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 31 毫秒
1.
The ion conductors Li4+xAlxSi1‐xO4‐yLi3PO4 (x = 0 to 0.5, y = 0 to 0.6) were prepared by the Sol‐Gel method. The powder and sintered samples were characterized by DTA‐TG, XRD, SEM, and AC impedance techniques. The conductivity and sinterability increased when y increased from 0 to 0.4 in the Li4+xAlxSi1‐xO4‐yLi3PO4. The particle size of the powder samples is about 0.13 μm. The maximum conductivity at 20 °C is 3.128 × 10?5s cm?1 for Li4.4Al0.4Si0.6O4‐0.4 Li3PO4.  相似文献   

2.
The Li4+xMxSi4+xO4‐yLi2O (M=Al, B; x = 0 to 0.6, y = 0 to 0.5) ion conductors were prepared by the Sol‐Gel method and examined in detail. The powder and sintered samples were characterized by DTA‐TG, XRD, SEM, and AC impedance techniques. The experimental results show that the conductivity and sinterability in creased with the amount of excess lithium oxide in the silicate. The Li2O phase acts as a flux to accelerate the sintering process and to obtain high conductivity of grain boundaries. The particle size of the sintered pellets is about 0.25 μm. The maximum conductivity at 200 °C is 5.40 × 10?3s cm?1 for Li4.4Al0.4 Si0.6O4‐0.3Li2O.  相似文献   

3.
IntroductionLithiumionconductorsarepromisingmaterialsformanykindsofelectrochemicalapplication ,suchaselec trolytesforhigh energydensitybatteries .1Thepropertiesofhighionicconductivity ,highdecompositionpotential,stabilityandcompatibilityagainstelectrodess…  相似文献   

4.
刘华亭  陈汝芬  宋秀芹 《中国化学》2002,20(12):1536-1539
Introduction  InthesearchfornewLi+ ionconductingsolidswithpotentialapplicationsassolidelectrolytesinhigh energydensitybatteries ,considerableworkhasbeendoneonavarietyofLi+ ionelectrolytes .Li4 SiO4 basedsolidsolu tionsarewellknownfortheirgreatincreaseincon…  相似文献   

5.
Two ranges of solid solutions were prepared in the system Li4SiO4Li3VO4: Li4?xSi1?xVxO4, 0 < x ? 0.37 with the Li4SiO4 structure and Li3+yV1?ySiyO4, 0.18 ? y ? 0.53 with a γ structure. The conductivity of both solid solutions is much higher than that of the end members and passes through a maximum at ~40Li4SiO4 · 60Li3VO4 with values of ~1 × 10?5 ohm?1 cm?1 at 20°C, rising to ~4 × 10?2 ohm?1 cm?1 at 300°C. These conductivities are several times higher than in the corresponding Li4SiO4Li3(P,As)O4 systems, especially at room temperature. The solid solutions are easy to prepare, are stable in air, and maintain their conductivity with time. The mechanism of conduction is discussed in terms of the random-walk equation for conductivity and the significance of the term c(1 ? c) in the preexponential factor is assessed. Data for the three systems Li4SiO4Li3YO4 (Y = P, As. V) are compared.  相似文献   

6.
Polyvinyl formal (PVFM)‐based dense polymer membranes with nano‐Al2O3 doping are prepared via phase inversion method. The membranes and also their performances as gel polymer electrolytes (GPEs) for lithium ion battery are studied by field emission scanning electron microscope, X‐ray diffraction, differential scanning calorimetry, mechanical strength test, electrolyte uptake test, electrochemical impedance spectroscopy, cyclic voltammetry, and charge–discharge test. The polymer membrane with 3 wt % nano‐Al2O3 doping shows the improved mechanical strength of 12.16 MPa and electrolyte uptake of 431.25% compared with 10.47 MPa and 310.59% of the undoped sample, respectively. The membrane absorbs and swells liquid electrolyte to form stable GPE with ionic conductivity of 4.92 × 10?4 S cm?1 at room temperature, which is higher than 1.77 × 10?4 S cm?1 of GPE from the undoped membrane. Moreover, the Al2O3‐modified membrane supporting GPE exhibits wide electrochemical stability window of 1.2–4.8 V (vs. Li/Li+) and good compatibility with LiFePO4 electrode, which implies Al2O3‐modified PVFM‐based GPE to be a promising candidate for lithium ion batteries. © 2014 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014 , 52, 572–577  相似文献   

7.
The nanocrystalline cubic Phase of zirconia was found to be thermally stabilized by the addition of 2.56 to 17.65 mol % Y2O3 (5.0 to 30.0 mol % Y, 95.0 to 70.0 mol % Zr cation content). The cubic phase of yttria stabilized zirconia was prepared by thermal decomposition of the hydroxides at 400°C for 1 hr. 2.56 mol % Y2O3‐ZrO2 was stable up to 800°C in an argon atmosphere. The samples with 4.17 to 17.65 mol % Y2O3 were stable to 1200°C and higher. All samples at temperatures between 1450°C to 1700°C were cubic except the sample with 2.56 mol % Y2O3 which was tetragonal. The crystallite sizes observed for the cubic phase ranged from 50 to 150 Å at temperatures below 900°C and varied from 600 to 800 nm between 1450°C and 1700°C. Control of furnace atmosphere is the main factor for obtaining the cubic phase of Y‐SZ at higher temperature. Nanocrystalline cubic Fe‐SZ (Iron Stabilized Zirconia) with crystallite sizes from 70 to 137 Å was also prepared at 400°C. It transformed isothermally at temperatures above 800°C to the tetragonal Fe‐SZ and ultimately to the monoclinic phase at 900°C. The addition of up to 30 mol % Fe(III) thermally stabilized the cubic phase above 800°C in argon. Higher mol % resulted in a separation of Fe2O3. The nanocrystalline cubic Fe‐SZ containing a minimum 20 mol % Fe (III) was found to have the greatest thermal stability. The particle size was a primary factor in determining cubic or tetragonal formation. The oxidation state of Fe in zirconia remained Fe3+. Fe‐SZ lattice parameters and rate of particle growth were observed to decrease with higher iron content. The thermal stability of Fe‐SZ is comparable with that of Ca‐SZ, Mg‐SZ and Mn‐SZ prepared by this method.  相似文献   

8.
A new series of (Y2‐yLiy)Ti2O7‐y having an ordered pyrochlore phase was prepared by a solid state reaction method with a solid solution range of 0.05 ≥ y ≥ 0.10. Unit cell parameters obtained by the Rietveld refinement method shows that the a‐axis decreases linearly with increasing the amount of Li ion addition, indicating the successful incorporation of the Li ion into unit cell. The average x‐fractional coordinate of the O(1) site depends on the ionic radius ratio of r(A3+)/r(Ti4+) in the A2Ti2O7 with a pyrochlore phase. The Ti K‐edge XANES spectra of the (Y2‐yLiy)Ti2O7‐y show that the valence of the Ti ions is slightly less than 4 so that Ti is in the mixed valence state. Average particle size increases with increasing the amount of extra Li ion addition, which acts as a flux to lower the melting point of the materials.  相似文献   

9.
Graphitized carbon (GC) and graphene (GE) modified Fe2O3/Li4Ti5O12 (LTO) composites have been synthesized via a solid‐state reaction, respectively. The structure, morphology and electrochemical performance of the materials have also been characterized with X‐ray diffraction (XRD), scanning electron microscope (SEM) with an energy dispersive spectroscopy (EDS) system, X‐ray photoelectron spectrometer (XPS), Fourier transform infrared spectroscopy (FTIR) and electrochemical measurements. The discharge capacities of Fe2O3/LTO, GC/Fe2O3/LTO and GE/Fe2O3/LTO are 100.2 mAh g?1, 207.5 mAh g?1 and 238.9 mAh g?1 after 100 cycles at the current density of 176 mA g?1. The cyclic stability and rate capability are in the order of GE/Fe2O3/LTO > GC/Fe2O3/LTO > Fe2O3/LTO because of the synergistic effect between GC (GE) and Fe2O3/LTO. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

10.
Conductivity data for the lithium ion conducting solid electrolyte, LISICON, Li2+2xZn1?xGeO4 over a particularly wide composition range, 0.15 < x < 0.85, and over the temperature range ~25 to 150°C show that both the activation energy and preexponential factor pass through maxima around x ~ 0.4 to 0.5, at which the preexponential factor exhibits anomalously high values, ~1013 ohm?1 cm?1 K. An explanation is offered which involves the trapping of mobile Li+ ions by the immobile sublattice at lower temperatures. This model also accounts for ageing effects observed at lower temperatures in which the conductivity decreases slowly with time. In the isostructural Li+ electrolytes, Li3+xSixY1?xO4 (Y = P, As, V), the compositional dependence of both the preexponential factor and activation energy is less marked and no evidence for ion trapping effects is observed.  相似文献   

11.
In order to enhance dielectric properties and energy storage density of poly(vinylidene fluoride‐hexafluoro propylene) (PVDF‐HFP), surface charged gas‐phase Al2O3 nanoparticles (GP‐Al2O3, with positive surface charges, ε’ ≈ 10) are selected as fillers to fabricate PVDF‐HFP‐based composites via simple physical blending and hot‐molding techniques. The results show that GP‐Al2O3 are dispersed homogeneously in the PVDF‐HFP matrix and the existence of nanoscale interface layer (matrix‐filler) is investigated by SAXS. The dielectric constant of the composites filled with 10 wt % GP‐Al2O3 is 100.5 at 1 Hz, which is 5.6 times higher than that of pure PVDF‐HFP. The maximum energy storage density of the composite is 4.06 J cm?3 at an electrical field of 900 kV mm?1 with GP‐Al2O3 content of 1 wt %. Experimental results show that GP‐Al2O3 could induce uniform fillers’ distribution and increase the concentration of electroactive β‐phase as well as enhance interfacial polarization in the matrix, which resulted in enhancements of dielectric constant and energy storage density of the PVDF‐HFP composites. This work demonstrates that surface charged inorganic‐oxide nanoparticles exhibit promising potential in fabricating ferroelectric polymer composites with relatively high dielectric constant and energy storage. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 574–583  相似文献   

12.
The new lithium ionic conductors, thio-LISICON (LIthium SuperIonic CONductor), were found in the ternary Li2S-SiS2-Al2S3 and Li2S-SiS2-P2S5 systems. Their structures of new materials, Li4+xSi1−xAlxS4 and Li4−xSi1−xPxS4 were determined by X-ray Rietveld analysis, and the electric and electrochemical properties were studied by electronic conductivity, ac conductivity and cyclic voltammogram measurements. The structure of the host material, Li4SiS4 is related to the γ-Li3PO4-type structure, and when the Li+ interstitials or Li+ vacancies were created by the partial substitutions of Al3+ or P5+ for Si4+, large increases in conductivity occur. The solid solution member x=0.6 in Li4−xSi1−xPxS4 showed high conductivity of 6.4×10-4 S cm−1 at 27°C with negligible electronic conductivity. The new solid solution, Li4−xSi1−xPxS4, also has high electrochemical stability up to ∼5 V vs Li at room temperature. All-solid-state lithium cells were investigated using the Li3.4Si0.4P0.6S4 electrolyte, LiCoO2 cathode and In anode.  相似文献   

13.
We have reported for the first time the preparation of yolk–shell‐structured Li4Ti5O12 powders for use as anode materials in lithium‐ion batteries. One Li4Ti5O12 yolk–shell‐particle powder is directly formed from each droplet containing lithium, titanium, and carbon components inside the hot wall reactor maintained at 900 °C. The precursor Li4Ti5O12 yolk–shell‐particle powders, which are directly prepared by spray pyrolysis, have initial discharge and charge capacities of 155 and 122 mA h g?1, respectively, at a current density of 175 mA g?1. Post‐treatment of the yolk–shell‐particle powders at temperatures of 700 and 800 °C improves the initial discharge and charge capacities. The initial discharge capacities of the Li4Ti5O12 powders with a yolk–shell structure and a dense structure post‐treated at 800 °C are 189 and 168 mA h g?1, respectively. After 100 cycles, the corresponding capacities are 172 and 152 mA h g?1, respectively (retentions of 91 and 90 %).  相似文献   

14.
Single Crystals of Y3F[Si3O10] with Thalenite-Type Structure Colourless, diamond-shaped single crystals of Y3F[Si3O10] (monoclinic, P21/n; a = 730.38(5), b = 1112.47(8), c = 1037.14(7) pm, β = 97.235(6)°, Z = 4) with thalenite-type structure are obtained upon the reaction of YF3 with Y2O3 and SiO2 (1 : 4 : 9 molar ratio) in evacuated silica tubes at 700 °C in the presence of CsCl as flux within seven days. The crystal structure consists of triangular [FY3]8+ cations and catena-trisilicate anions [Si3O10]8–, which exhibit a horseshoe-shape resulting from two vertex-shared terminal [SiO4] tetrahedra with both staggered and eclipsed conformation relative to the central one. The Y3+ cations have coordination numbers of seven plus one (Y1) or seven (Y2 and Y3), but only one F anion belongs to each and vice versa, the remainder ligands being oxygen members of [Si3O10]8– anions.  相似文献   

15.
The Li-rich Li1.3[Ni0.35Mn0.65]O2+x microspheres are firstly prepared and subsequently transferred into the Al2O3-coated Li-rich Li1.3[Ni0.35Mn0.65]O2+x microspheres by a simple deposition method. The as-prepared samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge/discharge tests. The results reveal that the Al2O3-coated Li-rich Li1.3[Ni0.35Mn0.65]O2+x sample has a typical α-NaFeO2 layered structure with the existence of Li2MnO3-type integrated component, and the Al2O3 layer is uniformly coated on the surface of the spherical Li-rich Li1.3[Ni0.35Mn0.65]O2+x particles with a thickness of about 4 nm. Importantly, the Al2O3-coated Li-rich sample exhibits obviously improved electrochemical performance compared with the pristine one, especially the 2 wt.% Al2O3-coated sample shows the best electrochemical properties, which delivers an initial discharge capacity of 228 mAh g?1 at a rate of 0.1 C in the voltage of 2.0–4.6 V, and the first coulombic efficiency is up to 90 %. Furthermore, the 2 wt.% Al2O3-coated sample represents excellent cycling stability with capacity retention of 90.9 % at 0.33 C after 100 cycles, much higher than that of the pristine one (62.2 %). Particularly, herein, the typical inferior rate capability of Li-rich layered cathode is apparently improved, and the 2 wt.% Al2O3-coated sample also shows a high rate capability, which can deliver a capacity of 101 mAh g?1 even at 10 C. Besides, the thin Al2O3 layer can reduce the charge transfer resistance and stabilize the surface structure of active material during cycling, which is responsible for the improvement of electrochemical performance of the Li-rich Li1.3[Ni0.35Mn0.65]O2+x .  相似文献   

16.
The valence distributions of Fe and Mn in yttrium orthoferrite (YFeO,), YFe0.6Mn0.4O3 and Y0.9Ca0.1Fe0.6Mn0.4O3.8 were studied by the measurement of thermal power. Pure YFeO3 shows the n‐type electrical conductivity associated with small polaron hopping between Fe2+ and Fe3+. Both YFe0.4Mn0.4‐O3 and Y0–9Ca0–1.Fe0–6Mn0–4O3–8 show n‐type and p‐type conductivities at high and low temperatures respectively associated with small polaron hopping between Mn3+ and Mn4+, iron has only oxidation state of Fe3+ and does not have contribution to the electrical conductivity.  相似文献   

17.
Synthesis of Y2O2(CN2) and Luminescence Properties of Y2O2(CN2):Eu Crystalline powders of the new compound Y2O2(CN2) were prepared by solid state reactions from different mixtures of YCl3/YOCl/Y2O3 and Li2(CN2) at temperatures between 620 °C and 650 °C. Structure refinements based on X‐ray powder diffraction revealed that trigonal Y2O2(CN2) crystallizes with a structure that is closely related to that of Y2O2S, whereas linear N‐C‐N units replace sulphur atoms in Y2O2S. In addition, a hexagonal polytype of Y2O2(CN2) was obtained in which a different stacking sequence of yttrium atoms creates a doubling of the c‐axis. Europium‐doped samples of Y2O2(CN2) were prepared and the luminescence properties of Y2O2(CN2):Eu are presented.  相似文献   

18.
The effect of chemical composition to ionic conductivity and activation energy of vitreous solid electrolytes (SE) based on Li2O-P2O5-LiF system (Li2O ≥ 45.4 mol %) was detected. The temperature effect to conductivity and activation energy was studied. An original technology was designed to prepare vitreous SEs in Li2O-P2O5-LiF system containing up to 20 mol % LiF and characterized with ionic conductivity up to 4.4 × 10?7 S cm?1 (24°C) and activation energy about 0.567 eV. The synthesized materials are characterized with high X-ray amorphism and technological performance.  相似文献   

19.
Preparation of lithium garnet Li7La3Zr2O12 (LLZ) in cubic phase by solid state method requires high temperature sintering around 1,200 °C for 36 h in Al2O3 crucible with intermittent grinding. Synthesis of LLZ in cubic phase at lower temperatures by wet chemical methods was reported earlier, however that decompose at high temperature around 850 °C. In this work we report the systematic studies on synthesis of garnet structured electrolytes by modified sol–gel method by the simultaneous substitution of Li+ and Y3+ for Zr4+ according to the formulae Li7+x La3Y x Zr2-x O12 (x = 0, 0.1, 0.2, 0.3 and 0.4). The present investigation revealed that the cubic garnet phase is obtained at much lower temperature for Li7La3Zr2O12 and the simultaneous increase of both Li+ and Y3+ in Li7+x La3Y x Zr2-x O12 requires slightly higher sintering temperatures for the formation of cubic garnet phase. SEM micrographs of the Li7+x La3Y x Zr2-x O12 (x = 0, 0.1, 0.2, 0.3 and 0.4) annealed at minimum sintering temperature required for the formation of cubic garnet phase revealed the increase in grain size and relatively dense structure with increase of x in Li7+x La3Y x Zr2-x O12.  相似文献   

20.
The properties of tetragonal yttria-stabilized zirconia composites with the small addition of alumina (Al2O3?Y2O3?ZrO2 composite) obtained on two ways of synthesis were studied in terms of usability for anode materials in solid oxide fuel cell. Both methods were based on citric synthesis: in the first one, Al2O3 was coprecipitated with the tetragonal ZrO2 in the form of citrate by citric acid, while in the second Al2O3 was impregnated in the form of aluminium nitrate precursor on tetragonal ZrO2 matrix. The obtained materials were analysed by X-ray diffraction, dilatometry and impedance spectroscopy. The results of measurements show that regardless of synthesis method, the addition of Al2O3 influences the conductivity of samples by increasing their grain boundaries conductivity as an effect of removing of SiO2 and decreasing of conductivity activation energy. The impregnation of Al2O3 on tetragonal ZrO2 and sintering of this material above shrinking temperature cause, however, radical decrease of porosity of materials, which disqualifies these samples as anode materials. In the case of samples obtained by coprecipitation the significant decrease of porosity is not observed.  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