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1.
The electrochemical performance of Li 3V 2(PO 4) 3/C was investigated at various low temperatures in the electrolyte 1.0 mol dm −3 LiPF 6/ethyl carbonate (EC)+diethyl carbonate (DEC)+dimethyl carbonate (DMC) (volume ratio 1:1:1). The stable specific discharge
capacity is 125.4, 122.6, 119.3, 116.6, 111.4, and 105.7 mAh g −1 at 26, 10, 0, −10, −20, and −30 °C, respectively, in the voltage range of 2.3–4.5 V at 0.2 C rate. When the temperature decreases
from −30 to −40 °C, there is a rapid decline in the capacity from 105.7 to 69.5 mAh g −1, implying that there is a nonlinear relationship between the performance and temperature. With temperature decreasing, R
ct (corresponding to charge transfer resistance) increases rapidly, D (the lithium ion diffusion coefficients) decreases sharply, and the performance of electrolyte degenerates obviously, illustrating
that the low-temperature electrochemical performance of Li 3V 2(PO 4) 3/C is mainly limited by R
ct, D
Li, and electrolyte. 相似文献
2.
Li(3)V(2)(PO(4))(3)/graphene nanocomposites have been firstly formed on reduced graphene sheets as cathode material for lithium batteries. The nanocomposites synthesized by the sol-gel process exhibit excellent high-rate and cycling stability performance, owing to the nanoparticles connected with a current collector through the conducting graphene network. 相似文献
3.
Various structures and morphologies of Li 3V 2(PO 4) 3 precursors are synthesized by a novel ionothermal method using three kinds of imidazolium-based ionic liquids as both reaction mediums and structure-directing agents at ambient pressure. Nanostructured Li 3V 2(PO 4) 3/C cathode materials can be successfully prepared by a subsequent short calcination process. The structures, morphologies, and electrochemical properties are characterized by X-ray diffractometry, thermogravimetry, scanning and transmission electron microscopy, charge–discharge test, cyclic voltammetry, and electrochemical impedance spectroscopy. It shows that three kinds of materials synthesized present different morphologies and particle sizes. The result can be due to imidazolium-based ionic liquids, which combined with different anions play important role in forming the size and morphology of Li 3V 2(PO 4) 3 material. These materials present excellent performance with high rate capacity and cycle stability. Especially, the Li 3V 2(PO 4) 3/C material prepared in 1-ethyl-3-methylimadozolium trifluoromethanesulfonate ([emim][OTf]) can deliver discharge capacities of 127.4, 118.9, 105.5, and 92.8 mAh?g ?1 in the voltage range of 3.0–4.3 V at charge–discharge rate of 0.1, 1, 10, and 20 C after 50 cycles, respectively. The excellent rate performance can be attributed to the uniform nanostructure, which can make the lithium-ion diffusion and electron transfer more easily across the Li 3V 2(PO 4) 3/electrolyte interfaces. 相似文献
5.
The carbon-coated monoclinic Li 3V 2(PO 4) 3 (LVP/C) cathode materials can be synthesized by one-step heat treatment from a sucrose-containing precursor. Properties of the prepared composite material were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), pore size distribution and specific surface area analyzer, optical particle size analyzer and electrochemical methods. X-ray diffraction results show that LVP sample is monoclinic structure. The sample presents initial discharge capacity of 127.2 mA h/g (at 0.2 C rate), and exhibits better cycling stability (115.1 mA h/g at 30th cycle at 0.2 C rate) and better rate capability (83.1 mA h/g at 50th cycle under 6 C rate) in the voltage range of 3.0–4.3 V. In the voltage range of 3.0–4.8 V, it exhibits a initial discharge capacity of 169.1 mA h/g and good cycling stability (104.9 mA h/g at 20th cycle at 0.5 C rate). 相似文献
6.
Nano-structured Li 3V 2(PO 4) 3/carbon composite (Li 3V 2(PO 4) 3/C) has been successfully prepared by incorporating the precursor solution into a highly mesoporous carbon with an expanded pore structure. X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy were used to characterize the structure of the composites. Li 3V 2(PO 4) 3 had particle sizes of < 50 nm and was well dispersed in the carbon matrix. When cycled within a voltage range of 3 to 4.3 V, a Li 3V 2(PO 4) 3/C composite delivered a reversible capacity of 122 mA h g ? 1 at a 1C rate and maintained a specific discharge capacity of 83 mA h g ? 1 at a 32C rate. These results demonstrate that cathodes made from a nano-structured Li 3V 2(PO 4) 3 and mesoporous carbon composite material have great potential for use in high-power Li-ion batteries. 相似文献
7.
Journal of Solid State Electrochemistry - Li0.995Nb0.005Mn0.85Fe0.15PO4/C was prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron... 相似文献
8.
Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate). 相似文献
9.
Na-doped Li 3V 2(PO 4) 3/C (LVP/C) cathode materials are prepared by a sol–gel method. X-ray diffraction results show that the Na ion has been well doped into the crystal structure of LVP/C and does not disturb the extraction–insertion behavior of lithium ion seriously. The initial discharge capacity of the Na-doped LVP/C is 112.2?mA?h g ?1 at 5?C, and the capacity retention reaches 98.3?% over 80 cycles. Cyclic voltammetry and electrochemical impedance spectra indicate that the reversibility of electrochemical redox reaction and the charge-transfer resistance of LVP/C cathode material have been significantly improved by Na doping. The improved performances can be attributed to the more convenient route for lithium ion diffusion and the lower activation energy of the extraction–insertion of lithium ion due to the weakness of Li-O bond. 相似文献
10.
A series of Li 3V 2(PO 4) 3/C cathode materials with different morphologies were successfully prepared by controlling temperatures using maleic acid as carbon source via a simple sol–gel reaction method. The Li 3V 2(PO 4) 3/C nanorods synthesized at 700 °C with diameters of about 30–50 nm and lengths of about 800 nm show the highest initial discharge capacity of 179.8 and 154.6 mA h g −1 between 3.0 and 4.8 V at 0.1 and 0.5 C, respectively. Even at a discharge rate of 0.5 C over 50 cycles, the products still can deliver a discharge capacity of 140.2 mA h g −1 in the potential region of 3.0–4.8 V. The excellent electrochemical performance can be attributed to one-dimensional nanorod structure and uniform particle size distribution. All these results indicate that the resulting Li 3V 2(PO 4) 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
11.
Na 3V 2(PO 4) 3 is a very prospective sodium-ion batteries (SIBs) electrode material owing to its NASICON structure and high reversible capacity. Conversely, on account of its intrinsic poor electronic conductivity, Na 3V 2(PO 4) 3 electrode materials confront with some significant limitations like poor cycle and rate performance which inhibit their practical applications in the energy fields. Herein, a simple two-step method has been implemented for the successful preparation of carbon-coated Na 3V 2(PO 4) 3 materials. As synthesized sample shows a remarkable electrochemical performance of 124.1 mAh/g at 0.1 C (1 C = 117.6 mA/g), retaining 78.5 mAh/g under a high rate of 200 C and a long cycle-performance (retaining 80.7 mAh/g even after 10000 cycles at 20 C), outperforming the most advanced cathode materials as reported in literatures. 相似文献
12.
A convenient method named wet coordination is used to prepare the sample or carbon-coated Li 3V 2(PO 4) 3 in the furnace with a flowing argon atmosphere at 600 °C for 1 h. The sample is characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and energy dispersive analysis of X-rays (EDAX). Galvanostatic charge–discharge between 3.3 and 4.3 V (vs. Li/Li +) shows that the sample exhibits a high discharge capacity of 128 mAh g ?1 with a good reversible performance under a current density of 95 mA g ?1. It suggests that carbon-coated Li 3V 2(PO 4) 3 with good electrochemical performance can be obtained via this method, which is suitable for large-scale production. 相似文献
13.
Journal of Solid State Electrochemistry - Na3V2(PO4)3/C composite nanofibers are prepared successfully through a coaxial electrospinning technique and subsequent calcination. The diameter of the... 相似文献
14.
随着市场对锂离子电池(LIB)需求的日趋增长,对电极活性物质的要求也在朝着高能量密度、低成本、安全稳定、环境友好的方向努力,其中正极材料相对负极材料的发展较为缓慢,成为制约LIB发展的瓶颈。NASICON结构的Li3V2(PO4)3属于单斜晶系,相对金属锂具有很高的电势,理论容量高达19 相似文献
15.
A series of Cr-doped Li3V2 − x
Cr
x
(PO4)3 (x = 0, 0.1, 0.25, and 0.5) samples are prepared by a sol–gel method. The effects of Cr doping on the physical and chemical characteristics of Li3V2(PO4)3 are investigated. Compared with the XRD pattern of the undoped sample, the XRD patterns of the Cr-doped samples have no extra reflections, which indicates that Cr enters the structure of Li3V2(PO4)3. As indicated by the charge–discharge measurements, the Cr-doped Li3V2 − x
Cr
x
(PO4)3 (x = 0.1, 0.25, and 0.5) samples exhibit lower initial capacities than the undoped sample at the 0.2 C rate. However, both the discharge capacity and cycling performance at high rates (e.g., 1 and 2 C) are enhanced with proper amount of Cr doping (x = 0.1). The highest discharge capacity and capacity retention at the rates of 1 and 2 C are obtained for Li3V1.9Cr0.1(PO4)3. The improvement of the electrochemical performance can be attributed to the higher crystal stability and smaller particle size induced by Cr doping. 相似文献
16.
Composite Li 3V 2(PO 4) 3/C cathode material can be synthesized by spray-drying and carbothermal method. The monoclinic-phase Li 3V 2(PO 4) 3/C was prepared with the process of double spray drying at 260 °C and subsequent heat treatment at 750 °C for 12 h. The results
indicate that the Li 3V 2(PO 4) 3/C presents large reversible discharge capacity of 121.9 mA h g −1 and charge capacity of 131.8 mA h g −1 at the current density of C/ 5, good rate capability with 61.1 mA h g −1 at 20C, and excellent capacity retention rate close to 100% at various current densities in the region of 3.0–4.3 V. 相似文献
17.
Journal of Solid State Electrochemistry - Considering the poor electronic conductivity of the pure Li9V3(P2O7)3(PO4)2, we have successfully synthesized a series of Li9?xMgxV3(P2O7)3(PO4)2... 相似文献
18.
The effect of Al 2O 3 -coating on Li 3V 2(PO 4) 3/C cathode material for lithium-ion batteries has been investigated. The crystalline structure and morphology of the synthesized powders have been characterized by XRD, SEM, and HRTEM, and their electrochemical performances are evaluated by CV, EIS, and galvanostatic charge/discharge tests. It is found that Al 2O 3 -coating modification stabilizes the structure of the cathode material, decreases the polarization of electrode and suppresses the rise of the surface film resistance. Electrochemical tests indicate that cycling performance and rate capability of Al 2O 3-coated Li 3V 2(PO 4) 3/C are enhanced, especially at high rates. The Al 2O 3-coated material delivers discharge capacity of 123.03 mAh g ?1 at 4 C rate, and the capacity retention of 94.15 % is obtained after 5 cycles. The results indicate that Al 2O 3 -coating should be an effective way to improve the comprehensive properties of the cathode materials for lithium-ion batteries. 相似文献
19.
Fe/FeO/Fe 3O 4 composite was synthesized by a simple solid method using ferric citrate and phenolic resin as raw materials. The reaction processes of raw materials mixture were characterized by thermogravimetric analysis (TGA) under nitrogen. X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the structure and morphology of the products. The results showed that the obtained material was octahedral Fe/FeO/Fe 3O 4 composite with a size of 2-4 μm. The electrochemical performances of Fe/FeO/Fe 3O 4 composite as anode material were also evaluated, which exhibited a stable specific capacity of 260.3 mAh g -1 and an ideal initial coulombic efficiency of 90.8% in the range of 0.05~3 V at the 5C rate. A good rate capacity of Fe/FeO/Fe 3O 4 composite electrode was also shown by the charge-discharge testing even at the rate of 60C. The better rate capability of Fe/FeO/Fe 3O 4 electrode could be measured in higher temperature. 相似文献
20.
The flake-like Li 3V 2(PO 4) 3/C has been successfully synthesized by rheological phase method using polyvinyl alcohol (PVA) as template; the Li 3V 2(PO 4) 3/C without PVA assistance has been prepared for comparison. X-ray diffraction analysis shows that the two samples are well crystallized, and no impurity phases are detected. The scanning electron microscopy results reveal that there is a significant difference in morphologies between PVA-assisted sample and sample without PVA; the former shows a flake-like morphology, while the latter presents regular granular shape with some agglomeration. Transmission electron microscopy images reveal that Li 3V 2(PO 4) 3 particles are coated with a uniform surface carbon layer. The lattice fringes with a spacing of 0.428 nm can be clearly seen from the high-resolution transmission electron microscopy image. The PVA-assisted sample shows a discharge capacity of 120, 110, and 96 mAh g ?1 at 1 C, 20 C, and 50 C, respectively; however, the sample without PVA exhibits a lower discharge capacity. Based on the analysis of electrochemical impedance spectroscopy, the lithium ion diffusion coefficients of Li 3V 2(PO 4) 3/C and PVA-assisted Li 3V 2(PO 4) 3/C are 4.19?×?10 ?9 and 4.99?×?10 ?8 cm 2 s ?1, respectively. In summary, it is demonstrated that using PVA as a template can obtain flake-like morphology and significantly improve the comprehensive electrochemical performances of Li 3V 2(PO 4) 3/C cathode material. 相似文献
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