共查询到20条相似文献,搜索用时 31 毫秒
1.
Guixin Wang Kangping Yan Zuolong Yu Meizhen Qu 《Journal of Applied Electrochemistry》2010,40(4):821-831
A modified ball-milling-assisted green solid reaction method is provided to prepare Li4Ti5O12/C composite materials with controllable carbon content. Thermal analysis was utilized to investigate the reaction process
and the temperature for eliminating carbon. The added carbon and the time for eliminating the carbon can affect the particle
size and greatly improve the cycling stability and rate performance. Besides, the particle size can reach ~60 nm, the Li4Ti5O12 eliminated carbon at 600 °C has ~178% higher discharge capacity than that without added carbon after 500 cycles under the
same conditions. As for the Li4Ti5O12 with a carbon weight of 10.6%, the second discharge capacity can reach 177.2 and 120.8 mAh g−1 at 1 and 20 C rates, respectively. Its discharge capacity still remains at 118.3 mAh g−1 after 500 cycles under various current rates. The results are comparable to those of the reported Li4Ti5O12/PAS composite. 相似文献
2.
Jea Hyeok Ryu Bo Gun Park Seuk Buom Kim Yong Joon Park 《Journal of Applied Electrochemistry》2009,39(7):1059-1066
The effect of surface area on the electrochemical properties and thermal stability of Li[Ni0.2Li0.2Mn0.6]O2 powders was characterized using a charge/discharge cycler and DSC (Differential Scanning Calorimeter). The surface area of
the samples was successfully controlled from ~4.0 to ~11.7 m2 g−1 by changing the molar ratio of the nitrate/acetate sources and adding an organic solvent such as acetic acid or glucose.
The discharge capacity and rate capability was almost linearly increased with increase in surface area of the sample powder.
A sample with a large surface area of 9.6–11.7 m2 g−1 delivered a high discharge capacity of ~250 mAh g−1 at a 0.2 C rate and maintained 62–63% of its capacity at a 6 C rate versus a 0.2 C rate. According to the DSC analysis, heat
generation by thermal reaction between the charged electrode and electrolyte was not critically dependent on the surface area.
Instead, it was closely related to the type of organic solvent employed in the fabrication process of the powder. 相似文献
3.
Hong Yan Chu Qiong Yu Lai Yan Jing Hao Yan Zhao Xiao Yun Xu 《Journal of Applied Electrochemistry》2009,39(10):2007-2013
Spinel Li4Mn5O12 was prepared by a sol–gel method. The manganese oxide and activated carbon composite (MnO2-AC) were prepared by a method in which KMnO4 was reduced by activated carbon (AC). The products were characterized by XRD and FTIR. The hybrid supercapacitor was fabricated
with Li4Mn5O12 and MnO2-AC, which were used as materials of the two electrodes. The pseudocapacitance performance of the Li4Mn5O12/MnO2-AC hybrid supercapacitor was studied in various aqueous electrolytes. Electrochemical properties of the Li4Mn5O12/MnO2-AC hybrid supercapacitor were studied by using cyclic voltammetry, electrochemical impedance measurement, and galvanostatic
charge/discharge tests. The results show that the hybrid supercapacitor has electrochemical capacitance performance. The charge/discharge
test showed that the specific capacitance of 51.3 F g−1 was obtained within potential range of 0–1.3 V at a charge/discharge current density of 100 mA g−1 in 1 mol L−1 Li2SO4 solution. The charge/discharge mechanism of Li4Mn5O12 and MnO2-AC was discussed. 相似文献
4.
D. Zhang X. L. Wang Y. J. Mai X. H. Xia C. D. Gu J. P. Tu 《Journal of Applied Electrochemistry》2012,42(4):263-269
Iron disulfide (FeS2) powders were successfully synthesized by hydrothermal method. Cetyltrimethylammonium bromide (CTAB) had a great influence
on the morphology, particle size, and electrochemical performance of the FeS2 powders. The as-synthesized FeS2 particles with CTAB had diameters of 2–4 μm and showed a sphere-like structure with sawtooth, while the counterpart prepared
without CTAB exhibited irregular morphology with diameters in the range of 0.1–0.4 μm. As anode materials for Li-ion batteries,
their electrochemical performances were investigated by galvanostatic charge–discharge test and electrochemical impedance
spectrum. The FeS2 powder synthesized with CTAB can sustain 459 and 413 mAh g−1 at 89 and 445 mA g−1 after 35 cycles, respectively, much higher than those prepared without CTAB (411 and 316 mAh g−1). The enhanced rate capability and cycling stability were attributed to the less-hindered surface layer and better electrical
contact from the sawtooth-like surface and micro-sized sphere morphology, which led to enhanced process kinetics. 相似文献
5.
The nanosized Mn3O4 particles were prepared by microwave-assisted reflux synthesis method. The prepared sample was characterized using various techniques such as X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), Raman analysis, and transmission electron microscopy (TEM). Electrochemical properties of Mn3O4 nanoparticles were investigated using cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge analysis in different electrolytes such as 1 M KCl, 1 M Na2SO4, 1 M NaNO3, and 6 M KOH electrolytes. XRD pattern reveals the formation of single-phase Mn3O4 nanoparticles. The FT-IR and Raman analysis also assert the formation of Mn3O4 nanoparticles. The TEM image shows the spherical shape particles with less than 50 nm sizes. Among all the electrolytes, the Mn3O4 nanoparticles possess maximum specific capacitance of 94 F g−1 in 6 M KOH electrolyte calculated from CV. The order of capacitance obtained by various electrolytes is 6 M KOH > 1 M KCl > 1 M NaNO3 > 1 M Na2SO4. The EIS and galvanostatic charge–discharge results further substantiate with the CV results. The cycling stability of Mn3O4 electrode reveals that the prepared Mn3O4 nanoparticles are a suitable electrode material for supercapacitor application. 相似文献
6.
With a view to minimize the unavoidable large volume changes of tin based Cu6Sn5 alloy anodes, a composite Cu6Sn5/graphite anode has been prepared via. a mechanical alloying process and subsequently coated with disordered carbon through
pyrolysis of PVC. Phase pure products with better crystallinity and preferred surface morphology were obtained, as evident
from PXRD and SEM respectively. Upon electrochemical charge-discharge, the intermetallic Cu6Sn5 alloy-graphite composite anode was found to exhibit an enhanced initial discharge capacity of 564 mAh g−1 followed by significant capacity fade (>20%) especially after five cycles. On the other hand, carbon coated Cu6Sn5 alloy-graphite composite demonstrated promising electrochemical properties such as steady reversible capacity (∼200 mAh g−1), excellent cycle performance (<5% capacity fade) and high coulombic efficiency (∼98%) via. significant reduction of volume
changes. The carbon coating offers buffering and conductive actions on the anode active material and thereby enhances the
electrochemical behavior of carbon coated Cu6Sn5 alloy/graphite composite anode material. 相似文献
7.
A. M. Starik B. I. Lukhovitskii N. S. Titova 《Combustion, Explosion, and Shock Waves》2008,44(3):249-261
The possibility of intensification of ignition of a methane-oxygen mixture in a supersonic flow behind the front of an oblique
shock wave by means of excitation of O2 molecules to the states a
1Δg and b
1Σg+ in an electric discharge is discussed. Through numerical simulations, activation of O2 molecules by an electric discharge is demonstrated to speed up chain reactions in the CH4-O2 mixture and to reduce the induction-zone length. Even a small amount of energy input to O2 molecules in the discharge (≈3·0−2 J/cm3) can reduce the ignition-delay length by a factor of hundreds and initiate combustion at distances of ≈1 m from the discharge
zone at comparatively low temperatures of the gas behind the front (≈1000 K) and moderate pressures (≈105 Pa). Excitation of O2 molecules by an electric discharge is much more efficient than simple heating of the mixture.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 3, pp. 3–16, May–June, 2008. 相似文献
8.
Yongli Cui Zheng Yuan Wenjing Bao Quanchao Zhuang Zhi Sun 《Journal of Applied Electrochemistry》2012,42(10):883-891
Spinel LiMn2O4 was prepared by sol–gel method and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscope. Cyclic voltammogram, galvanostatic charge/discharge testing, and electrochemical impedance spectroscopy (EIS) techniques were employed to evaluate the electrochemical behaviors of LiMn2O4 in 1 M Li2SO4 aqueous solution. Two redox couples at E SCE = 0.78/0.73 and 0.91/0.85 V were observed, corresponding to those found at E Li/Li += 4.05/3.95 and 4.06/4.18 V in organic electrolyte. The discharge capacity of pristine LiMn2O4 in aqueous electrolyte was 57.57 mAh g−1, and the capacity retention of the electrode is 53.7 % after 60 cycles. Only one semicircle emerged in EIS at different potentials in aqueous electrolyte, while three semicircles were observed in organic electrolytes. There was no solid electrolyte interface film on the surface of spinel LiMn2O4 electrode in aqueous electrolyte. The change of kinetic parameters of lithium ion insertion in spinel LiMn2O4 with potential in aqueous electrolyte for initial charge process was discussed in detail, and a suitable model was proposed to explain the impedance response of the insertion materials of lithium ion batteries in different electrolytes. 相似文献
9.
Co3O4 nanorods have been successfully synthesized by thermal decomposition of the precursor prepared via a facile and efficient
microwave-assisted hydrothermal method, using cetyltrimethylammonium bromide (CTAB) with ordered chain structures as soft
template for the first time. The obtained Co3O4 was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM),
and electrochemical measurements. The results demonstrate that the as-synthesized nanorods are single crystalline with an
average diameter of about 20 to 50 nm and length up to several micrometers. Preliminary electrochemical studies, including
cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) measurements, are
carried out in 6 M KOH electrolyte. Specific capacitance of 456 F g−1 for a single electrode could be achieved even after 500 cycles, suggesting its potential application in electrochemical capacitors.
This promising method could provide a universal green chemistry approach to synthesize other low-cost and environmentally
friendly transition metal hydroxide or oxide. 相似文献
10.
N. Jayaprakash N. Kalaiselvi C. H. Doh Gangulibabu D. Bhuvaneswari 《Journal of Applied Electrochemistry》2010,40(12):2193-2202
A series of LiM1xM2yMn2−x−yO3.8F0.2 (M1 = Cr, M2 = V; x = y = 0.2) cathodes, viz., LiMn2O3.8F0.2, LiCr0.2Mn1.8O3.8F0.2 and LiCr0.2V0.2Mn1.6O3.8F0.2 along with native LiMn2O4 have been synthesized by Citric Acid assisted Modified (CAM) sol–gel method, with a view to understand the effect of synthesis
methodology and the effect of dual category dopants, viz., anion and/or cation upon spinel cathodes individually. An acceptable
capacity retention (94%) observed up to 50 cycles for native LiMn2O4 cathodes is attributed to the significance of CAM sol–gel method. Similarly, the encouraging charge–discharge results of
LiMn2O3.8F0.2 (130 mAh g−1) and LiCr0.2Mn1.8O3.8F0.2 (142 mAh g−1) cathodes revealed a possible augmentation in the reversible capacity behavior of the spinels upon F− substitution at 32e site and the simultaneous substitution of Cr3+ and F− at 16d and 32e sites respectively. 相似文献
11.
Feng Wu Huaquan Lu Yuefeng Su Ning Li Liying Bao Shi Chen 《Journal of Applied Electrochemistry》2010,40(4):783-789
The Li-rich layered cathode material, Li[Ni0.2Li0.2Mn0.6]O2, was synthesized via a “mixed oxalate” method, and its structural and electrochemical properties were compared with the same
material synthesized by the sol–gel method. X-ray diffraction (XRD) shows that the synthesized powders have a layered O3–LiCoO2-type structure with the R-3m symmetry. X-ray photoelectron spectroscopy (XPS) indicates that in the above material, Ni and Mn exist in the oxidation states
of +2 and +4, respectively. The layered material exhibits an excellent electrochemical performance. Its discharge capacity
increases gradually from the initial value of 228 mA hg−1 to a stable capacity of over 260 mA hg−1 after the 10th cycle. It delivers a larger capacity of 258 mA hg−1 at the 30th cycle. The dQ/dV curves suggest that the increasing capacity results from the redox-reaction of Mn4+/Mn3+. 相似文献
12.
Yourong Wang Yafang Chen Siqing Cheng Liangnian He 《Korean Journal of Chemical Engineering》2011,28(3):964-968
Olivine structure LiMnPO4/C as cathode materials for Li-ion batteries were synthesized via a simple solidstate reaction. Improvement of the electrochemical
performance of LiMnPO4/C cathode material was realized significantly by the method of doping Zn. The obtained LiMn0.95Zn0.05PO4/C electrode material was studied by the measurements of X-ray diffraction pattern, scanning electronic microscopy, electrochemical
impedance spectroscopy and electrochemical performance. The results indicate that the LiMn0.95Zn0.05PO4/C materials exhibit discharge specific capacity of 140.2 mA h g−1 at 0.02 C rate and better rate capability. These excellent results are elucidated by EIS test, which showed that there was
the decrease of charge transfer resistance and faster lithium-ion diffusion in LiMnPO4/C cathode materials after Zn doping. 相似文献
13.
E. Marin A. Lanzutti L. Guzman L. Fedrizzi 《Journal of Coatings Technology and Research》2012,9(3):347-355
In this study, innovative TiO2/Al2O3 mono/multilayers were applied by atomic layer depositions (ALD) on ASTM-AZ-31 magnesium/aluminum alloy to enhance its well-known
scarce corrosion resistance. Four different configurations of ALD layers were tested: single TiO2 layer, single Al2O3 layer, Al2O3/TiO2 bilayer and Al2O3/TiO2/Al2O3/TiO2 multilayer deposited using Al[(CH3)]3 (trimethylaluminum, TMA), and TiCl4 and H2O precursors. All depositions were performed at 120°C to obtain an amorphous-like structure of both oxide layers. The four
coatings were then investigated using different techniques, such as scanning electron microscope (SEM), stylus profilometer,
glow discharge optical emission spectrometry (GDOES) and polarization curves in 0.05-M NaCl solution. The thickness of all
the coatings was around 100 nm. The layers compositions were successfully investigated by the GDOES technique, although obtained
data seem to be affected by substrate roughness and differences in sputtering rates between ceramic oxides and metallic magnesium
alloy. Corrosion resistance showed to be strongly enhanced by the nanometric coatings, giving lower corrosion current densities
in 0.05-M NaCl media with respect to the uncoated substrate (from 10−4 to 10−6 A/cm2 for the single layers and from 10−4 to 10−8 A/cm2 for the bi- and multilayers). All polarization curves on coated samples also showed a passive region, wider for the bi-layer
(from −0.58 to −0.43 V with respect to Ag/AgCl) and multilayer (from −0.53 to −0.38 V with respect to Ag/AgCl) structures. 相似文献
14.
Yong-Li Cui Zhi Sun Quan-Chao Zhuang 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(4):893-899
The LiNi0.5Mn1.5O4 cathode material for high power lithium-ion battery is successfully synthesized by sol–gel method. The structure, the morphology
and the electrochemical characteristics of the compound are studied by X-ray diffraction (XRD), a field emission scanning
electron microscope (FE-SEM), cyclic voltammogram (CV) and charge–discharge techniques, respectively. The results indicate
that LiNi0.5Mn1.5O4 sample has cubic spinel structure and its particles crystallized well with submicro size. There are a higher voltage plateau
around 4.7 V and a lower voltage plateau above 4 V at 3.3–5.0 V in the charge–discharge curves of LiNi0.5Mn1.5O4, corresponding to two redox peaks of Ni2+/Ni4+ and Mn3+/Mn4+ of its CV respectively. The LiNi0.5Mn1.5O4 with ordered Fd3m space group has 150.57 mAh g−1 initial charge capacity and 139.57 mAh g−1 initial discharge capacity, showing excellent electrochemical performance. A short arc at more high frequency zone from 4.4 V
potential emerges in electrochemical impedance spectroscopy (EIS), attributing to oxidative decomposition of the electrolyte
at high voltage. The equivalent circuit selected could fit the EIS experiment data very well. 相似文献
15.
Ben Niu En-lei Qi Jie-qiang Wang 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(4):906-912
A novel method was used to synthesize LiFePO4, using inorganic salts as raw materials, and PEG-4000 as the surfactant. The results show that LiFePO4 powders with various morphologies were prepared by microwave hydrothermal method, and it is very important to synthesize
the LiFePO4 powders with well-defined shape and size controlling experimental conditions, such as the solution pH and surfactant. The
modified preparation of LiFePO4 was built. The coating carbon on LiFePO4 powders as a core–shell structure was carried out by annealing in 3%H2/97%N2 at 700 °C for 2 h. As a result, the diffusion coefficient of lithium ions can be increased, and the reversibility of lithium
intercalation and deintercalation can be improved markedly. In addition, LiMn0.08Fe0.92PO4 powders were synthesized, which were observed in an ordered olivine structure, but great changes occurred in morphology.
Doping Mn2+ does not destroy the lattice structure and enlarges the lattice volume. Consequently, the conductivity can be enhanced, and
the lithium ion diffusion coefficient can be boosted. Initial discharge capacity is improved obviously, and increases to 99.6 mA h g−1 and 93.8 mA h g−1 respectively. The microwave assisted hydrothermal approach presented here opens a potential avenue to explore the synthesis
of LiFePO4 powders. 相似文献
16.
Liangyu Gong Xiaohong Liu Linghao Su 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(4):866-870
Nickel hydroxide nanosheets were successfully synthesized by facile solvothermal method without any template. The structure
and morphology of the as-prepared sample were characterized by X-ray diffraction, Fourier transform infrared spectroscopy
and transmission electron microscopy. The observations revealed the formation of hexagonal phase β-Ni(OH)2 nanosheets with an average diameter of about 100–120 nm. Electrochemical studies were carried out using cyclic voltammetry
and galvanostatic charge–discharge tests, respectively. A maximum specific capacitance of 2,342 F g−1, which is the highest reported for a β-Ni(OH)2 electrode, could be achieved in 6 mol L−1 KOH electrolyte within the potential range of 0–0.50 V (vs. SCE) for the obtained β-Ni(OH)2 electrode at 0.4 A g−1, suggesting its potential application in the electrode material for electrochemical capacitors. 相似文献
17.
Pristine activated carbon (AcC) was oxidized by H2O2 under ultrasonic conditions. Compared with pristine AcC, the H2O2-oxidized AC possesses higher accumulation ability to trace levels of Cd2+. Based on this, a highly sensitive, simple and rapid electrochemical method was developed for the determination of Cd2+. In 0.01 mol L−1 HClO4 solution, Cd2+ was effectively accumulated at the surface of H2O2-oxidized AcC modified paste electrode, and then reduced to Cd under −1.10 V. During the following potential sweep from −1.10
to −0.50 V, reduced Cd was oxidized and a sensitive stripping peak appears at −0.77 V. The stripping peak current of Cd2+ changes linearly with concentration over the range 5.0 × 10−8 to 5.0 × 10−6 mol L−1. The limit of detection was found to be 3.0 × 10−8 mol L−1 for 2-min accumulation. Finally, this new sensing method was successfully used to detect Cd2+ in waste water samples. 相似文献
18.
Weiyong Zou Li Wang Baoyi Lu Hong Li Hongyu Chen 《Journal of Applied Electrochemistry》2009,39(10):2015-2020
The electrochemical assembly of [Ru(bpy)2tatp]2+ (where bpy = 2,2′-bipyridine, tatp = 1,4,8,9-tetra-aza-triphenylene) on the multi-walled carbon nanotubes-modified glassy
carbon electrode (MWNTs/GC) in the presence of anionic and cationic surfactants has been investigated. A diffusion-controlled
wave and three prewaves are exhibited on the differential pulse voltammogram of [Ru(bpy)2tatp]2+. The formal potential of the prewaves is found to be much negative than that of the diffusion-controlled wave. An appropriate
amount of anionic surfactants including dihexadecyl phosphate (DHP) and deoxyribonucleic acid (DNA) can prompt the assembly
of [Ru(bpy)2tatp]2+ on the MWNTs/GC electrode by using the method of repetitive voltammetric sweeping. In contrast, cationic surfactant such
as hexadecyl trismethyl ammonium chrolide (HTAC) dispersed on the MWNTs surface is found to inhibit the assembly of [Ru(bpy)2tatp]2+. Meanwhile, the assembled principle of [Ru(bpy)2tatp]2+ on the MWNTs/GC electrode with the participation of surfactants is discussed in detail. 相似文献
19.
Shiquan Wang Guohua Li Guodong Du Li Li Xueya Jiang Chuanqi Feng Zaiping Guo Seungjoo Kim 《Nanoscale research letters》2010,5(8):1301-1306
Cobalt-doped tungsten disulfide nanorods were synthesized by an approach involving exfoliation, intercalation, and the hydrothermal
process, using commercial WS2 powder as the precursor and n-butyllithium as the exfoliating reagent. XRD results indicate that the crystal phase of the sample is 2H-WS2. TEM images show that the sample consists of bamboo-like nanorods with a diameter of around 20 nm and a length of about 200 nm.
The Co-doped WS2 nanorods exhibit the reversible capacity of 568 mAh g−1 in a voltage range of 0.01–3.0 V versus Li/Li+. As an electrode material for the lithium battery, the Co-doped WS2 nanorods show enhanced charge capacity and cycling stability compared with the raw WS2 powder. 相似文献
20.
F. Lian P. Axmann C. Stinner Q. G. Liu M. Wohlfahrt-Mehrens 《Journal of Applied Electrochemistry》2008,38(5):613-617
Positive electrode material LiNi1/2Mn1/2O2 was synthesized via the carbonate co-precipitation method and the hydroxide precipitation route to study the effects of the
precursor on its structural and electrochemical properties. The results of X-ray diffraction and Rietveld refinement show
that the carbonate precursor of Ni2+ and Mn2+ exhibits one phase at a pH of 8.5, while the hydroxide deposit separates into Ni(OH)2 and Mn(OH)2 phases under the same experimental conditions. LiNi1/2Mn1/2O2 material prepared from the hydroxide precursor shows 8.9% Li/Ni exchange and a large capacity loss of 11.3% in the first
10 cycles. By contrast, more uniform distribution of transition metal ions and stable Mn2+ in the carbonate precursor contribute to only 7.8% Li/Ni disorder in the obtained LiNi1/2Mn1/2O2, which delivers a reversible capacity of about 182 mAh g−1 at a current rate of 14 mA g−1 between 2.5 and 4.8 V. 相似文献