Novel composite polymer electrolytes based on poly(ether-urethane) network polymer and modified montmorillonite

Novel composite solid polymer electrolytes (CSPEs) and composite gel polymer electrolytes (CGPEs) have been prepared. CSPE consists of poly(ether-urethane) network polymer, which is superior to poly(ethylene oxide) in mechanical stability due to its cross-linked structure, modified montmorillonite (MMMT) and LiClO₄, and CGPE with good mechanical strength comprises of the CSPE and LiClO₄–PC (propylene carbonate) solution. The ionic conductivity can be enhanced after the addition of MMMT, and CGPE exhibits ionic conductivity in the order of 10⁻³ S/cm at room temperature. The temperature dependence of the ionic conductivity of the CSPE follows the Vogel–Tamman–Fulcher (VTF) equation. The effects of MMMT on the interactions in these systems and the possible conduction mechanisms are also discussed.     

Network polymer electrolytes based on poly(ester diacrylate), ethylene carbonate,and LiClO<Subscript>4</Subscript>

Network polymer electrolytes based on poly(ester diacrylate), LiClO₄, and ethylene carbonate are synthesized and investigated via the methods of electrochemical impedance spectroscopy, DSC, and thermal analysis. It is found that, for the polymer-LiClO₄ system, the conductivity is 4.2 × 10⁻⁷ S/cm at 20°C. With a gradual increase in the amount of ethylene carbonate, the conductivity first decreases and then increases. It is shown that, when poly(ester diacrylate) is crosslinked in ethylene carbonate, up to 45.5% of the latter compound is retained in the polymer and not lost during heating to 100°C. The conductivity of the electrolyte containing 45.6 wt % poly(ester diacrylate), 45.5 wt % ethylene carbonate, 7.5 wt % LiClO₄, and 1.4 wt % benzoyl peroxide achieves 1.9 × 10⁻⁴ S/cm at 20°C.     

Enhanced electrochemical properties of polyethylene oxide-based composite solid polymer electrolytes with porous inorganic–organic hybrid polyphosphazene nanotubes as fillers

Solid composite polymer electrolytes consisting of polyethylene oxide (PEO), LiClO₄, and porous inorganic–organic hybrid poly (cyclotriphosphazene-co-4, 4′-sulfonyldiphenol) (PZS) nanotubes were prepared using the solvent casting method. Differential scanning calorimetry and scanning electron microscopy were used to determine the characteristics of the composite polymer electrolytes. The ionic conductivity, lithium ion transference number, and electrochemical stability window can be enhanced after the addition of PZS nanotubes. The electrochemical impedance showed that the conductivity was improved significantly. Maximum ionic conductivity values of 1.5 × 10⁻⁵ S cm⁻¹ at ambient temperature and 7.8 × 10⁻⁴ S cm⁻¹ at 80 °C were obtained with 10 wt.% content of PZS nanotubes, and the lithium ion transference number was 0.35. The good electrochemical properties of the solid-state composite polymer electrolytes suggested that the porous inorganic–organic hybrid polyphosphazene nanotubes had a promising use as fillers in SPEs and the PEO₁₀–LiClO₄–PZS nanotube solid composite polymer electrolyte might be used as a candidate material for lithium polymer batteries.     

Investigation on the effect of nanosilica towards corn starch–lithium perchlorate-based polymer electrolytes

Biodegradable corn starch–lithium perchlorate (LiClO₄)-based solid polymer electrolytes with addition of nano-sized fumed silica (SiO₂) were prepared by solution casting technique. Ionic conductivity at ambient temperature was measured by AC impedance spectroscopy. Upon addition of nano-sized SiO₂, the ionic conductivity at room temperature is increased. The optimum ionic conductivity value obtained was 1.23?×?10^?4?S?cm^?1 at 4?wt% SiO₂. This may be attributed to the low crystallinity of the polymer electrolytes resulting from the dispersed nanosilica particles. Fourier–transform infrared spectroscopy studies confirmed the complexation between corn starch, lithium perchlorate, and silica. The thermal properties of the prepared samples were investigated with differential scanning calorimetry and thermogravimetric analysis. The surface morphology of the polymer electrolytes confirmed the agglomeration of particles after excess dispersion of inorganic filler. This was proven in the scanning electron microscopy studies.     

Electrochemical properties of PEO/PMMA blend-based polymer electrolytes using imidazolium salt-supported silica as a filler

In this study, the composite polymer electrolytes (CPEs) were prepared by solution casting technique. The CPEs consisted of PEO/PMMA blend as a host matrix doped with LiClO₄. Propylene carbonate (PC) was used as plasticizer and a small amount of imidazolium salt-supported amorphous silica (IS-AS) as a filler was prepared by the sol–gel method. At room temperature, the highest conductivity was obtained for the composition having PEO–PMMA–LiClO₄–PC–4wt. % IS-AS with a value of 1.15 × 10^?4 S/cm. In particular, the CPE using the IS-AS filler showed a higher conductivity than any other sample (fumed silica, amorphous silica). Studies of differential scanning calorimetry and scanning electron microscopy indicated that the ionic conductivity increase was due to an expansion in the amorphous phase which enhances the flexibility of polymeric chains and the homogeneous structure of CPEs. It was found that the ionic conductivity and interfacial resistance stability of CPEs was significantly improved by the addition of IS-AS. In other words, the resistance stability and maximum ambient ionic conductivity of CPEs containing IS-AS filler were better than CPEs containing any other filler.     

Improved properties of polymer electrolyte by ionic liquid PP1.3TFSI for secondary lithium ion battery

A new kind of polymer electrolyte is prepared from N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) imide (PP1.3TFSI), polyethylene oxide (PEO), and lithium bis (trifluoromethanesulfonyl) imide (LiTFSI). IR and X-ray diffraction results demonstrate that the addition of ionic liquid decreases the crystallization of PEO. Thermal and electrochemical properties have been tested for the solid polymer electrolytes, the addition of the room temperature molten salt PP1.3TFSI to the conventional P(EO)₂₀LiTFSI polymer electrolyte leads to the improvement of the thermal stability and the ionic conductivity (x = 1.27, 2.06 × 10⁻⁴ S cm⁻¹ at room temperature), and the reasonable lithium transference number is also obtained. The Li/LiFePO₄ cell using this polymer electrolyte shows promising reversible capacity, 120 mAh g⁻¹ at room temperature and 164 mAh g⁻¹ at 55 °C.     

Synthesis and electrochemical characterization of aPEO-based polymer electrolytes

In this paper, the preparation and purification of an amorphous polymer network, poly[oxymethylene-oligo(oxyethylene)], designated as aPEO, are described. The flexible CH₂CH₂O segments in this host polymer combine appropriate mechanical properties, over a critical temperature range from −20 to 60 °C, with labile salt-host interactions. The intensity of these interactions is sufficient to permit solubilisation of the guest salt in the host polymer while permitting adequate mobility of ionic guest species. We also report the preparation and characterisation of a novel polymer electrolyte based on this host polymer with lithium tetrafluoroborate, LiBF₄, as guest salt. Electrolyte samples are thermally stable up to approximately 250 °C and completely amorphous above room temperature. The electrolyte composition determines the glass transition temperature of electrolytes and was found to vary between −50.8 and −62.4 °C. The electrolyte composition that supports the maximum room temperature conductivity of this electrolyte system is n = 5 (2.10 × 10⁻⁵ S cm⁻¹ at 25 °C). The electrochemical stability domain of the sample with n = 5 spans about 5 V measured against a Li/Li⁺ reference. This new electrolyte system represents a promising alternative to LiCF₃SO₃ and LiClO₄-doped PEO analogues.     

Effect of ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide on the properties of poly(glycidyl methacrylate) based solid polymer electrolytes

A free standing polymer electrolytes films, containing poly(glycidyl methacrylate) (PGMA) as the polymer host, lithium perchlorate (LiClO₄), and ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide [Bmim][TFSI] as a plasticizer was successfully prepared via the solution casting method. The XRD analysis revealed the amorphous nature of the electrolyte. ATR-FTIR and thermal studies confirmed the interaction and complexation between the polymer host and the ionic liquid. The maximum ionic conductivity of the solid polymer electrolyte was found at 2.56 × 10^–5 S cm^–1 by the addition of 60 wt % [Bmim][TFSI] at room temperature and increased up to 3.19 × 10^–4 S cm^–1 at 373 K, as well as exhibited a transition of temperature dependence of conductivity: Arrhenius-like behavior at low and high temperatures.     

Conductivity studies of polymer electrolytes based on aliphatic polyesters

A series of aliphatic polyesters of sebacoyl chloride and poly(ethylene glycol) containing a different number of ethylene oxide groups was synthesized and characterized. These polyesters were complexed with lithium perchlorate to obtain a new class of polymer electrolyte. The relationships between the structure and properties of these polymer electrolytes were investigated. The main factor that affects the ionic conductivity in these systems was found to be the solvating capacity of the polyester for the lithium salt. These polymer electrolytes showed ionic conductivities up to 10^?5 ? 10^?4 S/cm at 25°C. The mechanical strength was improved by cross-linking, and the cross-linked polyester complexed with a LiCIO₄ salt showed an ionic conductivity of 2 × 10^?5 S/cm at room temperature. ⁷Li NMR spin-spin relaxation and dielectric relaxation studies were also carried out to investigate the local environments and dynamics of ions in the polymer electrolytes. © 1995 John Wiley & Sons, Inc.     

The network gel polymer electrolyte based on poly(acrylate-co-imide) and its transport properties in lithium ion batteries

Poly (acrylate-co-imide)-based gel polymer electrolytes are synthesized by in situ free radical polymerization. Infrared spectroscopy confirms the complete polymerization of gel polymer electrolytes. The ionic conductivity of gel polymer electrolytes are measured as a function of different repeating EO units of polyacrylates. An optimal ionic conductivity of the poly (PEGMEMA₁₁₀₀-BMI) gel polymer electrolyte is determined to be 4.8 × 10^–3 S/cm at 25 °C. The lithium transference number is found to be 0.29. The cyclic voltammogram shows that the wide electrochemical stability window of the gel polymer electrolyte varies from −0.5 to 4.20 V (vs. Li/Li⁺). Furthermore, we found the transport properties of novel gel polymer electrolytes are dependent on the EO design and are also related to the rate capability and the cycling ability of lithium polymer batteries. The relationship between polymer electrolyte design, lithium transport properties and battery performance are investigated in this research.     

Synthesis and properties of all solid polymer electrolytes based on poly(vinyl acetate‐co‐acetyl ethylene oxide acrylate)

Poly(acetyl ethylene oxide acrylate‐co‐vinyl acetate) (P(AEOA‐VAc)) was synthesized and used as a host for lithium perchlorate to prepare an all solid polymer electrolyte. Introduction of carbonyl groups into the copolymer increased ionic conductivity. All solid polymer electrolytes based on P(AEOA‐VAc) at 14.3 wt% VAc with 12wt% LiClO₄ showed conductivity as high as 1.2 × 10^?4 S cm^?1 at room temperature. The temperature dependence of the ionic conductivity followed the VTF behavior, indicating that the ion transport was related to segmental movement of the polymer. FTIR was used to investigate the effect of the carbonyl group on ionic conductivity. The interaction between the lithium salt and carbonyl groups accelerated the dissociation of the lithium salt and thus resulted in a maximum ionic conductivity at a salt concentration higher than pure PAEO‐salts system. Copyright © 2010 John Wiley & Sons, Ltd.     

New solid polymer electrolytes based on polyester diacrylate for lithium power sources

New solid polymer electrolytes are developed for a lithium power source used at the temperatures up to 100°C. Polyester diacrylate (PEDA) based on oligohydroxyethylacrylate and its block copolymers with polyethylene glycol were offered for polymer matrix formation. The salt used was LiClO₄. The ionic conductivity of electrolytes was measured in the range of 20 to 100°C using the electrochemical impedance method. It is shown that the maximum conductivity in the whole temperature range is characteristic of the electrolyte based on the PEDA copolymer and polyethylene glycol condensation product (2.8 × 10^?6 S cm^?1 at 20°C, 1.8 × 10^?4 S cm^?1 at 95°C).     

Investigations on poly(methyl methacrylate)-poly(ethylene oxide) hybrid polymer electrolytes with dioctyl phthalate, dimethyl phthalate and diethyl phthalate as plasticizers

Plasticizers can be used to change the mechanical and electrical properties of polymer electrolytes by reducing the degree of crystallinity and lowering the glass transition temperature. The transport properties of gel-type ionic conducting membranes consisting of poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), LiClO₄ and dioctyl phthalate, diethyl phthalate or dimethyl phthalate (DMP) are studied. The polymer films are characterized by X-ray diffraction, Fourier transform infrared and impedance spectroscopic studies. It is found that the addition of DMP as the plasticizer in the PEO-PMMA-LiClO₄ polymer complex favours an enhancement in ionic conductivity. The maximum conductivity value obtained for the solid polymer electrolyte film at 305 K is 3.529×10^{– 4} S cm^–1. Electronic Publication     

Preparation and characterization of lithium ion conducting ionic liquid-based biodegradable corn starch polymer electrolytes

Thin films of biodegradable corn starch-based biopolymer electrolytes were prepared by solution casting technique. Lithium hexafluorophosphate (LiPF₆) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BmImTf) were employed as lithium salt and ionic liquid, respectively. With reference to the temperature dependence study, Arrhenius relationship was observed. The highest ionic conductivity of (6.00 ± 0.01) × 10⁻⁴ S cm⁻¹ was obtained at 80 °C. Based on x-ray diffraction (XRD) result, the peaks became broader with doping of ionic liquid revealing the higher amorphous region of the biopolymer electrolytes. Ionic liquid-based biopolymer electrolytes exhibited lower glass transition temperature (T _g).     

ETHYLENE OXIDE-ETHYLENE TEREPHTHALATE SEGMENTED COPOLYMER SOLID ELECTROLYTE8

 A series of ethylene oxide-ethylene terephthalate segmented copolymers (EOET) weresynthesized and complexed with LiClO₄ to form some new polymer electrolytes. The EOET-LiClO₄ electrolytes exhibit not only high ionic conductivity, but also good mechanical strengthand toughness. The EOET 3400--25--LiClO₄ complex possesses the highest conductivity (4. 65×10^-5s·cm^-1 at room temperature when the ratio [Li⁺]/[EO] equals 1/16. The structures of these electrolytes were examined with FTIR analysis, X-ray diffraction and DSC thermograms,and the results of high ionic conductivity of the segmented copolymers were discussed.     

Electrical and electrochemical studies on magnesium ion-based polymer gel electrolytes

The development of polymer gel electrolyte system with high ionic conductivity is the main objective of polymer research. Electrochemical devices based on lithium ion-conducting polymer electrolyte are not safe due to the explosive nature of lithium. An attempt has been made to synthesize magnesium ion-conducting polymeric gel electrolytes, poly (vinylidene fluoride-co-hexafluoropropylene)–propylene carbonate–magnesium perchlorate, PVdF(HFP)-PC–Mg(ClO₄)₂ using standard solution-cast techniques. The maximum room temperature ionic conductivity of the synthesized electrolyte system has been observed to be 5.0 × 10⁻³ S cm⁻¹, which is quite acceptable from a device fabrication point of view. The temperature-dependent conductivity and the dielectric behavior were also analyzed. The pattern of the temperature-dependent conductivity shows the Arrhenius behavior. The dielectric constant ε _r and dielectric loss ε _i increases with temperature in the low-frequency region but almost negligible in the high-frequency region. This behavior can be explained on the basis of electrode polarization effects. The real part M _r and imaginary part M _i versus frequency indicate that the systems are predominantly ionic conductors. Further, the synthesized electrolyte materials have been checked for its suitability in energy storage devices namely redox supercapacitor with conducting polymer polypyrrole as electrode materials, and finally, it was observed that it shows good capacitive behavior in low-frequency region. Preliminary studies show that the overall capacitance of 22 mF cm⁻² which is equivalent to a single electrode specific capacitance of 117 F gm⁻¹ was observed for the above said supercapacitors.     

Effect of solvents on properties of polymer gel-electrolyte based on polyester diacrylate

New polymer gel electrolytes based on polyester diacrylates and LiClO₄ salt solutions in organic solvents are developed for lithium ion and lithium polymer batteries with a high ionic conductivity up to 2.7 × 10^?3 Ohm^?1cm^?1 at the room temperature. To choose the optimum liquid electrolyte composition, the dependence is studied of physico-chemical parameters of new gel electrolytes on the composition of the mixture of aprotic organic solvents: ethylene carbonate, propylene carbonate, and λ-butyrolacton. The bulk conductivity of gel electrolytes and exchange currents at the gel electrolyte/Li interface are studied using the electrochemical impedance method in symmetrical cells with two Li electrodes. The glass transition temperature and gel homogeneity are determined using the method of differential scanning calorimetry. It is found that the optimum mixture is that of propylene carbonate and λ-butyrolacton, in which a homogeneous polymer gel is formed in a wide temperature range of ?150 to +50°C.     

A polymer electrolyte containing ionic liquid for possible applications in photoelectrochemical solar cells

Various iodide ion conducting polymer electrolytes have been studied as candidate materials for fabricating photoelectrochemical (PEC) solar cells and energy storage devices. In this study, enhanced ionic conductivity values were obtained for the ionic liquid tetrahexylammonium iodide containing polyethylene oxide (PEO)-based plasticized electrolytes. The analysis of thermal properties revealed the existence of two phases in the electrolyte, and the conductivity measurements showed a marked conductivity enhancement during the melting of the plasticizer-rich phase of the electrolyte. Annealed electrolyte samples showed better conductivity than nonannealed samples, revealing the existence of hysteresis. The optimum conductivity was shown for the electrolytes with PEO:salt = 100:15 mass ratio, and this sample exhibited the minimum glass transition temperature of 72.2 °C. For this optimum PEO to salt ratio, the conductivity of nonannealed electrolyte was 4.4 × 10⁻⁴ S cm⁻¹ and that of the annealed sample was 4.6 × 10⁻⁴ S cm⁻¹ at 30 °C. An all solid PEC solar cell was fabricated using this annealed electrolyte. The short circuit current density (I _SC), the open circuit voltage (V _OC), and the power conversion efficiency of the cell are 0.63 mA cm⁻², 0.76 V, and 0.47% under the irradiation of 600 W m⁻² light.     

Solid polymer electrolytes based on crosslinkable polyoctahedral silsesquioxanes (POSS) for room temperature lithium polymer batteries

Solid polymer electrolytes (SPE), based on polyoctahedral silsesquioxanes (POSS) as a crosslinking agent, were prepared by radical polymerization. The ionic conductivity is greatly enhanced by introduction of crosslinkable POSS with multifunctional groups. The SPE prepared with 5 wt.% crosslinking agent shows an ionic conductivity of 5.3?×?10^?4 S cm^?1 at room temperature. The content of nonvolatile plasticizer, poly(ethylene glycol) dimethyl ether, in the SPE, could be raised to 95 wt.% without any leakage. The SPE is found to be electrochemically stable up to 5.3 V. Lithium polymer cell consisting of Li/SPE/LiCoO₂ exhibits 80% of initial discharge capacity even at the rate of 0.1 C at room temperature after 20 cycles, which is a substantial improvement for practical consideration of lithium polymer batteries at room temperature.     

Effect of nanoscale CeO<Subscript>2</Subscript> on PVDF-HFP-based nanocomposite porous polymer electrolytes for Li-ion batteries

New poly (vinylidenefluoride-co-hexafluoro propylene) (PVDF-HFP)/CeO₂-based microcomposite porous polymer membranes (MCPPM) and nanocomposite porous polymer membranes (NCPPM) were prepared by phase inversion technique using N-methyl 2-pyrrolidone (NMP) as a solvent and deionized water as a nonsolvent. Phase inversion occurred on the MCPPM/NCPPM when it is treated by deionized water (nonsolvent). Microcomposite porous polymer electrolytes (MCPPE) and nanocomposite porous polymer electrolytes (NCPPE) were obtained from their composite porous polymer membranes when immersed in 1.0 M LiClO₄ in a mixture of ethylene carbonate/dimethyl carbonate (EC/DMC) (v/v = 1:1) electrolyte solution. The structure and porous morphology of both composite porous polymer membranes was examined by scanning electron microscope (SEM) analysis. Thermal behavior of both MCPPM/NCPPM was investigated from DSC analysis. Optimized filler (8 wt% CeO₂) added to the NCPPM increases the porosity (72%) than MCPPM (59%). The results showed that the NCPPE has high electrolyte solution uptake (150%) and maximum ionic conductivity value of 2.47 × 10⁻³ S cm⁻¹ at room temperature. The NCPPE (8 wt% CeO₂) between the lithium metal electrodes were found to have low interfacial resistance (760 Ω cm²) and wide electrochemical stability up to 4.7 V (vs Li/Li⁺) investigated by impedance spectra and linear sweep voltammetry (LSV), respectively. A prototype battery, which consists of NCPPE between the graphite anode and LiCoO₂ cathode, proves good cycling performance at a discharge rate of C/2 for Li-ion polymer batteries.