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1.
Hard carbon/lithium composite anode electrode is prepared to reduce the initial irreversible capacity of hard carbon, which hinders practical application of hard carbon in lithium ion batteries, by introducing lithium into hard carbon. Lithium foil effectively compensates the irreversible capacity of hard carbon in the first cycle. A full cell using LiCoO2 cathode and the composite anode shows much higher initial coulombic efficiency than that of a cell using LiCoO2 cathode and hard carbon anode. This paves the way to reduce the large initial irreversible capacity of hard carbon. Besides that, this composite anode enables conductive polymer/sulfur composite cathode to be used in Li-ion batteries with non-lithiated anode materials.  相似文献   

2.
The buffering effect of carbon on the structural stability of amorphous silicon films, used as an anode for lithium ion rechargeable batteries, has been studied during long term discharge/charge cycles. To this extent, the electrochemical performance of a prototype material consisting of amorphous Si thin film (∼250 nm) deposited by radio frequency magnetron sputtering on amorphous carbon (∼50 nm) thin films, denoted as a-C/Si, has been investigated. In comparison to pure amorphous Si thin film (a-Si) which shows a rapid fade in capacity after 30 cycles, the a-C/Si exhibits excellent capacity retention displaying ∼0.03% fade in capacity up to 50 cycles and ∼0.2% after 50 cycles when cycled at a rate of 100 μA/cm2 (∼C/2) suggesting that the presence of thin amorphous C layer deposited between the Cu substrate and a-Si acts as a buffer layer facilitating the release of the volume induced stresses exhibited by pure a-Si during the charge/discharge cycles. This structural integrity combined with microstructural stability of the a-C/Si thin film during the alloying/dealloying process with lithium has been confirmed by scanning electron microscopy (SEM) analysis. The buffering capacity of the thin amorphous carbon layer lends credence to its use as the likely compliant matrix to curtail the volume expansion related cracking of silicon validating its choice as the matrix for bulk and thin film battery systems.  相似文献   

3.
MXenes, an emerging family of two-dimensional materials, were promising electrode materials due to their excellent electronic conductivity and hydrophilicity. MXenes exhibit extraordinary rate performance and cycling stability when serving as the anode materials for Li-ion batteries, but they have relatively low capacities. We thus prepared Ti3C2Tx/TiO2 composites using a simple route to coat TiO2 nanoparticles onto the delaminated few-layered MXenes, which functioned as spacers in the composite to suppress the restacking of MXene layers. The sample demonstrated excellent performance in the galvanostatic charge-discharge test, where a reversible capacity of 143?mA?h?g?1 could still be maintained after 200 cycles at 0.5?A?g?1 and a distinct plateau region could be clearly observed in the charge-discharge profiles. Density Theory Function calculation revealed that the hybridization of few-layered MXene was able to improve the structural stability of the composite during the insertion/de-insertion of Li atoms.  相似文献   

4.
通过将亚微米硅与石墨烯进行原位还原复合(SG1)和机械混合(SG2)这2种方式制备了不同的石墨烯/硅复合锂离子电池负极材料。SEM结果显示,2种复合物中硅颗粒都被石墨烯片层所包夹,且分散均匀;充放电测试表明,这2种复合方式均使复合电极的首次容量损失大大减小,循环稳定性得到很大提高,其首次放电比容量分别为2 070.5mAh/g和1 534.2mAh/g,循环12次后均保持在1 000mAh/g以上;通过EIS阻抗谱对硅复合电极的导电性以及电极结构的初步研究,发现复合电极本身导电性以及材料的电接触性远优于纯硅,电极结构也相对稳定。  相似文献   

5.
Silicon electrode with sandwich structure as anode of lithium ion batteries is fabricated by adding a carbon layer between current collector and active coating. The prepared silicon electrode with the sandwich structure can exhibit high reversible capacity of 2500 mAh g−1 for 30 cycles, which is much higher than that of bare silicon electrode with normal structure. The electrochemical impedance spectroscopy and electrode morphologies characterizations show that the improved performance of sandwich electrode is attributed to the carbon layer, which not only enhances the electric conductivity at the current collector/active coating interface but also releases the rigid stress caused by volume change of silicon. The results demonstrate that such sandwich structure is a potential facile method for performance improvement of silicon-based anode compared with the previous reports.  相似文献   

6.
Mn(II) oxide/graphene oxide (MnO/RGO) composites were synthesized by an easy and cost-effective graphenothermal reduction method. The surface morphology, structure, chemical composition and electrochemical behaviour of the resulting composites were investigated in detail. The MnO/RGO composite exhibited a high surface area (115.7 m2/g), which led to the high discharge capacity, enhanced cycling stability, and outstanding rate capability as anode in Li-ion batteries (LIBs). The MnO/RGO composite exhibited an higher initial discharge capacity of 1607 mA h/g at a current density of 100 mA/g and maintained 94% of its reversible capacity over 100 consecutive cycles. Furthermore, MnO/RGO composite could preserve a significantly higher capacity of 847 mA h/g for 150 cycles even at a high current density of 250 mA/g. The excellent electrochemical properties result from the existence of highly conductive RGO and a short transportation span for both Li-ions and electrons. The developed MnO/RGO composite materials hold highly promising prospects in LIBs.  相似文献   

7.
H. Dong  R.X. Feng  X.P. Ai  Y.L. Cao  H.X. Yang   《Electrochimica acta》2004,49(28):5217-5222
A Fe–Si (FeSi2 + Si)/C composite was prepared by mechanical ball milling and investigated as a new inserting anode for use in Li-ion batteries. The composite so prepared has a sandwich structure with the alloy particles as middle cores and the graphite layer as outer shells. The charge-discharge measurements revealed that the Fe–Si/C composite not only had a quite high initial capacity of approximately 680 mAh g−1, but also exhibited greatly improved capacity retention with a reversible capacity of approximately 500 mAh g−1 after 15 cycles in comparison with pure Si and Fe–Si alloy. Based on XRD, XPS, SEM, Raman and EIS analysis of the composite electrode in different lithiated states, the mechanism for improved cycleability is found to be due to the effective buffering of the volumetric changes of the Fe–Si particles by the graphite shell.  相似文献   

8.
A novel process was attempted to prepare nano-scale Cu2Sb alloy powders as anode materials for Li-ion batteries. The preparation started with chemical reduction of Cu2Sb in an aqueous solution with sodium citrate as a complexing agent and KBH4 as a reducer. The analysis of scanning electron microscopy and X-ray diffraction showed that as-prepared nano-scale Cu2Sb powders presented tetragonal structure with particle size of 50-70 nm. Cycling between 0 and 1.2 V, the nano-scale Cu2Sb alloy showed good cyclability with a stable specific capacity of 200 mAh g−1 within 25 cycles.  相似文献   

9.
In this study, we investigated the effects of substituting Li+ for Co2+ at the B sites of the spinel lattice on the structural, magnetic and magnetostrictive properties of cobalt ferrites. The Li+ substituted cobalt ferrites, Co1-xLixFe2O4, with x varying from 0 to 0.7 in 0.1 increments, were synthesized with a sol-gel auto-combustion method using the cathode materials of spent Li-ion batteries. X-ray diffraction analysis revealed that all the Co1-xLixFe2O4 nanopowders had a single-phase spinel structure and the lattice parameters decreased with increasing Li+ content, which can be proved by slight shifts towards higher diffraction angle values of the (311) peak. Field emission scanning electron microscopy was used to observe the fractured inner surface of the sintered cylindrical rods and the increased porosity resulted in a decreased magnetostriction. The oxidation states of Co and Fe in the cobalt ferrite samples were examined by X-ray photoelectron spectroscopy. High resolution transmission electron microscopy micrographs showed that most particles were roughly spherical and with sizes of 25–35?nm. Li+ substitution had a strong effect on the saturation magnetization and coercivity, which were characterized with a vibrating sample magnetometer. The Curie temperature was reduced due to the decrease in magnetic cations and the weakening of the exchange interactions. The magnetostrictive properties were influenced by the incorporation of Li+ at the B sites of the spinel structure and correlated with the changes in porosity, magnetocrystalline anisotropy and the cation distribution.  相似文献   

10.
SnO2/multi-walled carbon nanotube (MWCNT) composites were prepared by the solvothermal method and subsequent heat treatment at 360 °C. The samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Results on the higher SnO2 content composite sample indicate that a uniform layer of SnO2 nanocrystals with crystal size around 5 nm was deposited on the surface of the carbon nanotubes. The composite demonstrates a reversible lithium storage capacity of 709.9 mAh g−1 at the first cycle and excellent cyclic retention up to 100 cycles as anode for lithium ion batteries.  相似文献   

11.
Ti3C2, the most widely studied MXene, was successfully synthesised by etching Al layers from Ti3AlC2 in HF solution. Given its distinct 2D layered structure, Ti3C2 is a promising anode material in Li-ion batteries because of its efficient ion transport, available large surface areas for improved ion adsorption and fast surface redox reactions. Herein, the effects of synthesis temperature on the phase structure, morphology and electrochemical performance were investigated. The materials synthesised at different temperatures were characterised by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Optimal etching occurred at 100?°C, and the synthesised Ti3C2 exhibited smooth surface and large layer space. The synthesised Ti3C2, as anode material for Li-ion batteries, can accommodate more Li+ than those of others, and it exhibits the most ideal electrochemical performance.  相似文献   

12.
The LiZnxMn2−xO4 (x = 0.00-0.15) cathode materials for rechargeable lithium-ion batteries were synthesized by simple sol-gel technique using aqueous solutions of metal nitrates and succinic acid as the chelating agent. The gel precursors of metal succinates were dried in vacuum oven for 10 h at 120 °C. After drying, the gel precursors were ground and heated at 900 °C. The structural characterization was carried out by X-ray powder diffraction and X-ray photoelectron spectroscopy to identify the valance state of Mn in the synthesized materials. The sample exhibited a well-defined spinel structure and the lattice parameter was linearly increased with increasing the Zn contents in LiZnxMn2−xO4. Surface morphology and particle size of the synthesized materials were determined by scanning electron microscopy and transmission electron microscopy, respectively. Electrochemical properties were characterized for the assembled Li/LiZnxMn2−xO4 coin type cells using galvanostatic charge/discharge studies at 0.5 C rate and cyclic voltammetry technique in the potential range between 2.75 and 4.5 V at a scan rate of 0.1 mV s−1. Among them Zn doped spinel LiZn0.10Mn1.90O4 has improved the structural stability, high reversible capacity and excellent electrochemical performance of rechargeable lithium batteries.  相似文献   

13.
In this work, hierarchical structure Nd10W22O81 nanowires are successfully prepared by a feasible electro-spinning technique followed by heat treatment. The structure, morphology and electrochemical characteristics of Nd10W22O81 nanowires are investigated and compared with Nd10W22O81 particles fabricated by a high temperature solid state reaction. It can be observed that Nd10W22O81 nanowires display a “nanoparticle-in-nanowire” architecture. For comparison, solid state formed Nd10W22O81 is composed of irregular microsized particles. This hierarchical architecture makes Nd10W22O81 nanowires have higher Li-storage capacity and better rate performance, contributing to the larger ion channels and shorter ion transportation pathways. In addition, an in-situ X-ray diffraction investigation is also operated to study the structural evolution and reaction mechanism during the charge/discharge process. All these evidences indicate that hierarchical structure Nd10W22O81 nanowires could be a potential high capacity anode material for rechargeable lithium-ion batteries.  相似文献   

14.
Micro-scaled spherical CoSn2/Sn alloy powders synthesized from oxides of Sn and Co via carbothermal reduction at 800 °C were examined for use as anode materials in Li-ion battery. The phase composition and particle morphology of the CoSn2/Sn alloy composite powders were investigated by XRD, SEM and TEM. The prepared CoSn2/Sn alloy composite electrode exhibits a low initial irreversible capacity of ca. 140 mAh g−1, a high specific capacity of ca. 600 mAh g−1 at constant current density of 50 mA g−1, and a good rate capability. The stable discharge capacities of 500-515 mAh g−1 and the columbic efficiencies of 95.8-98.1% were obtained at current density of 500 mA g−1. The relatively large particle size of CoSn2/Sn alloy composite powder is apparently favorable for the lowering of initial capacity loss of electrode, while the loose particle structural characteristic and the Co addition in Sn matrix should be responsible for the improvement of cycling stability of CoSn2/Sn electrode.  相似文献   

15.
Thin Cu2Sb films have been prepared by heat-treating Sb films, electrodeposited on Cu substrates. The influence of the electrodeposition conditions and the heat-treatment period on composition and morphology of the films were investigated (SEM and XRD) and the obtained films were tested as anode materials for Li-ion batteries. The Cu2Sb material showed a stable capacity of 290 mAh g−1 (close to the theoretical capacity of 323 mAh g−1) during more than 60 cycles. The presence of 9-11% (w/w) Sb2O3 in the electrodeposited films resulted in smaller particles but also slowed down formation of Cu2Sb during the heat-treatment step. The presence of Sb2O3 was found to decrease the cycling stability although structural reversibility of Cu2Sb was obtained both with and without Sb2O3. Longer heat-treatments of pure Sb films resulted in the formation of Cu9Sb2 which was shown to be reduced at a lower potential than Cu2Sb. The Cu9Sb2 was converted to Cu2Sb during repeated cycling and the capacity of the latter Cu2Sb material was found to be 230 mAh g−1. While reduction of the materials was complicated by simultaneous formation of an SEI layer, three plateaus could be identified during the oxidation of Li3Sb, indicating the presence of three separate one-electron oxidation reactions.  相似文献   

16.
A novel VO2(B)-multiwall carbon nanotube (MWCNT) composite with a sheet-like morphology was synthesized by a simple in situ hydrothermal process. The morphology and structural properties of the samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). FE-SEM observations demonstrated that the nanosheets are frequently grown together in the form of bundles composed of numerous nanosheets, each with a smooth surface and a typical length of 300-500 nm, width of 50-150 nm, and thickness of 10-50 nm. Electrochemical measurements were carried out using different discharge cut-off voltages. Electrochemical tests show that the VO2(B)-MWCNT composite cathode features long-term cycling stability and high discharge capacity (177 mAh g−1) in the voltage range of 2.0-3.25 V at 1 C with a capacity retention of 92% after 100 cycles. The electrochemical impedance spectra (EIS) indicate that the VO2(B)-MWCNT composite electrode has very low charge-transfer resistance compared with pure VO2(B), indicating the enhanced ionic conductivity of the VO2(B)-MWCNT composite. The enhanced cycling stability is attributed to the fact that the VO2(B)-MWCNT composite can prevent the aggregation of active materials, accommodate the large volume variation, and maintain good electronic contact. We strongly believe that the VO2(B)-MWCNT composite can be considered as a potential cathode material for lithium-ion batteries.  相似文献   

17.
Flower-like Zn2SnO4 composites had been prepared through a green hydrothermal synthesis. The structural, morphological and electrochemical properties were investigated by means of XRD, BET, SEM, TEM, and electrochemical measurement. The results show that the as-prepared sample is in high purity phase and of good crystallinity; meanwhile it has a particular 3-D structure and large surface area. Electrochemical measurement suggests that flower-like Zn2SnO4 composites exhibit better cycling properties and lower initial irreversible capacities than the solid Zn2SnO4 cubes. The first discharge and charge capacities of the material are 1750 mA h g−1 and 880 mA h g−1 respectively. A higher reversible capacity of 501 mA h g−1 was obtained after 50 cycles at a current density of 300 mA g−1. The higher reversible capacity and good stability can be related to the special nanostructural features of the material. Such Zn2SnO4 structures synthesized by the simple and cheap method are expected to have potential application in energy storage.  相似文献   

18.
《Ceramics International》2017,43(15):11556-11562
The ternary composite, carbon coated hollow ZnSnO3 (ZS@C) cubes encapsulated in reduced graphene oxide sheets (ZS@C/rGO), was synthesized via low-temperature coprecipitation and colloid electrostatic self-assembly. The uniform carbon-coating layer not only plays a role in buffering the volume change of ZnSnO3 cubes in the charging/discharging processes, but also forms three-dimensional network with the cooperation of graphene to maintain the structural integrity and improve the electrical conductivity. The results show that the reduced graphene oxide sheets encapsulated ZS@C microcubes with a typical core-shell structure of ~700 nm in size exhibit an improved electrochemical performance compared with bare ZS@C microcubes. The ZS@C/rGO electrode delivered an initial discharge capacity of 1984 mA h g−1 at a current density of 0.1 A g−1 and maintained a capacity of 1040 mA h g−1 after 45 cycles. High specific capacity and superior cycle stability indicate that the ZS@C/rGO composite has a great potential for the application of lithium-ion anode material.  相似文献   

19.
通过水热法合成了NiFe2O4/Graphene纳米复合材料,采用XRD和SEM对其晶相结构和形貌进行了表征,并将其作为锂离子电池活性材料组装成模拟电池,考查电化学性能。结果表明NiFe2O4/Graphene复合材料在100mA/g的电流密度下首次放电容量达970mAh/g,循环20次后,容量保持在668mAh/g,相比纯的NiFe2O4,具有较好的循环稳定性,这种优异的电化学性能归因于复合材料的纳米结构和NiFe2O4与Graphene的协同作用。  相似文献   

20.
硬脂酸/二氧化硅复合相变储热材料制备及性能研究   总被引:7,自引:0,他引:7  
张正国  黄弋峰  方晓明  邵刚 《化学工程》2005,33(4):34-37,43
采用“溶胶-凝胶”工艺制备出具有不同硬脂酸质量分数的硬脂酸/二氧化硅复合相变储热材料,运用SEM、XRD和DSC等手段对复合相变储热材料的结构与性能进行了表征和测试。复合相变储热材料是硬脂酸嵌入到二氧化硅三维纳米网孔中形成的,其相变温度和相变潜热均随硬脂酸质量分数的增加而增大,且相变温度低于纯硬脂酸,相变潜热与对应质量分数下的硬脂酸相当。实验结果表明,硬脂酸/二氧化硅复合相变储热材料具有储热密度大、性能稳定以及导热系数较高等优点。  相似文献   

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