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1.
To investigate the crystal structure and electrochemical performance of samples synthesized under different microwave solid-state synthesis condition, a series of Li3V2(PO4)3 samples has been synthesized at five different temperatures for 3-5 min and at 750 °C for various time. The as-synthesized Li3V2(PO4)3 samples are characterized and studied by ICP-AES analysis, X-ray diffraction (XRD), Rietveld analysis, scanning and transmission electron microcopy (SEM and TEM). At relatively lower temperature (650 °C) and very short reaction time (3 min), pure phase of Li3V2(PO4)3 could be synthesized in microwave irradiation field. The crystal structure and Li atomic fractional coordinate present a significant deviation upon the change of microwave irradiation temperature and time. Relatively, the diffusion ability of lithium cations and the electrochemical performance are affected. Under the proper reaction temperature and time, the carbon-free samples MW750C5m and MW850C3m show the best specific discharge capacity 126.4 and 132 mAh g−1 at the voltage range of 3.0-4.3 V, near the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133 mAh g−1). At the voltage range of 3-4.8 V, the sample MW750C5m presents the best initial specific charge capacity of 197 mAh g−1, equivalent to the reversible cycling of three lithium ions per Li3V2(PO4)3 formula unit (197 mAh g−1). The initial discharge capacity, the samples MW750C5m and MW850C3m present high specific discharge capacity 183.4 and 175.7 mAh g−1, respectively. The relationship among microwave irradiation condition, crystal structure, lithium atomic fractional coordinates and the electrochemical performance have been discussed in detail. 相似文献
2.
An improved solid-state coordination method namely wet coordination has been developed to synthesize carbon-coated monoclinic Li3V2(PO4)3 rapidly at a low temperature of 600 °C in 1 h. The structure of the sample was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and energy dispersive analysis of X-rays (EDAX). The diffusion coefficient of the lithium ions was measured by cyclic voltammetry (CV). The electrochemical behavior of the sample exhibits a high initial discharge capacity of 130 mAh g−1, which is very close to its theoretical capacity of 132 mAh g−1 under 95 mA g−1 (0.67 C) in the range of 3.3-4.3 V (vs. Li/Li+). These results suggest that wet coordination is a promising method for large-scale production of carbon-coated Li3V2(PO4)3. 相似文献
3.
Electrochemical performance of the carbon coated Li3V2(PO4)3 cathode material synthesized by a sol-gel method 总被引:1,自引:0,他引:1
A carbon coated Li3V2(PO4)3 cathode material for lithium ion batteries was synthesized by a sol-gel method using V2O5, H2O2, NH4H2PO4, LiOH and citric acid as starting materials, and its physicochemical properties were investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), transmission electron microscope (TEM), and electrochemical methods. The sample prepared displays a monoclinic structure with a space group of P21/n, and its surface is covered with a rough and porous carbon layer. In the voltage range of 3.0-4.3 V, the Li3V2(PO4)3 electrode displays a large reversible capacity, good rate capability and excellent cyclic stability at both 25 and 55 °C. The largest reversible capacity of 130 mAh g−1 was obtained at 0.1C and 55 °C, nearly equivalent to the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133 mAh g−1). It was found that the increase in total carbon content can improve the discharge performance of the Li3V2(PO4)3 electrode. In the voltage range of 3.0-4.8 V, the extraction and reinsertion of the third lithium ion in the carbon coated Li3V2(PO4)3 host are almost reversible, exhibiting a reversible capacity of 177 mAh g−1 and good cyclic performance. The reasons for the excellent electrochemical performance of the carbon coated Li3V2(PO4)3 cathode material were also discussed. 相似文献
4.
X.H. Rui 《Electrochimica acta》2009,54(12):3374-3380
The carbon-coated monoclinic Li3V2(PO4)3 (LVP) cathode materials were synthesized by a solid-state reaction process under the same conditions using citric acid, glucose, PVDF and starch, respectively, as both reduction agents and carbon coating sources. The carbon coating can enhance the conductivity of the composite materials and hinder the growth of Li3V2(PO4)3 particles. Their structures and physicochemical properties were investigated using X-ray diffraction (XRD), thermogravimetric (TG), scanning electron microscopy (SEM) and electrochemical methods. In the voltage region of 3.0-4.3 V, the electrochemical cycling of these LVP/C electrodes all presents good rate capability and excellent cycle stability. It is found that the citric acid-derived LVP owns the largest reversible capacity of 118 mAh g−1 with no capacity fading during 100 cycles at the rate of 0.2C, and the PVDF-derived LVP possesses a capacity of 95 mAh g−1 even at the rate of 5C. While in the voltage region of 3.0-4.8 V, all samples exhibit a slightly poorer cycle performance with the capacity retention of about 86% after 50 cycles at the rate of 0.2C. The reasons for electrochemical performance of the carbon coated Li3V2(PO4)3 composites are also discussed. The solid-state reaction is feasible for the preparation of the carbon coated Li3V2(PO4)3 composites which can offer favorable properties for commercial applications. 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.
Li3V2(PO4)3 cathode materials were synthesized by a simple carbon-thermal reduction method using polystyrene as a carbon source. The residual carbon produced by the pyrolysis of polystyrene produced fine particle sizes and uniform carbon distribution on the Li3V2(PO4)3 particle surface. By increasing the amount of polystyrene added in the range of 0-16 wt.%, the thickness of the carbon coating increased, and the coating thickness was found to influence the electrochemical performance of the Li3V2(PO4)3 significantly. Our results indicate that the 6 wt.% polystyrene added Li3V2(PO4)3 with a 0.5-1 nm thick carbon coating possesses the highest initial discharge capacity of 132.7 mAh g−1 between 3.0 and 4.3 V at 0.1 C. However, at high current densities, the higher polystyrene added Li3V2(PO4)3/C with a thicker carbon coating shows better performance in terms of the discharge capacity and cycling stability than that with the thin carbon coating. The improved cycling performance at higher current densities is attributed to the relatively small particle size and the suppressed impedance increase because of the thicker carbon coating. 相似文献
7.
Xuechou Zhou 《Electrochimica acta》2009,54(8):2253-2258
The effects of reduction agent on the electrochemical properties of Li3V2(PO4)3/C positive materials were studied. An one-step solid-state reaction route was applied to synthesize Li3V2(PO4)3/C samples. The humic acid, glucose and carbon were used as reduction agent. SEM images show that the particles of sample with humic acid as reduction agent merge with each other and form a porous structure, and yet the particles of sample synthesized using carbon as reduction agent are wrapped with small carbon particles and separate each other. Electrochemical tests show that the samples using humic acid and glucose as reduction agents have better cyclic performance than the one using carbon as reduction agent. At the 200th cycle, the sample using humic acid as reduction agent still keeps 145.2 mAh g−1 at 1 C charge and discharge rates. However, the sample using carbon as reduction agent shows a fast decline in capacity during cycling and has 54.5% capacity loss of the initial value after 200 cycles. The results indicate that different reduction agents can obviously affect the morphologies and electrochemical properties of the products. 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.
Carbon coated Li3V2(PO4)3 cathode material was prepared by a poly(vinyl alcohol) (PVA) assisted sol-gel method. PVA was used both as the gelating agent and the carbon source. XRD analysis showed that the material was well crystallized. The particle size of the material was ranged between 200 and 500 nm. HRTEM revealed that the material was covered by a uniform surface carbon layer with a thickness of 80 Å. The existence of surface carbon layer was further confirmed by Raman scattering. The electrochemical properties of the material were investigated by charge-discharge cycling, CV and EIS techniques. The material showed good cycling performance, which had a reversible discharge capacity of 100 mAh g−1 when cycled at 1 C rate. The apparent Li+ diffusion coefficients of the material ranged between 9.5 × 10−10 and 0.9 × 10−10 cm2 s−1, which were larger than those of olivine LiFePO4. The large lithium diffusion coefficient of Li3V2(PO4)3 has been attributed to its special NASICON-type structure. 相似文献
10.
Co-doped Li3V2−xCox(PO4)3/C (x = 0.00, 0.03, 0.05, 0.10, 0.13 or 0.15) compounds were prepared via a solid-state reaction. The Rietveld refinement results indicated that single-phase Li3V2−xCox(PO4)3/C (0 ≤ x ≤ 0.15) with a monoclinic structure was obtained. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the cobalt is present in the +2 oxidation state in Li3V2−xCox(PO4)3. XPS studies also revealed that V4+ and V3+ ions were present in the Co2+-doped system. The initial specific capacity decreased as the Co-doping content increased, increasing monotonically with Co content for x > 0.10. Differential capacity curves of Li3V2−xCox(PO4)3/C compounds showed that the voltage peaks associated with the extraction of three Li+ ions shifted to higher voltages with an increase in Co content, and when the Co2+-doping content reached 0.15, the peak positions returned to those of the unsubstituted Li3V2(PO4)3 phase. For the Li3V1.85Co0.15(PO4)3/C compound, the initial capacity was 163.3 mAh/g (109.4% of the initial capacity of the undoped Li3V2(PO4)3) and 73.4% capacity retention was observed after 50 cycles at a 0.1 C charge/discharge rate. The doping of Co2+into V sites should be favorable for the structural stability of Li3V2−xCox(PO4)3/C compounds and so moderate the volume changes (expansion/contraction) seen during the reversible Li+ extraction/insertion, thus resulting in the improvement of cell cycling ability. 相似文献
11.
Li3V2(PO4)3/C composite cathode material was synthesized via carbothermal reduction process in a pilot scale production test using battery grade raw materials with the aim of studying the feasibility for their practical applications. XRD, FT-IR, XPS, CV, EIS and battery charge-discharge tests were used to characterize the as-prepared material. The XRD and FT-IR data suggested that the as-prepared Li3V2(PO4)3/C material exhibits an orderly monoclinic structure based on the connectivity of PO4 tetrahedra and VO6 octahedra. Half cell tests indicated that an excellent high-rate cyclic performance was achieved on the Li3V2(PO4)3/C cathodes in the voltage range of 3.0-4.3 V, retaining a capacity of 95% (96 mAh/g) after 100 cycles at 20C discharge rate. The low-temperature performance of the cathode was further evaluated, showing 0.5C discharge capacity of 122 and 119 mAh/g at −25 and −40 °C, respectively. The discharge capacity of graphite//Li3V2(PO4)3 batteries with a designed battery capacity of 14 Ah is as high as 109 mAh/g with a capacity retention of 92% after 224 cycles at 2C discharge rates. The promising high-rate and low-temperature performance observed in this work suggests that Li3V2(PO4)3/C is a very strong candidate to be a cathode in a next-generation Li-ion battery for electric vehicle applications. 相似文献
12.
Electrochemical and thermal properties of Co3(PO4)2- and AlPO4-coated LiNi0.8Co0.2O2 cathode materials were compared. AlPO4-coated LiNi0.8Co0.2O2 cathodes exhibited an original specific capacity of 170.8 mAh g−1 and had a capacity retention (89.1% of its initial capacity) between 4.35 and 3.0 V after 60 cycles at 150 mA g−1. Co3(PO4)2-coated LiNi0.8Co0.2O2 cathodes exhibited an original specific capacity of 177.6 mAh g−1 and excellent capacity retention (91.8% of its initial capacity), which was attributed to a lithium-reactive Co3(PO4)2 coating. The Co3(PO4)2 coating material could react with LiOH and Li2CO3 impurities during annealing to form an olivine LixCoPO4 phase on the bulk surface, which minimized any side reactions with electrolytes and the dissolution of Ni4+ ions compared to the AlPO4-coated cathode. Differential scanning calorimetry results showed Co3(PO4)2-coated LiNi0.8Co0.2O2 cathode material had a much improved onset temperature of the oxygen evolution of about 218 °C, and a much lower amount of exothermic-heat release compared to the AlPO4-coated sample. 相似文献
13.
Electrochemical performance of Li3V2(PO4)3/C cathode materials using stearic acid as a carbon source
The Li3V2(PO4)3/C cathode materials are synthesized by a simple solid-state reaction process using stearic acid as both reduction agent and carbon source. Scanning electron microscopy and transmission electron microscopy observations show that the Li3V2(PO4)3/C composite synthesized at 700 °C has uniform particle size distribution and fine carbon coating. The Li3V2(PO4)3/C shows a high initial discharge capacity of 130.6 and 124.4 mAh g−1 between 3.0 and 4.3 V, and 185.9 and 140.9 mAh g−1 between 3.0 and 4.8 V at 0.1 and 5 C, respectively. Even at a charge–discharge rate of 15 C, the Li3V2(PO4)3/C still can deliver a discharge capacity of 103.3 and 112.1 mAh g−1 in the potential region of 3.0–4.3 V and 3.0–4.8 V, respectively. Based on the analysis of cyclic voltammograms and electrochemical impedance spectra, the apparent diffusion coefficients of Li ions in the composites are in the region of 1.09 × 10−9 and 4.95 × 10−8 cm2 s−1. 相似文献
14.
Yinghua Chen Yanming Zhao Xiaoning An Jianmin Liu Youzhong Dong Ling Chen 《Electrochimica acta》2009,54(24):5844-5850
Cr-doped Li3V2−xCrx(PO4)3/C (x = 0, 0.05, 0.1, 0.2, 0.5, 1) compounds have been prepared using sol–gel method. The Rietveld refinement results indicate that single-phase Li3V2−xCrx(PO4)3/C with monoclinic structure can be obtained. Although the initial specific capacity decreased with Cr content at a lower current rate, both cycle performance and rate capability have excited improvement with moderate Cr-doping content in Li3V2−xCrx(PO4)3/C. Li3V1.9Cr0.1(PO4)3/C compound presents an initial capacity of 171.4 mAh g−1 and 78.6% capacity retention after 100 cycles at 0.2C rate. At 4C rate, the Li3V1.9Cr0.1(PO4)3/C can give an initial capacity of 130.2 mAh g−1 and 10.8% capacity loss after 100 cycles where the Li3V2(PO4)3/C presents the initial capacity of 127.4 mAh g−1 and capacity loss of 14.9%. Enhanced rate and cyclic capability may be attributed to the optimizing particle size, carbon coating quality, and structural stability during the proper amount of Cr-doping (x = 0.1) in V sites. 相似文献
15.
Y.Q. Qiao J.P. Tu J.Y. Xiang X.L. Wang Y.J. Mai D. Zhang W.L. Liu 《Electrochimica acta》2011,(11):301
Three different synthetic routes, including solid-state reaction, sol–gel and hydrothermal methods are successfully used for preparation of Li3V2(PO4)3/C. Ascorbic acid is used as a reducing agent and/or as a chelating agent. The Li3V2(PO4)3/C synthesized by hydrothermal method with fine particles exhibits lower impedance and smaller potential difference values between oxidation and reduction peaks than those by solid-state reaction and sol–gel methods. Thus as cathode material for Li-ion batteries, the Li3V2(PO4)3/C synthesized by hydrothermal method shows higher discharge capacity, better rate capability and cyclic performance. Even at a high charge–discharge rate of 10 C, it still can deliver a discharge capacity of 101.4 mAh g−1 and 106.6 mAh g−1 in the potential range of 3.0–4.3 V and 3.0–4.8 V, respectively. The hydrothermal synthesis has been considered to be a competitive process to prepare Li3V2(PO4)3/C cathode materials with excellent electrochemical performances. 相似文献
16.
Yuzhan Li 《Electrochimica acta》2007,52(15):4922-4926
Li3V2(PO4)3/carbon composite material was synthesized by a promising sol-gel route based on citric acid using V2O5 powder as a vanadium source. Citric acid acts not only as a chelating reagent but also as a carbon source, which enhance the conductivity of the composite material and hinder the growth of Li3V2(PO4)3 particles. The structure and morphology of the sample were characterized by TG, XRD and TEM measurements. XRD results reveal that Li3V2(PO4)3/carbon was successfully synthesized and has a monoclinic structure with space group P21/n. TEM images show Li3V2(PO4)3 particles are about 45 nm in diameter embeded in carbon networks. Galvanostatic charge/discharge and cyclic voltammetry measurements were used to study its electrochemical behaviors which indicate the reversibility of the lithium extraction/insertion processes. Li3V2(PO4)3/carbon performed in a voltage window (3.0-4.8 V) exhibits higher discharge capacity, better cycling stability and its discharge capacity maintains about 167.6 mAh/g at a current density of 28 mA/g after 50 cycles. 相似文献
17.
Uniform and spherical Li(Ni1/3Co1/3Mn1/3)O(2−δ)Fδ powders were synthesized via NH3 and F− coordination hydroxide co-precipitation. The effect of F− coordination agent on the morphology, structure and electrochemical properties of the Li(Ni1/3Co1/3Mn1/3)O(2−δ)Fδ were studied. The morphology, size, and distribution of (Ni1/3Co1/3Mn1/3)(OH)(2−δ)Fδ particle diameter were improved in a shorter reaction time through the addition of F−. The study suggested that the added F improves the layered characteristics of the lattice and the cyclic performance of Li(Ni1/3Co1/3Mn1/3)O2 in the voltage range of 2.8-4.6 V. The initial capacity of the Li(Ni1/3Co1/3Mn1/3)O1.96F0.04 was 178 mAh g−1, the maximum capacity was 186 mAh g−1 and the capacity after 50 cycles was 179 mAh g−1 in the voltage range of 2.8-4.6 V. 相似文献
18.
Li2FeSiO4/carbon/carbon nano-tubes (Li2FeSiO4/C/CNTs) and Li2FeSiO4/carbon (Li2FeSiO4/C) composites were synthesized by a traditional solid-state reaction method and characterized comparatively by X-ray diffraction, scanning electron microscopy, BET surface area measurement, galvanostatic charge-discharge and AC impedance spectroscopy, respectively. The results revealed that the Li2FeSiO4/C/CNT composite exhibited much better rate performance in comparison with the Li2FeSiO4/C composite. At 0.2 C, 5 C and 10 C, the former composite electrode delivered a discharge capacity of 142 mAh g−1, 95 mAh g−1, 80 mAh g−1, respectively, and after 100 cycles at 1 C, the discharge capacity remained 95.1% of its initial value. 相似文献
19.
Structure and electrochemical properties of nanocarbon-coated Li3V2(PO4)3 prepared by sol-gel method
A liquid-based sol-gel method was developed to synthesize nanocarbon-coated Li3V2(PO4)3. The products were characterized by XRD, SEM and electrochemical measurements. The results of Rietveld refinement analysis indicate that single-phase Li3V2(PO4)3 with monoclinic structure can be obtained in our experimental process. The discharge capacity of carbon-coated Li3V2(PO4)3 was 152.6 mAh/g at the 50th cycle under 1C rate, with 95.4% retention rate of initial capacity. A high discharge capacity of 184.1 mAh/g can be obtained under 0.12C rate, and a capacity of 140.0 mAh/g can still be held at 3C rate. The cyclic voltammetric measurements indicate that the electrode reaction reversibility is enhanced due to the carbon-coating. SEM images show that the reduced particle size and well-dispersed carbon-coating can be responsible for the good electrochemical performance obtained in our experiments. 相似文献
20.
Van Hiep Nguyen Dong-Hee Lee Sae-Yane Baek Hal-Bon Gu Young Ho Kim 《Ceramics International》2018,44(11):12504-12510
In this study, silicon and its effect on the properties of Li3V2(PO4)3 were studied for lithium-ion battery applications. The composite material was synthesized and found to show enhanced capacity and cyclability. The presence of silicon in the composites was confirmed. Furthermore, large particles with rough, corroded-like structures formed, and these were distributed well with the silicon particles. The Li3V2(PO4)3-Si battery had good properties showing improved cyclability, an improved high performance rate, smaller impedance values and improved lithium-ion diffusion coefficients, as determined by cyclic voltammetry. Furthermore, the optimization of the silicon content led to a Li3V2(PO4)3-Si battery with a 2?wt% silicon loading that had a discharge capacity of 181?mA?h?g?1. At 2?C, Li3V2(PO4)3-Si (2?wt%) still demonstrated a capacity of 111.8?mA?h?g?1, which was 83.8% of its original capacity (compared with 70.3?mA?h?g?1 and 63.8% for Li3V2(PO4)3) after 400 cycles. 相似文献