共查询到20条相似文献,搜索用时 15 毫秒
1.
This paper describes the preparation and characterization of a high-voltage lithium-ion battery based on Sn-decorated reduced graphene oxide and LiNi0.5Mn1.5O4 as the anode and cathode active materials, respectively. The Sn-decorated reduced graphene oxide is prepared using a microwave-assisted hydrothermal synthesis method followed by reduction at high temperature of a mixture of (C6H5)2SnCl2 and graphene oxide. The so-obtained anode material is characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and electron diffraction spectroscopy. The LiNi0.5Mn1.5O4 is a commercially available product. The two materials are used to prepare composite electrodes, and their electrochemical properties are investigated by galvanostatic charge/discharge cycles at various current densities in lithium cells. The electrodes are then used to assemble a high-voltage lithium-ion cell, and the cell is tested to evaluate its performance as a function of discharge rate and cycle number. 相似文献
2.
M. I. Pantyukhina M. S. Shchelkanova A. P. Stepanov A. L. Buzlukov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(5):653-655
Lithium ionic conductivity and spin-lattice relaxation rates were measured in Li8ZrO6 and Li6Zr2O7 solid electrolytes. It was found that the Li8ZrO6 solid electrolyte undergoes a transition to the superionic state in the temperature range 673–703 K. It was shown that Li+ ions are mobile in particular lattice positions of the Li6Zr2O7 phase, and that ionic conductivity is monotonic at an activation energy of 79.4 kJ/mol. 相似文献
3.
A. N. Vasil’ev O. L. Ignatchik A. N. Sokolov Z. Hiroi M. Isobe Y. Ueda 《JETP Letters》2003,78(9):551-554
Formation of a long-range magnetic order is observed at low temperatures in NaCrSi2O6 and NaCrGe2O6 quasi-one-dimensional metal oxide compounds with a pyroxene structure. The first of these compounds, NaCrSi2O6, is an antiferromagnet with the Néel temperature T N =3 K, while the second, NaCrGe2O6, is a ferromagnet with the Curie temperature T C =6 K. From the measurements of magnetization and specific heat of these compounds, the main parameters of their magnetic subsystems are determined. In NaCrSi2O6, a spin-flip transition is observed. A change in the type of magnetic order that accompanies the replacement of Si by Ge can be attributed to a change in the parameters of the competing direct antiferromagnetic Cr-Cr and indirect ferromagnetic Cr-O-Cr interactions in isolated chains of CrO6 octahedra. 相似文献
4.
Transverse flow transversely excited (TFTE) CO2 lasers are easily scalable to multikilowatt level. The laser power can be scaled up by increasing the volumetric gas flow
and discharge volume. It was observed in a TFTE CW CO2 laser having single row of pins as an anode and tubular cathode that the laser power was not increasing when the discharge
volume and the gas volumetric flow were increased by increasing the electrode separation keeping the gas flow velocity constant.
The discharge voltage too remained almost constant with the change of electrode separation at the same gas flow velocity.
This necessitated revision of the scaling laws for designing this type of high power CO2 laser. Experimental results of laser performance for different electrode separations are discussed and the modifications
in the scaling laws are presented. 相似文献
5.
A. Akrap R. Gaal L. Forró 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(3):287-291
We investigate the pressure and temperature behavior of current-dependent resistivity of β-SrV6O15. We observe a switching between states of different resistivities in the insulating state of β-SrV6O15. In the low pressure phase, the resistive switching appears at temperatures below the semiconductor-insulator transition.
In the high pressure phase, under ~1.6 GPa, the switching appears in the temperature range of the phase transition. The existence
of switching may imply an important role of strontium off-stoichiometry for the electrical transport in β-SrV6O15. No electric-field-induced enhancement of the conductivity is observed. However, the conduction is significantly nonlinear
under ~1.6 GPa, indicating that the charge order pattern in the high pressure phase is considerably different from that of
the low pressure phase. 相似文献
6.
We have carried out experimental and theoretical
studies on electron scattering from the C3H6 isomers and
C3F6 molecules and we report on total, differential as well
as theoretical integral elastic cross-sections for these
molecules. Vibrational excitation functions are also presented for
the typical vibrational peaks in C3H6 and cyclo-C3H6
for the angle of 90○, impact energy range of 1–16 eV
and loss energies of 0.12 eV and 0.13 eV, respectively. In the
cross-sections, clear differences in peak positions and magnitudes
between the C3H6 isomers can be viewed as the isomer effect.
The same is observed between C3H6 and C3F6 in a clear
manifestation of the fluorination effect. The resemblance of the
π* shape resonance in the cross-sections, observed at about
2.2 eV for C3H6 and 3.5 eV for C3F6, to those in
C2H4 and C2F4 clearly points to the effect of the
double bond in the molecular structures for these molecules.
Theoretical analysis is performed to provide rationales for the
scattering dynamics. 相似文献
7.
Juntian Fan Tao Dong Daliang Fang Xuefeng Li Xian’en Mo Kaihua Wen Shimou Chen Suojiang Zhang 《Ionics》2018,24(10):2965-2972
In this work, Li2ZrF6, a lithium salt additive, is reported to improve the interface stability of LiNi0.5Mn1.5O4 (LNMO)/electrolyte interface under high voltage (4.9 V vs Li/Li+). Li2ZrF6 is an effective additive to serve as an in situ surface coating material for high-voltage LNMO half cells. A protective SEI layer is formed on the electrode surface due to the involvement of Li2ZrF6 during the formation of SEI layer. Charge/discharge tests show that 0.15 mol L?1 Li2ZrF6 is the optimal concentration for the LiNi0.5Mn1.5O4 electrode and it can improve the cycling performance and rate property of LNMO/Li half cells. The results obtained by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) demonstrate that Li2ZrF6 can facilitate the formation of a thin, uniform, and stable solid electrolyte interface (SEI) layer. This layer inhibits the oxidation decomposition of the electrolyte and suppresses the dissolution of the cathode materials, resulting in improved electrochemical performances. 相似文献
8.
V. A. Stefanovich L. M. Suslikov Z. P. Gad’mashi E. Yu. Peresh V. I. Sidei O. V. Zubaka I. V. Galagovets 《Physics of the Solid State》2004,46(6):1024-1026
Raman scattering in Rb2TeBr6 and Cs2TeBr6 crystals is studied. The phonon spectra of the crystals are calculated using the factor group method. The number of Raman-active modes, their symmetries, and selection rules are found. Observed Raman spectrum lines are identified with atomic vibration modes of the crystal. 相似文献
9.
The nanostructured Na3V2(PO4)3 (NVP) cathode material has been synthesized using the sol-gel route for different molar fractions of citric acid as a carbon source during the synthesis. The nanostructured NVP as cores with carbonic shell structures are fabricated with two different citric acid molar ratios. The thermal treatment has been optimized to convert the amorphous carbon shell into graphitic carbon to realize the better electrical conductivity and thus effective electron transfer during the electrochemical charge transfer process. The X-ray diffraction measurements confirmed the rhombohedral crystallographic phase (space group R-3c) with average crystallite size ~28 ± 5 nm. The coin cells are assembled in a hybrid rechargeable electrochemical cell configuration with lithium as a counter electrode and LiPF6-EC:DEC:DMC (1:1:1 ratio) as the electrolyte. The electrochemical charge/discharge measurements are carried out at C/10 and C/20 rates and the measured specific capacities are 80 and 120 mAhg?1 for samples with lower and higher citric acid molar ratios, respectively. The studies suggest that NVP can be used as an effective cathode material in hybrid electrochemical cells, and a higher concentration of citric acid may result in the effective carbonic shell for optimal electron transfer and thus enhanced electrochemical performance. 相似文献
10.
Li-rich layered-layered-Spinel structure spherical Li1.3Mn4/6Ni1/6Co1/6O2.40 particles was successfully prepared and coated with a uniform layer by a two-step co-precipitation method and evaluated in lithium cells. The structures and electrochemical properties of pristine Li1.3Mn4/6Ni1/6Co1/6O2.40 and AlF3-coated Li1.3Mn4/6Ni1/6Co1/6O2.40 were characterized. When the coating amount was 2 wt%, the cathode showed the best cycling performance and rate capability compared to others. The AlF3-coated Li1.3Mn4/6Ni1/6Co1/6O2.40 Li-ion cell cathode had a capacity retention of 90.07 % after 50 cycles at 0.5 C over 2.0–4.8 V, while the pristine Li1.3Mn4/6Ni1/6Co1/6O2.40 exhibited capacity retention of only 80.73 %. Moreover, the rate capability and cyclic performance also improved. Electrochemical impedance spectroscopy testing revealed that the improved electrochemical performance might attribute to the AlF3 coating layer which can suppress the increase of impedance during the charging and discharging process by preventing direct contact between the highly delithiated active material and electrolyte. 相似文献
11.
AlF3-coating is attempted to improve the performance of LiNi0.5Mn1.5O4 cathode materials for Li-ion batteries. The prepared powders are characterized by scanning electron microscope, powder X-ray
diffraction, charge/discharge, and impedance. The coated LiNi0.5Mn1.5O4 samples show higher discharge capacity, better rate capability, and higher capacity retention than the uncoated samples.
Among the coated samples, 1.0 mol% AlF3-coated sample shows highest capacity after charge–discharged at 30 mA/g for 3 cycles, but 4.0 mol% coated sample exhibits
the highest capacity and cycling stability when cycled at high rate of 150 and 300 mA/g. The 40th cycle discharge capacity
at 300 mA/g current still remains 114.8 mAh/g for 4.0 mol% AlF3-coated LiNi0.5Mn1.5O4, while only 84.3 mAh/g for the uncoated sample. 相似文献
12.
D. N. Sandzhiev K. G. Abdulvakhidov V. Yu. Shonov I. P. Raevskii 《Technical Physics》2009,54(11):1622-1625
The structure, microstructure, and temperature and field dependences of the dielectric properties of thin (0.5–8.0μm) Sn2P2S6 ferroelectric films deposited onto glass and aluminum foil substrates by thermal vacuum evaporation in a quasi-closed volume
are studied. The film-thickness and frequency dependences of the dielectric properties and the unipolarity of the C–V characteristics are explained by the presence of near-surface Schottky-type barrier layers. 相似文献
13.
The layered Li-rich Mn-based cathode materials Li[Li0.2Mn0.54Ni0.13Co0.13]O2 were prepared by using co-precipitation technique at different temperatures, and their crystal microstructure and particle morphology were observed and analyzed by XRD and SEM. The electrochemical properties of these samples were investigated by using charge-discharge tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), respectively. The results indicated that all samples are of high purity. When the precursors were co-precipitated at 50 °C, their cathode materials have the most uniform and full particles and exhibit the highest initial discharge capacity (289.4 mAh/g at 0.1C), the best cycle stability (capacity retention rate of 91.2 % after 100 cycles at 0.5C), and the best rate performance. The EIS results show that the lower charge transfer resistance of 50 °C sample is responsible for its superior discharge capacity and rate performance. 相似文献
14.
P. A. Rodnyĭ I. V. Berezovskaya A. S. Voloshinovskii G. B. Stryganyuk A. S. Potapov 《Optics and Spectroscopy》2003,94(4):550-555
Spectral and kinetic characteristics of the luminescence and luminescence excitation spectra of polycrystalline SrB4O7:Pr (1%) and SrB6O10:Pr (1%) samples are studied at 150–170 K. The samples show an intense luminescence band in the vicinity of 405 nm (1 S 0→1 I 6 transitions of Pr3+) and shorter wavelength bands also assigned to transitions from the 1 S 0 level. The main luminescence decay constant is ~2×10?7 s. The excitation spectra of the 1 S 0 luminescence in these crystals are significantly different. The SrB4O7:Pr crystal shows three well-resolved bands at 6.14, 6.55, and 6.91 eV in the region of the 4f 2→4f 15d transitions and a complex structure in the region of interband transitions (7.1–20 eV), whereas the SrB6O10:Pr crystal shows a weakly structured band at 6.31 eV and no excitation in the region of the interband transitions. The physical mechanisms that may be responsible for the observed features of the spectra are discussed. 相似文献
15.
Polymer composite comprising polyvinylidene fluoride (PVDF) and potassium hexatitante (K2Ti6O13) was synthesized by solution casting. The effect of K2Ti6O13 on surface, thermal, and electrical properties of polymer composite were investigated. The addition of K2Ti6O13 with polymer leads to thermal degradation and transition of polymer composite from semi-crystalline to amorphous phase. The optimum results of contact angle for different loading wt% of K2Ti6O13 were directly correlated with the surface morphology. Our experimental results confirmed the incorporation of K2Ti6O13 in polymer by SEM micrographs. The evaluated dielectric properties (ε' = 424; tan δ = 2.14 at 130 °C and 100 Hz frequency for 20 wt% loading of K2Ti6O13) for polymer composite are higher in compared to pure polymer. The enhancement in dielectric constant and changing the surface properties of polymer composite can be used for the development of electrochemical storage device applications. 相似文献
16.
Superconductivity was achieved in Ti-doped iron-arsenide compound Sr4Cr0.8Ti1.2O6Fe2As2 (abbreviated as Cr-FeAs-42622). The X-ray diffraction measurement shows that this material has a layered structure with the space group of P4/nmm, and with the lattice constants a = b = 3.9003 Å and c = 15.8376 Å. Clear diamagnetic signals in ac susceptibility data and zero-resistance in resistivity data were detected at about 6 K, confirming the occurrence of bulk superconductivity. Meanwhile we observed a superconducting transition in the resistive data with the onset transition temperature at 29.2 K, which may be induced by the nonuniform distribution of the Cr/Ti content in the FeAs-42622 phase. 相似文献
17.
I. V. Kedyk P. Mathey G. Gadret A. A. Grabar K. V. Fedyo I. M. Stoika I. P. Prits Y. M. Vysochanskii 《Applied physics. B, Lasers and optics》2008,92(4):549-554
In this work we report results on electro-physical, optical and photorefractive investigations for Sb-doped Sn2P2S6 crystals. The crystals are obtained by two methods: the vapour-transport technique and the Bridgman technique using stoichiometric
Sn2P2S6 composition with different amounts of antimony in the initial compound. The good optical quality of the crystals obtained
with the Bridgman technique is underlined. The dependences of the photorefractive two-beam coupling coefficient and the grating
build-up time are investigated at the wavelength of 633 nm. It is found that the sample doped with 1.5% of Sb is characterized
by an optimal combination of the main photorefractive parameters exhibiting a fairly high two-beam coupling coefficient (up
to 20 cm−1) and a short response time (1.3 ms) that is the shortest among all the previously studied Sn2P2S6 crystals in the red spectral region. 相似文献
18.
H. Martínez F. B. Yousif 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):493-498
This paper considers the electrical and optical characterization of glow
discharge pulsed plasma in N2/H2 gas mixtures at a pressures range
between 0.5 and 4.0 Torr and discharge current between 0.2 and 0.6 A.
Electron temperature and ion density measurements were performed employing a
double Langmuir probe. They were found to increase rapidly as the H2
percentage in the mixture was increased up to 20%. This increase slows
down as the H2 percentage in the gas mixture was increased above 20%
at the same pressure. Emission spectroscopy was employed to observe emission from the pulsed
plasma of a steady-state electric discharge. The discharge mainly emits
within the range 280–500 nm. The emission consists of N2 (C-X) 316, 336,
358 nm narrow peaks and a broad band with a maximum at λmax = 427 nm. Also lines of N2, N2
+ and NH excited states were
observed. All lines and bands have their maximum intensity at the discharge
current of 0.417 A. The intensities of the main bands and spectral lines are
determined as functions of the total pressure and discharge current.
Agreement with other theoretical and experimental groups was established. 相似文献
19.
V. Yu. Topolov 《Physics of the Solid State》2003,45(7):1295-1297
A new model of the elastic matching of phases is proposed, and heterophase structures near the morphotropic phase boundary in 0.10PbTiO3-0.90Pb(Zn1/3Nb2/3)O3 crystals are studied. Unique behavior of the unit cell parameters is found to favor the elastic matching of the ferroelectric tetragonal and orthorhombic phases under the conditions of complete or partial relaxation of internal mechanical stresses at a volume concentration ratio of these phases of about 20/80% and temperatures of T=20–300 K. Interrelations between the volume concentrations of different domain (twin) types and of the coexisting phases are analyzed. 相似文献
20.
The preparation of (La9.33−2x/3Sr
x
□0.67−x/3)Si6O24O2 (0 ≤ x ≤ 2) samples with different amounts of cation vacancies is reported. Structure and unit-cell parameters were deduced by Rietveld
analysis of XRD patterns. Structural features that enhance oxygen conductivity in Sr-doped apatites are discussed. Up to three
components were detected in 29Si MAS-NMR spectra which change with the amount and distribution of cation vacancies. In general, oxygen conductivity increases
with the amount of vacancies at La1 (6h) sites, passing through a maximum for x = 0.4. In the case of activation energy, a minimum is detected near x = 1.2, indicating that entropic and enthalpic change in different ways. The presence of cation vacancies should enhance oxygen
hopping along c-axis; however, the analysis of the frequency dependence of conductivity suggests that oxygen motions are produced along three
axes. 相似文献