Structure,thermal properties,conductivity and electrochemical stability of di-urethanesil hybrids doped with LiCF<Subscript>3</Subscript>SO<Subscript>3</Subscript>

Variable chain length di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrid networks were prepared by application of a sol-gel strategy. These materials, designated as di-urethanesils (represented as d-Ut(Y′), where Y′ indicates the average molecular weight of the polymer segment), were doped with lithium triflate (LiCF₃SO₃). The two host hybrid matrices used, d-Ut(300) and d-Ut(600), incorporate POE chains with approximately 6 and 13 (OCH₂CH₂) repeat units, respectively. All the samples studied, with compositions ∞ > n ≥ 1 (where n is the molar ratio of (OCH₂CH₂) repeat units per Li⁺), are entirely amorphous. The di-urethanesils are thermally stable up to at least 200 °C. At room temperature the conductivity maxima of the d-Ut(300)- and d-Ut(600)-based di-urethanesil families are located at n = 1 (approximately 2.0 × 10⁻⁶ and 7.4 × 10⁻⁵ Scm⁻¹, respectively). At about 100 °C, both these samples also exhibit the highest conductivity of the two electrolyte systems (approximately 1.6 × 10⁻⁴ and 1.0 × 10⁻³ Scm⁻¹, respectively). The d-Ut(600)-based xerogel with n = 1 displays excellent redox stability.     

New ternary molten salt electrolyte based on alkali metal triflates

A novel molten salt electrolyte composed of lithium triflate (CF₃SO₃Li, LiTf), sodium triflate (CF₃SO₃Na, NaTf), and potassium triflate (CF₃SO₃K, KTf) has been prepared and characterized by thermogravimetry/differential thermal analysis (TG/DTA), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry. TG/DTA shows that the electrolyte was thermally stable when the temperature was under 400 °C. Its thermal stability gradually decreased with increase of LiTf concentration. The ionic conductivity of molten salt electrolyte has been evaluated by EIS and its value exceeds 10⁻² Scm⁻¹ in the temperature range from 230 to 270 °C. The electrochemical window of the electrolyte at the molar ratio of 0.5/1/1 is about 4.7 V at 250 °C. This electrolyte with low melting point exhibits promising characteristics for high-temperature lithium batteries.     

Impedance and FTIR studies on plasticized PMMA–LiN(CF<Subscript>3</Subscript>SO<Subscript>2</Subscript>)<Subscript>2</Subscript> nanocomposite polymer electrolytes

Plasticized polymer electrolytes composed of poly(methyl methacrylate) (PMMA) as the host polymer and lithium bis(trifluoromethanesulfonyl)imide LiN(CF₃SO₂)₂ as a salt were prepared by solution casting technique at different ratios. The ionic conductivity varied slightly and exhibited a maximum value of 3.65 × 10⁻⁵ S cm⁻¹ at 85% PMMA and 15% LiN(CF₃SO₂)₂. The complexation effect of salt was investigated using FTIR. It showed some simple overlapping and shift in peaks between PMMA and LiN(CF₃SO₂)₂ salt in the polymer electrolyte. Ethylene carbonate (EC) and propylene carbonate (PC) were added to the PMMA–LiN(CF₃SO₂)₂ polymer electrolyte as plasticizer to enhance the conductivity. The highest conductivities obtained were 1.28 × 10⁻⁴ S cm⁻¹ and 2.00 × 10⁻⁴ S cm⁻¹ for EC and PC mixture system, respectively. In addition, to improve the handling of films, 1% to 5% fumed silica was added to the PMMA–LiN(CF₃SO₂)₂–EC–PC solid polymer electrolyte which showed a maximum value at 6.11 × 10⁻⁵ S cm⁻¹ for 2% SiO₂.     

Coordination of Eu3+ in mono-urethane cross-linked hybrid xerogels

A novel family of Eu³⁺-doped hybrid materials namedmono-urethanesils is investigated. The host organic/inorganic matrix, preparedvia the sol-gel process, is a siliceous network to which methyl end-capped pendant oligopolymer chains containing seven oxyethylene units are covalently bonded by means of urethane cross-links, -NHC(=O)O-. The lanthanide cations have been introduced as europium triflate, Eu(CF₃SO₃)₃. The xerogels have been identified by the designation m-Ut(350)_nEu(CF₃SO₃)₃, where Ut represents the urethane linkages, 350 indicates the average molecular weight of the organic component and n denotes the number of (OCH₂CH₂) repeat units per Eu³⁺ ion. The mono-urethanesil samples examined, with compositions ranging between n=∞ and 40, are totally amorphous. The spectral and thermal data provide conclusive evidence that in these materials the lanthanide ions are preferentially coordinated by the carbonyl oxygens of the urethane moieties, rather than by the ether oxygens of the polymer chains. The location of the characteristic bands of the triflate ions in the FTIR spectra of these Eu³⁺-based xerogels indicates that the anions interact weakly with the cations over the entire range of guest salt concentration studied. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.     

FTIR spectra of plasticized high molecular weight PVC–LiCF3SO3 electrolytes

Fourier transform infrared spectroscopy studies have been conducted to investigate the interaction among components in a system of high molecular weight polyvinylchloride (PVC)–lithium trifluoromethanesulfonate (LiCF₃SO₃) incorporated with different type of plasticizers, namely, ethylene carbonate (EC), propylene carbonate (PC), and dibutylphthalate (DBP). Interaction between PVC and LiCF₃SO₃ was confirmed by C–H rocking mode at 1,255 cm⁻¹ for PVC shift to 1,252 cm⁻¹ in PVC–LiCF₃SO₃. The plasticizers’ carbonyl (C=O) oxygen atom which carries lone pair electrons interact with Li⁺ of LiCF₃SO₃ and methine hydrogen of PVC in LiCF₃SO₃–plasticizer system and PVC–plasticizer system, respectively. Changes in peaks assigned to 1,264 cm⁻¹ (ν _as(SO₃)), 1,033 cm⁻¹ (ν _s(SO₃)), 1,181 cm⁻¹ (ν _as(CF₃)), 1,230 cm⁻¹ (ν _s(CF₃)), 765 cm⁻¹ (δ _s(CF₃)), 644 cm⁻¹ (δ _s(SO₃)), 578 cm⁻¹ (δ _as(CF₃)), and 519 cm⁻¹ (δ _as(SO₃)) indicate the occurrence of complexation in the PVC–LiCF₃SO₃ system, LiCF₃SO₃–plasticizer system, and PVC–LiCF₃SO₃–plasticizer system.     

Paramagnetic relaxation of Er in an Er single crystal

The paramagnetic relaxation of Er in an Er single crystal was measured atT≫T _N and compared to the relaxation of Er ions in a polycrystalline Pb host. The results indicate an enhancement of at most 50% of the f-conduction electron exchange interaction in Er, as expected for highly ionic f-orbitals. The ratio of the quadrupole moments of the¹⁵⁴ Er(I ^π=11⁻) and the¹⁵⁵ Er(I ^π=13/2⁺) isomers was measured to be 1.18(3) indicating onset of nuclear deformation at N=87. Deceased May, 1986     

Polymer–ion–clay interaction based model for ion conduction in intercalation-type polymer nanocomposite

A series of polymer nanocomposite films based on intercalation of (PAN)₈LiCF₃SO₃ into the nanometric clay channels of an organomodified clay has been prepared using the standard solution-casting technique. The role of organoclay concentration on polymer–ion interaction, ion–ion interaction, and ion–clay interaction in clay-based nanocomposite films has been analyzed using Fourier transform infrared (FTIR) analysis. Substantial ion dissociation is observed even at a very low clay loading (1–2 wt.%) in the nanocomposites. FTIR results suggest the presence of both uncoordinated CF₃SO₃ ⁻ (free-anions) and ion pairs in the nanocomposite evidenced by changes in CF₃SO₃ ⁻ symmetry from C3ν to Cs and marked asymmetry in the profile of degenerate δ_d(CF₃ ⁻) mode. The experimental results suggest a direct correlation of clay-assisted ion dissociation process with variation in conductivity (σ _dc) and glass transition temperature (T _g) as a function of clay concentration. A model has been proposed to explain the observed correlation on the basis of polymer–ion–clay interaction. The proposed scheme of ion transport mechanism appears to be consistent with the experimental observation.     

Vibrational spectroscopic and electrochemical characteristics of poly (propylene glycol)-silver triflate polymer electrolyte system

Fourier transform infrared spectroscopic and electrochemical complex impedance studies have been carried out on a series of complexes containing poly(propylene glycol) of molecular weight 4,000 and silver triflate (AgCF₃SO₃) salt corresponding to the ether oxygen to metal cation ratios (O : M) in the range 16:1 to 12:1. The formation of ion pairs and aggregates noticed in the case of specimens having high salt concentrations as well as the complete coordination of the cation with the ether oxygen at low salt concentrations within the PPG4000-AgCF₃SO₃ polymer electrolyte system have been confirmed. The appearance of two weak triflate bands at 1,032 and 1,272 cm⁻¹ in the absorption spectra in respect of low salt concentrations is indicative of the fact that triflate ions are free within the polymer matrix. The room temperature (298 K) electrical conductivity is found to increase with increasing ether oxygen content while exhibiting the maximum value of 7.1 × 10⁻⁵ Scm⁻¹ possibly due to silver ionic transport in the case of the typical composition having an O : M ratio of 16:1.     

Di-urethanesil hybrid electrolytes doped with Mg(CF3SO3)2

Two siloxane-based di-urethanesil frameworks incorporating poly(oxyethylene) (POE) chains have been synthesized by the sol–gel process and doped with magnesium triflate (Mg(CF₃SO₃)₂) with the goal of developing electrolytes for the fabrication of solid-state rechargeable magnesium batteries. In these matrices, short POE chains are covalently bonded to the siloxane network via urethane linkages. The xerogels have been represented by the notation d-Ut(Y) _n Mg(CF₃SO₃)₂, where Y?=?300 and 600 represents the average molecular weight of the POE chains and n stands for salt composition (molar ratio of OCH₂CH₂ units per Mg²⁺). Xerogels with compositions ranging from 2?≤?n?<?∞ were prepared. A crystalline POE/Mg(CF₃SO₃)₂ complex of unknown stoichiometry is formed in the d-Ut(300) _n Mg(CF₃SO₃)₂ materials with n?≤?6 and in the d-Ut(600) _n Mg(CF₃SO₃)₂ materials with n?≤?5. The organically modified silicate electrolytes with the highest conductivity of the d-Ut(300) _n Mg(CF₃SO₃)₂ and d-Ut(600) _n Mg(CF₃SO₃)₂ series are the samples with n?=?6 (3.9?×?10^?8 S cm^?1 at 26 °C and 8.7?×?10^?5 S cm^?1 at 97 °C) and n?=?100 (2.63?×?10^?7 S cm^?1 at 20 °C and 1.4?×?10^?5 S cm^?1 at 85 °C), respectively. Since the electrolytes for Mg batteries that have been proposed up to now have many intrinsic problems and although the room temperature conductivity values exhibited by the systems developed in the present study are still low in view of practical application, this work opens new directions for the development of solid-state Mg ion electrolytes.     

Optically active Er3+ centers in Si/Si1 ? x Ge x structures under optical pumping

The Si/Si_{1 − x} Ge _x :Er/Si heterostructures, which are of interest for laser applications, have been investigated. The types of optically active Er³⁺ centers making a dominant contribution to the photoluminescence response of the structures studied are analyzed and their relationship with the parameters of the Si_{1 − x} Ge _x :Er heterolayer and the post-growth annealing conditions is shown. On the basis of the PL kinetic analysis of the structures with an isolated type of optically active Er³⁺ centers, it is concluded that population inversion of Er³⁺ ion states can be obtained under optical pumping and the effect of nonradiative recombination channels in Si_{1 − x} Ge _x :Er heterolayers on the excitation efficiency of Er centers and the conditions for population inversion is shown. Original Russian Text ? L.V. Krasilnikova, N.A. Baidakova, M.V. Stepikhova, Z.F. Krasilnik, V.Yu. Chalkov, V.G. Shengurov, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 1, pp. 103–108.     

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.     

Vibrational spectra of two BEDT-TTF-based organic conductors: charge order

Infrared and Raman investigations of two phases of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) based organic conductors with the same CF₃CF₂SO₃⁻ anion: β′-(BEDT-TTF)₂CF₃CF₂SO₃ and δ′-(BEDT-TTF)₂CF₃CF₂SO₃, are shortly reviewed and compared with the most typical infrared properties of the family of (BEDT-TTF)₂RR′SO₃ organic conductors, where R = SF₅, CF₃, and R′ are CH₂, CF₂, CHF, CHFCF₂, and CH₂CF₂. The role of the molecular structur and spatial organization of the counterions is discussed. Presented at 2-nd International Conference on Functional Materials and Devices, ICFMD 2008, June 16–19, 2008, Kuala Lumpur, Malaysia     

Effect of ZnO nanoparticles filler concentration on the properties of PEO-ENR50-LiCF<Subscript>3</Subscript>SO<Subscript>3</Subscript> solid polymeric electrolyte

A solid polymer electrolyte comprising blend of poly(ethylene oxide) and 50% epoxidized natural rubber (ENR50) as a polymer host, LiCF₃SO₃ as a salt and nanoparticle ZnO as an inorganic filler was prepared by solution-casting technique. The effect of filler on the electrolyte properties was characterized and analysed. FESEM analysis showed that the filler was well distributed in the polymer matrix, while the effective interaction between the salt and the polymer host was reduced by the addition of filler. As evidenced by FTIR analysis, which showed the formation of triplet peak at C-O-C stretching region. Ionic conductivity was found to decrease from 1.4 × 10⁻⁴ Scm⁻¹ to 2.5 × 10⁻⁶ Scm⁻¹ upon the addition of filler, due to the blocking effect of filler into the electrolyte conduction pathways. The temperature dependence on the electrolyte conductivity obeys Arrhenius rule in two temperature regions.     

Morphology,chemical interaction,and conductivity of a PEO-ENR50 based on solid polymer electrolyte

A solid polymer electrolytes (SPE) comprising blend of poly(ethylene oxide; PEO) and epoxidized natural rubber as a polymer host and LiCF₃SO₃ as a dopant were prepared by solution-casting technique. The SPE films were characterized by field emission scanning electron microscopy to determine the surface morphology, X-ray diffraction, and differential scanning calorimeter to determine the crystallinity and thermogravimetric analysis to confirm the mass decrease caused by loss of the solvent. While the presence of the complexes was investigated by reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Electrochemical impedance spectroscopy was conducted to obtain ionic conductivity. Scanning electron microscopy analysis showed that a rough surface morphology of SPE became smoother with addition of salt, while ATR-FTIR spectroscopy analysis confirmed the polymer salt complex formation. The interaction occurred between the salt, and ether group of polymer host where the triple peaks of ether group in PEO merged and formed one strong peak at 1,096 cm⁻¹. Ionic conductivity was found to increase with the increase of salt concentration in the polymer blend complexes. The highest conductivity achieved was 1.4 × 10⁻⁴ Scm⁻¹ at 20 wt.% of LiCF₃SO₃, and this composition exhibited an Arrhenius-like behavior with the activation energy of 0.42 eV and the preexponential factor of 1.6 × 10³ Scm⁻¹.     

Influence of MgO codoping on the optical properties of Er3+-doped near-stoichiometric LiNbO3

Four near-stoichiometric lithium niobate (NSLN) crystals codoped with Er³⁺ (1 mol%) and MgO (0, 0.5, 1.0, and 2.0 mol%) were grown from K₂O-based flux in air using top seeded solution growth technique. The [Li]/[Nb] ratio, estimated from the blueshift of ultraviolet absorption edge, is 97.2% in NSLN:Er. MgO; codoping can increase the segregation coefficient of Er³⁺ in NSLN:Er:MgO crystal. The photorefractive damage threshold is enhanced by three orders of magnitude for NSLN:Er codoped with 1 mol% MgO, it coincides with the peak shift of OH⁻ absorption spectrum from 3481 to 3535 cm⁻¹. Judd–Ofelt theory based on absorption spectra is used to analyze the influence of MgO concentration on the Judd–Ofelt intensity parameter, transition strength, fluorescence branching ratio, and stimulated emission cross section. From the time-resolved emission spectra and the comparison among emission spectra, two Er³⁺ crystal-field sites are ascertained in NSLN:Er codoped with 2 mol% MgO, this coincides with the bimodal structure in X-ray photoelectron spectrometry spectra. The upconversion processes under pulse excitation is proposed based on the pump energy dependence and decay kinetics. The distribution of Er³⁺-clustered sites in NSLN:Er:MgO series is discussed based on the nonexponential decay curves monitored at 550 nm under two-photon excitation.     

Er<Superscript>3+</Superscript> as glass structure modifier of Ga–Ge–S chalcogenide system

Er³⁺ clustering phenomenon in Ga–Ge–S chalcogenide system is studied using Raman spectroscopy. The Raman spectra from 10 to 500 cm⁻¹ for glasses (100−y)[15Ga₂S₃–85GeS₂]–yEr₂S₃ (y=0.08−5.00 mol. %) have been analyzed. To reveal the influence of the chemical composition on the glass structure the intensity of the peak corresponding to Ge–Ge (Ga–Ga) homopolar bonds has been examined. The peak intensity increase with Er₂S₃ concentration change in the region 0<C(Er₂S₃)<2 mol. % has been interpreted in terms of the sulphur deficiency in the glass resulting in the formation of S₃Ge–GeS₃ (S₃Ga-GaS₃) structural units. The further increase in concentration beyond 2 mol. % reduces the sulphur deficiency, which can be attributed to the formation of the ternary compound Er₃GaS₆. The structural units Er₃GaS₆ contain a large mol. fraction of Er³⁺ or, in other words, Er³⁺ clusters. The data obtained from the low-frequency Raman spectra (boson band) indicate strong variations of the medium-range order (MRO) in the glasses induced by Er³⁺. The observed behavior of the MRO size (the correlation length) with increasing of Er₂S₃ concentration provides for additional evidence of the Er³⁺ clustering.     

The mechanism of formation of the hydroperoxyl radical in the CF<Subscript>3</Subscript>COOH + <Superscript>3</Superscript>O<Subscript>2</Subscript> system: a quantum-chemical study

Ab initio quantum-chemical calculations of the (CF₃CO₂H₂⁺…³O₂) and (CF₃CO₂⁻…³O₂) complexes were performed by the MP2 method. It was found that these complexes were characterized by low complex formation energies, of 2.97 and 1.72 kcal/mol, respectively. According to the MP2(full)/6-311++G(d, p) calculation data, the bridge stabilization of oxygen by linking with both the CF₃CO₂H₂⁺ cation and CF₃CO₂⁻ anion is much more favorable energetically. A study of the potential energy surface of the joint molecular system (CF₃CO₂H₂⁺…³O₂…CF₃CO₂⁻) shows that proton experiences activationless transfer from the cation to the ³O₂ molecule accompanied by electron transfer from the CF₃COO⁻ anion. An analysis of spin density distribution shows that two radicals are stabilized in the (CF₃CO₂….OOH….O=C(OH)CF₃) complex in the triplet state observed on the potential energy surface.     

Spectroscopic properties of Er3+ ions in cadmium and alkali cadmium borosulphate glasses

Spectroscopic properties of Er³⁺:CBS (CdSO₄+B₂O₃ and R₂SO₄+CdSO₄+B₂O₃, R₂SO₄=Li₂SO₄.H₂O, Na₂SO₄, K₂SO₄ and Gd₂(SO₄)₃.8H₂O) glasses are reported. The assigned energy level data of Er³⁺(4f ¹¹) in these glasses are analysed in terms of a parametrized model Hamiltonian. The standard deviations of the data fits are between 39 and 47 cm⁻¹ so that the energy level schemes of the Er³⁺(4f ¹¹) ions in borosulphate (CBS) glasses are reasonably well reproduced. Radiative properties for the fluorescent levels of Er³⁺:CBS glasses are determined by using the Judd-Ofelt theory. The potential laser transitions are identified with the help of predicted radiative properties which are compared and discussed with similar results.     

Polycaproamide films containing ionic liquids: Microstructure and properties

Films of polycaproamide and its composites containing ionic liquids (ILs) derived from 1-methyl-3-ethylimidazolium cation and N(CF₃SO₂)₂ or N(CN)₂ anions having crystalline structures were cast from solutions in formic acid. The structure and concentration of the ILs were shown to affect the conductivity (up to ∼10⁻⁴ S cm⁻¹ 25°C), microstructure (studied by X-ray diffraction, SEM, and AFM), and thermomechanical properties of the films.     

Lithium ion transport in PVC/PEG 2000 blend polymer electrolytes complexed with LiX (X=ClO 4? , BF 4? , and CF3SO 3? )

This paper describes preparation and characterization of polyvinyl chloride and polyethylene glycol 2000 blend polymer electrolytes with LiX (X=ClO₄⁻, BF₄⁻, and CF₃SO₃⁻) salt by solution casting technique. Ethylene carbonate and propylene carbonate mixture was used as the plasticizers. LiClO₄-based electrolytes exhibited better ionic conduction behavior than other salts. The thermal profiles ascertain the stability of the membranes up to 120°C by differential scanning calorimetry. Complexation and crystallinity were studied through X-ray diffraction measurements. Phase morphological study reveals the porous nature of the polymer electrolyte membranes.