共查询到20条相似文献,搜索用时 15 毫秒
1.
N. V. Kosova E. T. Devyatkina V. V. Kaichev D. G. Kellerman 《Russian Journal of Electrochemistry》2008,44(5):543-549
The cathode materials of the composition LiNi1 − 2x
Co
x
Mn
x
O2 (x = 0.1, 0.2. 0.33) synthesized from the Ni, Co, Mn mixed hydroxides and LiOH by using mechanical activation method are studied.
It is shown that all synthesized compounds have layered structure described by the space group R-3m. With the decreasing of the nickel content the cell volume and the degree of structure disordering decrease. According to
XPS data, the electronic main state of d-ions at the prepared samples’ surfaces corresponds to Ni2+, Co3+, and Mn4+. An increase in the nickel content leads to the increase of the Ni2p
3/2 and Co2p
3/2 binding energy, which points to the change in the Me-O bond covalence. According to magnetic susceptibility measurements
data, the nickel ions in LiNi0.6Co0.2Mn0.2O2 exist in the two oxidation states: Ni2+ and Ni3+. It is shown that this sample has the highest specific discharge capacity (∼170 mAh/g). The positions of redox peaks in the
differential capacitance curves depend on the sample composition: with the increasing of nickel content they are shifted toward
lower voltages.
Based on the paper presented in the IX International Conference “Basic Problems of Energy Conversion in Lithium Electrochemical
Systems” (Ufa, 2006). 相似文献
2.
Li Wang Jiangang Li Xiangming He Weihua Pu Chunrong Wan Changyin Jiang 《Journal of Solid State Electrochemistry》2009,13(8):1157-1164
Lithium cobalt oxide, LiCoO2, has been the most widely used cathode material in commercial lithium ion batteries. Nevertheless, cobalt has economic and
environmental problems that leave the door open to exploit alternative cathode materials, among which LiNi
x
CoyMn1 − x − y
O2 may have improved performances, such as thermal stability, due to the synergistic effect of the three ions. Recently, intensive
effort has been directed towards the development of LiNi
x
Co
y
Mn1 − x − y
O2 as a possible replacement for LiCoO2. Recent advances in layered LiNi
x
CoyMn1 − x − y
O2 cathode materials are summarized in this paper. The preparation and the performance are reviewed, and the future promising
cathode materials are also prospected. 相似文献
3.
《Solid State Sciences》2001,3(1-2):81-92
When tuning the exchange capacity of a Co2+, Al3+ containing layered double hydroxyde's (LDH's) material, a concomitant phenomenon of oxidation-migration of the cations is observed for one of the end members. X-ray absorption spectroscopy, performed at the cobalt and aluminum k-edge, shows that part of the Co2+ cations are oxidized to Co3+, while Al3+ cations have left the LDH's layers, leading to a [Co2+xCo3+] intralayer composition. Interlamellar AlO6 polyhedra are present after repetitive washing and exchange reactions, suggesting strong interactions with the LDH's layers. 相似文献
4.
Maria I. B. Bernardi Vinícius D. Araújo Caue Ribeiro Waldir Avansi Elson Longo Nilson J. A. de Albuquerque Simoni M. P. Meneghetti Rusiene M. Almeida Humberto V. Fajardo 《Chemical Papers》2014,68(9):1213-1218
Wurtzite-type Zn1?x Mn x O (x = 0, 0.03, 0.05, 0.07) nanostructures were successfully synthesised using a simple microwave-assisted hydrothermal route and their catalytic properties were investigated in the cellulose conversion. The morphology of the nanocatalysts is dopant-dependent. Pure ZnO presented multi-plate morphology with a flower-like shape of nanometric sizes, while the Zn0.97Mn0.03O sample is formed by nanoplates with the presence of spherical nanoparticles; the Zn0.95Mn0.05O and Zn0.93Mn0.07O samples are mainly formed by nanorods with the presence of a small quantity of spherical nanoparticles. The catalyst without Mn did not show any catalytic activity in the cellulose conversion. The Mn doping promoted an increase in the density of weak acid sites which, according to the catalytic results, favoured promotion of the reaction. 相似文献
5.
Hilde Lea Lein Øystein Skottun Andersen Per Erik Vullum Edgar Lara-Curzio Randi Holmestad Mari-Ann Einarsrud Tor Grande 《Journal of Solid State Electrochemistry》2006,10(8):635-642
Young’s modulus, strain–stress behavior, fracture strength, and fracture toughness of (0≤×≤1) materials have been investigated in the temperature range 20–1,000°C. Young’s moduli of and , measured by resonant ultrasound spectroscopy, were 130±1 and 133±3 GPa, respectively. The nonlinear stress–strain relationship
observed by four-point bending at room temperature was inferred as a signature of ferroelastic behavior of the materials.
Above the ferroelastic to paraelastic transition temperature, the materials showed elastic behavior, but due to high-temperature
creep, a nonelastic respond reappeared above ∼800°C. The room temperature fracture strength measured by four-point bending
was in the range 107–128 MPa. The corresponding fracture toughness of , measured by single edge V-notch beam method, was 1.16±0.12 MPa·m1/2. The measured fracture strength and fracture toughness were observed to increase with increasing temperature. The fracture
mode changed from intragranular at low temperature to intergranular at high temperature. Tensile stress gradient at the surface
of the materials caused by a frozen-in gradient in the oxygen content during cooling was proposed to explain the low ambient
temperature fracture strength and toughness. 相似文献
6.
P. Mohan K. Arunsunai Kumar G. Paruthimal Kalaignan V. S. Muralidharan 《Journal of Solid State Electrochemistry》2012,16(12):3695-3702
Pristine- and chromium-substituted LiNiO2 nanoparticles were synthesized by sol-gel method using nitrate precursor at 800?°C for 12?h. Physical properties of the synthesized product were analyzed using Fourier transform infrared, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive analysis X-ray. XRD studies revealed a well-defined layer structure and a linear variation of lattice parameters with the addition of chromium and no impurities. Surface morphology and particle size of synthesized materials were changed with chromium addition using SEM and TEM analyses. Assembled lithium-ion cells were evaluated for charge/discharge studies at different rates, cyclic voltammetry, and electrochemical impedance spectra. The initial discharge capacity of LiNiO2 cathode material was found to be 168?mA hg?1; however, discharge capacity increased in chromium substitution. Electrochemical impedance spectroscopy revealed that LiCr0.10Ni0.90O2 could enhance charge transfer resistance upon cycling. The substitution of Ni with chromium, LiCr0.10Ni0.90O2, had better cycle life, low irreversible capacity, and excellent electrochemical performance. 相似文献
7.
A. C. Tavares M. A. M. Cartaxo M.I. da Silva Pereira F. M. Costa 《Journal of Solid State Electrochemistry》2001,5(1):57-67
Studies on the electrochemical behaviour of Ni1−
x
Cu
x
Co2O4 (x ≤ 0.75) and NiCo2−
y
Cu
y
O4 (y ≤ 0.30) electrodes in 5 mol dm−3 KOH aqueous solutions are presented. The oxide layers have been prepared by thermal decomposition of aqueous nitrate solutions
on nickel supports at 623 K. Powder samples were also prepared by thermal decomposition under the same conditions. The powder
samples and the oxide layers were characterised by X-ray powder diffraction. The influence of the copper content on the voltammetric
response of the electrodes and activity towards oxygen evolution reaction is analysed and correlated with the surface composition
of the electrodes by means of X-ray photoelectron spectroscopy data. The analysis of the results reveals that the presence
of Cu affects the electrode behaviour and its influence depends on which cation has been replaced.
Received: 22 February 1999 / Accepted: 26 October 1999 相似文献
8.
V. N. Krasil’nikov O. I. Gyrdasova I. V. Baklanova L. Yu. Buldakova M. Yu. Yanchenko R. F. Samigullina O. V. Koryakova 《Russian Journal of Inorganic Chemistry》2013,58(2):120-126
Quasi-one-dimensional (1D) solid solutions Ti1 ? x Fe x (OCH2CH2O)2 ? x/2 (0 < x ≤ 0.1) with the structure of anatase were prepared by heating the glycolate Ti1 ? x Fe x (OCH2CH2O)2 ? x/2 in an atmosphere of air at a temperature of >450°C. The conditions of formation and the properties of the new glycolate Ti3Fe2(OCH2CH2O)9 were described. It was found that the synthesized Ti1 ? x Fe x O2 ? 2x/2 solid solutions exhibit photocatalytic activity in the reaction of hydroquinone oxidation in an aqueous solution on irradiation with UV light. A correlation between the rate of oxidation of hydroquinone and the concentration of iron in the catalyst was established. A procedure for the preparation of titanium dioxide with the structure of anatase doped with iron and carbon (Ti1 ? x Fe x O(2 ? x/2) ? yCy) and also composites on its basis, which contain an excess amount of carbon, was proposed. 相似文献
9.
Wen-lan Wu Ju Liang Ji Yan Wen-feng Mao 《Journal of Solid State Electrochemistry》2013,17(7):2027-2033
Li3Ni x V2?x (PO4)3/C (x?=?0, 0.02, 0.04 and 0.06) samples have been synthesized via an improved sol–gel method. X-ray diffraction patterns indicate that the structure of the prepared samples retains monoclinic, and the single phase has not been changed with Ni doping. From the analysis of electrochemical performance, the Li3Ni0.04?V1.96(PO4)3/C sample exhibits the best electrochemical property. It delivers a discharge capacity of 112.1 mAh?g?1 with capacity retention of 95.2 % over 300 cycles at 10 C rate in the range of 3.0–4.8 V; cyclic voltammetry and electrochemical impedance spectra testing further prove that the electrochemical reversibility and lithium ion diffusion behavior of Li3V2(PO4)3 have also been effectively improved through Ni doping. 相似文献
10.
The present contribution reports on our results concerning the synthesis of different binary and ternary oxide systems by
using hybrid materials as “composite” precursors. In the last years, we have developed and explored a valuable strategy to
yield a very homogeneous dispersion of nanoparticles of early metal transition oxide, MO2 (M = Zr, Hf) inside a silica matrix. This route is based on the use of the sol–gel process to obtain organic–inorganic hybrid
silica-based materials embedding the oxide precursors (Zr and/or Hf oxoclusters), which are then calcined at high (T > 500 °C)
temperatures to give the desired oxides. The “precursor” hybrid materials are prepared by a modified sol–gel process, involving
the copolymerisation of the organically modified oxozirconium or oxohafnium clusters (M4O2(OMc)12 (M = Zr, Hf and OMc = methacrylate) with (methacryloxymethyl)triethoxysilane (MAMTES) or (methacryloxypropyl)trimethoxysilane
(MAPTMS). Free radical copolymerisation of the 12 methacrylate groups of the oxoclusters with the methacrylate-functionalised
siloxanes allows a stable anchoring of the oxoclusters to the silica network formed by the hydrolysis and condensation of
the alkoxy groups. The sol–gel reactions of the two methacrylate-modified silanes methacryloxymethyltriethoxysilane and methacryloxypropyltrimethoxysilane
were followed by using two independent time-resolved spectroscopic methods, viz., IR ATR and NMR with the aim to optimise
their pre-hydrolysis times and consequently their use as precursors for hybrid materials. As mentioned, thermal treatment
at high temperature of the hybrid yields a very homogeneous dispersion of ZrO2 and/or HfO2 nanoparticles in the silica matrix, since the molecular homogeneity of the starting hybrid is retained in the final mixed
oxide. This route was successfully applied both to the synthesis of bulk materials and thin films characterised by different
compositions (in term of M/Si molar ratios and M nature), heating route (conventional or microwave-assisted) and final temperature
of annealing (from RT to 1,100 °C). The first example of the ZrO2–HfO2–SiO2 ternary oxide system was also prepared by this approach. The prepared systems, both in the form of hybrid materials as well
as in the final form of binary or ternary oxides, were thoroughly characterised by a wide variety of analytical tools from
a compositional, structural, morphological point of view. Moreover, in the case of the binary ZrO2–SiO2 bulk materials, also the evolution under heating was followed by different methods. In particular, the composition of the
hybrid as well as of the final oxidic materials was determined by X-Ray Photoelectron Spectroscopy and elemental analysis,
whereas FT-IR and multinuclear solid-state NMR spectroscopies shed light on the changes occurring in the composition upon
thermal heating and the degree of condensation of the silica network. The morphology and the microstructure of the hybrids
and of the oxides were studied by nitrogen sorption and Scanning Electron Microscopy. X-Ray Diffraction, Transmission Electron
Microscopy and X-ray Absorption Fine Structure Spectroscopy X-ray Absorption Fine Structure Spectroscopy were used to follow
the conversion of the amorphous oxides to the final materials consisting of crystalline zirconia or hafnia dispersed in amorphous
silica. On selected systems, functional properties (surface reactivity, dielectric properties) were furthermore investigated.
The obtained binary oxides were also used as substrates for functionalisation experiments with (1) dialkycarbamates and (2)
long alkyl chains to produce functional materials for catalysis and HPLC applications, respectively. 相似文献
11.
Research on Chemical Intermediates - A new magnetic nanocomposite based on layered double hydroxides (LDHs) was synthesized by coprecipitation of (Cu/Ni)–Al LDHs and nano-Fe3O4 and... 相似文献
12.
A facile two-step hydrothermal method is developed for the large-scale preparation of lithium nickel manganese oxide spinel as a cathode material for lithium ion batteries. In the reaction, nickel is introduced in a first step at neutral pH, followed by lithium insertion under base to form a product having composition Li(1.02)Ni(0.5)Mn(1.5)O(3.88). The X-ray diffraction pattern and Raman spectroscopy of the synthesized material support a cubic Fd3m structure in which Ni and Mn are disordered on the 16d Wyckoff site, necessary for good cycling characteristics. XP spectroscopy and elemental analysis confirms that Mn remains reduced in the final product (Z(Mn) = 3.82) and that two different chemical environments for Ni exist on the surface. SEM imaging shows a primary particle size of ~200 nm, and galvanostatic cycling of the material vs. Li(+/0) gives a reversible gravimetric capacity of ~120 mA h g(-1) at 1 C rate (147 mA g(-1)) with reversible cycling up to 1470 mA g(-1), supported by rapid Li(+) diffusion. The capacity fade at 1 C is substantial, 17.3% over the first 100 cycles between 3.4 and 5.0 V. However, when the voltage limits are altered, the capacity retention is excellent: nearly 100% when cycled either between 3.4 and 4.4 V (where oxygen vacancies are not electrochemically active) or 89% when cycled between 4.4 and 5.0 V (where the Jahn-Teller active Mn(4+/3+) couple is not accessed). 相似文献
13.
A. Kaddouri S. Bassil B. Béguin P. Gélin 《Journal of Sol-Gel Science and Technology》2013,67(1):175-181
A sol–gel route to synthesize nanocrystalline praseodymium-, samarium- and gadolinium-doped ceria powders for solid oxides fuel Cells SOFCs is presented. The method involves metal nitrates with propionic acid (both as chelating ligand and solvent), gel formation, liquid nitrogen quenching, drying at 150 °C/24 h, and finally decomposition at 450 °C in nitrogen followed by calcination at 650 °C in air. TG–DTA, BET, XRD, FTIR, UV–vis and catalytic tests were used to characterize the samples. Ce0.8Pr0.2O2?δ sample exhibited the best catalytic performance in methane steam reforming under water deficient conditions, closely followed by Ce0.9Gd0.1O2?δ, Ce0.8Sm0.2O2?δ and Ce0.8Gd0.2O2?δ catalysts. The superior catalytic performance of Ce0.8Pr0.2O2?δ sample was attributed to the existence of praseodymium species (Pr4+/Pr3+) strongly interacting with ceria. The two systems act synergistically in the catalytic steam reforming of methane. 相似文献
14.
15.
Subsolidus region of the ternary systems Rb2MoO4-AMoO4-R2(MoO4)3, in which variable-composition phases Rb1 ? x A1 ? x R1 + x (MoO4)3 crystallizing in the monoclinic system (space group C2) are formed, was studied. Their crystallographic parameters were calculated; temperature dependences of the electrical conductivity, dielectric constant, and dielectric loss tangent were analized. 相似文献
16.
《Electrochemistry communications》2002,4(6):492-498
The electrochemical reactions of lithium with layered composite electrodes (x)LiMn0.5Ni0.5O2·(1−x)Li2TiO3 were investigated at low voltages. The metal oxide 0.95LiMn0.5Ni0.5O2·0.05Li2TiO3 (x=0.95) which can also be represented in layered notation as Li(Mn0.46Ni0.46Ti0.05Li0.02)O2, can react with one equivalent of lithium during an initial discharge from 3.2 to 1.4 V vs. Li0. The electrochemical reaction, which corresponds to a theoretical capacity of 286 mAh/g, is hypothesized to form Li2(Mn0.46Ni0.46Ti0.05Li0.02)O2 that is isostructural with Li2MnO2 and Li2NiO2. Similar low-voltage electrochemical behavior is also observed with unsubstituted, standard LiMn0.5Ni0.5O2 electrodes (x=1). In situ X-ray absorption spectroscopy (XAS) data of Li(Mn0.46Ni0.46Ti0.05Li0.02)O2 electrodes indicate that the low-voltage (<1.8 V) reaction is associated primarily with the reduction of Mn4+ to Mn2+. Symmetric rocking-chair cells with the configuration Li(Mn0.46Ni0.46Ti0.05Li0.02)O2/Li(Mn0.46Ni0.46Ti0.05Li0.02)O2 were tested. These electrodes provide a rechargeable capacity in excess of 300 mAh/g when charged and discharged over a 3.3 to −3.3 V range and show an insignificant capacity loss on the initial cycle. These findings have implications for combating the capacity-loss effects at graphite, metal–alloy, or intermetallic negative electrodes against lithium metal-oxide positive electrodes of conventional lithium-ion cells. 相似文献
17.
The preparation of stable alcoholic solution of tungstosilicic acid and silicon alkoxide, which can be used for xWO3 (1 – x)SiO2 thin film deposition by dipping, is described. After thermal treatment at temperatures 440 to 500°C in nitrogen films with x higher than 0.6 exhibit electrochromic coloration ability. After coloring the film by H+ imtercalation (by contact with an indium wire trough a drop of aqueous solution of H2SO4) the luminous transmittance (illuminant D65, wavelength range from 380 to 780 nm, summation at 10 nm intervals) of glass coated with 90 nm thick xWO3(1 – x)SiO2 thin film decreases from 71.7 to 28.6% and the IR reflection increases to over 30%. At the same time the surface resistance decreases from a few M/ to about 400/. The thermal decomposition of tungstosilic acid embedded in alkoxy-hydroxy-oxy-silicon matrix is investigated with DTA, TGA, XRD and FTIR spectroscopy. 相似文献
18.
We have compared the structure, microstructure, and electrochemical characteristics of xLi2MnO3–(1−x)Li(Mn0.375Ni0.375Co0.25)O2 (0.0 ≤ x ≤ 1.0) thin films with their bulk cathode laminate counterparts of identical compositions. Pure Li(Mn0.375Ni0.375Co0.25)O2 as well as the synthesized composite films partially transform into cubic spinel structure during charge–discharge cycling. In contrast, such layered to spinel phase transformation has only been identified in bulk cathode laminates with x ≥ 0.75. At a current density 0.05 mAcm−2, the discharge capacity of Li(Mn0.375Ni0.375Co0.25)O2 thin film was measured to be ∼60 μAhcm−2. The discharge capacity (∼217 μAhcm−2) was markedly improved in x∼0.5 composite thin film. The capacity retention after 20 charge discharge cycles are improved in composite films; however, their capacity fading could not be eliminated completely. 相似文献
19.
《Electrochemistry communications》2002,4(3):205-209
The electrochemical properties of 0.95LiMn0.5Ni0.5O2·0.05Li2TiO3 have been investigated as part of a study of xLiMO2·(1−x)Li2M′O3 electrode systems for lithium batteries in which M=Co, Ni, Mn and M′=Ti, Zr, Mn. The data indicate that the electrochemically inactive Li2TiO3 component contributes to the stabilization of LiMn0.5Ni0.5O2 electrodes, which improves the coulombic efficiency of Li/xLiMn0.5Ni0.5O2·(1−x)Li2TiO3 cells for x<1. The 0.95LiMn0.5Ni0.5O2·0.05Li2TiO3 electrodes provide a rechargeable capacity of approximately 175 mAh/g at 50 °C when cycled between 4.6 and 2.5 V; there is no indication of spinel formation during electrochemical cycling. 相似文献
20.
《Solid State Sciences》2001,3(1-2):143-153
The hydrothermal synthesis, single crystal structure analysis, spectroscopic and thermal stability studies of the compounds Ba3(In1−xMx)2(HXO4)6 (0≤x≤1; M=Cr, Fe; X=P, As) are reported. The 3D framework of these new phosphates can be described as a pillared layered framework. The metal cations (In3+, Fe3+, and Cr3+) occupy two crystallographically independent octahedral sites, M(1) and M(2). The layers are formed of M(2)O6 octahedra and (HPO4) tetrahedra sharing corners, with M(1)O6 octahedra serving as pillars between adjacent layers. Single crystal study of Ba3(In0.5Fe0.5)(HPO4)6 shows that indium and iron segregate between the two metal sites with Fe occupying primarily the site M(1) and In located primarily in M(2) site. Interactions between the building units within the layers occur through hydrogen bonding. Barium cations are located between the pillars, in 8-membered ring tunnels and are coordinated by 12 oxides. The phases loose three water molecules through condensation of six HXO4 groups to form Ba2M2(X2O7)3 at temperatures between 480 and 600 °C. Mössbauer spectroscopy shows the presence of high-spin Fe3+ in octahedral coordination. 相似文献