首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 375 毫秒
1.
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.  相似文献   

2.
Summary.  Density and viscosity of NaNO3 and KNO3 in aqueous and in H2O-urea solutions were determined as a function of electrolyte concentrations at 308, 313, 318, 323, and 328 K, respectively. The apparent molal volume (φ v ) of the electrolytes were found to be linear functions of the square root of the solute molality (b). The φ v and data were fitted to the Masson equation [1] by the least square method to obtain the apparent molar volume at infinite dilution (φ v ^), which is practically equal to the partial molar volume . The viscosity coefficients A and B were calculated on the basis of the viscosity of the solutions and the solvent concerned using the JonesDole [2] equation. The activation parameters for viscous flow (ΔG , ΔS , and ΔH ) were calculated according to Eyring [3]. The values of for the two systems were also calculated from B-coefficient data. The results were found to be of opposite nature in the two electrolyte systems. Where sodium nitrate showed structure making behaviour both in aqueous and in H2O-urea solutions, KNO3 showed structure breaking behaviour in aqueous solutions and structure making behaviour in 5 molal H2O-urea solutions in the studied temperature range. The behaviour of these two electrolytes in aqueous binary and in aqueous-urea ternary systems are discussed in terms of charge, size, and hydrogen bonding effects. Corresponding author. E-mail: chemistry_ru@yahoo.com Received January 24, 2002; accepted (revised) April 5, 2002  相似文献   

3.
Olivine-structured LiCoPO4 is synthesized by a Pechini-type polymer precursor method. The structure and the morphology of the compounds are studied by the Rietveld-refined X-ray diffraction, scanning electron microscopy, Brunauer, Emmett, and Teller surface area technique, infrared spectroscopy, and Raman spectroscopy techniques, respectively. The ionic conductivity (σ ionic), dielectric, and electric modulus properties of LiCoPO4 are investigated on sintered pellets by impedance spectroscopy in the temperature range, 27–50 °C. The σ (ionic) values at 27 and 50 °C are 8.8 × 10−8 and 49 × 10−8 S cm−1, respectively with an energy of activation (E a) = 0.43 eV. The electric modulus studies suggest the presence of non-Debye type of relaxation. Preliminary charge–discharge cycling data are presented.  相似文献   

4.
The lithium-rich silicide Li4Pt3Si was synthesised from the elements by high-temperature synthesis in a sealed niobium ampoule. Its structure was refined on the basis of single-crystal X-ray diffraction data: R32, a = 693.7(2), c = 1627.1(4) pm, wR2 = 0.0762, 525 F2 values and 21 variables. The striking structural motifs of the Li4Pt3Si structure are silicon atoms with a slightly distorted trigonal prismatic platinum coordination with short Si–Pt distances (238–246 pm). Always two trigonal prisms are condensed via a common Pt3 triangle, and these double units built up a three-dimensional network by condensation via common corners. The channels left by this prismatic network are filled by two crystallographically independent lithium sites in a 3:1 ratio. The single crystal X-ray data were fully confirmed by neutron powder diffraction and 7Li magic-angle spinning (MAS)–nuclear magnetic resonance (NMR) results. The two distinct lithium sites are well differentiated by their 7Li isotropic chemical shift and nuclear electric quadrupolar interaction parameters. MAS-NMR spectra reveal signal coalescence effects above 300 K, indicating chemical exchange between the lithium sites on the millisecond timescale. The spectra can be simulated with a simple two-site exchange model. From the resulting temperature-dependent correlation times, an activation energy of 50 kJ/mol is extracted.  相似文献   

5.
Summary.  Single crystals of MgAl2F8(H2O)2 have been obtained under hydrothermal conditions (250°C, 14 d) from a starting mixture of AlF3 and MgAlF5(H2O)2 in a 5% (w/w) HF solution. The crystal structure has been determined and refined from single crystal data (Fmmm (#69), Z = 4, a = 7.2691(7), b = 7.0954(16), c = 12.452(2) ?, 281 structure factors, 27 parameters, R(F 2 > 2σ (F 2)) = 0.0282, wR(F 2 all) = 0.0885). The obtained crystals were systematically twinned according to (010/100/001) as twinning matrix, reflecting the pseudo-tetragonal metric. The crystal structure is composed of perowskite-type layers built of corner sharing AlF6 octahedra with an overall composition of AlF4 which are connected via common fluorine atoms of [MgF4/2(H2O)2/1] octahedra. Group-subgroup relations of MgAl2F8(H2O)2 to WO3(H2O)0.33 and to other M(II)M(III)2 F8(H2O)2 structures are briefly discussed. Above 570°C, MgAl2F8(H2O)2 decomposes under elimination of water into α-AlF3, β-AlF3, and MgF2. Received October 29, 2001. Accepted (revised) December 6, 2001  相似文献   

6.
The binary phase, porous, nanocomposite xα-Fe/(1 − x)Ce0.9–K0.1–O (x = 0.05–0.2) catalysts and the catalyst-coated honeycomb ceramic device have been prepared by the citrate-gel thermal decomposition-reduction process and the sol–gel assisted dip-coating method, respectively. The nanocomposite of fluorite-type structure CeO2 nanoparticles about 18–51 nm and α-Fe nanoparticles about 32 nm is obtained at 600 °C for 2 h in a deoxidization atmosphere and the α-Fe in nanocomposite has the suppression effect on grain growth of CeO2. With Fe content increasing from 0.05 to 0.1, the specific surface area for the nanocomposites increases dramatically from about 4.4 to 43.0 m2/g, reaching a maximum value 57.7 m2/g at x = 0.15, and the pores vary from macropores to micro- or mesopores. Due to the presence of nano α-Fe, all the catalysts exhibit a very high soot catalytic activity, with the lowest T20 (255 °C) and T50 (291 °C) for the nanocomposite with x = 0.15, and it is confirmed by the bench test under practical diesel exhaust gases.  相似文献   

7.
Summary.  Hydrazinium(+2) fluoroarsenate(III) fluoride was prepared by the reaction of hydrazinium(+2) fluoride and liquid arsenic trifluoride. N2H6AsF4F is stable at 273 K, but decomposes slowly at room temperature. N2H6AsF4F crystallizes in the orthorhombic space group Pnn2 with a = 774.0(2) pm, b = 1629.2(4) pm and c = 436.6(1) pm; V = 0.5506(3) nm3, Z = 4 and d c  = 2.461 g cm−3. The structure consists of N2H6 2+ cations, AsF4 anions, and F anions and is interconnected by a hydrogen bonding network. Distorted trigonal-bipyramidal AsF4 units are very weakly interconnected and form chains along the b axis. Bands in the Raman spectrum are assigned to the vibrations of N2H6 +2 cations and AsF4 anions. Corresponding author. E-mail: adolf.jesih@ijs.si Received April 18, 2002; accepted July 15, 2002  相似文献   

8.
The present work presents an alternative approach to ethanol production from sweet sorghum: without detoxification, acid-impregnated fresh sweet sorghum stem which contains soluble (glucose and sucrose) and insoluble carbohydrates (cellulose and hemicellulose) was steam pretreated under mild temperature of 100 °C. Simultaneous saccharification and fermentation experiments were performed on the pretreated slurries using Saccharomyces cerevisiae. Experimentally, ground fresh sweet sorghum stem was combined with H2SO3 at dosages of 0.25, 0.50, and 0.75 g/g dry matter (DM) and steam pretreated by varying the residence time (60, 120, or 240 min). According to enzymatic hydrolysis results and ethanol yields, H2SO3 was a powerful and mild acid for improving enzymatic digestibility of sorghum stem. At a solid loading of 10% (w/v) and acid dosage of 0.25 g/g DM H2SO3 at 100 °C for 120 min, 44.5 g/L ethanol was obtained after 48 ± 4 h of simultaneous saccharification and fermentation. This corresponded to an overall ethanol yield of 110% of the theoretical one, based on the soluble carbohydrates in the fresh sweet sorghum stem. The concentrations of hydroxymethylfurfural and furfural of the sulfurous acid pretreated samples were below 0.4 g/L. Ethanol would not inhibit the cellulase activity, at least under the concentration of 34 g/L.  相似文献   

9.
In this work, an enzyme biosensor based on the immobilization of horseradish peroxidase (HRP) on SiO2/BSA/Au/thionine/nafion-modified gold electrode was fabricated successfully. Firstly, nafion was dropped on the surface of the gold electrode to form a nafion film followed by chemisorption of thionine (Thi) as an electron mediator via the ion-exchange interaction between the Thi and nafion. Subsequently, the SiO2/BSA/Au composite nanoparticles were assembled onto Thi film through the covalent bounding with the amino groups of Thi. Finally, HRP was immobilized on the SiO2/BSA/Au composite nanoparticles due to the covalent conjugation to construct an enzyme biosensor. The surface topographies of the SiO2/BSA/Au composite nanoparticles were investigated by using scanning electronic microscopy. The stepwise self-assemble procedure of the biosensor was further characterized by means of cyclic voltammetry and chronoamperometry. The enzyme biosensor showed high sensitivity, good stability and selectivity, a wide linear response to hydrogen peroxide (H2O2) in the range of 8.0 × 10-6 ∼ 3.72 × 10-3 mol/L, with a detection limit of 2.0 × 10-6 mol/L. The Michaelies-Menten constant KMapp K_M^{app} value was estimated to be 2.3 mM.  相似文献   

10.
The plasticized polymer electrolytes composed of poly(epichlorohydrin-ethyleneoxide) (P(ECH-EO)) as host polymer, lithium perchlorate (LiClO4) as salt, γ-butyrolactone (γ-BL), and propylene carbonate (PC) as plasticizer have been prepared by simple solution casting technique. The effect of mixture of plasticizers γ-BL and PC on conductivity of the polymer electrolyte P(ECH-EO):LiClO4 has been studied. The band at 457 cm−1 in the Raman spectra of plasticized polymer electrolyte is attributed to both the ring twisting mode of PC and the perchlorate ν 2(ClO4) bending. The maximum conductivity value is observed to be 4.5 × 10−4 S cm−1 at 303 K for 60P(ECH-EO):15PC:10γ-BL:15LiClO4 electrolyte system. In the present investigation, an attempt has been made to correlate the Raman and conductivity data.  相似文献   

11.
Electrolytes of 1 M blend salts (LiPF6 and tetraethylammonium tetrafluoroborate, Et4NBF4) have been investigated in supercapacitor battery system with composite LiMn2O4 and activated carbon (AC) cathode, and Li4Ti5O12 anode. The results obtained with the blend salts electrolytes are compared with those obtained with cells build using standard 1 M LiPF6 dissolved in ethylene carbonate + dimethyl carbonate + ethyl (methyl) carbonate (EC + DMC + EMC, 1:1:1 wt.%) as electrolyte. It is found that the blend salts electrolyte performs better on both electrochemical and galvanostatic cycling stability, especially cycled at 4 C rate. When the concentration of LiPF6 is 0.2 M and Et4NBF4 is 0.8 M, the capacity retention of the battery is 96.23% at 4 C rate after 5,000 cycles, much higher than that of the battery with standard 1 M LiPF6 electrolyte, which is only 62.35%. These results demonstrate that the blend salts electrolyte can improve the galvanostatic cycling stability of the supercapacity battery. Electrolyte of 0.2 M LiPF6 + 0.8 M Et4NBF4 in EC + DMC + EMC (1:1:1 wt.%) is a promising electrolyte for (LiMn2O4 + AC)/Li4Ti5O12.  相似文献   

12.
Three selected materials have been prepared and shaped as cathode of half cells using the proton-conducting electrolyte BaCe0.9Y0.1O3 − δ (BCY10): two perovskite compounds, Ba0.5Sr0.5Co0.8Fe0.2O3 − δ (BSCF) and La0.6Sr0.4Fe0.8Co0.2O3 − δ (LSFC), and the praseodymium nickelate Pr2NiO4 + δ (PRN) having the K2NiF4-type structure. The electrochemical properties of these compounds have been studied under zero current conditions (two-electrode cell) and under polarization (three-electrode cell). Their measured area-specific resistances were about 1–2 Ω cm2 at 600 °C. Under direct current polarization, it appears that the three compounds show almost similar values of current densities at 625 °C; however, at lower temperatures, BSCF appears to be the most efficient cathode material.  相似文献   

13.
Mesoporous CeO2 and yttrium doped CeO2 (YDC) were prepared by a sol–gel process and characterized by a variety of techniques. XRD patterns showed that the undoped and doped samples had a cubic fluorite structure. The grain size decreased from 24.8 to 6.1 nm at 500 °C for pure CeO2 and YDC, respectively. N2 adsorption–desorption isotherms showed that the samples possessed typical mesopore characteristics. The BET specific surface area of the samples increased from 23.04 to 151.49 m2/g for 300 °C calcination after mesoporous CeO2 was doped with Y. It is found that the introduction of Y can inhibit the grain growth, and the presence of the pores also can be related to this obstacle to grain growth. These results are of great significance for the control of porous microstructure, crystallinity, and applications for the development of nanostructured mesoporous materials.  相似文献   

14.
Nano-composites of SnO(V2O3) x (x = 0, 0.25, and 0.5) and SnO(VO)0.5 are prepared from SnO and V2O3/VO by high-energy ball milling (HEB) and are characterized by X-ray diffraction (XRD), scanning electron microscopy, and high-resolution transmission electron microscopy techniques. Interestingly, SnO and SnO(VO)0.5 are unstable to HEB and disproportionate to Sn and SnO2, whereas HEB of SnO(V2O3) x gives rise to SnO2.VO x . Galvanostatic cycling of the phases is carried out at 60 mA g−1 (0.12 C) in the voltage range 0.005–0.8 V vs. Li. The nano-SnO(V2O3)0.5 showed a first-charge capacity of 435 (±5) mAh g−1 which stabilized to 380 (±5) mAh g−1 with no noticeable fading in the range of 10–60 cycles. Under similar cycling conditions, nano-SnO (x = 0), nano-SnO(V2O3)0.25, and nano-SnO(VO)0.5 showed initial reversible capacities between 630 and 390 (±5) mAh g−1. Between 10 and 50 cycles, nano-SnO showed a capacity fade as high as 59%, whereas the above two VO x -containing composites showed capacity fade ranging from 10% to 28%. In all the nano-composites, the average discharge potential is 0.2–0.3 V and average charge potential is 0.5–0.6 V vs. Li, and the coulombic efficiency is 96–98% after 10 cycles. The observed galvanostatic cycling, cyclic voltammetry, and ex situ XRD data are interpreted in terms of the alloying–de-alloying reaction of Sn in the nano-composite “Sn-VO x -Li2O” with VO x acting as an electronically conducting matrix.  相似文献   

15.
Highly ordered mesoporous cerium dioxide (meso-CeO2) was successfully synthesized using a facile solvent-free infiltration method from a mesoporous silica template, KIT-6. The meso-CeO2 material, thus obtained, exhibited well-defined mesostructure and high surface area (153 m2 g−1). The physicochemical properties of meso-CeO2 material and Pd-supported on meso-CeO2 (Pd/meso-CeO2) were characterized by electron microscopy, X-ray diffraction, N2 adsorption–desorption, and temperature-programmed experiments. The Pd/meso-CeO2 catalyst exhibited excellent catalytic activity for CO oxidation compared with those of other Pd/CeO2 catalysts which were prepared using nanocrystalline CeO2 and bulk-CeO2 as the supports. Moreover, a hydrogen pretreatment of the Pd/meso-CeO2 catalyst resulted in a remarkable increase of catalytic activity (T 100 = 52 °C).  相似文献   

16.
We have determined the parameters of the Arrhenius equation (E, log A) for reactions between \textNO2+ {\text{NO}}_2^{+} ions and C3-C8 alkanes in HNO3–93 wt.% H2SO4 solutions at 277–353 K, and we have also estimated the activation parameters E j , log A j for secondary and tertiary C—H bonds of these alkanes. We show that the following compensation relations are satisfied: E = 2.3R βlog A + C with isokinetic temperature β = 360 ± 65 K, and also E j =2.3Rβ j log A j  + C j , for secondary C—H bonds, β2 =300 ± 60, and for tertiary C—H bonds, β3 =310 ± 50.  相似文献   

17.
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.  相似文献   

18.
Molybdenum trioxide (MoO3) xerogel films modified with poly(vinyl alcohol)+poly(vinyl pyrrolidone) (PVP+PVA) polyblends were obtained by ion-exchange method with sol-gel technique. Investigations were conducted using X-ray “diffractometry”, Fourier transform infrared spectroscopy, and cyclic voltammetry. The results show that the H atoms in polyblend are H-bonded with the O atoms in the Mo=O bonds of MoO3 xerogel, which effectively shield the electrostatic interaction between MoO3 interlayer and Li+ ions when MoO3 xerogel is modified by the intercalation of (PVP+PVA). The reversibility of the insertion/extraction of Li+ ions is greatly improved by the modification with polyblend of MoO3 nanocomposite films. MoO3 and (PVP+PVA) x MoO3 (x = 0, 0.5) nanobelts were obtained by a simple hydrothermal process from MoO3 sol. The electrochemical cells with configuration Li/(LiPF6+EC+DMC)/MoO3 modified by (PVP+PVA) were fabricated and their discharge profiles studied.  相似文献   

19.
For studying the adiabatic and nonadiabatic mechanisms of the ClO (X 2Π) + ClO (X 2Π) → ClOOCl → 2Cl (2 P u) + O2 (X 3Σ g ) reaction (1) and the ClO (X 2Π) + ClO (X 2Π) → ClOOCl → Cl2 (X 1Σ g +) + O2 (X 3Σ g ) reaction (2), we calculated, by partial geometry optimizations under the C2 constraint, the O–O and O–Cl dissociation potential energy curves (PECs) from the five low-lying states of ClOOCl at the CASPT2 level. The CASSCF minimum-energy crossing point (MECP) between the potential energy surfaces of the 1 1A ground state [correlating with the product of reaction (1)] and the 1 3B state [correlating with the product of reaction (2)] states was also determined. Based on the CAS calculation results (PECs, energies, and spin–orbit coupling at the MECP), we predict that reaction (1) occurs along pathway 1: ClO (X 2Π) + ClO (X 2Π) → ClOOCl (1 1A) → 2Cl (2 P u) + O2 (X 3Σ g ) and that reaction (2) occurs along pathway 2: ClO (X 2Π) + ClO (X 2Π) → ClOOCl (1 1A) → 1 1A/1 3B MECP (142.4 cm−1) → ClOOCl (1 3B) → Cl2 (X 1Σ g +) + O2 (X 3Σ g ). The needed energies (relative to the reactant) for pathways 1 and 2 are predicted to be 5.3 and 11.1 kcal/mol, respectively, which indicates that reaction (1) is more favorable than reaction (2). The present work supports the traditional photochemical model for ozone degradation: ClOOCl (1 1A), formed by two ClO (X 2Π), can directly produce O2 plus two Cl atoms.  相似文献   

20.
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.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号