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1.
The olivine-type cathode materials of LiFePO 4 were prepared via solid-state reaction under argon atmosphere and doped by chlorine to improve their electrochemical performances.
The crystal structure, morphology, and electrochemical properties of the prepared samples were investigated using thermogravimetry–differential
scanning calorimetry, X-ray diffraction, Fourier transform infrared, scanning electron microscopy, cyclic voltammetry, and
charge–discharge cycle measurements. The result showed that the electrochemical performance of LiFePO 4 had been improved by chlorine doping, and the effect of chlorine in lattice was discussed. The heavily doped samples show
better electrochemical performance in relative high rates. 相似文献
2.
Three kinds of LiFePO 4 materials, mixed with carbon (as LiFePO 4/C), doped with Ti (as Li 0.99Ti 0.01FePO 4), and treated both ways (as Li 0.99Ti 0.01FePO 4/C composite), were synthesized via ball milling by solid-state reaction method. The crystal structure and electrochemical
behavior of the materials were investigated using X-ray diffraction, SEM, TEM, cyclic voltammetry, and charge/discharge cycle
measurements. It was found that the electrochemical behavior of LiFePO 4 could be increased by carbon coating and Ti-doping methods. Among the materials, Li 0.99Ti 0.01FePO 4/C composite presents the best electrochemical behavior, with an initial discharge capacity of 154.5 mAh/g at a discharge
rate of 0.2 C, and long charge/discharge cycle life. After 120 cycles, its capacity remains at 92% of the initial capacity.
The Li 0.99Ti 0.01FePO 4/C composite developed here can be used as the cathode material for lithium ion batteries. 相似文献
3.
LiFePO 4/C composites were synthesized by pyrolysis of LiFePO 4/polypyrrole (PPy), which was obtained by an in situ chemical polymerization involving pyrrole monomer and hydrothermal synthesis LiFePO 4. All samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy,
cyclic voltammetry, and galvanostatic charge–discharge techniques. The results showed the LiFePO 4/C sintered at 800 °C containing 2.8 wt.% carbon exhibited a higher discharge capacity of 49.6 mAh·g −1 at 0.1 C, and bare LiFePO 4 only delivered 11.6 mAh·g −1 in 2 M LiNO 3 aqueous electrolyte. The possible reason for the improvement of electrochemical performance was discussed and could be attributed
to the formation of aromatic compounds during the carbonization of PPy. 相似文献
4.
以乙二醇为溶剂,采用溶剂热法一步合成圆饼状LiFePO 4,然后以葡萄糖为碳源与合成的LiFePO 4前躯体高温烧结得到碳包覆的LiFePO 4/C复合材料,其振实密度高达1.3 g·cm -3。采用X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对LiFePO 4/C复合材料进行了物相和形貌表征,研究结果表明制备得到的LiFePO 4呈圆饼状,且生成的圆饼是由单晶LiFePO 4纳米片堆积而成。此外,LiFePO 4颗粒表面碳层包覆均匀。将制备的LiFePO 4/C用作锂离子电池正极材料,电化学性能测试表明其具有高的充放电比容量(在0.1C时放电,其初始放电比容量为157.7 mAh·g -1)与良好的循环性能(500次循环后容量保持率为82.4%)。 相似文献
5.
以乙二醇为溶剂,采用溶剂热法一步合成圆饼状LiFePO_4,然后以葡萄糖为碳源与合成的LiFePO_4前躯体高温烧结得到碳包覆的LiFePO_4/C复合材料,其振实密度高达1.3 g·cm~(-3)。采用X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对LiFePO_4/C复合材料进行了物相和形貌表征,研究结果表明制备得到的LiFePO_4呈圆饼状,且生成的圆饼是由单晶LiFePO_4纳米片堆积而成。此外,LiFePO_4颗粒表面碳层包覆均匀。将制备的LiFePO_4/C用作锂离子电池正极材料,电化学性能测试表明其具有高的充放电比容量(在0.1C时放电,其初始放电比容量为157.7 mAh·g~(-1))与良好的循环性能(500次循环后容量保持率为82.4%)。 相似文献
6.
The yeast cells are adopted as a template and cementation agent to prepare LiFePO 4/C with high surface area by co-precipitation and microwave processing. The electrochemical properties of the resultant products
are investigated. The synthesized LiFePO 4/C is characterized by means of X-ray diffraction, transmission electron microscopy (TEM), Brunauer–Emmett–Teller method,
and battery test instrument. The LiFePO 4/C particles with average size of 35-100 nm coated by porous carbon are observed by TEM. The LiFePO 4/C, with the specific surface area of 98.3 m 2/g, exhibits initial discharge specific capacity of 147 mAh/g and good cycle ability. The yeast cells as a template are used
to synthesize the precursor LiFePO 4/cells compounds. In microwave heating process, the use of yeast cells as reducing matter and cementation agent results in
the enhancement of the electrochemical properties. 相似文献
7.
Nanocrystalline LiFePO 4 and LiFe 0.97Sn 0.03PO 4 cathode materials were synthesized by an inorganic-based sol–gel route. The physicochemical properties of samples were characterized
by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and
elemental mapping. The doping effect of Sn on the electrochemical performance of LiFePO 4 cathode material was extensively investigated. The results showed that the doping of tin was beneficial to refine the particle
size, increase the electrical conductivity, and facilitate the lithium-ion diffusion, which contributed to the improvement
of the electrochemical properties of LiFePO 4, especially the high-rate charge/discharge performance. At the low discharge rate of 0.5 C, the LiFe 0.97Sn 0.03PO 4 sample delivered a specific capacity of 158 mAh g −1, as compared with 147 mAh g −1 of the pristine LiFePO 4. At higher C-rate, the doping sample exhibited more excellent discharge performance. LiFe 0.97Sn 0.03PO 4 delivered specific capacity of 146 and 128 mAh g −1 at 5 C and 10 C, respectively, in comparison with 119 and 107 mAh g −1 for LiFePO 4. Moreover, the doping of Sn did not influence the cycle capability, even at 10 C. 相似文献
8.
采用氧化物前驱体对磷酸铁锂(LiFePO 4)进行少量金属离子掺杂,并用XRD,SEM和恒电流充放电对掺杂的LiFePO 4进行了研究。结果表明,少量的掺杂离子在很大程度上提高了LiFePO 4的电化学性能,特别是大电流放电性能。1.0 mol%的Nb 5+掺杂LiFePO 4的0.1 C放电容量约150 mAh·g -1;即使在3 C倍率下放电,也有117 mAh·g -1的容量。掺杂的效果与掺杂离子的半径、价态密切相关,半径小、价态高的离子对提高LiFePO 4的电化学性能有利。在掺杂量较小时(<2.0 mol%),掺杂效果与掺杂离子的浓度关系不大。 相似文献
9.
以FeSO 4·7H 2O、NH 4H 2PO 4、H 2O 2、Li 2CO 3、C 6H 12O 6和自制的氧化石墨烯(GO)为原料,分别采用原位包覆法和非原位包覆法制备了石墨烯磷酸铁锂样品:LiFePO 4/C/G-1和LiFePO 4/C/G-2。用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、交流阻抗(EIS)和充放电测试研究了两种包覆方法制备的样品的晶体结构、形貌和电化学性能。结果表明原位法包覆所得复合材料LiFePO 4/C/G-1具有更优秀的电性能:在2.5~4.1V充放电,0.1C和1C首次放电比容量分别为158.15和150.5mAh·g -1,在1C倍率下循环500次后容量保持率达到98.3%。 相似文献
10.
A fast and convenient sol–gel route was developed to synthesize LiFePO 4/C composite cathode material, and the sol–gel process can be finished in less than an hour. Polyethyleneglycol (PEG), d-fructose, 1-hexadecanol, and cinnamic acid were firstly introduced to non-aqueous sol–gel system as structure modifiers and
carbon sources. The samples were characterized by X-ray powder diffraction, field emission scanning electron microscopy, and
elemental analysis measurements. Electrochemical performances of LiFePO 4/C composite cathode materials were characterized by galvanostatic charge/discharge and AC impedance measurements. The material
obtained using compound additives of PEG and d-fructose presented good electrochemical performance with a specific capacity of 157.7 mAh g −1 at discharge rate 0.2 C, and the discharge capacity remained about 153.6 mAh g −1 after 50 cycles. The results indicated that the improved electrochemical performance originated mainly from the microporous
network structure, well crystalline particles, and the increased electronic conductivity by proper carbon coating (3.11%). 相似文献
11.
Hybrid materials xLiFePO 4·(1 − x)Li 3V 2(PO 4) 3 were synthesized by sol–gel method, with phenolic resin as carbon source and chelating agent, methylglycol as surfactant.
The crystal structure, morphology and electrochemical performance of the prepared samples were investigated by X-ray diffraction
(XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge–discharge test and particle size
analysis. The results show that LiFePO 4 and Li 3V 2(PO 4) 3 co-exist in hybrid materials, but react in single phase. Compared with individual LiFePO 4 and Li 3V 2(PO 4) 3 samples, hybrid materials have smaller particle size and more uniform grain distribution. This structure can facilitate Li
ions extraction and insertion, which greatly improves the electrochemical properties. The sample 0.7LiFePO 4·0.3Li 3V 2(PO 4) 3 retains the advantages of LiFePO 4 and Li 3V 2(PO 4) 3, obtaining an initial discharge capacity of 166 mA h/g at 0.1 C rate and 109 mA h/g at 20 C rate, with a capacity retention
rate of 73.3% and an excellent cycle stability. 相似文献
12.
A novel LiFePO 4/Carbon aerogel (LFP/CA) nanocomposite with 3D conductive network structure was synthesized by using carbon aerogels as both
template and conductive framework, and subsequently wet impregnating LiFePO 4 precursor inside. The LFP/CA nanocomposite was characterized by X-ray diffraction (XRD), TG, SEM, TEM, nitrogen sorption,
electrochemical impedance spectra and charge/discharge test. It was found that the LFP/CA featured a 3D conductive network
structure with LiFePO 4 nanoparticles ca. 10–30 nm coated on the inside wall of the pore of CA. The LFP/CA electrodes delivered discharge capacity
for LiFePO 4 of 157.4, 147.2, 139.7, 116.3 and 91.8 mA h g −1 at 1 °C, 5 °C, 10 °C, 20 °C and 40 °C, respectively. In addition, the LFP/CA electrode exhibited good cycling performance,
which lost less than 1% of discharge capacity over 100 cycles at a rate of 10 °C. The good high rate performances of LiFePO 4 were attributed to the unique 3D conductive network structure of the nanocomposite. 相似文献
13.
采用柠檬酸辅助水热法合成了高分散性树叶状LiFePO 4/C复合正极材料。利用X射线衍射、傅里叶红外光谱、扫描电镜、高分辨率透射电镜和选区电子衍射分析了材料的形貌结构。结果表明,柠檬酸对树叶状LiFePO 4/C复合材料的形成具有促进作用。该材料的最大暴露晶面为(010)晶面,且分散性较好。与颗粒状LiFePO 4/C材料相比,该材料呈现出更高的放电比容量和更好的倍率性能,在0.1C和5C倍率下,放电比容量分别为158和126mAh·g -1,其原因是由于锂离子沿[010]方向的扩散距离缩短,从而使锂离子扩散系数显著增大。 相似文献
14.
Lithium iron phosphate (LiFePO4) cathode materials were synthesized by the solvothermal method with the assistance of different surfactants. The influences of polyethylene glycol 2000 (PEG 2000), polyvinylpyrrolidone (PVP), and cetyltrimethyl ammonium bromide (CTAB) on the microstructure and electrochemical performance of LiFePO4 were investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), electrochemical impedance spectroscopy (EIS), and charge/discharge measurements. The particle size of the LiFePO4 synthesized with the assistance of PEG was uniform and showed a flat rhombohedron-like shape. The initial discharge specific capacity is up to 122.80 mAh/g with an initial coulombic efficiency of 95.50% at 0.1C. LiFePO4 synthesized with PVP-assisted presents a porous structure with an initial discharge specific capacity of 91.01 mAh/g. LiFePO4 synthesized with CTAB-assisted shows a flower-like morphology with an initial discharge specific capacity of 100.44 mAh/g. Though the initial discharge capacities of the LiFePO4 materials prepared with the assistance of CTAB and PVP are lower than those of the LiFePO4 prepared without the assistance of surfactant, the two materials exhibited excellent cyclic stability at 0.1C. 相似文献
15.
LiFePO 4-C nanoparticles were synthesized by a hydrothermal method and subsequent high-energy ball-milling. Different carbon conductive
additives including nanosized acetylene black (AB) and multi-walled carbon nanotube (MWCNT) were used to enhance the electronic
conductivity of LiFePO 4. The structural and morphological performance of LiFePO 4-C nanoparticles was investigated by X-ray diffraction (XRD) and scanning electron microscopy. The electrochemical properties
of LiFePO 4-C/Li batteries were analyzed by cyclic voltammetry and charge/discharge tests. XRD results demonstrate that LiFePO 4-C nanoparticles have an orthorhombic olivine-type structure with a space group of Pnma. LiFePO 4-C/Li battery with 5 wt% MWCNT displays the best electrochemical properties with a discharge capacity of 142 mAh g −1 at 0.25 C at room temperature. 相似文献
16.
以三价铁盐为铁源,采用多元醇还原法在低温下制备出了具有不同长径比的棒状LiFePO 4材料. 通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、循环伏安(CV)、交流阻抗谱(EIS)和恒电流充放电测试等手段分析了不同回流反应时间下制备出的前驱体和最终的LiFePO 4/C 样品. 结果表明:回流反应时间对LiFePO 4的形貌和特性有明显的影响. 通过把回流反应时间从4 h延长至16 h,材料的形貌由不规则的短棒状颗粒变为规则的长棒状颗粒,且棒的直径明显变小. 当回流反应时间为10 h 时,样品复合了多种形貌,有利于电子的传输,在低倍率下具有优秀的性能,0.1C放电比容量为163 mAh·g -1;当回流反应时间为16 h 时,样品具有最大的长径比,有利于锂离子的扩散,在高倍率下具有良好的性能,1C、3C、5C、10C、20C倍率下放电比容量分别为135、125、118、110、98 mAh·g -1,循环性能良好,几乎无衰减. 相似文献
17.
Olivine LiFePO 4/C nanocomposite cathode materials with small-sized particles and a unique electrochemical performance were successfully prepared
by a simple solid-state reaction using oxalic acid and citric acid as the chelating reagent and carbon source. The structure
and electrochemical properties of the samples were investigated. The results show that LiFePO 4/C nanocomposite with oxalic acid (oxalic acid: Fe 2+= 0.75:1) and a small quantity of citric acid are single phase and deliver initial discharge capacity of 122.1 mAh/g at 1
C with little capacity loss up to 500 cycles at room temperature. The rate capability and cyclability are also outstanding
at elevated temperature. When charged/discharged at 60 °C, this materials present excellent initial discharge capacity of
148.8 mAh/g at 1 C, 128.6 mAh/g at 5 C, and 115.0 mAh/g at 10 C, respectively. The extraordinarily high performance of LiFePO 4/C cathode materials can be exploited suitably for practical lithium-ion batteries. 相似文献
18.
LiFePO 4/C composites are prepared by using two types of carbon source: one using polymer (PAALi) and the other using sucrose. The physical characteristics of LiFePO 4/C composites are investigated by X-ray diffraction), scanning electron microscopy, BET, laser particle analyzer, and Raman spectroscopy. Their electrochemical properties are characterized by cyclic voltammograms, constant current charge–discharge, and electrochemical impedance spectra. These analyses indicate that the carbon source and carbon content have a great effect on the physical and electrochemical performances of LiFePO 4/C composites. An ideal carbon source and appropriate carbon content can effectively increase the lithium-ion diffusion coefficient and exchange current density, decrease the charge transfer resistance ( R ct), and enhance the electrochemical performances of LiFePO 4/C composite. The results show that PAALi is a better carbon source for the synthesis of LiFePO 4/C composites. When the carbon content is 4.11 wt.% (the molar ratio of PAALi/Li 2C 2O 4 was 2:1), as-prepared LiFePO 4/C composite shows the best combination between electrochemical performances and tap density. 相似文献
19.
Core–shell LiFePO 4/C composite was synthesized via a sol–gel method and doped by fluorine to improve its electrochemical performance. Structural
characterization shows that F − ions were successfully introduced into the LiFePO 4 matrix. Transmission electron microscopy verifies that F-doped LiFePO 4/C composite was composed of nanosized particles with a ~3 nm thick carbon shell coating on the surface. As a cathode material
for lithium-ion batteries, the F-doped LiFePO 4/C nanocomposite delivers a discharge capacity of 162 mAh/g at 0.1 C rate. Moreover, the material also shows good high-rate
capability, with discharge capacities reaching 113 and 78 mAh/g at 10 and 40 C current rates, respectively. When cycled at
20 C, the cell retains 86% of its initial discharge capacity after 400 cycles, demonstrating excellent high-rate cycling performance. 相似文献
20.
Olivine LiFePO 4/C cathode materials for lithium ion batteries were synthesized using monodisperse polystyrene (PS) nano-spheres and other
carbon sources. The structure, morphology, and electrochemical performance of LiFePO 4/C were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge–discharge tests,
electrochemical impedance spectroscopy (EIS) measurements, and Raman spectroscopy measurements. The results demonstrated that
LiFePO 4/C materials have an ordered olivine-type structure with small particle sizes. Electrochemical analyses showed that the LiFePO 4/C cathode material synthesized from 7 wt.% PS nano-spheres delivers an initial discharge capacity of 167 mAh g -1 (very close to the theoretical capacity of 170 mAh g -1) at 0.1 C rate cycled between 2.5 and 4.1 V with excellent capacity retention after 50 cycles. According to Raman spectroscopy
and EIS analysis, this composite had a lower I
D/ I
G, sp
3/ sp
2 peak ratio, charge transfer resistance, and a higher exchange current density, indicating an improved electrochemical performance,
due to the increased proportion of graphite-like carbon formed during pyrolysis of PS nano-spheres, containing functionalized
aromatic groups. 相似文献
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