Formation of double-surface-silvered polyimide films via a direct ion-exchange self-metallization technique: The case of BPADA/ODA and [Ag(NH3)2]+

Double-surface-silvered polyimide (PI) films have been successfully fabricated via a direct ion-exchange self-metallization method using silver ammonia complex cation ([Ag(NH₃)₂]⁺) as silver resource and bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride/4,4′-oxydianiline (BPADA/ODA)-based poly(amic acid) (PAA) as the PI precursor. The alkaline characteristic of the silver precursor dramatically improves the efficiency of the ion exchange and film metallization process. By using an aqueous [Ag(NH₃)₂]⁺ solution with a concentration of only 0.01M and an ion-exchange time of only 5 min, metallized films with desirable performance could be easily obtained by simply heating the silver(I)-doped PAA films to 300°C. The strong hydrolysis effect of the basic [Ag(NH₃)₂]⁺ cations on the flexible and acidic BPADA/ODA PAA chains was observed during the ion exchange process by the quantitative evaluation of the mass loss of PAA matrix. Nevertheless, under the present experimental conditions, the final metallized film essentially retained the basic structural, thermal, and mechanical properties of the pristine PI, which make it a truly applicable material. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ionic conductivity of hybrid films based on polyacrylonitrile and their battery application

The alternate current (AC) and direct current (DC) ionic conductivity of hybrid films composed of polyacrylonitrile (PAN), lithium perchlorate (LiClO₄), and a plasticizer was studied. Three kinds of the plasticizer [ethylene carbonate (EC), propylene carbonate (PC), N,N-dimethylformamide (DMF)] were used. Suitability of these hybrid films for lithium battery was investigated. The AC conductivity, which represents bulk ionic conductivity, was dependent on the component and the composition of the hybrid films, ranging from 10^?4?10^?8 Scm^?1. The AC conductivity was mainly determined by the molar ratio of [plasticizer]/[LiClO₄] in the hybrid films and increased with the increase in this ratio. The effect of the plasticizer on the enhancement in the AC conductivity was in the following order. DMF>EC>PC. The hybrid films with both electrodes of lithium showed the stable DC conductivity of about 1/10 of the AC conductivity, except for the hybrid films containing DMF. The hybrid films were found to be effective as a lithium ionic conductor. The galvanic cell. Li/sample/MnO₂, at the discharge current density of 90 μA/cm² showed the stable electromotive force of about 3 V for 70 h.     

Solid polymer electrolytes V: microstructure and ionic conductivity of epoxide-crosslinked polyether networks doped with LiClO4

A crosslinked polyether network was prepared from poly(ethylene glycol) diglycidyl ether (PEGDE) cured with poly(propylene oxide) polyamine. Significant interactions between ions and polymer host have been observed for the crosslinked polyether network in the presence of LiClO₄ by means of FT-IR, DSC, TGA, and ⁷Li MAS solid-state NMR. Thermal stability and ionic conductivity of these complexes were also investigated by TGA and AC impedance measurements. The results of FT-IR, DSC, TGA and ⁷Li MAS solid-state NMR measurements indicate the formation of different types of complexes through the interaction of ions with different coordination sites of polymer electrolyte networks. The dependence of ionic conductivity was investigated as a function of temperature, LiClO₄ concentration and the molecular weight of polyether curing agents. It is observed that the behavior of ion transport follows the empirical Vogel-Tamman-Fulcher (VTF) type relationship for all the samples, implying the diffusion of charge carrier is assisted by the segmental motions of polymer chains. Moreover, the conductivity is also correlated with the interactions between ions and polymer host, and the maximum ionic conductivity occurs at the LiClO₄ concentration of [O]/[Li⁺]=15.     

Conductance of tetraalkyl ammonium halides in ethanol-water mixtures

The conductance measurements are reported for tetraalkyl ammonium halides, Me₄NCl, Me₄NBr, Me₄Nl, Et₄NBr, n-Pr₄NBr, n-Pr₄NCl, n-Pr₄Nl, n-Bu₄NBr, in ethanol-water mixtures at 25, 30, 35 and 40‡C. The conductance data were extrapolated by the Fuoss-Onsager conductance theory. From the value of transference number of KCl, ionic cation and halides anion conductance can be readily separated. The effect of temperature and composition of solvent on the ionic mobility and conductance-viscosity product for cation and halide anion is discussed. The results indicates that the halide anion, K⁺ and Me₄N⁺ ions are structure breaking ion and the structure breaking powers of these ions are maximum at 0.1 mole fraction ethanol and increase in the order Cl^-< I^-< Br^-< K⁺< Me₄N⁺. The value of limiting ionic conductance-viscosity products relative to their values for pure water.R _w ^x , increase in the order Et₄N⁺ < n-Pr₄N⁺ < n-Bu₄N⁺.     

Physical and electrochemical properties of low molecular weight poly(ethylene glycol)‐bridged polysilsesquioxane organic–inorganic composite electrolytes via sol–gel process

A new class of ionic conducting organic/inorganic hybrid composite electrolyte with high conductivity, better electrochemical stability and mechanical behavior was prepared through the sol–gel processing between ethylene‐bridged polysilsesquioxane and poly(ethylene glycol) (PEG). The composite electrolyte with 0.05 LiClO₄ per PEG repeat unit has the best conductivity up to 10^?4 S/cm at room temperature with the transference number up to 0.48 and an electrochemical stability window as high as 5.5 V versus Li/Li⁺. Moreover, the effect of the PEG chain length on the properties of the composite electrolyte has also been studied. The interactions between ions and polymer have also been investigated for the composite electrolyte in the presence of LiClO₄ by means of FTIR, DSC, and TGA. The results indicated the interaction of Li⁺ ions with the ether oxygen of the PEG, and the formation of transient crosslinking with LiClO₄, resulting in an increase of the T_g of the composite electrolyte. The VTF‐type behavior of the ionic conductivity implied that the diffusion of the charge carriers was assisted by the segmental motions of the polymer chains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2752–2758, 2007     

Physical and electrochemical properties of 1-(2-hydroxyethyl)-3-methyl imidazolium and N-(2-hydroxyethyl)-N-methyl morpholinium ionic liquids

Various ionic liquids (ILs) were prepared via metathesis reaction from two kinds of 1-(2-hydroxyethyl)-3-methyl imidazolium ([HEMIm]⁺) and N-(2-hydroxyethyl)-N-methyl morphorinium ([HEMMor]⁺) cations and three kinds of tetrafluoroborate ([BF₄]⁻), bis(trifluoromethanesulfonyl)imide ([TFSI]⁻) and hexafluorophosphate ([PF₆]⁻) anions. All the [HEMIm]⁺ derivatives were in a liquid state at room temperature. In particular, [HEMIm][BF₄] and [HEMIm][TFSI] showed no possible melting point from −150 °C to 200 °C by DSC analysis, and their high thermal stability until 380-400 °C was verified by TGA analysis. Also, their stable electrochemical property (electrochemical window of more than 6.0 V) and high ionic conductivity (0.002-0.004 S cm⁻¹) further confirm that the suggested ILs are potential electrolytes for use in electrochemical devices. Simultaneously, the [HEMMor]⁺ derivatives have practical value in electrolyte applications because of their easy synthesis procedures, cheap morpholinium cation sources and possibilities of high Li⁺ mobility by oxygen group in the morpholinium cation. However, [HEMMor]⁺ derivatives showing high viscosity usually had lower ionic conductivities than [HEMIm]⁺ derivatives.     

Evaluation of solvated radii of ions in non-aqueous solvents

In addition to the solvents reported in the previous paper, the empirically modified form of the Stokes' law as proposed from this laboratory has been found to be applicable for Et₄N⁺ ion in some more non-aqueous solvents. By the use of such a modified equation the ionic radii for Me₄N⁺, Pr₄N⁺ and Bu₄N⁺ ions in solution of various non-aqueous solvents have been calculated. These values of ionic radii in solution show that Me₄N⁺ ion is solvated by most of the non-aqueous solvents while Pr₄N⁺ and Bu₄N⁺ ions possess ionic radii in solution, which in most of the solvents agree well with the corresponding crystallographic radii estimated by Coetzee and Cunningham from Fisher—Taylor—Hirschfelder models.     

Ionic conductivity of glasses in the Me nOm-P2O5-M 2O systems and the effect of reduction in the percolation volume

This paper reports on the results of the investigations into the ionic conductivity and the effect of reduction in the percolation volume. It is demonstrated that the ionic conductivity of glasses in the Me _nO_m-P₂O₅-Li₂O (Na₂O) systems (Me = W, Nb, Ti, Mo, V, Bi) is poorly correlated with the Li₂O (Na₂O) content and, in a number of cases, the dependence between these quantities is altogether absent. In the case when the ratio [Li₂O]/[P₂O₅] is used instead of the [Li₂O] content as the argument, the data on the ionic conductivity σ for all the systems are approximated by the logarithmic dependences-logσ = f([Li₂O]/[P₂O₅]) with a high degree of reliability. The ionic conductivity for the glasses under investigation, as for the (AgI)_x-(AgPO₃)_{1 ? x} superionic glasses, obeys the percolation law σ ～ (y ? y _crit)^μ with the parameters y _crit and μ close to those for the silver-containing glasses but with y = [Li₂O]/[P₂O₅] instead of x for AgI. The observed dependences are explained within the Goodman strained mixed cluster model and two-dimensional percolation through the polar structural fragments containing Li⁺ ions over the surface of an infinite percolation phosphate cluster reduced by Me _nO_m oxide in the glass volume.     

Synthesis and NMR studies of the polymer membranes based on poly(4-vinylbenzylboronic acid) and phosphoric acid

Proton conduction in novel anhydrous membranes based on host polymer, poly(4-vinylbenzylboronic acid), (P4VBBA) and phosphoric acid, (H₃PO₄) as proton solvent was studied. The materials were prepared by the insertion of the proton solvent into P4VBBA at different stoichiometric ratios to get P4VBBA·xH₃PO₄ composite electrolytes. Homopolymer and the composite materials were characterized by FT-IR, ¹¹B MAS NMR and ³¹P MAS NMR. ¹¹B MAS NMR results suggested that acid doping favors or leads to a four-coordinated boron arrangement. ³¹P MAS NMR results illustrated the immobilization of phosphoric acid to the polymer through condensation with boron functional groups (B-O-P and/or B-O-P-O-B). Thermogravimetric analysis (TGA) showed that the condensation of composite materials starts approximately at 140 °C. An exponential weight loss above this temperature was attributed to intermolecular condensation of acidic units forming cross-linked polymer. The insertion of phosphoric acid into the matrix softened the materials shifting T_g to lower temperatures. The temperature dependence of the proton conductivity was modeled with Arrhenius relation. P4VBBA·2H₃PO₄ has a maximum proton conductivity of 0.0013 S/cm at RT and 0.005 S/cm at 80 °C.     

Ion exchange properties of NASICON-type ceramics—Application to ion selective electrodes

The ion-exchange properties of NASICON type ceramics of composition Na₃Zr₂Si₂PO₁₂ were investigated in aqueous solutions of NaCl, LiCl and KCl. The solution analysis shows that the [Zr₂Si₂PO₁₂] framework strongly prefers Na⁺ ion relative to K⁺ and Li⁺. The exchange current density of the alkali-cations at the NASICON/solution interface determined by impedance measurements varies in the order Na⁺>Li⁺>K⁺. These results agree well with the selectivity coefficients of Na⁺ ion selective electrodes based on NASICON. The interference process to alkali-cations in the NASICON based electrode was shown to result from an ionic exchange. The selectivity was suggested to be governed by the mobility of the cation inside the NASICON framework.     

LiFePO4 cathode in N-methyl-N-propylpiperidinium and N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide

Ternary [Li⁺][MePrPip⁺][NTf₂⁻] and [Li⁺][MePrPyrr⁺][NTf₂⁻] room temperature ionic liquids (ILs) were obtained by dissolution of solid lithium bis(trifluoromethanesulfonyl)imide (LiNTf₂) in liquid N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide and N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, respectively, and studied as electrolytes for the use in Li/LiFePO₄ or C(Li)/LiFePO₄ batteries. The cell worked properly in the presence of 10 wt% of vinylene carbonate (VC). Impedance-spectroscopy studies showed that the additive (VC) forms a protective coating on the anode. The LiFePO₄ cathode shows good efficiency (135 mAh g⁻¹) working together with [Li⁺][MePrPip⁺][NTf₂⁻] + VC and [Li⁺][MePrPyrr⁺][NTf₂⁻] + VC ionic liquid electrolytes. The flash point of ionic liquid electrolytes containing 10 wt% of VC is above 300 °C, which makes them practically non-flammable.     

Preparation and characterization of new anhydrous, conducting membranes based on composites of ionic liquid trifluoroacetic propylamine and polymers of sulfonated poly (ether ether) ketone or polyvinylidenefluoride

A novel ionic liquid of trifluoroacetic propylamine, i.e., [CH₃CH₂CH₂NH₃⁺] [CF₃COO⁻] (TFAPA), was synthesized from trifluoroacetic acid and propylamine. The ionic liquid of TFAPA was used to prepare anhydrous, conducting membranes based on polymers of sulfonated poly (ether ether) ketone (SPEEK) or polyvinylidenefluoride (PVDF). The ionic conductivity and mechanical strength of the composite membranes were investigated at elevated temperatures and under anhydrous conditions. Conductivity of 0.030 S/cm was achieved with TFAPA at 180 °C, and of 0.019 S/cm with a membrane containing 70% (wt) TFAPA in SPEEK with a sulfonation degree of 86% at 160 °C. Increasing either ionic liquid content or temperature reduced the mechanical strength of the composite membrane. Efforts were made to improve the strength of TFAPA/SPEEK composite membranes by cross-linking the SPEEK, which led to some strength enhancement at 110 °C and 130 °C.     

Crystallinity,thermal properties,morphology and conductivity of quaternary plasticized PEO‐based polymer electrolytes

Quaternary plasticized solid polymer electrolyte (SPE) films composed of poly(ethylene oxide), LiClO₄, Li_1.3Al_0.3Ti_1.7(PO₄)₃, and either ethylene carbonate or propylene carbonate as plasticizer (over a range of 10–40 wt%) were prepared by a solution‐cast technique. X‐ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) indicated that components such as LiClO₄ and Li_1.3Al_0.3Ti_1.7(PO₄)₃ and the plasticizers exerted important effects on the plasticized quaternary SPE systems. XRD analysis revealed the influence from each component on the crystalline phase. DSC results demonstrated the greater flexibility of the polymer chains, which favored ionic conduction. SEM examination revealed the smooth and homogeneous surface morphology of the plasticized polymer electrolyte films. EIS suggested that the temperature dependence of the films' ionic conductivity obeyed the Vogel–Tamman–Fulcher (VTF) relation, and that the segmental movement of the polymer chains was closely related to ionic conduction with increasing temperature. The pre‐exponential factor and pseudo activation energy both increased with increasing plasticizer content and were maximized at 40 wt% plasticizer content. The charge transport in all polymer electrolyte films was predominantly reliant on lithium ions. All transference numbers were less than 0.5. Copyright © 2006 Society of Chemical Industry     

Conductance investigation of p‐MIECs fabricated by poly(3,4‐ethylenedioxy thiophene), polyacrylic acid,polyethylene oxide,and lithium‐ion salt

Polymer blends and composite films were facilely prepared from their aqueous solutions with varying contents of poly(3,4‐ethylenedioxythiophene) (PEDOT), polyethylene oxide (PEO), and polyacrylic acid (PAA). The physicochemical and electric properties of the composite films were analyzed by Raman spectra, infrared spectra (FT‐IR), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), and four‐point probe method. PEDOT was successfully incorporated into each blend which was confirmed by spectra analysis. The crystallization of PAA or PEO and the structure of PEDOT should be taken into consideration for the electronic conductivity. According to Raman spectra, in the case of PEDOT–PAA–PEO, conformation of the PEDOT backbone changed from the quinoid to the benzoid structure partly. The ionic conductivities of lithium‐ion salt‐mixed PAA–PEO and ternary blend were characterized by AC impedance spectroscopy. The ternary blend with LiCoO₂ presents good electronic and ionic conductivity, and it appears to be a new candidate for polymeric mixed ionic electronic conductor. POLYM. COMPOS., 36:2076–2083, 2015. © 2014 Society of Plastics Engineer     

Ladder-Type Poly(3,4-ethylenedioxythiophene)–Poly(ethylene glycol)–Polyurethane Supramolecular Network for Gel Polymer Electrolyte

A ladder-type poly(3,4-ethylenedioxythiophene)–poly(ethylene glycol)–polyurethane (PEDOT–PEG–PU) supramolecular network was successfully synthesized using graft copolymerization of hydroxymethyl-EDOT with isocyanate-terminated PEG–PU prepolymer. PEDOT functionalized as the frame for a ladder-type supramolecular structure and PEG–PU as the rung. The successful formation of supramolecular network was confirmed by analyzing the Fourier transform infrared spectroscopy. A series of PEDOT–PEG–PU gel polymer electrolytes by linking the LiClO₄ were prepared as a function of [O/Li⁺] ratios. The pH effect of their electrical capacitances was investigated using cyclic voltammetry. Ionic conductivities of different PEDOT–PEG–PU/Li⁺ complexes at a fixed pH were also evaluated through impedance analysis.     

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.     

Lithium mobility along conduction channels of ceramic LiTa2PO8

In the next generation of lithium-ion batteries, the liquid electrolyte is considered to be replaced by its solid counterpart. Recently, a novel Li-ion conductor based on metal oxides emerged – LiTa₂PO₈. Due to the high value of bulk conductivity of ca. 10⁻³ S∙cm⁻¹, it is believed to be a potential candidate for application as a solid electrolyte in all-solid-state battery technology. In this work, we investigate LiTa₂PO₈ ceramics synthesized by a conventional solid-state reaction method with an excess of the lithium-containing substrate to compensate for the loss of Li⁺ during sintering. The properties of LiTa₂PO₈ ceramics were studied using X-ray diffractometry (XRD), ⁶Li and ³¹P magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), thermogravimetry (TG), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), impedance spectroscopy (IS), DC potentiostatic polarization technique and density method. Referring to the experimental results, increasing of the Li⁺ content above the stoichiometric one lowers the total ionic conductivity. The reasons for the deterioration and correlations between microstructure, phase composition, and ionic conductivity are presented and discussed. The MAS NMR spectroscopy has been used to explain high bulk ionic conductivity of LiTa₂PO₈ ceramics. A maximum value of total ionic conductivity, 4.5 × 10⁻⁴ S∙cm⁻¹, was obtained at room temperature for the sample without any excess of Li⁺ source.     

Radiotracer self-diffusion measurements in poly(ethylene oxide) and poly(propylene oxide) electrolytes

Radiotracer measurements of the ²²Na⁺ and S¹⁴CN^? diffusion coefficients in PEO-NaSCN (x = 6, 8 and 12) and PPO-NaSCN (x = 8) are reported, where PEO = poly(ethylene oxide), PPO = poly(propylene oxide), and x = [EO units]/[NaSCN] or [PO units]/[NaSCN]. The results are compared with ionic conductivity measurements on the same samples. Measurements for the PEO samples were taken above the melting point of pure PEO and the results interpreted, particularly for the sample most dilute in salt, in terms of ‘free ions’ as the dominant charge carriers. For PPO the results are less clear, although there is good evidence for the onset of ion aggregation prior to separation of salt at higher temperatures.     

Cationic conduction in oligoether salt–comblike polyether complex

Polymeric solid electrolytes, with excellent cationic conductivity, were prepared from the complexation of lithium methoxyoligo(oxyethylene) sulfate and lithium methoxyoligo(oxyethylene) sulfonate with poly[methoxyoligo(oxyethylene)methacrylate-co-acrylamide]. The electrolytes exhibit low glass transition temperature and have almost no crystal. Their ionic conductivities at 25°C are over 10^?5 S/cm. The carrier number in the complex decreases while ionic mobility increases considerably with increasing considerably with increasing temperature. The polarization reversing method confirms that the cationic transference numbers are all over 0.9. The electrolytes have single ion conduction characteristics in DC polarization. © 1995 John Wiley & Sons, Inc.     

Preparation and Characterisation of Proton Exchange Membranes Based on Crosslinked Polybenzimidazole and Phosphoric Acid

Crosslinked polybenzimidazole (PBI) was synthesised via free radical polymerisation between N‐vinylimidazole and vinylbenzyl substituted PBI. The degree of crosslinking increases with increasing content of the crosslinker. The phosphoric acid doping behaviour, mechanical properties, proton conductivity and acid migration stability of crosslinked PBI and linear PBI are discussed. The results show that the acid doping ability decreases with increasing degree of crosslinking of PBI. The introduction of N‐vinylimidazole in PBI is beneficial to its oxidation stability. The mechanical stability of crosslinked PBI/H₃PO₄ membrane is better than that of linear PBI/H₃PO₄ membrane. The proton conductivity of the acid doped membranes can reach ∼10^–4 S cm^–1 for crosslinked PBI/H₃PO₄ composite membranes at 150 °C. The temperature dependence of proton conductivity of the acid doped membranes can be modelled by an Arrhenius relation. The proton conductivity of crosslinked PBI/H₃PO₄ composite membranes is a little lower than that of linear PBI/H₃PO₄ membranes with the same acid content. However, the migration stability of H₃PO₄ in crosslinked PBI/H₃PO₄ membranes is improved compared with that of linear PBI/H₃PO₄ membranes.