共查询到20条相似文献,搜索用时 31 毫秒
1.
M. Vijayakumar Sebastien Kerisit Kevin M. RossoSarah D. Burton Jesse A. SearsZhenguo Yang Gordon L. GraffJun Liu Jianzhi Hu 《Journal of power sources》2011,196(4):2211-2220
Synthesis of the spinel lithium titanate Li4Ti5O12 by an alkoxide-free sol-gel method is described. This method yields highly pure and crystalline Li4Ti5O12 samples at relatively low temperature (850 °C) and via short thermal treatment (2 h). 6Li magic angle spinning nuclear magnetic resonance (MAS NMR) measurements on these samples were carried out at high magnetic field (21.1 T) and over a wide temperature range (295-680 K). The temperature dependence of the chemical shifts and integral intensities of the three 6Li resonances demonstrates the migration of lithium ions from the tetrahedral 8a to the octahedral 16c sites and the progressive phase transition from a spinel to a defective NaCl-type structure. This defective structure has an increased number of vacancies at the 8a site, which facilitate lithium diffusion through 16c → 8a → 16c pathways, hence providing an explanation for the reported increase in conductivity at high temperatures. Molecular dynamics simulations of the spinel oxides Li4+xTi5O12, with 0 ≤ x ≤ 3, were also performed with a potential shell model in the temperature range 300-700 K. The simulations support the conclusions drawn from the NMR measurements and show a significant timescale separation between lithium diffusion through 8a and 16c sites and that out of the 16d sites. 相似文献
2.
The compatibility between dimethyl methylphosphonate (DMMP)-based electrolyte of 1 M LiPF6/EC + DMC + DMMP (1:1:2 wt.) and spinel materials Li4Ti5O12 and LiNi0.5Mn1.5O4 was reviewed, respectively. The cell performance and impedance of 3-V LiNi0.5Mn1.5O4/Li4Ti5O12 lithium-ion cell with the DMMP-based nonflammable electrolyte was compared with the baseline electrolyte of 1 M LiPF6/EC + DMC (1:1 wt.). The nonflammable DMMP-based electrolyte exhibited good compatibility with spinel Li4Ti5O12 anode and high-voltage LiNi0.5Mn1.5O4 cathode, and acceptable cycling performance in the LiNi0.5Mn1.5O4/Li4Ti5O12 full-cell, except for the higher impedance than that in the baseline electrolyte. All of the results disclosed that the 3 V LiNi0.5Mn1.5O4/Li4Ti5O12 lithium-ion battery was a promising choice for the nonflammable DMMP-based electrolyte. 相似文献
3.
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
4.
The structural changes of the composite cathode made by mixing spinel LiMn2O4 and layered LiNi1/3Co1/3Mn1/3O2 in 1:1 wt% in both Li-half and Li-ion cells during charge/discharge are studied by in situ XRD. During the first charge up to ∼5.2 V vs. Li/Li+, the in situ XRD spectra for the composite cathode in the Li-half cell track the structural changes of each component. At the early stage of charge, the lithium extraction takes place in the LiNi1/3Co1/3Mn1/3O2 component only. When the cell voltage reaches at ∼4.0 V vs. Li/Li+, lithium extraction from the spinel LiMn2O4 component starts and becomes the major contributor for the cell capacity due to the higher rate capability of LiMn2O4. When the voltage passed 4.3 V, the major structural changes are from the LiNi1/3Co1/3Mn1/3O2 component, while the LiMn2O4 component is almost unchanged. In the Li-ion cell using a MCMB anode and a composite cathode cycled between 2.5 V and 4.2 V, the structural changes are dominated by the spinel LiMn2O4 component, with much less changes in the layered LiNi1/3Co1/3Mn1/3O2 component, comparing with the Li-half cell results. These results give us valuable information about the structural changes relating to the contributions of each individual component to the cell capacity at certain charge/discharge state, which are helpful in designing and optimizing the composite cathode using spinel- and layered-type materials for Li-ion battery research. 相似文献
5.
A (Ni1/3Co1/3Mn1/3)CO3 precursor with an uniform, spherical morphology was prepared by coprecipitation using a continuously stirred tank reactor method. The as-prepared spherical (Ni1/3Co1/3Mn1/3)CO3 precursor served to produce dense, spherical Li1+x(Ni1/3Co1/3Mn1/3)1−xO2 (0 ≤ x ≤ 0.15) cathode materials. These Li-rich cathodes were also prepared by a second synthesis route that involved the use of an M3O4 (M = Ni1/3Co1/3Mn1/3) spinel compound, itself obtained from the carbonate (Ni1/3Co1/3Mn1/3)CO3 precursor. In both cases, the final Li1+x(Ni1/3Co1/3Mn1/3)1−xO2 products were highly uniform, having a narrow particle size distribution (10-μm average particle size) as a result of the homogeneity and spherical morphology of the starting mixed-metal carbonate precursor. The rate capability of the Li1+x(Ni1/3Co1/3Mn1/3)1−xO2 electrode materials, which was significantly improved with increased lithium content, was found to be better in the case of the denser materials made from the spinel precursor compound. This result suggests that spherical morphology, high density, and increased lithium content were key factors in enabling the high rate capabilities, and hence the power performances, of the Li-rich Li1+x(Ni1/3Co1/3Mn1/3)1−xO2 cathodes. 相似文献
6.
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
7.
Dong-Ju Lee Ki-Soo Lee Seung-Taek Myung Hitoshi YashiroYang-Kook Sun 《Journal of power sources》2011,196(3):1353-1357
The electrochemical performance of AlF3-coated Li1.1Al0.05Mn1.85O4 spinel was investigated. The morphology of the AlF3-coated Li1.1Al0.05Mn1.85O4 was observed by SEM and TEM, and the thickness of the coating layer was approximately 10 nm. Capacity retention and rate capability were substantially improved by the AlF3-coating, as compared to pristine Li1.1Al0.05Mn1.85O4. Manganese dissolution was also dramatically reduced for the AlF3-coated Li1.1Al0.05Mn1.85O4, which may reflect lower impedance for the coated spinel. The thermal stability of the AlF3-coated Li1.1Al0.05Mn1.85O4 was improved, exhibiting an exothermic reaction at higher temperature with reduced heat generation, compared to the pristine Li1.1Al0.05Mn1.85O4. 相似文献
8.
Effect of conductive additives and surface modification with NF3 and ClF3 on the charge/discharge behavior of Li4/3Ti5/3O4 (≈4.6 μm) was investigated using vapor grown carbon fiber (VGCF) and acetylene black (AB). VGCF and mixtures of VGCF and AB increased charge capacities of original Li4/3Ti5/3O4 and those fluorinated with NF3 by improving the electric contact between Li4/3Ti5/3O4 particles and nickel current collector. Surface fluorination increased meso-pore with diameter of 2 nm and surface area of Li4/3Ti5/3O4, which led to the increase in first charge capacities of Li4/3Ti5/3O4 samples fluorinated by NF3 at high current densities of 300 and 600 mA g−1. The result shows that NF3 is the better fluorinating agent for Li4/3Ti5/3O4 than ClF3. 相似文献
9.
J. Gao 《Journal of power sources》2009,191(2):644-647
The large irreversible capacity loss generally encountered with the high capacity layered oxide solid solutions between layered Li[Li1/3Mn2/3]O2 and LiMO2 (M = Mn, Ni, and Co) has been reduced by blending layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2, which is a solid solution between Li[Li1/3Mn2/3]O2 and Li[Mn1/3Ni1/3Co1/3]O2, with spinel Li4Mn5O12 or LiV3O8. The irreversible capacity loss decreases from 68 to 0 mAh g−1 as the Li4Mn5O12 content increases to 30 wt.% in the Li[Li0.2Mn0.54Ni0.13Co0.13]O2-Li4Mn5O12 composite and the LiV3O8 content increases to 18 wt.% in the Li[Li0.2Mn0.54Ni0.13Co0.13]O2-LiV3O8 composite. The decrease in irreversible capacity loss is due to the ability of Li4Mn5O12 or LiV3O8 to insert the extracted lithium that could not be inserted back into the layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 during the first cycle. The Li[Li0.2Mn0.54Ni0.13Co0.13]O2-LiV3O8 composite with ∼18 wt.% LiV3O8 exhibits a high capacity of ∼280 mAh g−1 with little or no irreversible capacity loss and good cyclability. 相似文献
10.
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
11.
The surface of a commercial Li[Ni0.4Co0.3Mn0.3]O2 cathode is modified using Li3PO4-based coating materials. The electrochemical properties of the coated materials are investigated as a function of the pH value of the coating solution and the composition of coating materials. The Li3PO4 coating solution with pH 2 is found to be favorable for the formation of stable coating layers having enhanced electrochemical properties. The Li3PO4, Li1.5PO4, and PO4 coating layers are formed as amorphous phases. However, the Li3−xNix/2PO4 coating layers are composed of small particles with a crystalline phase covered with an amorphous phase. Li3PO4 and Li1.5PO4 coatings considerably enhance the rate capability of the Li[Ni0.4Co0.3Mn0.3]O2 electrode. In contrast, the Li3−xNix/2PO4 coating material, which contained Ni, has an inferior rate capability compared to the LixPO4 series (x = 1.5 and 3), although the LiNiPO4-coated electrode shows a better rate capability than a pristine one. Li3PO4-based coating materials are effective at enhancing the cyclic performance of the electrode in the voltage range of 3.0-4.8 V. DSC analysis also confirms the improved thermal stability attained by coating the cathode with Li3PO4-based materials. 相似文献
12.
Li2Ti6O13 has been prepared from Na2Ti6O13 by Li ion exchange in molten LiNO3 at 325 °C. Chemical analysis and powder X-ray diffraction study of the reaction product respectively indicate that total Na/Li exchange takes place and the Ti-O framework of the Na2Ti6O13 parent structure is kept under those experimental conditions. Therefore, Li2Ti6O13 has been obtained with the mentioned parent structure. An important change is that particle size is decreased significantly which is favoring lithium insertion. Electrochemical study shows that Li2Ti6O13 inserts ca. 5 Li per formula unit in the voltage range 1.5-1.0 V vs. Li+/Li, yielding a specific discharge capacity of 250 mAh g−1 under equilibrium conditions. Insertion occurs at an average equilibrium voltage of 1.5 V which is observed for oxides and titanates where Ti(IV)/Ti(III) is the active redox couple. However, a capacity loss of ca. 30% is observed due to a phase transformation occurring during the first discharge. After the first redox cycle a high reversible capacity is obtained (ca. 160 mAh g−1 at C/12) and retained upon cycling. Taking into consideration these results, we propose Li2Ti6O13 as an interesting material to be further investigated as the anode of lithium ion batteries. 相似文献
13.
Structural changes and their relationship with thermal stability of charged Li0.33Ni1/3Co1/3Mn1/3O2 cathode samples have been studied using time-resolved X-ray diffraction (TR-XRD) in a wide temperature from 25 to 600 °C with and without the presence of electrolyte in comparison with Li0.27Ni0.8Co0.15Al0.05O2 cathodes. Unique phase transition behavior during heating is found for the Li0.33Ni1/3Co1/3Mn1/3O2 cathode samples: when no electrolyte is present, the initial layered structure changes first to a LiM2O4-type spinel, and then to a M3O4-type spinel and remains in this structure up to 600 °C. For the Li0.33Ni1/3Co1/3Mn1/3O2 cathode sample with electrolyte, additional phase transition from the M3O4-type spinel to the MO-type rock salt phase takes place from about 400 to 441 °C together with the formation of metallic phase at about 460 °C. The major difference between this type of phase transitions and that for Li0.27Ni0.8Co0.15Al0.05O2 in the presence of electrolyte is the delayed phase transition from the spinel-type to the rock salt-type phase by stretching the temperature range of spinel phases from about 20 to 140 °C. This unique behavior is considered as the key factor of the better thermal stability of the Li1−xNi1/3Co1/3Mn1/3O2 cathode materials. 相似文献
14.
Ki-Soo Lee Seung-Taek Myung Hyunjoo Bang Khaili Amine Dong-Won Kim Yang-Kook Sun 《Journal of power sources》2009
Metal oxide (Co3O4) was coated on spinel Li1.1Mn1.9O4 using glutamic acid. Powder X-ray diffraction pattern of Co3O4-coated spinel Li1.1Mn1.9O4 showed that the Co3O4 coating medium was not incorporated in the spinel bulk structure. Morphology of the Co3O4-coated spinel Li1.1Mn1.9O4 was observed by scanning electron microscopy and transmission electron microscopy. The cycling performance of the Co3O4-coated spinel Li1.1Mn1.9O4 was obviously improved, compared to the pristine Li1.1Mn1.9O4 at elevated temperature (55 °C). Improvement of rate capability was also achieved at high C-rates. 相似文献
15.
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
16.
Li4Ti5O12/Sn composite anodes for lithium-ion batteries: Synthesis and electrochemical performance 总被引:1,自引:0,他引:1
Rui Cai 《Journal of power sources》2010,195(24):8244-976
Li4Ti5O12/tin phase composites are successfully prepared by cellulose-assisted combustion synthesis of Li4Ti5O12 matrix and precipitation of the tin phase. The effect of firing temperature on the particulate morphologies, particle size, specific surface area and electrochemical performance of Li4Ti5O12/tin oxide composites is systematically investigated by SEM, XRD, TG, BET and charge-discharge characterizations. The grain growth of tin phase is suppressed by forming composite with Li4Ti5O12 at a calcination of 500 °C, due to the steric effect of Li4Ti5O12 and chemical interaction between Li4Ti5O12 and tin oxide. The experimental results indicate that Li4Ti5O12/tin phase composite fired at 500 °C has the best electrochemical performance. A capacity of 224 mAh g−1 is maintained after 50 cycles at 100 mA g−1 current density, which is still higher than 195 mAh g−1 for the pure Li4Ti5O12 after the same charge/discharge cycles. It suggests Li4Ti5O12/tin phase composite may be a potential anode of lithium-ion batteries through optimizing the synthesis process. 相似文献
17.
Computational and experimental work directed at exploring the electrochemical properties of tetrahedrally coordinated Mn in the +5 oxidation state is presented. Specific capacities of nearly 700 mAh g−1 are predicted for the redox processes of LixMnO4 complexes based on two two-phase reactions. One is topotactic extraction of Li from Li3MnO4 to form LiMnO4 and the second is topotactic insertion of Li into Li3MnO4 to form Li5MnO4. In the experiments, it is found that the redox behavior of Li3MnO4 is complicated by disproportionation of Mn5+ in solution to form Mn4+ and Mn7+ and by other irreversible processes; although an initial capacity of about 275 mAh g−1 in lithium cells was achieved. Strategies based on structural considerations to improve the electrochemical properties of MnO4n− complexes are given. 相似文献
18.
In this work structural and transport properties of layered Li1+x(Mn1/3Co1/3Ni1/3)1−xO2 oxides (x = 0; 0.03; 0.06) prepared by a “soft chemistry” method are presented. The excessive lithium was found to significantly improve transport properties of the materials, a corresponding linear decrease of the unit cell parameters was observed. The electrical conductivity of Li1.03(Mn1/3Co1/3Ni1/3)0.97O2 composition was high enough to use this material in a form of a pellet, without any additives, in lithium batteries and characterize structural and transport properties of deintercalated Li1.03−y(Mn1/3Co1/3Ni1/3)0.97O2 compounds. For deintercalated samples a linear increase of the lattice parameter c together with a linear decrease of the parameter a with the increasing deintercalation degree occurred, but only up to 0.4-0.5 mol of extracted lithium. Further deintercalation showed a reversal of the trend. Electrical conductivity measurements performed of Li1.03−y(Mn1/3Co1/3Ni1/3)0.97O2 samples (y = 0.1; 0.3; 0.5; 0.6) showed an ongoing improvement, almost two orders of magnitude, in relation to the starting composition. Additionally, OCV measurements, discharge characteristics and lithium diffusion coefficient measurements were performed for Li/Li+/Li1.03−y(Mn1/3Co1/3Ni1/3)0.97O2 cells. 相似文献
19.
Amorphous LiCo1/3Mn1/3Ni1/3O2 thin films were deposited on the NASICON-type Li-ion conducting glass ceramics, Li1+x+yAlxTi2−xSiyP3−yO12 (LATSP), by radio frequency (RF) magnetron sputtering below 130 °C. The amorphous films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Li/PEO18-Li(CF3SO2)2N/LATSP/LiCo1/3Mn1/3Ni1/3O2/Au all-solid-state cells were fabricated to investigate the electrochemical performance of the amorphous films. It was found that the low-temperature deposited amorphous cathode film shows a high discharge voltage and a high discharge capacity of around 130 mAh g−1. 相似文献
20.
A promising anode material for hybrid electric vehicles (HEVs) is Li4Ti5O12 (LTO). LTO intercalates lithium at a voltage of ∼1.5 V relative to lithium metal, and thus this material has a lower energy compared to a graphite anode for a given cathode material. However, LTO has promising safety and cycle life characteristics relative to graphite anodes. Herein, we describe electrochemical and safety characterizations of LTO and graphite anodes paired with LiMn2O4 cathodes in pouch cells. The LTO anode outperformed graphite with regards to capacity retention on extended cycling, pulsing impedance, and calendar life and was found to be more stable to thermal abuse from analysis of gases generated at elevated temperatures and calorimetric data. The safety, calendar life, and pulsing performance of LTO make it an attractive alternative to graphite for high power automotive applications, in particular when paired with LiMn2O4 cathode materials. 相似文献