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1.
Enhancing the elevated temperature performance of Li/LiMn2O4 cells by reducing LiMn2O4 surface area 总被引:1,自引:0,他引:1
Lithium-rich spinels were obtained with the same structure but different surface area by two different synthesis routes, namely the “once-annealed” and the “twice-annealed” methods. The elevated temperature performance of Li/Li1+xMn2O4 cell is significantly improved using a spinel cathode with a small surface area: the cell at 50°C lost 5% of the initial capacity over the first 100 cycles based on a spinel cathode with the small surface area of 1.2 m2/g compared to 8% based on a large one of 6.2 m2/g. Also the mechanism responsible for the reaction of LiMn2O4 with LiOH to form lithium-rich spinel has been investigated. 相似文献
2.
Li1.02Ni0.5Mn1.5O4 spinel cathode materials were successfully synthesized by a citric acid-assisted sol-gel method. The structure and morphology of the materials have been examined by X-ray diffraction and scanning electron microscopy, respectively. Electrochemical properties of the materials were investigated using cyclic voltammetry and galvanostatic charge/discharge measurements at two different temperatures (25 and 55 °C) using lithium anode. The initial capacity and capacity retention are highly dependent on the particle size, particle size distribution, crystallinity and purity of the materials. The Li1.02Ni0.5Mn1.5O4 materials synthesized both at 800 and 850 °C have shown best electrochemical performance in terms of capacity and capacity retention between 3.5 and 4.9 V with a LiPF6 based electrolyte. 相似文献
3.
X-ray absorption spectra of the spinel LiCu0.5Mn1.5O4 were recorded at the Cu K and L3, Mn K and L3, and O K edge. The spectra are aligned on a common energy scale with the aim to establish an experimental picture of the conduction band structure. The fine structures observed a few electron volts around the absorption thresholds are discussed in terms of hybridisation of cation and anion orbitals. Emphasis is put on the identification of spectral features correlated with the presence of lithium on the tetrahedral sites of the spinel structure. The consequences of lithium insertion/extraction on the intensities of these spectral structures are discussed. Previous studies by X-ray absorption spectroscopy of lithium insertion/extraction in various spinels are found to agree with our expectations. 相似文献
4.
LiNi0.5Mn1.5O4 was prepared through a solid-state reaction using various Ni precursors. The effect of precursors on the electrochemical performance of LiNi0.5Mn1.5O4 was investigated. LiNi0.5Mn1.5O4 made from Ni(NO3)2·6H2O shows the best charge–discharge performance. The reversible capacity of LiNi0.5Mn1.5O4 is about 145 mAh g−1 and remained 143 mAh g−1 after 10 cycles at 3.0–5.0 V. The XRD results showed that the precursors and the dispersion methods had significant effect on their phase purity. Pure spinel phase can be obtained with high energy ball-milling method and Ni(NO3)2·6H2O as precursor. Trace amount of NiO and Li2MnO3 phase were detected in LiNi0.5Mn1.5O4 with manual-mixture method and using Ni(CH3COO)2·6H2O, NiO and Ni2O3 as precursors. 相似文献
5.
As a novel partial substitution and surface modification process, we focused on a step-by-step (double-step) supersonic-wave treatment in a Zn-containing aqueous solution without any heat-treatments, and performed the treatment on LiMn2O4 powder. From XRD measurements, it was demonstrated that the lattice constant of LiMn2O4 decreased slightly by the treatments, indicating a partial substitution of Zn for Mn. It was also suggested by SEM–EDX and XPS that Zn was well dispersed in/on the samples and their surfaces were modified by Zn compounds. Such a partial substitution and surface modification was supported by crystal structure analysis based on the Rietveld method using neutron diffraction. Cycle performance of LiMn2O4 was significantly improved by the step-by-step supersonic-wave treatments. In the processes, it was especially effective for the improvement to apply lower and higher frequencies at the first and second steps, respectively, keeping the power higher. The cathode property improvement was considered due to the partial substitution and the surface coating caused by the step-by-step supersonic-wave treatments. From the investigation on the cathodes and electrolytes after the cycle tests, it was suggested that the crystal structure of LiMn2O4 was stabilized by the treatments. 相似文献
6.
LiNi0.5Mn0.5O2 thin films have been deposited on the NASICON-type glass ceramics, Li1+x+yAlxTi2−xSiyP3−yO12 (LATSP), by radio frequency (RF) magnetron sputtering followed by annealing. The films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. All-solid-state Li/PEO18-Li(CF3SO2)2N/LATSP/LiNi0.5Mn0.5O2/Au cells are fabricated using the LiNi0.5Mn0.5O2 thin films and the LATSP electrolyte. The electrochemical performance of the cells is investigated by galvanostatic cycling, cyclic voltammetry (CV), potentiostatic intermittent titration technique (PITT) and electrochemical impedance spectroscopy (EIS). Interfacial reactions between LiNi0.5Mn0.5O2 and LATSP occur at a temperature as low as 300 °C with the formation of Mn3O4, resulting in an increased obstacle for Li-ion diffusion across the LiNi0.5Mn0.5O2/LATSP interface. The electrochemical performance of the cells is limited by the interfacial resistance between LATSP and LiNi0.5Mn0.5O2 as well as the Li-ion diffusion kinetics in LiNi0.5Mn0.5O2 bulk. 相似文献
7.
Layered LiNi0.2Mn0.2Co0.6O2 phase, belonging to a solid solution between LiNi1/2Mn1/2O2 and LiCoO2 most commercialized cathodes, was prepared via the combustion method at 900 °C for a short time (1 h). Structural, electrochemical and magnetic properties of this material were investigated. Rietveld analysis of the XRD pattern shows this compound as having the α-NaFeO2 type structure (S.G. R-3m; a = 2.8399(2) ?; c = 14.165(1) ?) with almost none of the well-known Li/Ni cation disorder. SQUID measurements clearly indicate that the studied compound consists of Ni2+, Co3+ and Mn4+ ions in the crystal structure. X-ray analysis of the chemically delithiated LixNi0.2Mn0.2Co0.6O2 phases reveals that the rhombohedral symmetry was maintained during Li-extraction, confirmed by the monotonous variation of the potential-composition curve of the Li//LixNi0.2Mn0.2Co0.6O2 cell. LiNi0.2Mn0.2Co0.6O2 cathode has a discharge capacity of ∼160 mAh g−1 in the voltage range 2.7-4.3 V corresponding to the extraction/insertion of 0.6 lithium ion with very low polarization. It exhibits a stable capacity on cycling and good rate capability in the rate range 0.2-2 C. The almost 2D structure of this cathode material, its good electrochemical performances and its relatively low cost comparing to LiCoO2, make this material very promising for applications. 相似文献
8.
LiMn1.5Ni0.5O4 cathode material was prepared by sol–gel method and annealed at 850 °C for 15 h. The prepared powder was coated with ZnO by dissolving zinc acetate in methanol and LiMn1.5Ni0.5O4 powder was mixed in this solution followed by the continuous stirring for 4 h. The LiMn1.5Ni0.5O4 and ZnO-coated LiMn1.5Ni0.5O4 powder was structurally characterized using X-ray diffraction and scanning electron microscopy (SEM). The coin cell was fabricated using ZnO-coated LiMn1.5Ni0.5O4 as cathode materials, LiPF6, dissolved in ethylene carbonate (EC)/dimethyl carbonate (DMC) (1:1 wt ratio) as electrolyte, and Li foil as anode. It was found that ZnO-coated LiMn1.5Ni0.5O4 cathode materials had the initial discharge capacity of about 146 mA h g−1. The discharge capacity retention after 50 cycles was found to be nearly 97%. 相似文献
9.
In this work, poly(methyl methacrylate) (PMMA), a non-surfactant polymer was used to synthesize nonstoichiometric Li0.82Ni0.52Mn1.52O4−δ (0 ≤ δ ≤ 0.25) spinels. The presence of the polymer was found to be beneficial with a view to facilitating the use of the spinel in electrodes for lithium batteries. Thus, PMMA allowed spinel particles of a high crystallinity and uniform size and shape to be obtained, and particle size to be tailored by using an appropriate calcining temperature and time. By controlling these variables, spinels in nanometric, submicrometric and micrometric particle sizes were prepared and characterized by chemical analysis, X-ray diffraction, electron microscopy, thermogravimetry and nitrogen adsorptions measurements. The spinels were obtained as highly crystalline phases with lithium and oxygen deficiency and some cation disorder as revealed by chemical analysis, thermogravimetric and XRD data. Their electrochemical performance in two-electrode cells was tested at room temperature and 50 °C over a wide range of charge/discharge rates (from C/4 to 4C). Cell performance was found to depend on particle size rather than on structural properties. Thus, the spinel best performing at 50 °C was that consisting of submicrometric particles, which delivered a high capacity and exhibited the best capacity retention and rate capability. Particles of submicronic size share the advantages of nanometric particles (viz. the ability to withstand high charge/discharge rates) and micrometric particles (a high capacity and stability at low rates). 相似文献
10.
LiMn1.5Ni0.5O4 materials coated with AlPO4 are prepared by a sol-gel method with citric acid to improve their electrochemical performance; the physical and electrochemical properties are characterized by various analytical techniques. The coated AlPO4 layer completely covers the surfaces of the LiMn1.5Ni0.5O4 particles and the thickness of the coated layer is ∼15 nm. 1 wt.% AlPO4-coated LiMn1.5Ni0.5O4 has much lower surface and charge-transfer resistances and shows a higher lithium diffusion rate in comparison with the pristine sample. The modified material demonstrates dramatically enhanced electrochemical reversibility and stability under elevated temperature conditions. This is because the coated AlPO4 layer reduces the contact area between the electrode and electrolyte and suppresses the formation of undesirable solid electrolyte interface films. 相似文献
11.
Phase pure spinel LiMn2O4 nanoparticles can be directly synthesized by one-step hydrothermal reaction of γ-MnO2 with LiOH in an initial Li/Mn ratio of 1 at 200 °C. The reaction might involve a redox reaction between Mn4+ and OH−, and the formation of LiMn2O4 at the same time under the proposed hydrothermal conditions. This hydrothermal process is simple since only γ-MnO2 powders are used as the Mn source, whereas without use of any oxidants, reductants, or low valence Mn source. The electrochemical performance of the as-synthesized LiMn2O4 nanoparticles towards Li+ insertion/extraction was examined. Rather good capacity and cycle performance, and an especially excellent high rate capability, were observed for the sample that was hydrothermally reacted for 3 days. 相似文献
12.
Lithium-ion batteries are becoming more and more important not only for portable electronic devices, but also in prevision of high power electric vehicles. In such an optic, deep studies regarding all the components of a secondary battery are in development. In this study, high voltage cathode materials have been selected. Crystals with spinel structure have a 3D vacancy pathway suitable for Li-ions transport. The material under study was LiNi0.5Mn1.5O4 doped with magnesium replacing the nickel. Various samples were synthesized via three different routes: a solid-state method, a modified sol–gel method and a xerogel method. The structure and morphology of the powders were analyzed with HRTEM and XRD. Electrochemical tests were also performed. A wide range of particle sizes (from micro to nanosize) was the result of the different synthesis routes. Unfortunately pure materials were not always obtained. The electrochemical tests showed improvement of the material's cyclability, by reducing the particle size. The electrochemical tests further confirmed the existence of a Li1+dMn2−dO4 impurity. The results are quite promising, however, further improvement of the purity of the electrode composition are needed. 相似文献
13.
Yaser Hamedi JouybariSirous Asgari 《Journal of power sources》2011,196(1):337-342
Nitrates of lithium, cobalt and nickel are utilized to synthesize LiNi0.8Co0.2O2 cathode material through sol-gel technique. Various synthesis parameters such as calcination time and temperature as well as chelating agent are studied to determine the optimized condition for material processing. Using TG/DTA techniques, the optimized calcination temperatures are selected. Different characterization techniques such as ICP, XRD and TEM are employed to characterize the chemical composition, crystal structure, size and morphology of the powders. Micron and nano-sized powders are produced using citric/oxalic and TEA as chelating agent, respectively. Selected powders are used as cathode material to assemble batteries. Charge-discharge testing of these batteries show that the highest discharge capacity is 173 mAh g−1 at a constant current of 0.1 mA cm−2, between 3.0 and 4.2 V. This is obtained in a battery assembled with the nanopowder produced by TEA as chelating agent. 相似文献
14.
Micro-scale core-shell structured Li[(Ni1/3Co1/3Mn1/3)0.8(Ni1/2Mn1/2)0.2]O2 powders for use as cathode material are synthesized by a co-precipitation method. To protect the core material Li[Ni1/3Co1/3Mn1/3]O2 from structural instability at high voltage, a Li[Ni1/2Mn1/2]O2 shell, which provides structural and thermal stability, is used to encapsulate the core. A mixture of the prepared core-shell precursor and lithium hydroxide is calcined at 770 °C for 12 h in air. X-ray diffraction studies reveal that the prepared material has a typical layered structure with an space group. Spherical morphologies with mono-dispersed powders are observed in the cross-sectional images obtained by scanning electron microscopy. The core-shell Li[(Ni1/3Co1/3Mn1/3)0.8(Ni1/2Mn1/2)0.2]O2 electrode has an excellent capacity retention at 30 °C, maintaining 99% of its initial discharge capacity after 100 cycles in the voltage range of 3-4.5 V. Furthermore, the thermal stability of the core-shell material in the highly delithiated state is improved compared to that of the core material. The resulting exothermic onset temperature appear at approximately 272 °C, which is higher than that of the highly delithiated Li[Ni1/3Co1/3Mn1/3]O2 (261 °C). 相似文献
15.
Manganese oxide with high tap density was prepared by decomposition of spherical manganese carbonate, and then LiMn2O4 cathode materials were synthesized by solid-state reaction between the manganese oxide and lithium carbonate. Structure and properties of the samples were determined by X-ray diffraction, Brunauer–Emmer–Teller surface area analysis, scanning electron microscope and electrochemical measurements. With increase of the decomposition temperature from 350 °C to 900 °C, the tap density of the manganese oxide rises from 0.91 g cm−3 to 2.06 g cm−3. Compared with the LiMn2O4 cathode made from chemical manganese dioxide or electrolytic manganese dioxide, the LiMn2O4 made from manganese oxide of this work has a larger tap density (2.53 g cm−3), and better electrochemical performances with an initial discharge capacity of 117 mAh g−1, a capacity retention of 93.5% at the 15th cycle and an irreversible capacity loss of 2.24% after storage at room temperature for 28 days. 相似文献
16.
Hyun-Wook LeeP. Muralidharan Claudio M. MariRiccardo Ruffo Do Kyung Kim 《Journal of power sources》2011,196(24):10712-10716
One-dimensional ordered LiNi0.5Mn1.5O4 nanorods have been fabricated and investigated for use as a high power cathode in rechargeable Li-ion batteries. These highly crystalline nanorods, with an ordered spinel structure and diameters and lengths around 130 nm and 1.2 μm, respectively, were synthesized in two steps by using a hydrothermal reaction to produce β-MnO2 nanorods followed by solid-state lithiation. Electrochemical analysis showed the superior performance of nanorods as a cathode in Li-ion half cells. The specific charge and discharge capacities were found to be 120 and 116 mAh g−1 at a 0.5 C rate, and 114 and 111 mAh g−1 at a 1 C rate between 3.5 and 5.0 V vs. Li+/Li. Moreover, the nanorods exhibit high power capability, maintaining capacities of 103 and 95 mAh g−1 at specific currents of 732.5 and 1465 mA g−1 (5 and 10 C rates), respectively. 相似文献
17.
Research progress in high voltage spinel LiNi0.5Mn1.5O4 material 总被引:1,自引:0,他引:1
R. Santhanam 《Journal of power sources》2010,195(17):5442-51
Lithium-ion batteries are now considered to be the technology of choice for future hybrid electric and full electric vehicles to address global warming. LiCoO2 has been the most widely used cathode material in commercial lithium-ion batteries. Since LiCoO2 has economic and environmental issues, intensive research has been directed towards the development of alternative low cost, environmentally friendly cathode materials as possible replacement of LiCoO2. Among them, spinel LiNi0.5Mn1.5O4 material is one of the promising and attractive cathode materials for next generation lithium-ion batteries because of its high voltage (4.7 V), acceptable stability, and good cycling performance. Research advances in high voltage spinel LiNi0.5Mn1.5O4 are reviewed in this paper. Developments in synthesis, structural characterization, effect of doping, and effect of coating are presented. In addition to conventional synthesis methods, several alternative synthesis methods are also summarized. Apart from battery performance, the application of spinel LiNi0.5Mn1.5O4 material in asymmetric supercapacitors is also discussed. 相似文献
18.
The electrochemical performance of a Li-ion battery made from nanometric, highly crystalline LiNi0.5Mn1.5O4 as positive electrode and mesoporous carbon microbeads (MCMBs) as negative electrode was assessed. The best performance was obtained by using a slight excess of spinel (a cathode/anode mole ratio of 1.3) and lithium bis-oxalate borate (LiBOB) instead of LiPF6 as an electrolyte salt. Higher spinel contents caused the formation of metallic Li in the carbon and the rapid degradation of battery performance as a result. The calculated output energy was 322 Wh kg−1 which is higher than the value reported for the LiMn2O4/C cell (250 Wh kg−1). 相似文献
19.
R. Santhanam 《Journal of power sources》2010,195(21):7391-7396
Layered Li1+xNi0.30Co0.30Mn0.40O2 (x = 0, 0.05, 0.10, 0.15) materials have been synthesized using citric acid assisted sol-gel method. The materials with excess lithium showed distinct differences in the structure and the charge and discharge characteristics. The rate capability tests were performed and compared on Li1+xNi0.30Co0.30Mn0.40O2 (x = 0, 0.05, 0.10, 0.15) cathode materials. Among these materials, Li1.10Ni0.30Co0.30Mn0.40O2 cathode demonstrated higher discharge capacity than that of the other cathodes. Upon extended cycling at 1C and 8C, Li1.10Ni0.30Co0.30Mn0.40O2 showed better capacity retention when compared to other materials with different lithium content. Li1.10Ni0.30Co0.30Mn0.40O2 exhibited 93 and 90% capacity retention where as Li1.05Ni0.30Co0.30Mn0.40O2, Li1.15Ni0.30Co0.30Mn0.40O2, and Li1.00Ni0.30Co0.30Mn0.40O2 exhibited only 84, 71, and 63% (at 1C), and 79, 66 and 40% (at 10C) capacity retention, respectively, after 40 cycles. The enhanced high rate cycleability of Li1.10Ni0.30Co0.30Mn0.40O2 cathode is attributed to the improved structural stability due to the formation of appropriate amount of Li2MnO3-like domains in the transition metal layer and decreased Li/Ni disorder (i.e., Ni content in the Li layer). 相似文献
20.
The effect of the capacity matchup between cathode and anode in the LiNi0.5Mn1.5O4/Li4Ti5O12 cell system on cycling property, choice of electrolyte, high voltage and overcharge tolerances was investigated by comparing the cells with Li4Ti5O12 limiting capacity with the cells with LiNi0.5Mn1.5O4 limiting capacity. The former exhibits better cycling performance and less limitation of electrolyte choice than the latter. Furthermore, the Li4Ti5O12-limited cell exhibits better tolerance to high voltage and overcharge than the LiNi0.5Mn1.5O4-limited cell, owing to taking advantage of the extra capacity of Li4Ti5O12 below 1 V. It is thus recommended that the LiNi0.5Mn1.5O4/Li4Ti5O12 cell whose capacity is limited by Li4Ti5O12 anode should be used to extend the application of the state-of-the-art lithium-ion batteries. 相似文献