共查询到20条相似文献,搜索用时 15 毫秒
1.
The immiscible Al–Sn alloy thin films prepared by electron-beam deposition were first investigated as possible negative electrodes for lithium ion batteries. In the complex structure of the Al–Sn thin films, tiny Sn particles dispersed homogeneously in the Al active matrix. Their electrochemical characteristics were tested in comparison with the pure Al and Sn films. Cyclic voltammetry results indicated that the Li+-transport rates in these Al–Sn alloy films were significantly enhanced. Charge–discharge tests showed that the Al–Sn alloy film anodes had good cycle performance. The electrode with high Al content (Al–33 wt%Sn) delivered a high initial discharge capacity of 752 mAh g−1 while the electrode with high Sn content (Al–64 wt%Sn) had better cycleability with a stable specific capacity of about 300 mAh g−1 under 0.8 C rate. The good performance of these immiscible Al–Sn alloy film anodes was attributed to their unique microstructure. The mechanism of lithiation and delithiation reaction had been proposed based on cyclic voltammograms and impedance response of the Al–Sn alloy thin film electrodes. Our preliminary results demonstrate that the Al–Sn immiscible alloy is a potential candidate negative material for Li-ion battery. 相似文献
2.
We report on the origin of the surface structural disordering in graphite anodes induced by lithium intercalation and deintercalation processes. Average Raman spectra of graphitic anodes reveal that cycling at potentials that correspond to low lithium concentrations in LixC (0 ≤ x < 0.16) is responsible for most of the structural damage observed at the graphite surface. The extent of surface structural disorder in graphite is significantly reduced for the anodes that were cycled at potentials where stage-1 and stage-2 compounds (x > 0.33) are present. Electrochemical impedance spectra show larger interfacial impedance for the electrodes that were fully delithiated during cycling as compared to electrodes that were cycled at lower potentials (U < 0.15 V vs. Li/Li+). Steep Li+ surface-bulk concentration gradients at the surface of graphite during early stages of intercalation processes, and the inherent increase of the LixC d-spacing tend to induce local stresses at the edges of graphene layers, and lead to the breakage of C-C bonds. The exposed graphite edge sites react with the electrolyte to (re)form the SEI layer, which leads to gradual degradation of the graphite anode, and causes reversible capacity loss in a lithium-ion battery. 相似文献
3.
Gouri Cheruvally Jae-Kwang Kim Jae-Won Choi Jou-Hyeon Ahn Yong-Jo Shin James Manuel Prasanth Raghavan Ki-Won Kim Hyo-Jun Ahn Doo Seong Choi Choong Eui Song 《Journal of power sources》2007
A new class of polymer electrolytes (PEs) based on an electrospun polymer membrane incorporating a room-temperature ionic liquid (RTIL) has been prepared and evaluated for suitability in lithium cells. The electrospun poly(vinylidene fluoride-co-hexafluoropropylene) P(VdF-HFP) membrane is activated with a 0.5 M solution of LiTFSI in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMITFSI) or a 0.5 M solution of LiBF4 in 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4). The resulting PEs have an ionic conductivity of 2.3 × 10−3 S cm−1 at 25 °C and anodic stability at >4.5 V versus Li+/Li, making them suitable for practical applications in lithium cells. A Li/LiFePO4 cell with a PE based on BMITFSI delivers high discharge capacities when evaluated at 25 °C at the 0.1C rate (149 mAh g−1) and the 0.5C rate (132 mAh g−1). A very stable cycle performance is also exhibited at these low current densities. The properties decrease at the higher, 1C rate, when operated at 25 °C. Nevertheless, improved properties are obtained at a moderately elevated temperature of operation, i.e. 40 °C. This is attributed to enhanced conductivity of the electrolyte and faster reaction kinetics at higher temperatures. At 40 °C, a reversible capacity of 140 mAh g−1 is obtained at the 1C rate. 相似文献
4.
Ching-Fei LiWen-Hsien Ho Chi-Sheng JiangChien-Chang Lai Ming-Jia WangShiow-Kang Yen 《Journal of power sources》2011,196(2):768-775
Sn/Li2O composite coatings on stainless steel substrate, as anodes of thin-film lithium battery are carried out in SnCl2 and LiNO3 mixed solutions by using cathodic electrochemical synthesis and subsequently annealed at 200 °C. Through cathodic polarization tests, three major regions are verified: (I) O2 + 4H+ + 4e− → 2H2O (∼0.25 to −0.5 V), (II) 2H+ + 2e− → H2, Sn2+ + 2e− → Sn, and NO3− + H2O + 2e− → NO2− + 2OH− (−0.5 to −1.34 V), and (III) 2H2O + 2e− → H2 + 2OH− (−1.34 to −2 V vs. Ag/AgCl). The coated specimens are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and charge/discharge tests. The nano-sized Sn particles embedded in Li2O matrix are obtained at the lower part of region II such as −1.2 V, while the micro-sized Sn with little Li2O at the upper part, such as −0.7 V. Charge/discharge cycle tests elucidated that Sn/Li2O composite film showed better cycle performance than Sn or SnO2 film, due to the retarding effects of amorphous Li2O on the further aggregation of Sn particles. On the other hand, the one tested for cut-off voltage at 0.9 V (vs. Li/Li+) is better than those at 1.2 and 1.5 V since the incomplete de-alloy at lower cut-off voltage may inhibit the coarsening of Sn particles, revealing capacity 587 mAh g−1 after 50 cycle, and capacity retention ratio C50/C2 81.6%, higher than 63.5% and 49.1% at 1.2 and 1.5 V (vs. Li/Li+), respectively. 相似文献
5.
We show that anodes made by depositing thin films of polymer-derived silicon oxycarbide (SiCO) on copper have properties that are comparable to, or better than that of powder-based SiCO anodes. The great advantage of the thin film architecture is its simplicity, both in manufacturing and in application. The films are produced by spraying a film of the liquid polymer-precursor on copper, and then converting it into SiCO by heating at ∼1000 °C; at this point they are ready for constructing electrochemical cells. They show a capacity of ∼1000 mA h g−1, 100% coulombic efficiency, good capacity at very high C-rates, and minimal fading at ∼60 cycles. However, if the films are thick they delaminate due to the volume change as lithium is cycled in and out. The transition from thin-film to thick-film behavior occurs when the SiCO films are approximately 1 μm thick. An analytical method for estimating this transition is presented. 相似文献
6.
A composite anode materials was prepared that contained tin compounds of Sn6O4(OH)4, SnO2 and Sn3PO4 on the surface of carbonaceous mixture mesophase graphite particles (MGP) and nature graphite (NG). The nanosize tin compounds were electrolessly plated from aqueous solutions onto the carbonaceous mixture. The morphology and structure of tin compounds were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the tin compounds particle size was a crucial factor to improve Sn compounds/Carbon composite anodes for cyclability and reversible capacity. The homogeneous dispersion and smaller particle size of tin compounds was attributed to the additive of NG. As the carbonaceous substrate was C-C mixture carbon, the particle size of Sn compounds was about 20-30 nm. However, the particle size was 100-200 nm, as the carbon substrate was singular MGP. Electrochemical performance test of the Sn compounds/C-C composite electrode shows the maximum specific charge capacity of 583 mAh g−1 at the 5th cycle. The charge capacity retention of Sn compounds/C-C electrode was 85% after 20 cycles. The reversible capacity of Sn compounds/C-C electrode increased 292 and 97 mAh g−1 more than pristine (NG + MGP) electrode and Sn compounds/C electrode at the 5th cycle, respectively. 相似文献
7.
Tin-based intermetallic compounds of different compositions and with micro and nano-sized particles are studied as electrodes for lithium ion batteries. Crystalline microsized particles of CoSnx are obtained at high temperatures, while crystalline nano-sized particles are obtained at low-temperature following a one-pot method which is based on TEG solvent and reduction with NaBH4. The observed capacities of CoSnx compounds in lithium test cells depend on the tin content, electrochemical cycling conditions and crystallite size. The change of the 119Sn Mössbauer isomer shift upon the electrochemical reaction with lithium is more limited for the intermetallic compounds CoSnx than for pure Sn. Nano-sized CoSnx materials show superior specific capacity than microsized CoSnx powders. The maximum observed reversible capacity of nano-Co3Sn2 is equal to 544 m Ah g−1 in the first cycle, while 413 m Ah g−1 were observed for nano-CoSn. 相似文献
8.
An investigation is made of the high-rate capability (up to 10 C) of all-solid-state thin-film lithium batteries that comprise of Li/LiPON/LiCoO2 on a flexible substrate, as well as of the effect of high-rate cycling on the structure of these batteries. Raman spectroscopic analysis results reveal that an increase in the rate promotes film orientation of the LiCoO2 cathode with (1 0 1)/(1 0 4) planes and limited lithium intercalation and deintercalation within the layered hexagonal structure without a phase transition to monoclinic. Although with high-rate cycling the LiCoO2 columnar grains tend to aggregate and lose grain orientation, as observed by scanning electron microscopic imaging, the film morphology is efficiently preserved when there is exterior multilayered encapsulation on thin-film batteries. Encapsulated thin-film batteries at 10 C show excellent capacity retention of 95% over 800 cycles, delivering > 22 μAh cm−2 μm−1. The data contribute to a basic understanding of the structure-rate performance relationship of all-solid-state battery systems. 相似文献
9.
Three-dimensional Li2O–NiO–CoO composite thin-film electrodes deposited on stainless steel substrates were synthesized by the electrostatic spray deposition (ESD) technique at 240 and 295 °C. The morphology of the composite was investigated by scanning electron microscopy. X-ray diffraction indicated that the as-deposited films are composites of Li2O, NiO and CoO. The effects of the solvent used to dissolve the starting materials on the morphology and electrochemical performance of the thin-film electrodes were also investigated. It was found that the as-deposited thin-film electrodes exhibited a high reversible capacity (>800 mAh g−1 when cycled between 0.01 and 3 V at a cycling rate of 0.5 C), good capacity retention, and outstanding rate capability. The superior electrochemical performance may have resulted from the combination of the very porous structure and the three-dimensional network of the as-deposited thin-film electrodes, which contributed to a high surface area, favoured lithium-ion diffusion, and formed a stable integral structure. The thin-film electrodes could be promising anodes for use in high power and high energy density lithium-ion batteries. 相似文献
10.
Carbon coated LiFePO4 (LiFePO4/C) with different contents of high electron conductive iron phosphide phase was synthesized by an aqueous sol–gel method in a reductive sintering atmosphere. Different synthesis parameters were used for adjusting the microstructure and phase compositions of the products. The effects of the carbon coating and iron phosphides on the electrochemical properties of the LiFePO4/C electrodes were studied by means of testing the discharge capacities at rates of 0.1–5C (1C = 170 mAh g−1) and analyzing the CV curves. The results show that carbon coating in a content of 1.5 wt.% derived from the carbon source of ethylene glycol greatly decreases the particle size of LiFePO4 in one order in the specific surface area, and significantly improves the rate capability of LiFePO4. The effect of the content of FeP on the capacity of the carbon coated LiFePO4 was different at different discharge rates. Increasing the content of FeP from 1.2 to 3.7 wt.% slightly decreases the capacity of LiFePO4/C at low discharge rate (0.1C and 1C), but obviously increases the capacity of LiFePO4/C when the discharge rate is increased to 5C. For the carbon free sample, even it also has 1.8 wt.% FeP, it still possesses poor capacity due to the large particle size of LiFePO4 and the lack of conductivity. And too much iron phosphides lowers the discharge capacity of the electrode since they are inert for the deinsertion/insertion of lithium ion. 相似文献
11.
Martina Nádherná Jakub Reiter Jo?e Moškon Robert Dominko 《Journal of power sources》2011,196(18):7700-7706
Lithium bis(fluorosulfonyl)imide (LiFSI) in 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) was successfully tested as an electrolyte for graphite composite anodes at elevated temperature of 55 °C. The graphite anode showed a good cyclability during the galvanostatic testing at C/10 rate and 55 °C with the capacity close to theoretical. The formation of SEI in different electrolytes was the subject of study using impedance spectroscopy on symmetrical cells containing two lithium electrodes. The 0.7 m LiFSI in PYR14TFSI exhibits a good ionic conductivity (5.9 mS cm−1 at 55 °C) along with high electrochemical stability and high thermal stability. These properties allow their potential application in large-scale lithium ion batteries with improved safety. 相似文献
12.
Verónica Palomares Aintzane Goñi Izaskun Gil de Muro Iratxe de Meatza Miguel Bengoechea Oscar Miguel Teófilo Rojo 《Journal of power sources》2007
The freeze-drying method is proposed as an effective synthesis process for the obtaining of LiFePO4/C composites. The citric acid is used as a complexing agent and carbon source. After the low temperature annealing, the freeze-dried solution leads to a homogeneous carbon covered LiFePO4 sample. The chemical characterization of the material included ICP and elemental analysis, infrared spectroscopy, X-ray diffraction, magnetic measurements and thermal analysis. SEM and TEM microscopies indicate an aggregate morphology with tiny particles of lithium iron phosphate inside a carbon matrix. Impedance spectroscopy showed a 8.0 × 10−7 S cm−1 conductivity value. Cyclic voltammetry graphics displayed the two peaks corresponding to the Fe(II)/Fe(III) reaction and demonstrated the good reversibility of the material. The specific capacity value obtained at C/40 rate was 164 mAh g−1, with a slight decrease on greater C-rates reaching 146 mAh g−1 at C/1. The capacity retention study has evidenced good properties, with retention over 97% of the maximum values in the first 50 cycles, which allows an effective performance of the freeze-dried sample as cathodic material in lithium-ion batteries. 相似文献
13.
Mesoporous hollow TiO2 microspheres with controlled size and hierarchical nanostructures are designed from a process employing in suit template-assisted and hydrothermal methods. The results show that the hollow microspheres composed of mesoporous nanospheres possess very stable reversible capacity of 184 mAh g−1 at 0.25C and exhibit extremely high power of 122 mAh g−1 at the high rate of 10C. The superior high-rate and high-capacity performance of the sample is attributed to the efficient hierarchical nanostructures. The hollow structure could shorten the diffusion length for lithium ion in the microspheres. The large mesoporous channels between the mesoporous nanospheres provide an easily-accessed system which facilitates electrolyte transportation and lithium ion diffusion within the electrode materials. The electrolyte, flooding the mesoporous channels, can also lead to a high electrolyte/electrode contact area, facilitating transport of lithium ions across the electrolyte/electrode interface. The small mesopores in the meosporous nanospheres can make the electrolyte and lithium ion further diffuse into the interior of electrode materials and increase electrolyte/electrode contact area. The small nanoparticles can also ensure high reversible capacity. 相似文献
14.
The electrodeposited nickel nanocone-arrays without any template are introduced to Sn-based anode materials as current collector for lithium ion battery. Nickel nanocone-arrays are tightly wedged in the electrodeposited Sn film, and thereby enhance the interfacial strength between active materials and substrate. Furthermore, annealing is conducted to form Sn-Ni alloy, in which Ni renders an inactive matrix to buffer volume change during cyclic lithiation/delithiation. The nanocone-arrays supported Sn-Ni alloy anode shows satisfactory Li+ storage properties with the first reversible capacity of 807 mAh g−1. The charge capacity for the 50th cycle is 678 mAh g−1, delivering good retention rate of 99.6% per cycle. These improved performances of nickel nanocone-arrays supported Sn-Ni alloy anodes indicate the potential of their application as electrode materials for high performance energy storage. 相似文献
15.
Yu-Sheng LinJenq-Gong Duh 《Journal of power sources》2011,196(24):10698-10703
Lithium titanate is synthesized from titanium isopropoxide and lithium acetate solution under hydrothermal environment and calcinations. Introducing acidized carbon black during synthesis can produce mesoporous Li4Ti5O12. The crystalline structure and morphological observation of the as-synthesized mesoporous Li4Ti5O12 are characterized by X-ray diffraction (XRD) and scanning electron microscopy, respectively. The mesoporous structure can be directly observed through BEI images of the cross-section sample. Besides, N2 adsorption/desorption isotherm also displays a hysteresis loop, implying the beneficial evidence of mesoporous structure. The pore size distribution of mesoporous lithium titanate evaluated by BJH model is narrow, and the average size of voids is around 4 nm. It is demonstrated that the electrochemical performance is significantly improved by the mesoporous structure. The mesoporous lithium titanate exhibits a stable capacity of 140 mAhg−1 at 0.5 C. Besides, the reversible capacity at 30 C remains over half of that at 0.5 C. The superior C-rate performance is associated with the mesoporous structure, facilitating lithium transportation ability during cycling. 相似文献
16.
Chenge YangDawei Zhang Yongbin ZhaoYuhao Lu Long WangJohn. B. Goodenough 《Journal of power sources》2011,196(24):10673-10678
Sn-Co alloy films are deposited electrochemically directly onto nickel foam in an aqueous solution. The influence of electrochemical current density and heat treatment on the structure and morphology of the electrodeposited films is studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the Sn-Co alloy films are further investigated by galvanostatic charge-discharge tests. As anodes for lithium ion batteries, the Sn-Co alloy-film anodes, after further heat treatment at 200 °C for 30 min, delivers a specific capacity of 663 mAh g−1 after 60 cycles. This high capacity retention is attributed to the unique electrode configuration with an enhanced interface strength between the active material and the current collector formed in the heat-treatment process. 相似文献
17.
18.
Ibrahim IssacMarco Scheuermann Sebastian M. BeckerElisa Gil Bardají Christel AdelhelmDi Wang Christian KübelSylvio Indris 《Journal of power sources》2011,196(22):9689-9695
We prepared nanocrystalline Ti2/3Sn1/3O2 by a coprecipitation method starting from Ti(isopropoxide)4 and SnCl4·5H2O followed by calcination at 600 °C. TEM and XRD measurements reveal crystallite sizes of about 5 nm and a crystal structure equivalent to those of TiO2 rutile and SnO2 cassiterite. The local structure was investigated with 119Sn NMR and Sn Mössbauer spectroscopy. The material was cycled with C/20 at voltages between 3.0 and 0.02 V against Li metal. Specific capacities of 300 mAh g−1 were obtained for 100 cycles with voltage profiles very similar to those of pure SnO2. Faster cycling leads to strong decrease of the capacities but after returning to C/20 the initial values are obtained. 相似文献
19.
Ambient-temperature ionic liquids (IL) based on bis(fluorosulfonyl)imide (FSI) as anion and 1-ethyl-3-methyleimidazolium (EMI) or N-methyl-N-propylpyrrolidinium (Py13) as cations have been investigated with natural graphite anode and LiFePO4 cathode in lithium cells. The electrochemical performance was compared to the conventional solvent EC/DEC with 1 M LiPF6 or 1 M LiFSI. The ionic liquid showed lower first coulombic efficiency (CE) at 80% compared to EC–DEC at 93%. The impedance spectroscopy measurements showed higher resistance of the diffusion part and it increases in the following order: EC–DEC–LiFSI < EC–DEC–LiPF6 < Py13(FSI)–LiFSIE = MI(FSI)–LiFSI. On the cathode side, the lower reversible capacity at 143 mAh g−1 was obtained with Py13(FSI)–LiFSI; however, a comparable reversible capacity was found in EC–DEC and EMI(FSI)–LiFSI. The high viscosity of the ionic liquids suggests that different conditions such as vacuum and 60 °C are needed to improve impregnation of IL in the electrodes. With these conditions, the reversible capacity improved to 160 mAh g−1 at C/24. The high-rate capability of LiFePO4 was evaluated in polymer–IL and compared to the pure IL cells. The reversible capacity at C/10 decreased from 155 to only 126 mAh g−1 when the polymer was present. 相似文献
20.
Chae-Ho YimElena A. Baranova Fabrice M. CourtelYaser Abu-Lebdeh Isobel J. Davidson 《Journal of power sources》2011,196(22):9731-9736
A macroporous SnO2/C composite anode material was synthesized using an organic template-assisted method. Polystyrene spheres were synthesized and used as template and lead to macroporous morphology with pores of 300-500 nm in diameter and a surface area of 54.7 m2 g−1. X-ray diffraction showed that the SnO2 nanoparticles are crystallized in a rutile P42/mnm lattice with the presence of Sn metal traces. The synthesized macroporous SnO2/C composite provided promising performance in lithium half cells showing a discharge capacity of 607 mAh g−1 after 55 cycles. It was found that the macroporous SnO2/C composite is stable and resistant to pulverization upon cycling. 相似文献