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1.
Olivine LiFePO4/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 LiFePO4/C nanocomposite with oxalic acid (oxalic acid: Fe2+= 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 LiFePO4/C cathode materials can be exploited suitably for practical lithium-ion batteries.  相似文献   

2.
采用溶胶-凝胶法制备了锂离子电池正极材料LiFePO_4;探讨了pH对磷酸铁锂的形貌及电化学性能的影响.结果表明,随着pH的升高,LiFePO_4的粒径减小,粒径分布变窄,电化学性能提高.在不同pH下制备的LiFePO_4材料以0.2C的倍率放电,首次放电比容量分别为126.8mAh/g、132.4mAh/g、145.6mAh/g.  相似文献   

3.
Well-shaped and uniformly dispersed LiFePO_4 nanorods with a length of 400–500 nm and a diameter of about 100 nm, are obtained with participation of a proper amount of anion surfactant sodium dodecyl sulfonate(SDS) without any further heating as a post-treatment. The surfactant acts as a self-assembling supermolecular template, which stimulated the crystallization of LiFePO_4 and directed the nanoparticles growing into nanorods between bilayers of surfactant(BOS). LiFePO_4 nanorods with the reducing crystal size along the b axis shorten the diffusion distance of Li~+ extraction/insertion, and thus improve the electrochemical properties of LiFePO_4 nanorods. Such prepared LiFePO_4 nanorods exhibited excellent specific capacity and high rate capability with discharge capacity of 151 mAh/g, 122 mAh/g and 95 mAh/g at 0.1C, 1 C and 5 C, respectively. Such excellent performance of LiFePO_4 nanorods is supposed to be ascribed to the fast Li~+ diffusion velocity from reduced crystal size along the b axis and the well electrochemical conductivity. The structure, morphology and electrochemical performance of the samples were characterized by XRD, FE-SEM, HRTEM, charge/discharge tests, and EIS(electrochemical impedance spectra).  相似文献   

4.

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.

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5.
Layered Li-rich transition metal oxides are considered among the most promising cathode materials for high energy density lithium-ion batteries. It was studied how the method and conditions of synthesis of Li-rich oxides Li1.2Mn0.54Ni0.13Co0.13O2 affect their electrochemical properties. Coprecipitation methods and modified Pechini process were used. It was shown that it is necessary to carefully choose the synthesis conditions when using the modified Pechini method because of their significant effect on the morphology of Li-rich oxides. Samples were obtained with high electrochemical characteristics: capacity discharge of 260–270 mAh/g (16 mA/g) and 60–70 mAh/g (988 mA/g) within the voltage range of 2.5–4.8 V.  相似文献   

6.
Nanosized lithium iron phosphate (LiFePO4) and transition metal oxide (MO, where M is Cu, Ni, Mn, Co, and Fe) particles are synthesized continuously in supercritical water at 25?C30?MPa and 400??C under various conditions for active material application in lithium secondary ion batteries. The properties of the nanoparticles, including crystallinity, particle size, surface area, and electrochemical performance, are characterized in detail. The discharge capacity of LiFePO4 was enhanced up to 140?mAh/g using a simple carbon coating method. The LiFePO4 particles prepared using supercritical hydrothermal synthesis (SHS) deliver the reversible and stable capacity at a current density of 0.1?C rate during ten cycles. The initial discharge capacity of the MO is in the range of 800?C1,100?mAh/g, values much higher than that of graphite. However, rapid capacity fading is observed after the first few cycles. The continuous SHS can be a promising method to produce nanosized cathode and anode materials.  相似文献   

7.
Core–shell LiFePO4/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 LiFePO4 matrix. Transmission electron microscopy verifies that F-doped LiFePO4/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 LiFePO4/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.
《中国化学会会志》2018,65(8):977-981
LiFePO4/C and LiFe1–xNb xPO4/C composites were synthesized using a sol–gel method. The influence of niobium doping on the constitution, morphology, and electrochemical properties of the samples was studied in detail. X‐Ray diffraction patterns indicate that appropriate Nb doping does not alter seriously the structure of LiFePO4. Electrochemical characterization of the electrodes showed that the Li‐ion batteries based on LiFe1–xNb xPO4/C electrode exhibited better charge/discharge performance than those based on LiFePO4/C. The LiFe0.95Nb0.05PO4/C‐based cell had the specific capacity of 157, 121, and 85 mAh/g at 0.2, 2, and 5 C, respectively, in comparison with 126, 94, and 52 mAh/g for the LiFePO4/C cell. The results show that the addition of niobium promotes the electrochemical performance of the materials especially at high charge/discharge rates of the battery.  相似文献   

9.
We report on the synthesis and electrochemical characterization of nanohybrid polypyrrole (PPy) (PPy/Fe2O3) materials for electrochemical storage applications. We have shown that the incorporation of nanoparticles inside the PPy notably increases the charge storage capability in comparison to the “pure” conducting polymer. Incorporation of large anions, i.e., paratoluenesulfonate, allows a further improvement in the capacity. These charge storage modifications have been attributed to the morphology of the composite in which the particle sizes and the specific surface area are modified with the incorporation of nanoparticles. High capacity and stability have been obtained in PC/NEt4BF4 (at 20 mV/s), i.e., 47 mAh/g, with only a 3% charge loss after one thousand cyles. The kinetics of charge–discharge is also improved by the hybrid nanocomposite morphology modifications, which increase the rate of insertion–expulsion of counter anions in the bulk of the film. A room temperature ionic liquid such as imidazolium trifluoromethanesulfonimide seems to be a promising electrolyte because it further increases the capacity up to 53 mAh/g with a high stability during charge–discharge processes.  相似文献   

10.
《中国化学快报》2022,33(8):3931-3935
Iron fluoride (FeF3) is considered as a promising cathode material for Li-ion batteries (LIBs) due to its high theoretical capacity (712 mAh/g) with a 3e? transfer. Herein, we have designed a strategy of hierarchical and mesoporous FeF3/rGO hybrids for LIBs, where the hollow FeF3 nanospheres are the main contributor to the specific capacity and the 2D rGO nanosheets are the matrix elevating the electronic conductivity and buffering the volume expansion. The unique FeF3/rGO hybrid can be rationally synthesized by a non-aqueous in-situ precipitation method, offering the merits of large specific surface area with rich active sites, fast transport channels for lithium ions, effective alleviation of volume expansion during cycles, and accelerating the electrochemical reaction kinetics. The FeF3/rGO hybrid electrode possesses a high initial discharge capacity of 553.9 mAh/g at a rate of 0.5 C with 378 mAh/g after 100 cycles, acceptable rate capability with 168 mAh/g at 2 C, and feasible high-temperature operation (320 mAh/g at 70 °C). The superior electrochemical behaviors presented here demonstrates that the FeF3/rGO hybrid is a potential electrode for LIBs, which may open up a new vision to design high-efficiency energy-storage devices such as LIBs based on transition metal fluorides.  相似文献   

11.
The Ml-Mg-Ni-based (Ml = La-rich mixed lanthanide) hydrogen storage alloy Ml0.88Mg0.12Ni3.0-Mn0.10Co0.55Al0.10 was prepared by inductive melting. The micro-structure was analyzed by XRD and SEM. The alloy consists mainly of CaCu5-type phase, Ce2Ni7-type phase and Pr5Co19-type phase. The electrochemical measurements show that the maximum discharge capacity is 386 mAh/g, 16.3% higher than that of the commercial AB5-type alloy (332 mAh/g). At discharge current density of 1 100 mA/g, high rate dischargeability is 62%, while that of the AB5-type alloy is only 45%. The discharge capacity decreases to 315 mAh/g after 300 charge/ discharge cycles, 81.5% of the maximum discharge capacity. __________ Translated from Journal of Xi’an Jiao Tong University, 2008, 42(3) (in Chinese)  相似文献   

12.
Na+ doped sample Li0.95Na0.05FePO4/C was prepared through solid state method. Structure characterization shows Na+ is successfully introduced into the LiFePO4 matrix. Scanning electron microscopy shows the particle size mainly ranges in 1~3 μm. X-ray diffraction Rietveld refinement demonstrates lattice distortion with an increased cell volume. As one cathode material, it has a discharge capacity of 150 mAh/g at 0.1 C rate. The material exhibits a capacity of 109 and 107 mAh/g at 5 and 7.5 C respectively. When cycled at 1 and 5 C, the material retains 84% (after 1000 cycles) and 86% (after 350 cycles) of the initial discharge capacity respectively indicating excellent structure stability and cycling perfor-mance. Na+doping enhances the electrochemical activity especially the cycle performance effectively.  相似文献   

13.
Lithium sulfur batteries with high energy density are thought to be the most potential energy storage technology that can be commercialized.However,the shuttle effect of polysulfides deteriorates its electrochemical performance.Herein,a novel Co_9 S_8 nanostructure derived from metal organic framework material(MOF) was explored by simple liquid phase reaction and heat vulcanization of2-methylimidazole and Co(NO_3)_2·6 H_2 O on the surface of the original PP separator.The Co_9 S_8 nano-flower cluster array wall was vertically and closely arranged with the thickness of 200 nm,and the polysulfide can be adsorbed by its physical and chemical action to slow down the "shuttle effect".It is found that the cell with the modified separator can achieve an ideal discharge capacity of about 600 mAh/g at 1 C.The specific capacity is maintained at 500 mAh/g after 200 cycles,with only 0.11% of capacity decay per cycle.It provides a new way for the utilization of MOF material derivatives to modify the separator in order to improve the electrochemical performance of lithium-sulfur batteries.  相似文献   

14.
LiCoPO4-coated disordered carbon nanofibers (CNFs/LiCoPO4) were obtained by a sol–gel method, using triethyl phosphite or triethyl phosphate as the phosphorous source. The crystal structure of the products was analyzed by X-ray powder diffraction, while morphology was studied using scanning electron microscopy, transmission electron microscopy, Auger electron spectroscopy and X-ray photoelectron spectroscopy. Optimal synthesis conditions for the CNFs/LiCoPO4 in light of the best electrochemical performance are discussed. The best discharge capacity 105 mAh/g (or ca. 63% of the theoretical capacity) shows the material with 40% CNFs/LiCoPO4 and addition coating by carbon black. This composition has a best purity of active materials and point coverage of CNFs. The X-ray photoelectron C1s spectra of the CNFs surface without and with sputter erosion show enhancement of C–O bonds at the fiber surface, which does not influence significantly electrochemical behavior of the composite materials.  相似文献   

15.
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LiFePO4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LiFePO4/C 样品. 结果表明:回流反应时间对LiFePO4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   

16.
《中国化学快报》2020,31(9):2333-2338
Transition metal oxides with high capacity are considered a promising electrode material for lithium-ion batteries (LIBs). Nevertheless, the huge volume expansion and poor conductivity severely hamper their practical application. In this work, a carbon riveting method is reported to address the above issues by designing multilayered N-doped carbon (N-carbon) enveloped Fe3O4/graphene nanosheets. When evaluated as a negative electrode, the N-carbon/Fe3O4/graphene nanocomposites demonstrate greatly enhanced electrochemical properties compared with Fe3O4/graphene. The N-carbon/Fe3O4/graphene presents a superior reversible capacity (807 mAh/g) over Fe3O4/graphene (540 mAh/g). Furthermore, it affords a considerable capacity of 550 mAh/g at 1 A/g over 700 cycles, indicating superb cycling stability. The structure-property correlation studies reveal that the carbon riveting layer is essential for enhancing the lithium diffusion kinetics. The good electrochemical properties and effective structure design make the carbon riveting strategy quite general and reliable to manipulate high performance electrodes for future LIBs.  相似文献   

17.
《中国化学快报》2021,32(11):3570-3574
Na3V2(PO4)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, Na3V2(PO4)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 Na3V2(PO4)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   

18.
Uniform α-Fe2O3 nanocapsules with a high surface area were synthesized by a novel wrap–bake–peel approach consisting of silica coating, heat treatment and finally the removal of the silica coating layer. The length, diameter and shell thickness of the hematite nanocapsules were about 65, 15 and 5 nm, respectively. The electrochemical properties of the α-Fe2O3 nanocapsules were investigated by cyclic voltammetry and charge/discharge measurements. The α-Fe2O3 nanocapsules showed a high reversible capacity of 888 mAh/g in the initial cycle and 740 mAh/g after 30 cycles as well as good capacity retention. This excellent electrochemical performance was attributed to the high surface area, thin shell and volume space of the hollow structure.  相似文献   

19.
The rod-like and bundle-like γ-LiV2O5 were synthesized via a simple solvothermal process-ing. The rod-like γ-LiV2O5 with diameter of 500-800 nm and the bundle-like architectures are composed of several of order-attached rods with diameter of 100-600 nm. γ-LiV2O5 were synthesized using LiOH·H2O, NH4VO3, HNO3, C2H5OH without and with PVP as raw materials. At the same time, the actual formation mechanism of γ-LiV2O5 was also investigated. As the cathode materials for lithium ion batteries, the bundle-like γ-LiV2O5 prepared with PVP delivers a better electrochemical performance, which has an initial dis-charge capacity of 269.3 mAh/g at a current density of 30 mA/g and is still able to achieve 228 mAh/g after the 20th cycle. The good electrochemical properties of the as-synthesized γ-LiV2O5 coupled with the simple, relatively low temperature, and low cost of the prepara-tion method may make this material a promising candidate as a cathode material for lithium ion batteries.  相似文献   

20.
LiVPO4F/C composites with better electrochemical performance were prepared by calcination of LiF and amorphous vanadium phosphorus oxide (VPO) intermediate synthesized by a sol–gel method using H3PO4, V2O5 and citric acid as raw materials. The properties of LiVPO4F/C composites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The analysis of XRD patterns and Fourier transform infrared spectra (FTIR) reveal that VPO intermediate prepared by sol–gel method is amorphous and VPO4 may exist in VPO intermediate. The compositions of LiVPO4F/C composites are related to the calcination temperature for preparation of amorphous VPO/C intermediate and LiVPO4F/C composite prepared by VPO/C synthesized at 700°C consists of a single crystal phase of LiVPO4F. The electrochemical tests show that LiVPO4F/C composite prepared by VPO/C synthesized at 700°C exhibits higher discharge capacity and excellent cycle performance. This LiVPO4F/C composite displays discharge capacity of 133 mAh g−1 at 0.5 C (78 mA g−1) and remains capacity retention of 96.8% after 30 cycles, even at a high rate of 5 C, the composite exhibits high discharge capacity of 115 mAh g−1 and capacity retention of 97% after 100 cycles.  相似文献   

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