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1.
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
2.
Carbon free LiFe1−x
Mn
x
PO4 (x = 0, 0.05, 0.1, 0.2, 0.4) cathode materials were prepared by a direct-hydrothermal process at 170 °C for 10 h. The structural
and electrochemical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy
(SEM), charge–discharge experiments, cyclic voltammetry (CV) and alternating current (AC) impedance spectroscopy. The electrochemical
performance of LiFePO4 prepared in this manner showed to be positively affected by Mn2+-substitution. Among the Mn2+-substitution samples, the LiFe0.9Mn0.1PO4 exhibited an initial discharge capacity of 141.4 mA h g−1 at 0.1 C, and the capacity fading is only 2.7% after 50 cycles. 相似文献
3.
Ke Du Luo-Hu Zhang Yan-Bing Cao Hong-wei Guo Zhong-Dong Peng Guo-Rong Hu 《Journal of Applied Electrochemistry》2011,41(11):1349-1355
LiFe0.4Mn0.6−x
Ni
x
PO4/C(x = 0, 0.05, 0.1, and 0.2) composite cathode materials for lithium ion batteries have been prepared by the co-precipitation
method using oxalic acid as a precipitator. The structure and morphology of precursors and products have been investigated.
Electrochemical tests demonstrate that LiFe0.4Mn0.55Ni0.05PO4 can deliver a specific capacity of 142 mAh g−1 at 0.1 C, and retains 133 mAh g−1 after 60 cycles. The rate performance of LiFe0.4Mn0.6PO4 is obviously improved by doping Ni. The capacity of LiFe0.4Mn0.55Ni0.05PO4 at 2 C is 110 mAh g−1. 相似文献
4.
Li ion conducting polymer electrolyte films were prepared based on poly(vinyl alcohol) (PVA) with 5, 10, 15, 20, 25 and 30 wt%
lithium iron phosphate (LiFePO4) salt using a solution-casting technique. X-ray diffraction (XRD) was used to determine the complexation of the polymer with
LiFePO4 salt. Differential scanning (DSC) calorimetry was used to determine the melting temperatures of the pure PVA and complexed
films. The maximum ionic conductivity was found to be 1.18 × 10−5 S cm−1 for (PVA:LiFePO4) (75:25) film, which increased to 3.12 × 10−5 S cm−1 upon the addition of propylene carbonate (PC) plasticizer at ambient temperature. The Li+ ion transport number was found to be 0.40 for (PVA: LiFePO4) (75:25) film using AC impedance and DC polarization methods. Dielectric studies were performed for these polymer electrolyte
films in the frequency range of 10 Hz to 10 MHz at different temperatures. The activation energies of the complexed films
were calculated from the dielectric loss tangent spectra and were found to be 0.35, 0.30, 0.27 and 0.28 eV. The cyclic voltammogram
(CV) curves of (PVA: LiFePO4) (75:25)+PC film exhibited higher specific capacities than those for other films. 相似文献
5.
《Ceramics International》2015,41(4):5370-5379
In this study, crystalline LiFe0.95VxNi0.05−xPO4/C powders are successfully synthesized using the hydrothermal method. Materials characterization and the electrochemical performance of LiFe0.95VxNi0.05−xPO4/C are investigated. The structure, morphology, and electrochemical performances of the prepared samples are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry, and AC impedance. The XRD pattern indicates that the LiFe0.95VxNi0.05−xPO4/C powders are single-phased with an orthorhombic olivine structure. The LiFe0.95V0.05PO4 sample has the highest capacity of 141 mAh g−1, which is 6% higher than that of pure LiFePO4 at 0.1 C. As the discharge rate increases to 10 C, the LiFe0.95V0.04Ni0.01PO4 sample has the highest capacity of 100 mAh g−1, which is 18% higher than that of pure LiFePO4. The CV results prove that the LiFe0.95V0.04Ni0.01PO4 cathode has high capacity and good cyclic performance caused by the high lithium-ion diffusion transport, which is improved by Ni and V doping. 相似文献
6.
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
7.
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
8.
Synthesis and characterization of high-density LiFePO4/C composites as cathode materials for lithium-ion batteries 总被引:1,自引:0,他引:1
To achieve a high-energy-density lithium electrode, high-density LiFePO4/C composite cathode material for a lithium-ion battery was synthesized using self-produced high-density FePO4 as a precursor, glucose as a C source, and Li2CO3 as a Li source, in a pipe furnace under an atmosphere of 5% H2-95% N2. The structure of the synthesized material was analyzed and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrochemical properties of the synthesized LiFePO4/carbon composite were investigated by cyclic voltammetry (CV) and the charge/discharge process. The tap-density of the synthesized LiFePO4/carbon composite powder with a carbon content of 7% reached 1.80 g m−3. The charge/discharge tests show that the cathode material has initial charge/discharge capacities of 190.5 and 167.0 mAh g−1, respectively, with a volume capacity of 300.6 mAh cm−3, at a 0.1C rate. At a rate of 5C, the LiFePO4/carbon composite shows a high discharge capacity of 98.3 mAh g−1 and a volume capacity of 176.94 mAh cm−3. 相似文献
9.
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
10.
Hong Quan Liu Gang Zhou Qiu Sun Yi Jie Gu Xin Bing Zhao 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(4):858-861
The xPbTe/Yb0.2Co4Sb12 compounds were prepared by the ball-milling and hot-pressed process. Electrical conductivity of the composite samples are
reduced with a increase in PbTe content; and, their temperature dependence coefficients show the positive values. The maximum
electrical conductivity of composite materials is ~80000 Sm−1 at 800 K. The Seebeck coefficient (absolute value) of the composite material is obviously improved with an increase in the
dispersed phase (PbTe) content; the Seebeck coefficient (absolute value) of the 10PbTe sample is ~260 μVK−1 at 700 K, which increases by 13.6% relative to that of the Yb0.2Co4Sb12 sample. The thermal conductivity of the composite samples is improved due to introduction of PbTe, and the thermal conductivity
of the 10PbTe sample is ~3 Wm−1 K−1 at 550 K. The maximum value of ZT is 0.78 at 700 K for the 2.5PbTe sample. 相似文献
11.
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
12.
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
13.
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
14.
LiFe1−xNdxPO4/C (x = 0-0.08) cathode material was synthesized using a solid-state reaction. The synthesis conditions were optimized by thermal analysis of the precursor and magnetic properties of LiFePO4/C. The structure and electrochemical performances of the material were studied using XRD, FE-SEM, EDS, electrochemical impedance spectroscopy and galvanostatic charge-discharge. The results show that a small amount of aliovalent Nd3+ ion-dopant substitution on Fe2+ ions can effectively reduce the particle size of LiFePO4/C. Cell parameters of LiFe1−xNdxPO4 (x = 0.04-0.08) were calculated, and the results showed that LiFe1−xNdxPO4/C had the same olivine structure as LiFePO4. LiFe0.4Nd0.6PO4/C delivers the discharge capacity of 165.2 mAh g−1 at rate of 0.2 C and the capacity retention rate is 92.8% after 100 cycles. Charge-transfer resistance decreases with the addition of glucose and Nd3+ ions. Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) was synthesized and PZS nanorods were used as a carbon source to coat LiFePO4. All of the results show that aliovalent doping substitution of Fe in LiFePO4 is well tolerated. 相似文献
15.
B. Bellal B. Hadjarab N. Benreguia Y. Bessekhouad M. Trari 《Journal of Applied Electrochemistry》2011,41(7):867-872
High quality crednerite CuMnO2 was prepared by solid state reaction at 950 °C under argon flow. The oxide crystallizes in a monoclinically distorted delafossite
structure associated to the static Jahn–Teller (J–T) effect of Mn3+ ion. Thermal analysis showed that it converts reversibly to spinel Cu
x
Mn3−x
O4 at ~420 °C in air and further heating reform the crednerite above 940 °C. CuMnO2 is p-type, narrow semiconductor band gap with a direct optical gap of 1.31 eV. It exhibits a long-term chemical stability in basic
medium (KOH 0.5 M), the semi logarithmic plot gave an exchange current density of 0.2 μA cm−2 and a corrosion potential of ~−0.1 VSCE. The electrochemical oxygen insertion/desinsertion is evidenced from the intensity–potential characteristics. The flat band
potential (V
fb = −0.26 VSCE) and the holes density (N
A
= 5.12 × 1018 cm−3) were determined, respectively, by extrapolating the curve C
−2
versus the potential to the intersection with C
−2
= 0 and from the slope of the Mott–Schottky plot. From photoelectrochemical measurements, the valence band formed from Cu-3d wave function is positioned at 5.24 ± 0.02 eV below vacuum. The Nyquist representation shows straight line in the high frequency
range with an angle of 65° ascribed to Warburg impedance originating from oxygen intercalation and compatible with a system
under mass transfer control. The electrochemical junction is modeled by an equivalent electrical circuit thanks to the Randles
model. 相似文献
16.
Shengyao Chen Changhuan Mi Linghao Su Bo Gao Qingbin Fu Xiaogang Zhang 《Journal of Applied Electrochemistry》2009,39(10):1943-1948
LiMn2O4/multi-walled carbon nanotubes (MWNTs) composite was synthesized by mechanical activation reaction followed by a heat-treatment
(500 °C). The LiMn2O4 and LiMn2O4/MWNTs as cathodes were investigated in 1 M Li2SO4 by cyclic voltammetry (CV), galvanostatic charge/discharge (GC), and electrochemical impedance spectroscopy (EIS). The LiMn2O4/MWNTs cathode delivered higher discharge capacity (117 mAh g−1) than LiMn2O4 (84.6 mAh g−1). Furthermore, the results from EIS showed that LiMn2O4/MWNTs had a faster kinetic process for lithium ion intercalation/de-intercalation than LiMn2O4. Besides, LiMn2O4/MWNTs had better cycling stability and rate capability than LiMn2O4, which was confirmed by GC testing. SEM images showed that a three-dimensional network structure was formed during the mechanical
activation, giving a decrease of particle size. 相似文献
17.
Deyu Wang 《Electrochimica acta》2005,50(14):2955-2958
LiFePO4 doped by bivalent cation in Fe-sites show improved rate performance and cyclic stability. Under 10 C rate at room temperature, the capacities of LiFe0.9M0.1PO4 (M = Ni, Co, Mg) maintain at 81.7, 90.4 and 88.7 mAh/g, respectively, in comparison with 53.7 mAh/g for undoped LiFePO4 and 54.8 mAh/g for carbon-coated LiFePO4 (LiFePO4/C). The capacity retention is 95% after 100 cycles for doped samples while this value is only 70% for LiFePO4 and LiFePO4/C. Such a significant improvement in electrochemical performance should be partially related to the enhanced electronic conductivities (from 2.2 × 10−9 to <2.5 × 10−7 S cm−1) and probably the mobility of Li+ ions in the doped samples. 相似文献
18.
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
19.
Spherical LiNi1/2Mn1/2O 2 powders were synthesized from LiOH . H2O and coprecipitated metal hydroxide, (Ni1/2Mn1/2)(OH)2. The average particle size of the powders was about 10 m and the size distribution was quite narrow due to the homogeneity of the metal hydroxide, (Ni1/2Mn1/2)(OH)2. The tap-density of the LiNi1/2Mn1/2O2 powders was approximately 2.2 g cm–3, which is comparable to the tap-density of commercial LiCoO2. The LiNi1/2Mn1/2 O2electrode delivered a discharge capacity of 152, 163, 183, and 189 mA h g–1 in the voltage ranges of 2.8–4.3, 2.8–4.4, 2.8–4.5, and 2.8–4.6 V, respectively, with good cyclability. Furthermore, Al(OH)3-coated LiNi1/2Mn1/2O2exhibited excellent cycling behavior and rate capability compared to the pristine electrode. 相似文献
20.
In this work, the oxidative polycondensation reaction conditions of benzylidene-4′-hydroxyanilene (B-4′-HA) were studied using oxidants such as air O2, H2O2 and NaOCl in an aqueous alkaline medium between 40 and 95 ○C. Oligo-benzylidene-4′-hydroxyanilene was characterized by 1H-NMR, FT-IR, UV-Vis, size exclusion chromatography (SEC) and elemental analysis techniques. The solubility of oligomer using organic solvents such as DMF, THF, DMSO, methanol, ethanol, CHCl3, CCl4, toluene, acetonitrile, ethyl acetate was investigated. According to air O2 oxidant (flow rate 8.5 L/h), the conversion of B-4′-HA was 82.0% in optimum conditions such as [B-4′-HA]0=[KOH]0=0.1015 mol/L at 50 ○C for 25 h. According to the SEC analysis, the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of O-B-4′-HA were found to be 1852 g mol−1, 3101 g mol−1 and 1.675; 2123 g mol−1, 4073 g mol−1 and 1.919; 2155 g mol−1, 4164 g mol−1 and 1.932, using air oxygen, NaOCl and H2O2 oxidants, respectively. Also, Thermo gravimetric analysis (TGA) showed oligo-benzylidene-4′-hydroxyanilene to be unstable against thermo-oxidative decomposition. The weight loss of O-B-4′-HA was found to be 95.87% at 1000 ○C. 相似文献