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1.
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
2.
Crystalline LiFePO 4 nanoplates were incorporated with 5 wt.% multi-walled carbon nanotubes (CNTs) via a facile low temperature polyol process, in one single step without any post heat treatment. The CNTs were embedded into the LiFePO 4 particles to form a network to enhance the electrochemical performance of LiFePO 4 electrode for lithium-ion battery applications. The structural and morphological characters of the LiFePO 4–CNT composites were investigated by X-ray diffraction, Fourier Transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The electrochemical properties were analyzed by cyclic voltammetry, electrochemical impedance spectroscopy and charge/discharge tests. Primary results showed that well crystallized olivine-type structure without any impurity phases was developed, and the LiFePO 4–CNT composites exhibited good electrochemical performance, with a reversible specific capacity of 155 mAh g −1 at the current rate of 10 mA g −1, and a capacity retention ratio close to 100% after 100 cycles. 相似文献
3.
LiFePO 4/C composite is synthesized by oxalic acid-assisted rheological phase method. Fe 2O 3 and LiH 2PO 4 are chosen as the starting materials, sucrose as carbon sources, and oxalic acid as the additive. The crystalline structure
and morphology of the products are characterized by X-ray diffraction and field emission scanning electron microscopy. The
charge–discharge kinetics of LiFePO 4 electrode is investigated using cyclic voltammetry and electrochemical impedance spectroscopy. It is found that the introduction
of appropriate amount of oxalic acid leads to smaller particle sizes, more homogeneous size distribution, and some Fe 2P produced in the final products, resulting in reduced polarization, impedance, and improved Li + ion diffusion coefficient. The best cell performance is delivered by the sample with R = 1.5 ( R of the molar ratio of oxalic acid to LiH 2PO 4). Its discharge capacity is 154 mAh g −1 at 0.2 C rate and 120 mAh g −1 at 5.0 C rate. At the same time, it exhibits an excellent cycling stability; no obvious decrease even after 1,000 cycles
at 1.0 C rate. 相似文献
4.
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
5.
Nano-crystalline LiFePO 4 and LiMg 0.05Fe 0.95PO 4 cathode materials were synthesized by sol–gel method in argon atmosphere using succinic acid as a chelating agent. Physico-chemical
characterizations were done by thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy,
transmittance electron microscopy, and Raman spectroscopy. Electrochemical behavior of the cathode materials were analyzed
using cyclic voltammetry, and galvanostatic charge/discharge cycling studies were employed to characterize the reaction of
lithium-ion insertion into and extraction from virginal and magnesium-doped LiFePO 4, in the voltage range 2.5 to 4.5 V (Vs Li/Li +) using 1 M LiPF 6 with 1:1 ratio of ethylene carbonate and dimethyl carbonate as electrolytes. LiMg 0.05Fe 0.95PO 4 exhibits initial charge and discharge capacities of 159 and 141 mAh/g at 0.2 C rate respectively, as compared to 121 and
107 mAh/g of pristine LiFePO 4. Furthermore, LiMg 0.05Fe 0.95PO 4 has retained more than 89% of the capacity even after 60 cycles. Hence, LiMg 0.05Fe 0.95PO 4 is a promising cathode material for rechargeable lithium-ion batteries. 相似文献
6.
A LiFePO 4/C composite was obtained by a polymer pyrolysis reduction method, using lithium polyacrylate (LiPAA) as carbon source and
fractional lithium source, and FePO 4·2H 2O as iron and phosphorus source. The structure of the LiFePO 4/C composites was investigated by X-ray diffraction (XRD). The micromorphology of the precursors and LiFePO 4/C powders was observed using scanning electron microscopy (SEM). Laser particle analyzer and BET were also used to characterize
the materials. It was found that the micromorphology, particle size distribution and specific surface area of LiFePO 4/C composites were greatly influenced by the molecular weight of LiPAA. The electrochemical properties of the LiFePO 4/C composites were evaluated by cyclic voltammograms (CVs), electrochemical impedance spectra (EIS) and constant current charge/discharge
cycling tests. The results showed that the molecular weight of LiPAA, heating rate, synthetic temperature and sintering duration
directly affected the electrochemical properties of LiFePO 4/C composites. The sample with the optimized electrochemical properties were obtained in the following conditions, i.e., LiPAA
with the molecular weight of 20,000, heating rate of 10 °C min −1, synthetic temperature of 700 °C and sintering duration of 15 h. 相似文献
7.
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
8.
This study reports on the preparation of a composite polymer electrolyte for secondary lithium-ion battery. Poly(vinylidiene
fluoride-hexafluoropropylene) (P(VDF-HFP)) was used as the polymer host, and mesoporous SBA-15 (silica) ceramic fillers used
as the solid plasticizer were added into the polymer matrix. The SBA-15 fillers with mesoporous structure and high specific
surface can trap more liquid electrolytes to enhance the ionic conductivity. The ionic conductivity of P(VDF-HFP)/SBA-15 composite
polymer electrolytes was in the order of 10 −3 S cm −1 at room temperature. The characteristic properties of the composite polymer membranes were examined by using FTIR spectroscopies,
scanning electron microscopy (SEM), and an AC impedance method. For comparison, the LiFePO 4/Li composite batteries with a conventional microporous polyethylene (PE) separator and pure P(VDF-HFP) polymer membrane were
also prepared and studied. As a result, the LiFePO 4/Li composite battery comprised the P(VDF-HFP)/10 wt.% m-SBA-15 composite polymer electrolyte, which achieves an optimal discharge
capacity of 88 mAh g −1 at 20 C rate with a high coulomb efficiency of 95%. It is demonstrated that the P(VDF-HFP)/m-SBA-15 composite membrane exhibits
as a good candidate for application to LiFePO 4 polymer batteries. 相似文献
9.
采用溶剂热法制备正极材料LiFePO_4,采用溶胶凝胶法制备Li_(0.5)La_(0.5)TiO_3(LLTO)粉体,并通过酒精悬浮法对LiFePO_4进行修饰,修饰量为LiFePO_4质量的1%~4%,获得了薄壁蜂窝状自组装结构的LiFePO_4上修饰有球状LLTO纳米颗粒的复合正极材料。通过进行充放电测试、交流阻抗测试及循环伏安测试,研究了不同修饰量对电池的充放电比容量、循环性能及可逆性的影响,发现当LLTO含量为3%(w/w)时,以2C和5C倍率放电相对于没有修饰LLTO的LiFePO_4的比容量分别提高29.7%和31.6%,30次循环之后,容量损失率较未改性前减小4.13%,循环伏安曲线上氧化还原峰之间的电位差仅为0.117 V,以3%的LLTO修饰改性的LiFePO_4显著提高了电池的倍率性能、循环性能和低温性能。 相似文献
10.
Olivine-type LiFePO 4 composite materials for cathode material of the lithium-ion batteries were synthesized by using a sol-gel method and were
coated by a chemical deposition of silver particles. As-obtained LiFePO 4/C-Ag (2.1 wt.%) composites were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD),
conductivity measurements, cyclic voltammetry, as well as galvanostatic measurements. The results revealed that the discharge
capacity of the LiFePO 4/C-Ag electrode is 136.6 mAh/g, which is 7.6% higher than that of uncoated LiFePO 4/C electrode (126.9 mAh/g). The LiFePO 4/C coated by silver nanoparticles enhances the electrode conductivity and specific capacity at high discharge rates. The improved
capacity at high discharge rates may be attributed to increased electrode conductivity and the synergistic effect on electron
and Li + transport after silver incorporation. 相似文献
11.
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
12.
LiFePO 4/C cathode materials were synthesized through in situ solid-state reaction route using Fe 2O 3, NH 4H 2PO 4, Li 2C 2O 4, and lithium polyacrylate as raw materials. The precursor of LiFePO 4/C was investigated by thermogravimetric/differential thermal analysis. The effects of synthesis temperature and molar ratio
of organic lithium salts on the performance of samples were characterized by X-ray diffraction, scanning electron microscopy,
electrochemical impedance spectra, cyclic voltammogram, and constant current charge/discharge test. The sample prepared at
optimized conditions of synthesis temperature at 700 °C and molar ratio with 1.17:1 exhibits excellent rate performance and
cycling stability at room temperature. 相似文献
13.
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
14.
Electrochemical and interfacial characteristics of Li-ion battery system based on LiFePO 4 cathode and graphite anode with ionic liquid (IL) electrolytes have been investigated, both with and without addition of
a small amount of polymer to the electrolyte. The IL electrolyte consisted of bis(fluorosulfonyl)imide (FSI) as anion and
1-ethyl-3-methyleimidazolium (EMI) or N-methyl- N-propylpyrrolidinium (Py13) as cation, and operated at ambient temperature. We reported previously that the SEI formation
with IL was stabilized in the graphite anode at 80% coulombic efficiency (CE) in the first cycle, when FSI anion is used.
In this work, we extend the study to the LiFePO 4 cathode material. Gel polymer with IL is one part of this study. The stepwise impedance spectroscopy was used to characterize
the Li/IL-Gel polymer/LiFePO 4 at different states of charge. This technique revealed that the interface resistance was stabilized when the cathode is at
70% DoD (Depth of Discharge). The diffusion resistance is higher at the two extremes of discharge when monophase LiFePO 4 state (0%DoD and 100%DoD) obtains. When polymer is added to the IL, interface resistance is improved with 1 wt.% but results
with IL alone are not improved for the case of 5 wt.% polymer added. Good cycling life stability was obtained with Li/IL-FSI/LiFePO 4 cells, with or without polymer. The first evaluation of the Li-ion cell, LiFePO 4/IL-FSI-(5 wt.%) gel polymer/graphite, has shown low first CE at 68.4% but it recovers in the third cycle, to 96.5%. Some
capacity fade was noticed after 30 cycles. The rate capability of the Li-ion cell shows a stable capacity until 2 C discharge
rate.
Dedicated to Professor J.O’ M. Bockris, whose contributions to electrochemistry are inestimable and indelible, on his eighty-fifth
birthday. 相似文献
15.
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
16.
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
17.
Well-dispersed graphene materials reduced by Ac under hydrothermal condition were used as conductive additives to improve intrisic disadvantage of promising LiFePO 4 battery materials, which was synthesized at surface of graphene sheets. The as-prepared LiFePO 4/graphene composites were characterized by X-ray powder diffraction (XRD), scan electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge tests. The results show that, compared with conventional LiFePO 4 platelets, the composite deliver excellent electrochemical performances, due to flexible graphene-based porous conducting network. We believe that such a facile process will provide a new pathway for further enhancing its energy storage efficiency. 相似文献
18.
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
19.
LiFePO 4/C composite cathode material is prepared by ball milling with the assistance of EDTA chelation with using water as the media
of ball mill procedure. FePO 4 and LiOH are used as starting materials; a certain amount of glucose is used as carbon sources and reduction agent. The structure
and morphology of the composite are characterized by X-ray diffraction and scanning electron microscopy. Cyclic voltammetry,
AC impedance measurements, and galvanostatic charge–discharge and cycling performances are used to characterize its electrochemical
properties. The results indicate that the performances of composites prepared by chelation-assisted method are much better
than common ball milling method which using alcohol or acetone as the media of ball mill procedure. The stable discharge capacity
of the prepared composite is 150 and 105 mAh g −1 at 1 and 10 C rate, respectively. 相似文献
20.
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
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