Complicated phase behavior and ionic conductivities of PVP-co-PMMA-based polymer electrolytes

We have used DSC, FTIR spectroscopy, and ac impedance techniques to investigate the interactions that occur within complexes of poly(vinylpyrrolidone-co-methyl methacrylate) (PVP-co-PMMA) and lithium perchlorate (LiClO₄) as well as these systems' phase behavior and ionic conductivities. The presence of MMA moieties in the PVP-co-PMMA random copolymer has an inert diluent effect that reduces the degree of self-association of the PVP molecules and causes a negative deviation in the glass transition temperature (T_g). In the binary LiClO₄/PVP blends, the presence of a small amount of LiClO₄ reduces the strong dipole-dipole interactions within PVP and leads to a lower T_g. Further addition of LiClO₄ increases T_g as a result of ion-dipole interactions between LiClO₄ and PVP. In LiClO₄/PVP-co-PMMA blend systems, for which the three individual systems—the PVP-co-PMMA copolymer and the LiClO₄/PVP and LiClO₄/PMMA blends—are miscible at all compositional ratios, a phase-separated loop exists at certain compositions due to a complicated series of interactions among the LiClO₄, PVP and PMMA units. The PMMA-rich component in the PVP-co-PMMA copolymer tends to be excluded, and this phenomenon results in phase separation. At a LiClO₄ content of 20 wt% salt, the maximum ionic conductivity occurred for a LiClO₄/VP57 blend (i.e., 57 mol% VP units in the PVP-co-PMMA copolymer).     

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     

Ionic conductivity and interfacial properties of polymer electrolytes based on PEO and boroxine ring polymer

Blended polymer electrolytes based on poly(ethylene oxide) (PEO) and boroxine ring polymer (BP) solvated with lithium triflate were formulated and evaluated. Compared to PEO–salt polymer electrolyte, ionic conductivities of blended polymer electrolytes were two orders of magnitude higher in a low‐temperature range; as well, lithium transference numbers were increased to ～ 0.4. These were due to the increased mobility and anion trapping of boroxine rings. BP also exhibited the stabilizing effect on lithium–polymer electrolyte interface, and a reduced interfacial resistance between lithium metal and the polymer electrolyte was found with increasing of BP content. Polymer electrolytes based on PEO and BP are suitable for use in lithium secondary battery. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 17–21, 2002; DOI 10.1002/app.10090     

Effect of additives in PEO/PAA/PMAA composite solid polymer electrolytes on the ionic conductivity and Li ion battery performance

Polyethylene oxide (PEO) based-solid polymer electrolytes were prepared with low weight polymers bearing carboxylic acid groups added onto the polymer backbone, and the variation of the conductivity and performance of the resulting Li ion battery system was examined. The composite solid polymer electrolytes (CSPEs) were composed of PEO, LiClO_4, PAA (polyacrylic acid), PMAA (polymethacrylic acid), and Al₂O₃. The addition of additives to the PEO matrix enhanced the ionic conductivities of the electrolyte. The composite electrolyte composed of PEO:LiClO₄:PAA/PMAA/Li_0.3 exhibited a low polarization resistance of 881.5 ohms in its impedance spectra, while the PEO:LiClO₄ film showed a high value of 4,592 ohms. The highest ionic conductivity of 9.87 × 10⁻⁴ S cm⁻¹ was attained for the electrolyte composed of PEO:LiClO₄:PAA/PMAA/Li_0.3 at 20 °C. The cyclic voltammogram of Li⁺ recorded for the cell consisting of the PEO:LiClO₄:PAA/PMAA/Li_0.3:Al₂O₃ composite electrolyte exhibited the same diffusion process as that obtained with an ultra-microelectrode. Based on this electrolyte, the applicability of the solid polymer electrolytes to lithium batteries was examined for an Li/SPE/LiNi_0.5Co_0.5O₂ cell.     

Fluidizing efficiency of comb-like superplasticizers: The effect of the anionic function,the side chain length and the grafting degree

Superplasticizers and especially polycarboxylate grafted polyethylene oxide (PCE) demonstrated their efficiency to fluidify concrete. The aim of this work is to investigate the evolution of the fluidity as a function of adsorption in a sulfated solution with a wide variety of comb-like superplasticizers and at incomplete adsorption rate. Polymers with various side chain lengths, grafting ratios and also with modified anionic functions (carboxylate, dicarboxylate and phosphate) were synthesized. Inert calcite suspensions were used to mimic early age cementitious materials avoiding the cement hydration. Models of polymer conformation and yield stress prediction have been tested. But the most appropriate parameter which captures the fluidity/adsorption relationship is the mass of adsorbed polymer. A unique relationship “log(yield stress) vs. adsorbed mass of PCE” has been highlighted whatever the classical carboxylate PCE structure. The modification of the anionic function does not enhance the fluidizing efficiency. Each PCE has roughly the same fluidizing efficiency when it manages to adsorb in these ionic conditions.     

Effect of propylene carbonate on the ionic conductivity of polyacrylonitrile‐based solid polymer electrolytes

Solid polymer electrolyte membranes consisting of polyacrylonitrile (PAN) as a host polymer, ammonium nitrate (NH₄NO₃) as a complexing salt, and propylene carbonate (PC) as a plasticizer were prepared by a solution casting technique. An increase in the amorphous nature of the polymer electrolytes was confirmed by X‐ray diffraction analysis. A shift in the glass‐transition temperature of the PAN/NH₄NO₃/PC electrolytes was observed in the differential scanning calorimetry thermograms; this indicated interactions between the polymer and the salt. The impedance spectroscopy technique was used to study the mode of ion conduction in the plasticized polymer electrolyte. The highest ionic conductivity was found to be 7.48 × 10^?3 S/cm at 303 K for 80 mol % PAN, 20 mol % NH₄NO₃, and 0.02 mol % PC. The activation energy of the plasticized polymer electrolyte (80 mol % PAN/20 mol % NH₄NO₃/0.02 mol % PC) was found to be 0.08 eV; this was considerably lower than that of the film without the plasticizers. The dielectric behavior of the electrolyte is discussed in this article. A literature survey indicated that the synthesis and characterization of ammonium‐salt‐doped, proton‐conducting polymer electrolytes based on PAN has been rare. The use of the best composition membrane (80 mol % PAN/20 mol % NH₄NO₃/0.02 mol % PC) proton battery was constructed and evaluated. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41743.     

Sulfonate based ionic liquid incorporated polymer electrolytes for Magnesium secondary battery

The polymer electrolytes comprising of PVdF-HFP/PVAc/Mg(ClO₄)₂ as salt based polymer blend electrolytes derived from the addition of varying amounts of 1-ethyl – 3-methylimidazolium trifluoromethane sulfonate [EMITF], as dopant were synthesized in the form of films by solution-casting method. The XRD and FTIR patterns confirm the formation of an amorphous phase and also that complex formation between the polymers, salt and ionic liquid. The SEM images show that the polymer electrolyte exhibit a enormous pores, remarkably, the maximum ionic conductivity is obtained in the case of the typical polymer system I₃ is found to be 9.122 × 10^?4 Scm^?1at 303 K.     

Ternary polymer electrolytes with 1-methylimidazole based ionic liquids and aprotic solvents

New polymer gel electrolytes containing ionic liquids were developed for modern chemical power sources—supercapacitors and lithium-ion batteries. Ternary systems polymer-ionic liquid-aprotic solvent as well as materials containing also lithium salts (LiClO₄ or LiPF₆) were prepared by direct, thermally initiated polymerisation. Poly(2-ethoxyethyl methacrylate) PEOEMA was combined with various ionic liquids based on 1-methylimidazole. Only 1-butyl-3-methylimidazolium hexafluorophosphate BMIPF₆ formed a homogenous and slightly translucent polymer electrolyte, where aprotic solvents—propylene carbonate and ethylene carbonates were used as plasticisers. Materials were studied using the electrochemical and thermogravimetric methods and exhibit high ionic conductivity up to 0.94 mS cm⁻¹ at 25 °C together with high electrochemical stability: the accessible potential window on the glassy carbon was found ca. 4.3 V. Prepared non-volatile materials are long-term and thermally stable up to 150 °C.     

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.     

Thermal, electrical and mechanical properties of plasticized polymer electrolytes based on PEO/P(VDF-HFP) blends

The polymer electrolytes composed of a blend of poly(ethylene oxide) (PEO) and poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) as a host polymer, mixture of ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizer, and LiClO₄ as a salt were prepared by a solution casting technique. SEM micrographs show that P(VDF-HFP) is very compatible with PEO. The ionic conductivity of the electrolytes increases with increasing plasticizer content, while the mechanical properties become obviously worse. By addition of a certain content of PEO in P(VDF-HFP) matrix, a good compromise between high ionic conductivity and mechanical stability can be obtained.     

The correlation between the ionic degree of covalent bond comprising polymer main chain and the ionic yield due to mechanical fracture

The mechanical force to polymeric materials in vacuum at 77 K produces mechano radicals, mechano anions and mechano cations due to homogeneous and heterogeneous scissions of the covalent bonds comprising polymer main chain. The ionic degree of the covalent bond was estimated by calculating the “absolute ΔMulliken atomic charge,” which was defined as the difference between the Mulliken atomic charges of the two adjacent atoms comprising the covalent bond of the polymer main chain. The ionic yield of the covalent bond increased with increasing the absolute ΔMulliken atomic charge. The empirical formula for the ionic yield was obtained with the absolute ΔMulliken atomic charge, and indicates that the ionic yield could be estimated from its chemical structure.     

Preparation of polymer electrolytes based on the polymerized imidazolium ionic liquid and their applications in lithium batteries

The polymer electrolytes based on a polymerized ionic liquid (PIL) as polymer host and containing 1,2‐dimethyl‐3‐butylimidazolium bis(trifluoromethanesulfonyl)imide (BMMIM‐TFSI) ionic liquid, lithium TFSI salt, and nanosilica are prepared. The PIL electrolyte presents a high ionic conductivity, and it is 1.07 × 10^?3 S cm^?1 at 60°C, when the BMMIM‐TFSI content reaches 60% (the weight ratio of BMMIM‐TFSI/PIL). Furthermore, the electrolyte exhibits wide electrochemical stability window and good lithium stripping/plating performance. Preliminary battery tests show that Li/LiFePO₄ cells with the PIL electrolytes are capable to deliver above 146 mAh g^?1 at 60°C with very good capacity retention. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40928.     

Zinc ion conducting blended polymer electrolytes based on room temperature ionic liquid and ceramic filler

Zinc ion conducting nanocomposite gel polymer electrolytes (NCGPEs) comprising of poly(vinyl chloride) (PVC)/poly(ethyl methacrylate) (PEMA) blend, zinc triflate [Zn(OTf)₂] salt, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) ionic liquid (IL) and fumed silica (SiO₂) viz. [PVC/PEMA–Zn(OTf)₂–EMIMTFSI–SiO₂] exhibited the highest ionic conductivity value of 6.71 × 10⁻⁴ Scm⁻¹ at room temperature. The ion–filler–polymer interactions and probable conformational changes observed in the structure of the gel composites due to the entrapment of IL and dispersion of nano-sized SiO₂ were confirmed from X-ray diffraction (XRD) and Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. Scanning electron microscopic (SEM) images of NCGPEs demonstrated uniform surface with abundant interconnected micropores. The cationic transport number of NCGPE samples has been found to be appreciably enhanced up to a maximum of 0.69 thus demonstrating a considerable improvement in Zn²⁺ ion conductivity. The NCGPE film possesses an electrochemical stability window up to 5.07 V (vs. Zn/Zn²⁺) and ensures feasible zinc stripping/plating in the redox process. The addition of SiO₂ into the gel polymer electrolyte system has effectively reduced the glass-transition temperature (T_g) of the NCGPE films and also accomplished improved thermal stability up to approximately 180 °C which were ascertained from Differential scanning calorimetry (DSC) and Thermogravimetric (TG) results. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47654.     

Effect of a novel amphipathic ionic liquid on lithium deposition in gel polymer electrolytes

A novel dimeric ionic liquid based on imidazolium cation and bis(trifluoromethanesulfonyl) imide (TFSI) anion has been synthesized through a metathesis reaction. Its chemical shift values and thermal properties are identified via ¹H nuclear magnetic resonance (NMR) imaging and differential scanning calorimetry (DSC). The effect of the synthesized dimeric ionic liquid on the interfacial resistance of gel polymer electrolytes is described. Differences in the SEM images of lithium electrodes after lithium deposition with and without the 1,1′-pentyl-bis(2,3-dimethylimidazolium) bis(trifluoromethane-sulfonyl)imide (PDMITFSI) ionic liquid in gel polymer electrolytes are clearly discernible. This occurs because the PDMITFSI ionic liquid with hydrophobic moieties and polar groups modulates lithium deposit pathways onto the lithium metal anode. Moreover, high anodic stability for a gel polymer electrolyte with the PDMITFSI ionic liquid was clearly observed.     

Optical and electrical characterization of (PEO+methyl violet) polymer electrolytes

Optical properties and electrical conductivity of polyethylene oxide (PEO) with methyl violet dopant film have studied. The complexation of the methyl violet dopant with PEO was confirmed by X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopic studies. The microstructure morphology have been analyzed by scanning electron microscope (SEM) for pure and dopant films. The UV‐absorption studies were made in the wavelength range 190–1100 nm for pure and doped films. The dc electrical conductivity data was collected using two probe technique in the temperature range 303–333 K. The UV–visible spectra showed the absorption band at 190 nm for pure PEO and doped from 208–224 nm region with different absorption intensities. The absorption edge, direct and indirect band gap were estimated using Mott and Davis Model. The optical activation energy can be determined using the Urbach rule, for pure PEO it was found 2.38 eV and 1.28–4.08 eV for doped films. The absorption band was shifted toward the higher frequency, the direct and indirect band gap decreases with increasing of dopant concentration, corresponds to the allowed inter band transition of electron. The dc electrical conductivity results shows that it increases with increasing dopant weight percentage and temperature which corresponds to the enhancement of charge mobility in these dye doped polymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effect of ionic liquid fragment on the performance of polymer electrolytes

An ionic liquid 1‐methyl‐3‐[2‐(methacryloyloxy)ethyl]imidazolium bis(trifluoromethane sulfonylimide) (MMEIm‐TFSI) was synthesized and polymerized. Composite polymer electrolytes based on polymeric MMEIm‐TFSI (PMMEIm‐TFSI) and poly[(methyl methacrylate)‐co‐(vinyl acetate)] (P(MMA‐VAc)) were prepared, with lithium bis(trifluoromethane sulfonylimide) (LiTFSI) as target ions (Li⁺). DSC/TGA analysis showed good flexibility and thermal stability of the composite electrolyte membranes. The AC impedance showed that the ionic conductivity of the electrolytes increased with PMMEIm‐TFSI up to a maximum value of 1.78 × 10^?4 S cm^?1 when the composition was 25 wt% P(MMA‐VAc)/75 wt% PMMEIm‐TFSI/30 wt% LiTFSI at 30 °C. The composite electrolyte membrane (transmittance ≥ 90%) can also be used as the ion‐conductive layer material for electrochromic devices, and revealed excellent colorization performance. Copyright © 2011 Society of Chemical Industry     

Proton-conducting polymer electrolytes based on methacrylates

Proton-conducting polymer electrolytes based on methacrylates were prepared by direct, radical polymerization of ethyl (EMA), 2-ethoxyethyl (EOEMA), and 2-hydroxyethyl methacrylate (HEMA). Samples with embedded solutions of phosphoric acid in propylene carbonate (PC), γ-butyrolactone (GBL), N,N-dimethylformamide (DMF) and their mixtures were studied using impedance, voltammetrical and thermogravimetric methods. Membranes of long-term stability exhibit ionic conductivity up to 6.7 × 10⁻⁵ S cm⁻¹ at 25 °C reached for the sample PEMA-PC-H₃PO₄ (31:42:27 mol.%). The accessible electrochemical potential window is 2.2-3 V depending on the working electrode material (glassy carbon or platinum). The thermogravimetric analysis shows that the membranes are thermally stable up to 110-130 °C.     

Electrorheological fluids based on polymer electrolytes

The phenomenon of electrorheological activity taking part in so called electrorheological fluids (ERFs) relies on strong and reversible changes of fluid viscosity upon application of electric field and finds interesting technical applications. ERFs typically comprise dispersions of polarisable solid particles in liquid matrices. The paper describes studies on complexes of polyacrylonitrile with various salts of alkaline elements. The materials in a powder form were dispersed in silicone oil as well as in active matrices containing a liquid crystalline polymer. It was found that these novel systems were substantially anhydrous and electrorheologically active. The observed ER effect was relatively high and accompanied by very low current consumption. The magnitude of the ER effect was correlated with bulk ionic conductivity of the studied materials. The optimal bulk conductivity giving the highest ER effect at reasonably low currents amounted to about 10⁻⁵ S/cm. Higher conductivities resulted in higher currents only and saturation of the yield stress values. It was also shown that dispersions of the polymer complexes in a solution of poly(n-hexyl isocyanatye) in xylene manifested enhanced ER activity.