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1.
The LiZnxMn2−xO4 (x = 0.00-0.15) cathode materials for rechargeable lithium-ion batteries were synthesized by simple sol-gel technique using aqueous solutions of metal nitrates and succinic acid as the chelating agent. The gel precursors of metal succinates were dried in vacuum oven for 10 h at 120 °C. After drying, the gel precursors were ground and heated at 900 °C. The structural characterization was carried out by X-ray powder diffraction and X-ray photoelectron spectroscopy to identify the valance state of Mn in the synthesized materials. The sample exhibited a well-defined spinel structure and the lattice parameter was linearly increased with increasing the Zn contents in LiZnxMn2−xO4. Surface morphology and particle size of the synthesized materials were determined by scanning electron microscopy and transmission electron microscopy, respectively. Electrochemical properties were characterized for the assembled Li/LiZnxMn2−xO4 coin type cells using galvanostatic charge/discharge studies at 0.5 C rate and cyclic voltammetry technique in the potential range between 2.75 and 4.5 V at a scan rate of 0.1 mV s−1. Among them Zn doped spinel LiZn0.10Mn1.90O4 has improved the structural stability, high reversible capacity and excellent electrochemical performance of rechargeable lithium batteries. 相似文献
2.
Caixian Chang 《Electrochimica acta》2008,54(2):623-627
A novel hydrothermal synthesis was developed to prepare carbon-coated lithium vanadium phosphate (Li3V2(PO4)3) powders to be used as cathode material for Li-ion batteries. The structural, morphological and electrochemical properties were investigated by means of X-ray powder diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and constant current charge-discharge cycling. This material exhibits high initial discharge capacity of 178, 173 and 172 mAh g−1 at 0.1, 0.2 and 0.5 C between 3.0 and 4.8 V, respectively. Moreover, it displays good fast rate performance, which discharge capacities of 136, 132 and 127 mAh g−1 can be delivered after 100 cycles between 3.0 and 4.8 V versus Li at a different rate of 1, 2 and 5 C, respectively. For comparison, the electrochemical properties of carbon-coated lithium vanadium phosphate prepared by traditional solid-state reaction (SSR) method are also studied. 相似文献
3.
SnO2/multi-walled carbon nanotube (MWCNT) composites were prepared by the solvothermal method and subsequent heat treatment at 360 °C. The samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Results on the higher SnO2 content composite sample indicate that a uniform layer of SnO2 nanocrystals with crystal size around 5 nm was deposited on the surface of the carbon nanotubes. The composite demonstrates a reversible lithium storage capacity of 709.9 mAh g−1 at the first cycle and excellent cyclic retention up to 100 cycles as anode for lithium ion batteries. 相似文献
4.
Tungsten oxide (WO3) nanoplates were synthesized by a 270 W microwave-hydrothermal reaction of Na2WO4·2H2O and citric acid (C6H8O7·H2O) in deionized water. X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) were used to reveal the synthesis of WO3 complete rectangular nanoplates in the solution of 0.2 g citric acid for 180 min, with O-W-O FTIR stretching modes at 819 and 741 cm−1, and two prominent O-W-O Raman stretching modes at 804 and 713 cm−1. The 2.71 eV indirect energy gap, and 430-460 nm blue emission wavelength range of WO3 complete rectangular nanoplates were determined using UV-visible and photoluminescence (PL) spectrometers. The formation mechanism was also proposed according to the experimental results. 相似文献
5.
Caixian Chang 《Electrochimica acta》2008,53(5):2232-2237
Monoclinic lithium vanadium phosphate/carbon (Li3V2(PO4)3/C) cathode has been synthesized for applications in lithium ion batteries, via a rheological phase reaction (RPR) method. The sample is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). This material exhibits high initial discharge capacity of 189 and 177 mAh g−1 at 0.1 and 0.2 C between 3.0 and 4.8 V, respectively. Moreover, it displays good fast rate performance, which discharge capacities of 140, 133, 129 and 124 mAh g−1 can be delivered after 100 cycles between 3.0 and 4.8 V vs. Li at a different rate of 0.5, 1, 2 and 5 C, respectively. The electrochemical impedance spectroscopy (EIS) is also investigated. 相似文献
6.
SnOx thin films were prepared by reactive radio frequency magnetron sputtering with different sputtering powers. X-ray photoelectron spectroscopy suggested that all the films have similar chemical stoichiometry as SnO1.5. X-ray diffraction and transmission electro microscopy results showed that crystal size of the SnOx thin films gradually increases with increase of sputtering power from 50 to 150 W. Cyclic voltammetry and galvanostatic charge/discharge cycling measurements indicated that the electrochemical properties of SnOx films strongly rely on their crystal sizes as well as surface morphologies. The SnOx film deposited at sputtering power of 120 W exhibits the best electrochemical performances. It could deliver a reversible capacity of 670 μAh cm−2 μm−1 at 50 μA cm−2 in the voltage range of 0.1-1.2 V up to 50 cycles. 相似文献
7.
The TiO2 nanofibers and nanoparticles are prepared by electrospinning and molten salt method, respectively. The materials are characterized by X-ray diffraction scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and a thermal analysis. The SEM and TEM studies showed that fibers were of average diameter ∼100 nm and composed of nanocrystallites of size 10-20 nm. Electrochemical properties of the materials are evaluated using cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy. Cyclic voltammetric studies show a hysteresis (ΔV) between the cathodic and the anodic peak potentials for TiO2 nanofibers and nanoparticles (sizes ∼15-30 nm) are in the range, 0.23-0.30 V and a redox couple Ti4+/3+ around ∼1.74/2.0 V. Electrochemical cycling results revealed that the TiO2 nanofibers have lower capacity fading compared to that of the nanoparticles. The capacity fading for 2-50 cycles was ∼23% for nanofibers, which was nearly one-third of that of corresponding nanoparticles (∼63%). We discussed the effect of particle size on hysteresis and cycling performance of TiO2 nanoparticles. Impedance analysis of TiO2 nanofibers and nanoparticles during first discharge cycle is analyzed and interpreted. 相似文献
8.
The carbon coated monoclinic Li3V2(PO4)3 (LVP/C) cathode materials are synthesized via a sol-gel method using oxalic acid as a chelating reagent and maltose as a carbon source. The effect of carbon content on the synthesis of LVP/C composites is investigated using X-ray diffraction, scanning electron microscopy, galvanostatic charge/discharge and DC resistance measurements. The results show that, among the LVP/C powders with different carbon content (5.7, 9.6, 11.6 and 15.3 wt.%), the sample with 11.6 wt.% carbon content gives rise to the corresponding (LVP/C) ∥Li half cell with a low DC resistance and superior electrochemical performance, especially with excellent rate capability. Its discharge capacity decreases by only 7.2% from 125 mAh g−1 at 0.5 C to 116 mAh g−1 at 5 C between 3.0 and 4.3 V. The maltose-based sol-gel method is feasible for the preparation of LVP/C composites for high power lithium ion batteries. 相似文献
9.
Laura Pascual 《Electrochimica acta》2006,51(16):3193-3201
Lithium-deficient LiYMn2O4 spinels (LD-LiYMn2O4) with nominal composition (0.9 ≤ Y < 1) have been synthesized by melt impregnation from Mn2O3 and LiNO3 at temperatures ranging from 700 °C to 850 °C. X-ray diffraction data show that LD-LiYMn2O4 spinels are obtained as single phases in the range Y = 0.975-1 at 700 °C and 750 °C. Morphological characterization by transmission electron microscopy shows that the particle size of LD-LiYMn2O4 spinels increases on decreasing the Li-content. The influence of the Li-content and the synthesis temperature on the thermal and electrochemical behaviours has been systematically studied. Thermal analysis studies indicate that the temperature of the first thermal effect in the differential thermal analysis (DTA)/thermogravimetric (TG) curves, TC1, linearly increases on decreasing the Li-content. The electrochemical properties of LD-LiYMn2O4 spinels, determined by galvanostatic cycling, notably change with the synthesis conditions. So, the first discharge capacity, Qdisch., at C rate increases on rising the Li-content and the synthesis temperature. The sample Li0.975Mn2O4 synthesized at 700 °C has a Qdisch. = 123 mAh g−1 and a capacity retention of 99.77% per cycle. This LD-LiYMn2O4 sample had the best electrochemical characteristics of the series. 相似文献
10.
Le Yu 《Electrochimica acta》2010,56(2):767-775
FeOF thin film has been successfully fabricated by reactive pulsed laser deposition for the first time, and its electrochemical behavior was examined as a negative electrode active material in lithium-ion batteries. The electrochemical properties of the as-deposited FeOF thin film during the first charging and discharging have been investigated by the galvanostatic cycling and cyclic voltammetry measurements. By using ex situ X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected-area electron diffraction measurements (SAED), it can be found that FeOF was initially decomposed into Fe0, LiF, and Fe2O3 after discharging to 1.0 V. The newly formed Fe2O3 is then subsequently reduced into Li2O and Fe0 after further discharging to 0.01 V. In the subsequent cycle, the reduction peaks at 0.76 V and the oxidation-reduction peaks at 1.6 and 1.9 V could be attributed to the reversible decomposition and formation of Li2O with the conversion reaction of Fe2O3 into Fe. 相似文献
11.
Atef Y. Shenouda 《Electrochimica acta》2006,51(26):5973-5981
New vanadate compounds having the molecular structure LixMg1−xV2−xMoxO6 (0 ≤ x ≤ 1) were studied. Six samples were prepared by sol-gel process from precursor using the following ratios of x = 0, 0.2, 0.4, 0.6, 0.8 and 1, respectively. These samples were labeled S1, S2, S3, S4, S5 and S6. The final process of firing occurred at 750 °C for 18 h in air. The prepared materials were characterized by XRD, SEM, IR, electron spin resonance (ESR) and magnetic measurements. The morphologies of S1, S2, S5 and S6 are prismatic as they have monoclinic crystal structures. S3 and S4 differ in the crystal morphology from the other previous samples due to their triclinic crystal lattice structure. IR spectra revealed that the bond lengths of the vanadyl groups νVO, νsy V-O and σV-O increase in the same direction from S1 to S6. The data of the ESR explain the existence of V4+ beside V5+ in S1, S4 and S6 and also presence of Mo5+ with Mo6+ in S4 and S6. S4 exhibited better magnetic susceptibility and saturated magnetization than the other samples. The first specific discharge capacities of the samples were performed. S4 showed the maximum specific capacity of 265 mAh g−1 in comparison with the other samples. Cyclic voltammogram of S4 exhibited the highest current intensity in comparison with the other samples. This sample showed two peaks at 0.53 and 1.3 V versus Li/Li+ characterizing double de-insertions of two lithium atoms from Li1.6Mg0.4V1.4Mo0.6O6−x and Li0.6Mg0.4V1.4Mo0.6O6, respectively. Also, two additional peaks were characterized for the oxidation of Mo5+ to Mo6+ and V4+ to V5+ at 3.5 and 4 V, respectively. 相似文献
12.
A three-dimensional ordered macroporous (3DOM) cobalt ferrite (CoFe2O4) was prepared using polystyrene (PS) colloidal crystal template. The scanning electron microscopy (SEM) and the transmission electron microscopy (TEM) micrographs showed that the as-prepared CoFe2O4 material had a typical 3DOM structure, which was constructed with about 130 nm-sized macropores and 10-20 nm-sized walls. The obtained CoFe2O4 material had a specific surface area of 66.67 m2 g−1, and could deliver a relatively high capacity of 702 mAh g−1 (about double that of graphite) at a current density of 0.2 mA cm−2 after 30 cycles. Owing to the 3DOM nanoarchitecture, the as-prepared CoFe2O4 electrode exhibited a good rate performance. The results suggest a promising application of the 3DOM CoFe2O4 as anode material for lithium ion batteries. 相似文献
13.
Efficient microwave hydrothermal synthesis of nanocrystalline orthorhombic LiMnO2 cathodes for lithium batteries 总被引:1,自引:0,他引:1
Rod-like orthorhombic LiMnO2 nanocrystals were successfully synthesized using temperature-controlled microwave hydrothermal route (TCMH) in a short time (30 min) at a temperature as low as 160 °C. o-LiMnO2 obtained by two different methods was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemistry test. SEM revealed that the product obtained in case of TCMH was rod-like with a diameter of 40 nm, while the nanoparticles with 200 nm diameter were obtained by traditional hydrothermal route (TH). The dramatic formation of o-LiMnO2 in the microwave hydrothermal field influenced the morphology and crystal structure of the final products. The formation and preferred growth orientation mechanism of o-LiMnO2 in the microwave irradiation process was discussed. Electrochemistry performance exhibited that the as-synthesized o-LiMnO2 nanorods reached the maximum discharge capacity of 194.2 mAh g−1 at 0.1 C rate after several cycles between 2.2 and 4.4 V vs. Li+/Li at room temperature, which was higher than the electrochemical performance of o-LiMnO2 obtained by TH. The experimental results showed that the TCMH method provided an effective way for preparing o-LiMnO2 cathode material in lithium-ion batteries. 相似文献
14.
Chi-Lin Li 《Electrochimica acta》2008,53(22):6434-6443
Amorphous LiFe(WO4)2 thin films have been fabricated by radio-frequency (R.F.) sputtering deposition at room temperature. The as-deposited and electrochemically cycled thin films are, respectively, characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectra techniques. An initial discharge capacity of 198 mAh/g in Li/LiFe(WO4)2 cells is obtained, and the electrochemical behavior is mostly preserved in the following cycling. These results identified the electrochemical reactivity of two redox couples, Fe3+/Fe2+ and W6+/Wx+ (x = 4 or 5). The kinetic parameters and chemical diffusion coefficients of Li intercalation/deintercalation are estimated by cyclic voltammetry and alternate-current (AC) impedance measurements. All-solid-state thin film lithium batteries with Li/LiPON/LiFe(WO4)2 layers are fabricated and show high capacity of 104 μAh/cm2 μm in the first discharge. As-deposited LiFe(WO4)2 thin film is expected to be a promising positive electrode material for future rechargeable thin film batteries due to its large volumetric rate capacity, low-temperature fabrication and good electrode/electrolyte interface. 相似文献
15.
A series of spinel Li4Ti5O12 samples were synthesized via a composite molten-salt method (CMSM) using the mixtures of LiCl and KCl with different L values (L is defined as the molar ratio of LiCl:KCl) as the reaction media. It is found that the melting point of the composite molten salt can effectively influence the formation of particles, and leads to different electrochemical performances of the as-prepare Li4Ti5O12. The investigations of X-ray diffraction (XRD), particle size distribution (PSD), Brunauer-Emmet-Teller (BET) surface area, and scanning electron microscopy (SEM) indicate that the as-prepared Li4Ti5O12 with L = 1.5 is a pure phase, and has uniform homogeneous octahedral shape particles, rather narrow PSD, and high BET surface area. Electrochemical tests show that the optimized Li4Ti5O12 with L = 1.5 has an initial discharge capacity of 169 mAh g−1 and an initial charge-discharge efficiency of 94% at 0.2 C rate, and achieves good rate performances from 0.2 C to 5 C. 相似文献
16.
Spherical α-Ni(OH)2 architectures were synthesized by the microwave-assisted hydrothermal technique using PEG-6000 as the surfactant. NiO architectures with similar morphology were obtained by a simple thermal decomposition process of the precursor α-Ni(OH)2 at 400 °C for 2 h and were confirmed by the X-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) revealed that the synthesized spherical α-Ni(OH)2 and NiO architectures were composed of stacked lamellar sheets and transmission electron microscopy (TEM) showed that the α-Ni(OH)2 and NiO architectures were polycrystalline. The effect of the PEG-6000 concentration on particle size was investigated and it was found that the average particle size of α-Ni(OH)2 architectures decreased from 4.689 μm at CPEG=2 mmol L−1 to 3.907 μm at CPEG=4 mmol L−1, and the corresponding average particle size of NiO decreased from 2.818 μm to 2.492 μm. The optical absorption band gap of NiO architectures was determined to be about 2.7–3.0 eV by UV–vis spectroscopy. 相似文献
17.
Shaheen Sultana Sushama Talegaonkar Raisuddin Ali Gaurav Mittal Aseem Bhatnagar Farhan J. Ahmad 《Powder Technology》2011,211(1):1-9
The purpose of this research work was to formulate and evaluate alpha ketoglutarate nanoparticles as dry powder inhaler for treatment of cyanide poisoning. Non-polymeric particles were prepared by nano-precipitation technique using various stabilizers. Selection of co-solvent and stabilizer was a key to produce stabilized particles. A combination of lutrol F68 and PVA as a crystal growth inhibitor seems to be best in achieving minimum particle size of 110.2 nm. On the basis of preliminary trials a Box-Behnken statistical design was employed to study the effect of independent variables, drug concentration (X1), stirring speed (X2), stirring time (X3), PVA concentration (X4), poloxomer concentration (X5) and volume of co-solvent (X6) on average particle size. Particle size varied from 110 to 875 nm depending upon the significant terms. Optimized formulation was predicted at drug concentration (50 μg/ml), stirring speed (640 rpm), stirring time (1 min), PVA concentration (1%), poloxomer concentration (1.69%) and volume of co-solvent (30 ml) with 104.6% experimental validity. The nanosized particles were further characterized by X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy (FT-IR) analysis. The results of particle characterization indicate that there was no physical disparity when compared with the commercial α-KG sample. 相似文献
18.
Yoshihiro Kadoma 《Electrochimica acta》2007,53(4):1697-1702
The Li+ ion-exchange reaction of K+-type α-K0.14MnO1.93·nH2O containing different amounts of water molecules (n = 0-0.15) with a large (2 × 2) tunnel structure has been investigated in a LiNO3-LiCl molten salt at 300 °C. The Li+ ion-exchanged products were examined by chemical analysis, X-ray diffraction, and transmission electron microscopy measurements. The K+ ions and the hydrogens of the water molecules in the (2 × 2) tunnels of α-MnO2 were exchanged by Li+ ions in the molten salt, resulting in the Li+-type α-MnO2 containing different amounts of Li+ ions and lithium oxide (Li2O) in the (2 × 2) tunnels with maintaining the original hollandite structure.The electrochemical properties and structural variation with initial discharge and charge-discharge cycling of the Li+ ion-exchanged α-MnO2 samples have been investigated as insertion compounds in the search for new cathode materials for rechargeable lithium batteries. The Li+ ion-exchanged α-MnO2 samples provided higher capacities and higher Li+ ion diffusivity than the parent K+-type materials on initial discharge and charge-discharge cyclings, probably due to the structural stabilization with the existence of Li2O in the (2 × 2) tunnels. 相似文献
19.
Youyong Liu 《Electrochimica acta》2010,55(16):4694-19237
A simple and effective method, the ultrasonic-assisted co-precipitation method, was employed to synthesize nano-sized LiFePO4/C. A glucose solution was used as the carbon source to produce in situ carbon to improve the conductivity of LiFePO4. Ultrasonic irradiation was adopted to control the size and homogenize the LiFePO4/C particles. The sample was characterized by X-ray powder diffraction, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). FE-SEM and TEM show that the as-prepared sample has a reduced particle size with a uniform size distribution, which is around 50 nm. A uniform amorphous carbon layer with a thickness of about 4-6 nm on the particle surface was observed, as shown in the HRTEM image. The electrochemical performance was demonstrated by the charge-discharge test and electrochemical impedance spectra measurements. The results indicate that the nano-sized LiFePO4/C presents enhanced discharge capacities (159, 147 and 135 mAh g−1 at 0.1, 0.5 and 2 C-rate, respectively) and stable cycling performance. This study offers a simple method to design and synthesis nano-sized cathode materials for lithium-ion batteries. 相似文献
20.
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