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1.
In this study, spheroid LiNi1/3Co1/3Mn1/3O2 (NCM111) cathode material were synthesized using LiOH with Ni0.5Co0.2Mn0.3(OH)2 precursor by a simple solid-state reaction, and characterized by X-ray diffraction and scanning electron microscopy. Electrochemical behavior of NCM111 was investigated by electrochemical impedance spectroscopy (EIS) combining with cyclic voltammogram (CV) and charge/discharge test in the 1 M LiPF6-EC:EMC electrolyte with ethylene sulfate (DTD) and methylene methanedisulfonate (MMDS) additives either singly or in combination with high cutoff voltage of 3.0–4.5 V at room temperature of 25 °C or elevated temperature of 55 °C. It was found that DTD additive can increase the initial coulombic efficiency of NCM111, and the spheroid NCM111 can obtain the maximum initial discharge capacity of 177.81 mAh/g with the 2 wt% DTD, and keep 92.29% capacity retention after 80 cycles. The MMDS additives would decrease the initial discharge capacity of the NCM111, and enhance significantly long cycle life of the NCM111 with the capacity retention of 99.23% over 80 cycles at high voltage of 4.5 V. The additive combination 2 wt% DTD?+?1 wt% MMDS was an optimal additive combination, demonstrating the 102.2% capacity retention over 80 cycles at room temperature and the 94.2% capacity retention over 70 cycles at elevated temperature of 55 °C. EIS results revealed that the additive blend of 2 wt% DTD?+?1 wt% MMDS can drastically lower the kinetics impedance and suppress the growth rate of R ct for the NCM111 electrode.  相似文献   

2.
Nickel-rich layered materials are prospective cathode materials for use in lithium-ion batteries due to their higher capacity and lower cost relative to LiCoO2. In this work, spherical Ni0.8Co0.1Mn0.1(OH)2 precursors are successfully synthesized through a co-precipitation method. The synthetic conditions of the precursors - including the pH, stirring speed, molar ratio of NH4OH to transition metals and reaction temperature - are investigated in detail, and their variations have significant effects on the morphology, microstructure and tap-density of the prepared Ni0.8Co0.1Mn0.1 (OH)2 precursors. LiNi0.8Co0.1Mn0.1O2 is then prepared from these precursors through a reaction with 5% excess LiOH· H2O at various temperatures. The crystal structure, morphology and electrochemical properties of the Ni0.8Co0.1Mn0.1 (OH)2 precursors and LiNi0.8Co0.1Mn0.1O2 were investigated. In the voltage range from 3.0 to 4.3 V, LiNi0.8Co0.1Mn0.1O2 exhibits an initial discharge capacity of 193.0mAh g-1 at a 0.1 C-rate. The cathode delivers an initial capacity of 170.4 mAh g-1 at a 1 C-rate, and it retains 90.4% of its capacity after 100 cycles.  相似文献   

3.
A lithium insertion material having the composition LiNi0.3Co0.3Mn0.3Fe0.1O2 was synthesized by simple sol-gel method. The structural and electrochemical properties of the sample were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge-discharge method. Rietvelt analysis of the XRD patterns shows that this compound can be classified as α-NaFeO2 structure type (R3m; a=2.8689(5) Å and 14.296(5) Å in hexagonal setting). Rietvelt fitting shows that a relatively large amount of Fe and Ni ion occupy the Li layer (3a site) and a relatively large amount of Li occupies the transition metal layer (3b site). LiNi0.3Co0.3Mn0.3Fe0.1O2 when cycled in the voltage range 4.3–2.8 V gives an initial discharge capacity of 120 mAh/g, and stable cycling performance. LiNi0.3Co0.3Mn0.3Fe0.1O2 in the voltage range 2.8–4.5 V has a discharge capacity of 140 mAh/g, and exhibits a significant loss in capacity during cycling. Ex-situ XRD measurements were performed to study the structure changes of the samples after cycling between 2.8–4.3 V and 2.8–4.5 V for 20 cycles. The XRD and electrochemical results suggested that cation mixing in this layered structure oxide could be causing degradation of the cell capacity.  相似文献   

4.
Magnetic spindle-like Fe3O4 mesoporous nanoparticles with a length of 200 nm and diameter of 60 nm were successfully synthesized by reducing the spindle-like α-Fe2O3 NPs which were prepared by forced hydrolysis method. The obtained samples were characterized by transmission electron microscopy, powder X-ray diffraction, attenuated total reflection fourier transform infrared spectroscopy, field emission scanning electron microscopy, vibrating sample magnetometer, and nitrogen adsorption-desorption analysis techniques. The results show that α-Fe2O3 phase transformed into Fe3O4 phase after annealing in hydrogen atmosphere at 350°C. The as-prepared spindle-like Fe3O4 mesoporous NPs possess high Brunauer-Emmett-Teller (BET) surface area up to ca. 7.9 m2 g-1. In addition, the Fe3O4 NPs present higher saturation magnetization (85.2 emu g-1) and excellent magnetic response behaviors, which have great potential applications in magnetic separation technology.  相似文献   

5.
The optimum conditions for synthesizing LiNi1-y Co y O2 (y=0.1, 0.3 and 0.5) by a simplified combustion method, in which the preheating step is omitted, and the electrochemical properties of these materials were investigated. The optimum condition for synthesizing LiNi0.9Co0.1O2 by the simplified combustion method is calcination at 800 °C for 12 h in air in 3.6 mole ratio of urea to nitrate. The LiNi0.9Co0.1O2 synthesized under these conditions shows the smallest R-factor{(I 006+I 102)/I 101} and the largest I 003/I 104, indicating better hexagonal ordering and less cation mixing, respectively. The LiNi0.7Co0.3O2 synthesized at 800 °C for 12 h in air in 3.6 mole ratio of urea to nitrate has the largest first discharge capacity 156.2 mA h g−1 at 0.5C and shows relatively good cycling performance. This sample shows better hexagonal ordering and less cation mixing than the other samples. The particle size of the LiNi0.7Co0.3O2 is relatively small and its particles are spherical with uniform particle size.  相似文献   

6.
Improved electrochemical properties of Li(Ni0.7Co0.3)O2 cathode material are reported. Samples were synthesized by the co-precipitation method with various sintering conditions, namely temperature, time and atmosphere. Li(Ni0.7Co0.3)O2 sintered at 850 °C for 14 h in air exhibited the lowest unit cell volume accompanied with relatively higher values of c/a and I 103/I 104 reflection peaks ratios. This also exhibited superior electrochemical properties, such as high charge–discharge capacity, high Coulombic efficiency, and low irreversible capacity loss. This can be attributed to improved hexagonal ordering, crystallinity and morphology. The electrochemical cell parameters were better than the reported ones, probably due to controlled sintering conditions.  相似文献   

7.
Oxidative dehydrogenation of n-butene to 1,3-butadiene over Co9Fe3Bi1Mo12O51 catalyst was conducted in a continuous flow fixed-bed reactor. The effect of reaction conditions (steam/n-butene ratio, reaction temperature, and space velocity) on the catalytic performance of Co9Fe3Bi1Mo12O51 was investigated. Steam played an important role in decreasing contact time, suppressing total oxidation of n-butene, and removing coke during the reaction. Yield for 1,3-butadiene showed a volcano-shaped curve with respect to steam/n-butene ratio. The compensation between thermodynamic effect and kinetic effect led to a volcano-shaped curve of 1,3-butadiene yield with respect to reaction temperature. The Co9Fe3Bi1Mo12O51 catalyst showed the best catalytic performance at a certain value of space velocity. The optimum steam/n-butene ratio, reaction temperature, and gas hourly space velocity were found to be 15, 420 °C, and 675 h−1, respectively.  相似文献   

8.
A layered LiNi0.8Co0.2O2 solid solution, which is a promising cathode material for secondary lithium batteries, was successfully synthesized by an emulsion drying method. Because electrochemical properties significantly depend on the conditions of the synthesis, the calcination temperature was carefully determined on the basis of X-ray diffraction and TG studies. The prepared cathodes were characterized by means of SEM, BET, X-ray diffraction, Rietveld refinement, cyclic voltammetry and a charge-discharge experiment. From the Rietveld analysis, it was found that powder calcined at 800 °C for 12 h exhibits a well ordered and lower cation mixed layered structure than the others. The cyclic voltammetry experiment shows that phase transformation can be suppressed considerably by increasing the calcination temperature to 800 °C. The highest discharge capacity of 188.4 mA h g−1 was obtained from the sample prepared at 800 °C. Furthermore, a high capacity retention ratio of 88.1% was found for the initial value after 50 cycles at a constant current density of 40 mA g−1 between 2.7 VLi/Li+ and 4.3 VLi/Li+. In the rate capability test, the cathode delivered a higher discharge capacity of 153.1 mA h g−1 at a 4 C (800 mA g−1) rate.  相似文献   

9.
The hydrogel of the mixed oxide Al2O3-30% Y0.1Zr0.9O2 was prepared by precipitation of ammonia from a water-alcohol mixture (1 : 5). The Al2O3-30% Y0.1Zr0.9O2 compound thus synthesized was characterized using differential scanning calorimetry, transmission electron microscopy, and the BET adsorption method. The obtained sample consisted of spherical particles with an average size of 16–20 nm and a specific surface area of 167 m2/g. The Al2O3-30% Y0.1Zr0.9O2 powder was pressed at 300 MPa and then calcinated at 1600°C for 2 h in air. The topographic and structural features of the prepared ceramics were determined using atomic force microscopy and X-ray electron probe microanalysis. The porosity, the Vickers microhardness, and the tensile strength were determined by mercury porometry.  相似文献   

10.
The 0D-1D Lithium titanate (Li4Ti5O12) heterogeneous nanostructures were synthesized through the solvothermal reaction using lithium hydroxide monohydrate (Li(OH)·H2O) and protonated trititanate (H2Ti3O7) nanowires as the templates in an ethanol/water mixed solvent with subsequent heat treatment. A scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM) were used to reveal that the Li4Ti5O12 powders had 0D-1D heterogeneous nanostructures with nanoparticles (0D) on the surface of wires (1D). The composition of the mixed solvents and the volume ratio of ethanol modulated the primary particle size of the Li4Ti5O12 nanoparticles. The Li4Ti5O12 heterogeneous nanostructures exhibited good capacity retention of 125 mAh/g after 500 cycles at 1C and a superior high-rate performance of 114 mAh/g at 20C.  相似文献   

11.
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   

12.
In this work, porous TiO2 hollow spheres with an average diameter of 100 nm and shell thickness of 20 nm were synthesized by a facile hydrothermal method with NH4HCO3 as the structure-directing agent, and the formation mechanism for this porous hollow structure was proved to be the Ostwald ripening process by tracking the morphology of the products at different reaction stages. The product was characterized by SEM, TEM, XRD and BET analyses, and the results show that the as-synthesized products are anatase phase with a high surface area up to 132.5 m2/g. Gas-sensing investigation reveals that the product possesses sensitive response to methanal gas at 200°C due to its high surface area.  相似文献   

13.
The performance of La0.75Sr0.25Cr0.9M0.1O3 (M = Mn, Fe, Co, and Ni) perovskitic materials as anodes was studied for a CO-fueled solid oxide fuel cell. The electrocatalytic performance and the tolerance to carbon deposition were investigated, while electrochemical characterization was carried out via AC impedance spectroscopy and cyclic voltammetry. The La0.75Sr0.25Cr0.9Fe0.1O3 perovskite showed the best anode performance at temperatures above 900 °C; while at temperatures below 900 °C, the best performance was achieved with the La0.75Sr0.25Cr0.9Co0.1O3 material. AC impedance spectroscopy was used for a semi-quantitative analysis of the LSC-M0.1 anodes performance in view of total cell and charge transfer resistance. All anode materials exhibit high electronic conductivity and presumably do not substantially contribute to the overall cell resistance and concomitant ohmic losses.  相似文献   

14.
0.1 Fe/Ti mole ratio of Fe-TiO2 catalysts were synthesized via solvothermal method and calcined at various temperatures: 300, 400, and 500 °C. The calcined catalysts were characterized by XRD, N2-adsorption-desorption, UV-DRS, XRF, and Zeta potential and tested for photocatalytic degradation of alachlor under visible light. The calcined catalysts consisted only of anatase phase. The BET specific surface area decreased with the calcination temperatures. The doping Fe ion induced a red shift of absorption capacity from UV to the visible region. The Fe-TiO2 calcined at 400 °C showed the highest photocatalytic activity on degradation of alachlor with assistance of 30 mM H2O2 at pH 3 under visible light irradiation. The degradation fitted well with Langmuir-Hinshelwood model that gave adsorption coefficient and the reaction rate constant of 0.683 L mg−1 and 0.136 mg/L·min, respectively.  相似文献   

15.
The Sb2O3 doping lead-free glass in Bi2O3-B2O3-BaO ternary system were prepared in the composition of several different subsystem, and the glass powder was produced through the process of water quenching. Glass transition temperatures (T g ), glass soften temperatures(T s ), the volume resistivity (ρ) in the temperature range of 80–200°C, and linear thermal coefficients of expansion in the temperatures range of 25–300°C (α25–300) were measured for subsystems along with the different ratio of Bi2O3, B2O3 and BaO. For these subsystems, T g ranged from 458 to 481°C, and T s ranged from 490 to 512°C, both decreasing with the increasing of Bi2O3/B2O3 ratio, and increasing with the increasing of BaO/B2O3 ratio. The measured α25–300 ranged from 65.3 to 76.3 × 10−7 K−1, with values increasing with increasing Bi2O3/B2O3 and BaO/B2O3 ratio. The volume resistivity remains at a high standards, which may caused by it’s non-alkali composition, and it fluctuated from 1013 to 1011 Ω cm with the temperature varied from 80–200°C. The structure of Bi2O3-B2O3-BaO ternary leadfree glass system was mearsured by FT-IR. The IR studies indicate that these glasses are made up of [BiO6], [BO3], and [BO4] basic structural units, and it appears that Ba2+ acts as a glass-modifier in this ternary system, but the Bi3+ has entered the glass network when it is in relative high content so as to change the α25–300, T s and T g .  相似文献   

16.
Lead-free 0.98(Na0.5K0.5)NbO3-0.02Ba(Zr0.52Ti0.48)O3 [0.98NKN-0.02BZT] ceramics were fabricated by the conventional mixed oxide method with sintering temperature at 1,080°C to 1,120°C. The results indicate that the sintering temperature obviously influences the structural and electrical properties of the sample. For the 0.98NKN-0.02BZT ceramics sintered at 1,080°C to 1,120°C, the bulk density increased with increasing sintering temperature and showed a maximum value at a sintering temperature of 1,090°C. The dielectric constant, piezoelectric constant [d 33], electromechanical coupling coefficient [k p], and remnant polarization [P r] increased with increasing sintering temperature, which might be related to the increase in the relative density. However, the samples would be deteriorated when they are sintered above the optimum temperature. High piezoelectric properties of d 33 = 217 pC/N, k p = 41%, dielectric constant = 1,951, and ferroelectric properties of P r = 10.3 μC/cm2 were obtained for the 0.98NKN-0.02BZT ceramics sintered at 1,090°C for 4 h.  相似文献   

17.
The electrochemical performances of an electrical double layer capacitor were investigated regarding the activated carbon prepared from bamboo by a new approach, that is, the combination of delignification, addition of guanidine phosphate, and CO2 activation. In this study, a 1 M H2SO4 aqueous solution was used as the electrolyte of the capacitor. The physical properties, such as the BET specific surface area of the carbon material, depend on the preparation conditions of the activated carbon. A TEM image indicated that the addition of guanidine phosphate did not facilitate the graphitization and did not prevent activation by CO2. The apparent reaction equation for the CO2 activation was first-order, which is reasonable for physical activation. The electrochemical performances of the carbon material depended on the preparation conditions of the carbon material, such as the heat treatment temperature, amount of added guanidine phosphate, and CO2 activation time. The sample prepared under the following conditions (the amount of added guanidine phosphate: 9 wt%, the heat treatment temperature: 800 °C, CO2 activation time: 3 h) had the highest performance (153 F g?1 at 1000 mA g?1) because the sample had the highest BET specific surface area (2001 m2 g?1).  相似文献   

18.
La0.6Sr0.4Co0.2Fe0.8O3−δ oxides were synthesized by citrate method and hydrothermal method. The oxides prepared by citrate method are perovskite type structure, while the oxides by hydrothermal method have a small amount of secondary phase in the powder. Pyrex glass seal and Ag melting seal provided reliable gas-tight sealing of disk type dense membrane in the range of operation temperature, but commercial ceramic binder could not be removed from the support tube without damage to the tube or membrane. Though the degree of gas tightness increases in the order of glass>Ag>ceramic binder, in the case of glass seal, the undesired spreading of glass leads to an interfacial reaction between it and the membrane and reduction of effective permeation area. The oxygen flux of La0.6Sr0.4Co0.2Fe0.8O3−δ membrane increases with increasing temperature and decreasing thickness, and the oxygen permeation flux through 1.0 mm membrane exposed to flowing air (P h =0.21 atm) and helium (P1=0.037 atm) is ca. 0.33 ml/cm2·min at 950 °C. X-ray diffraction analysis for the membrane after permeation test over 160 h revealed that La2O3 and unknown compound were formed on the surface of membrane. The segregation compounds of surface elements formed on both surfaces of membrane irrespective of spreading of glass sealing material. This paper was presented at the 6 th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.  相似文献   

19.
《Ceramics International》2022,48(11):15252-15260
The Co3O4, as a potential anode of lithium-ion batteries, has gained considerable attention because of high theoretical capacity. However, the Co3O4 is suffering from serious structure deterioration and rapid capacity fading due to its bulky volume change during cyclic charge/discharge process. Herein, to stabilize the lithium storage performance of the Co3O4 nanoparticles, a characteristic carbon scaffold (HPC) integrating hollow and porous structures has been fabricated by a well-designed method for the first time. The ultrafine Co3O4 nanoparticles are cleverly anchored on the HPC (HPC@Co3O4) and hence achieve significantly improved electrochemical properties including high capacity, improved reaction kinetics and outstanding cycle stability, showing high capacity of 1084.7 mAh g-1 after 200 cycles at 200 mA g-1 as well as 681.4 mAh g-1 after 300 cycles at 1000 mA g-1. The HPC@Co3O4 therefore shows good promising for application in advanced lithium-ion battery anodes. The results of the systematically material and electrochemical characterizations indicate that the synergistic effects of ultrafine Co3O4 nanoparticles and well-designed HPC scaffolds are responsible for the outstand performance of the HPC@Co3O4 anode. Moreover, this work can enrich the understanding and development of stable and high-performance metal oxide-based lithium-ion battery anodes for advanced lithium storage.  相似文献   

20.
One of the most promising anode materials for Li-ion batteries, Li4Ti5O12, has attracted attention because it is a zero-strain Li insertion host having a stable insertion potential. In this study, we suggest two different synthetic processes to prepare Li4Ti5O12 using anatase TiO2 nanoprecursors. TiO2 powders, which have extraordinarily large surface areas of more than 250 m2 g-1, were initially prepared through the urea-forced hydrolysis/precipitation route below 100°C. For the synthesis of Li4Ti5O12, LiOH and Li2CO3 were added to TiO2 solutions prepared in water and ethanol media, respectively. The powders were subsequently dried and calcined at various temperatures. The phase and morphological transitions from TiO2 to Li4Ti5O12 were characterized using X-ray powder diffraction and transmission electron microscopy. The electrochemical performance of nanosized Li4Ti5O12 was evaluated in detail by cyclic voltammetry and galvanostatic cycling. Furthermore, the high-rate performance and long-term cycle stability of Li4Ti5O12 anodes for use in Li-ion batteries were discussed.  相似文献   

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