function of salt content at room temperature. Additionally, properties of neat low molar mass PEO were studied as function of temperature. Relaxation-coined dielectric behavior rules the system with PEO in the frequency that ranged up to 10⁶ Hz. Imaginary parts of impedance, tangent loss, and electric modulus spectra show distribution of relaxation times. Comparison of tangent loss (tan δ) spectra and imaginary part of electric modulus (M″) spectra reveals that localized motion dominates long-range motion of dipoles in the low-frequency range. However, discrepancy between them decreases with growing salt content. Scaling of tan δ spectra demonstrates that distribution of relaxation times does not depend on salt content in the range of low frequencies. The ENR-25 system exhibits solely relaxation like a macroscopic dipole. In conclusion, the system with PEO is characterized by individual relaxation of well-interacting dipoles, whereas the system based on ENR-25 is coined by immobilized dipoles that lead in the state of high-salt content to the relaxation behavior of a macroscopic dipole.