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1.
Yong-Jun LiuYan Cheng Tomonori OhbaKatsumi Kaneko Hirofumi Kanoh 《International Journal of Hydrogen Energy》2011,36(20):12902-12908
A nanocrystalline composite of lithium nitride and lithium carbide was synthesized through melt infiltration of lithium metal into the mesopores of carbon aerogels followed by nitrogenation with nitrogen gas. The structure, surface properties, and morphology of the prepared samples were examined by XRD, N2 adsorption at 77 K, FE-SEM, FE-TEM, and TPD/MS. It was found that some of the lithium metal reacted with the carbon to form lithium carbide, and some of the lithium metal was transformed into lithium nitride by nitrogenation, yielding a composite of lithium nitride and lithium carbide. Relative to the bulk lithium nitride, the lithium nitride in the composite showed a significantly enhanced sequential hydrogen absorption capacity and a lowered temperature of hydrogenation/dehydrogenation. 相似文献
2.
Henrietta W. Langmi Scott D. Culligan G. Sean McGrady 《International Journal of Hydrogen Energy》2009
The hydrogen storage systems Li3AlN2 and Li3FeN2 were synthesized mechanochemically by two different routes. In each case an intermediate material formed after milling, which transformed into Li3MN2 (M = Al or Fe) upon annealing. The synthesis route had a measurable effect on the hydrogen storage properties of the material: Li3AlN2 prepared from hydrogenous starting materials (LiNH2 and LiAlH4) performed better than that synthesized from non-hydrogenous materials (Li3N and AlN). For both Li3AlN2 materials, the hydrogen storage capacity and the absorption kinetics improved significantly upon cycling. Ti-doped Li3AlN2 synthesized from LiNH2 and LiAlH4 showed the best hydrogen storage characteristics of all, with the best kinetics for hydrogen uptake and release, and the highest hydrogen storage capacity of 3.2 wt.%, of which about half was reversible. Meanwhile, Li3FeN2 synthesized from Li3N and Fe displayed similar kinetics to that synthesized from Li3N and FexN (2 ≤ x ≤ 4), but demonstrated lower gravimetric hydrogen storage capacities. Li3FeN2 displayed a hydrogen uptake capacity of 2.7 wt.%, of which about 1.5 wt.% was reversible. For both Li3AlN2 and Li3FeN2, doping with TiCl3 resulted in enhancement of hydrogen absorption kinetics. This represents the first study of a ternary lithium-transition metal nitride system for hydrogen storage. 相似文献
3.
Henrietta W. Langmi 《Journal of power sources》2010,195(7):2003-2007
Mixtures of Li2O/Li3N and Na2O/Li3N have been investigated for hydrogen storage. When Li3N is doped with ca. 5 mol% Li2O and annealed, both binary compounds exist as separate phases as evident from powder X-ray diffraction. Li2O acts as a spectator in the hydrogen storage reactions and there is no evidence of enhanced Li+ or H+ mobility. Na2O (5 mol%) interacts more strongly with Li3N, leading to the generation of an unidentified phase, which also appears to play no part in the hydrogen storage reactions of the composite system. We conclude that addition of these levels of Li2O or Na2O to Li3N followed by annealing does not improve the hydrogen storage properties of Li3N. 相似文献
4.
Lijuan Wang 《Journal of power sources》2010,195(9):2844-198
The carbon-coated monoclinic Li3V2(PO4)3 (LVP) cathode materials can be synthesized by a low temperature solid-state reaction route. The influences of different heat treatments on the LVP have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical methods. In the range of 3.0-4.3 V, both LVP/C electrodes present good rate capability and excellent cyclic performance. It is found that the sample (LVP1/C) prepared by the two-step heat treatment with pre-sintering at 350 °C delivers the initial discharge capacity of 99.8 mAh g−1 at 10 C charge-discharge rate and still retains 95.8 mAh g−1 after 300 cycles. For the sample (LVP2/C) synthesized by the one-step heat treatment, 95.9 and 90.0 mAh g−1 are obtained in the 1st and 300th cycles at 10 C rate, respectively. Our results based on the XRD patterns and the SEM images suggest that the good rate capability and cyclic performance may be owing to the pure phases, small particles, large specific surface areas and residual carbon. In the range of 3.0-4.8 V, compared with the LVP2/C, the LVP1/C also exhibits better performance. 相似文献
5.
Jun-Chao Zheng Xin-Hai LiZhi-Xing Wang Hua-Jun GuoQi-Yang Hu Wen-Jie Peng 《Journal of power sources》2009
The monoclinic-type Li3V2(PO4)3 cathode material was synthesized via calcining amorphous Li3V2(PO4)3 obtained by chemical reduction and lithiation of V2O5 using oxalic acid as reducer and lithium carbonate as lithium source in alcohol solution. The amorphous Li3V2(PO4)3 precursor was characterized by using TG–DSC and XPS. The results showed that the V5+ was reduced to V3+ by oxalic acid at ambient temperature and pressure. The prepared Li3V2(PO4)3 was characterized by XRD and SEM. The results indicated the Li3V2(PO4)3 powder had good crystallinity and mesoporous morphology with an average diameter of about 30 nm. The pure Li3V2(PO4)3 exhibits a stable discharge capacity of 130.08 mAh g−1 at 0.1 C (14 mA g−1). 相似文献
6.
The electrochemical insertion properties and safety characteristics of the alternative Li-ion positive electrode material, lithium iron sulfide (Li2FeS2) are presented. The active material is synthesized by a low cost, proprietary solid-state method. In terms of specific energy, the Li2FeS2 material offers a significant advantage over conventional lithium-ion positive electrode materials. The fully de-lithiated (charged) Li2−xFeS2 phase also demonstrates outstanding thermal stability suggesting that it may represent an excellent choice for safe, large format Li-ion battery applications. 相似文献
7.
A lithium conductive Li3N film is successfully prepared on Li metal surface by the direct reaction between Li and N2 gas at room temperature. X-ray diffraction (XRD), Auger electron spectroscopy (AES), cyclic voltammetry (CV), scanning electron microscopy (SEM), AC impedance, cathodic polarization and galvanostatic charge/discharge cycling tests are applied to characterize the film. The experimental results show that the Li3N protective film is tight and dense with high stability in the electrolyte. Its thickness is more than 159.4 nm and much bigger than that of a native SEI film formed on the lithium surface as received. An exchange current as low as 3.244 × 10−7 A demonstrates the formation of a complete SEI film at the electrode|electrolyte interface with Li3N modification. The SEI film is very effective in preventing the corrosion of the Li electrode in liquid electrolyte, leading to a decreased Li|electrolyte interface resistance and an average short distance of 3.16 × 10−3 cm for Li ion diffusion from electrolyte to Li surface. The Li cycling efficiency depends on N2 exposing time and is obviously enhanced by the Li3N (1 h) modification. After cycling, a dense and homogeneous Li layer deposits on the Li3N (1 h) modified Li surface, instead of a loose and inhomogeneous layer on the Li surface as received. 相似文献
8.
Glass-ceramic and glass Li2S-GeSe2-P2S5 electrolytes were prepared by a single step ball milling (SSBM) process. Various compositions of Li4−xGe1−xPxS2(1+x)Se2(1−x) with/without heat treatment (HT) from x = 0.55 to x = 1.00 were systematically investigated. Structural analysis by X-ray diffraction (XRD) showed gradual increase of the lattice constant followed by significant phase change with increasing GeSe2. HT also affected the crystallinity. Incorporation of GeSe2 in Li2S-P2S5 kept high conductivity with a maximum value of 1.4 × 10−3 S cm−1 at room temperature for x = 0.95 in Li4−xGe1−xPxS2(1+x)Se2(1−x) without HT. All-solid-state LiCoO2/Li cells using Li2S-GeSe2-P2S5 as solid-state electrolytes (SE) were tested by constant-current constant-voltage (CCCV) charge-discharge cycling at a current density of 50 μA cm−2 between 2.5 and 4.3 V (vs. Li/Li+). In spite of the extremely high conductivity of the SE, LiCoO2/Li cells showed a large irreversible reaction especially during the first charging cycle. LiCoO2 with SEs heat-treated at elevated temperature exhibited a capacity over 100 mAh g−1 at the second cycle and consistently improved cycle retention, which is believed to be due to the better interfacial stability. 相似文献
9.
The hydrogenation and dehydrogenation behaviours of the YNi3.5Al0.5Mg compound were studied by in situ X-ray diffraction under hydrogen pressure and at room temperature. The changes of (i) the lattice parameters, (ii) the crystallite size and (iii) the lattice strain during the sorption process (i.e. along the PC isotherms) were studied. These results indicate that the crystallite size decreases by a factor of 2. The micro deformations increase at first and then tend to almost zero at the end of the sorption cycle. This behaviour is explained in terms of co-existence of the metal (i.e. α phase) and metal hydride (i.e. β phase) phases. The change in crystallinity is consistent with the hydrogen induced amorphisation process existing in a lot of AB2 compounds. No anisotropic effects can be highlighted on this pseudo-AB2 compounds in contrary with what could be observed in AB5 compounds. 相似文献
10.
Ji Woo Kim Jae-Hyeok Shim Seul Cham Kim Andreas Borgschulte Robin Gremaud Andreas Züttel Kyu Hwan Oh 《Journal of power sources》2009,192(2):582-587
Single crystalline titanium nitride (TiN) nanopowder is synthesized by a mechano-chemical reaction between titanium chloride (TiCl3) and lithium nitride (Li3N) by means of high-energy ball milling. The TiN nanopowder has an average particle size of 6 nm and is introduced into sodium alanate (NaAlH4) as a catalyst. During hydrogen sorption cycles, TiN-catalyzed NaAlH4 exhibits a greater hydrogen desorption rate and higher hydrogen capacity than TiCl3-catalyzed NaAlH4. Contradicting thermodynamic predictions, in situ X-ray diffraction results reveal that TiN nanopowder remains stable and produces no by-products (e.g., Ti-Al compounds) in the reaction with NaAlH4 during hydrogen desorption. In situ Raman spectroscopy also confirms the stability of TiN nanopowder in NaAlH4. This implies that the sustained hydrogen sorption kinetics and hydrogen capacity of TiN-catalyzed NaAlH4 originate from the structural and chemical stability of TiN nanopowder in NaAlH4 for the given conditions of the hydrogen cycle test. 相似文献
11.
The fast ionic conducting structure similar to thio-Lithium Super Ionic Conductor (LISICON) phase is synthesized in the Li2S-P2S5 system. The Li2S-P2S5 glass-ceramics with the composition of xLi2S·(100−x)P2S5 (75 ≤ x ≤ 80) are prepared by the heat-treatment of mechanically milled amorphous sulfide powders. In the binary Li2S-P2S5 system, 78.3Li2S·21.7P2S5 glass ceramic prepared by mechanical milling and subsequent heat-treatment at 260 °C for 3 h shows the highest conductivity of 6.3 × 10−4 S cm−1 at room temperature and the lowest activation energy for conduction of 30.5 kJ mol−1. The enhancement of conductivity with increasing x up to 78.3 is probably caused by the introduction of interstitial lithium ions at the Li sites which affects the Li ion distribution. The prepared electrolyte exhibits the lithium ion transport number of almost unity and voltage stability of 5 V vs. Li at room temperature. 相似文献
12.
The thermal properties of Li4/3Ti5/3O4 and Li1+xMn2O4 electrodes were investigated by isothermal micro-calorimetry (IMC). The 150-mAh g−1 capacity of a Li/Li4/3Ti5/3O4 half cell was obtained through the voltage plateau that occurs at 1.55 V during the phase transition from spinel to rock salt. Extra capacity below 1.0 V was attributed to the generation of a new phase. The small and constant entropy change of Li4/3Ti5/3O4 during the spinel/rock-salt phase transition indicated its good thermal stability. Accelerated rate calorimetry confirmed that Li4/3Ti5/3O4 has better thermal characteristics than graphite. The IMC results for a Li/Li1+xMn2O4 half cell indicated less heat variation due to the suppression of the order/disorder change by lithium doping. The heat profiles of the Li4/3Ti5/3O4/Li1+xMn2O4 full cell indicated less heat generation compared with a mesocarbon-microbead graphite/Li1+xMn2O4 cell. 相似文献
13.
You Na KoHye Young Koo Jung Hyun KimJang Heui Yi Yun Chan Kang Jong-Heun Lee 《Journal of power sources》2011,196(16):6682-6687
Li3V2(PO4)3 and Li3V2(PO4)3/C powders are prepared by ultrasonic spray pyrolysis from spray solutions with and without sucrose. The precursor powders have a spherical shape and the crystal structure of V2O3 irrespective of the concentration of sucrose in the spray solution. The powders post-treated at 700 °C have the pure crystal structure of the Li3V2(PO4)3 phase irrespective of the concentration of sucrose in the spray solution. The Li3V2(PO4)3 powders prepared from the spray solution without sucrose have a non-spherical shape and hard aggregation. However, the Li3V2(PO4)3/C powders prepared from the spray solution with sucrose have a spherical shape and non-aggregation characteristics. The Li3V2(PO4)3 powders prepared from the spray solution without sucrose have a low initial discharge capacity of 122 mAh g−1. However, the Li3V2(PO4)3/C powders prepared from the spray solutions with 0.1, 0.3, and 0.5 M sucrose have initial discharge capacities of 141, 130, and 138 mAh g−1, respectively. After 25 cycles, the discharge capacities of the powders formed from the spray solutions with and without 0.1 M sucrose are 70% and 71% of the initial discharge capacities, respectively. 相似文献
14.
The carbon coated monoclinic Li3V2(PO4)3 (LVP/C) powder is successfully synthesized by a carbothermal reduction method using crystal sugar as the carbon source. Its structure and physicochemical properties are investigated using X-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopy and electrochemical methods. The LVP/C electrode exhibits stable reversible capacities of 203 and 102 mAh g−1 in the potential ranges of 3.0-0.0 V and 3.0-1.0 V versus Li+/Li, respectively. It is identified that the insertion/extraction of Li+ undergoes a series of two-phase transition processes between 3.0 and 1.6 V and a single phase process between 1.6 and 0.0 V. The ex situ XRD patterns of the electrodes at various lithiated states indicate that the monoclinic structure can still be retained during charge-discharge process and the insertion/deinsertion of lithium ions occur reversibly, which provides an excellent cycling stability with high energy efficiency. 相似文献
15.
A synthesis of Li3V2(PO4)3 being a potential cathode material for lithium ion batteries was attempted via a glass-ceramic processing. A glass with the composition of 37.5Li2O-25V2O5-37.5P2O5 (mol%) was prepared by a melt-quenching method and precursor glass powders were crystallized with/without 10 wt% glucose in N2 or 7%H2/Ar atmosphere. It was found that heat treatments with glucose at 700 °C in 7%H2/Ar can produce well-crystallized Li3V2(PO4)3 in the short time of 30 min. The battery performance measurements revealed that the precursor glass shows the discharge capacity of 14 mAh g−1 at the rate of 1 μA cm−2 and the glass-ceramics with Li3V2(PO4)3 prepared with glucose at 700 °C in 7%H2/Ar show the capacities of 117-126 mAh g−1 (∼96% of the theoretical capacity) which are independent of heat treatment time. The present study proposes that the glass-ceramic processing is a fast synthesizing route for Li3V2(PO4)3 crystals. 相似文献
16.
Ke Wang Xuezhao Wang Hui Pan Yingliang Liu Shengang Xu Shaokui Cao 《International Journal of Hydrogen Energy》2018,43(1):91-99
Novel carbon dots (CDs)/graphitic carbon nitride (g-C3N4) hybrids were fabricated via an in situ thermal polymerization of the precursors, urea and glucose. This heterojunction catalyst exhibited enhanced photocatalytic H2 evolution activity under visible-light (λ > 420). A sample of CDs/g-C3N4 hybrids, CN/G0.5, which was prepared from 0.5 mg of glucose in 6.0 g of urea (8.3 × 10?3 wt% glucose), exhibited the best photocatalytic performance for hydrogen production from water under visible light irradiation, which is about 4.55 times of that of the bulk g-C3N4 (BCN). The improvement of photocatalytic activity was mainly attributed to the construction of built-in electric field at the interface of CDs and g-C3N4, which could improve the separation of photogenerated electron-hole pair. Moreover, the tight connection of CDs with g-C3N4 would serve as a well electron transport channel, which could promote the photocatalytic H2 evolution ability. 相似文献
17.
Y.Q. QiaoX.L. Wang Y.J. MaiJ.Y. Xiang D. ZhangC.D. Gu J.P. Tu 《Journal of power sources》2011,196(20):8706-8709
Plate-like Li3V2(PO4)3/C composite is synthesized via a solution route followed by solid-state reaction. The Li3V2(PO4)3/C plates are 40-100 nm in thicknesses and 2-10 μm in lengths. TEM images show that a uniform carbon layer with a thickness of 5.3 nm presents on the surfaces of Li3V2(PO4)3 plates. The apparent Li-ion diffusion coefficient of the plate-like Li3V2(PO4)3/C is calculated to be 2.7 × 10−8 cm2 s−1. At a charge-discharge rate of 3 C, the plate-like Li3V2(PO4)3/C exhibits an initial discharge capacity of 125.2 and 133.1 mAh g−1 in the voltage ranges of 3.0-4.3 and 3.0-4.8 V, respectively. After 500 cycles, the electrodes still can deliver a discharge capacity of 111.8 and 97.8 mAh g−1 correspondingly, showing a good cycling stability. 相似文献
18.
Li3V2(PO4)3, Li3V2(PO4)3/C and Li3V2(PO4)3/(Ag + C) composites as cathodes for Li ion batteries are synthesized by carbon-thermal reduction (CTR) method and chemical plating reactions. The microstructure and morphology of the compounds are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Li3V2(PO4)3/(Ag + C) particles are 0.5-1 μm in diameters. As compared to Li3V2(PO4)3, Li3V2(PO4)3/C, the Li3V2(PO4)3/(Ag + C) composite cathode exhibits high discharge capacity, good cycle performance (140.5 mAh g−1 at 50th cycle at 1 C, 97.3% of initial discharge capacity) and rate behavior (120.5 mAh g−1 for initial discharge at 5 C) for the fully delithiated (3.0-4.8 V) state. Electrochemical impedance spectroscopy (EIS) measurements show that the carbon and silver co-modification decreases the charge transfer resistance of Li3V2(PO4)3/(Ag + C) cathode, and improves the conductivity and boosts the electrochemical performance of the electrode. 相似文献
19.
Y.Q. QiaoJ.P. Tu X.L. WangD. Zhang J.Y. XiangY.J. Mai C.D. Gu 《Journal of power sources》2011,196(18):7715-7720
Spherical Li3V2(PO4)3/C composites are synthesized by a soft chemistry route using hydrazine hydrate as the spheroidizing medium. The electrochemical properties of the materials are investigated by galvanostatic charge-discharge tests, cyclic voltammograms and electrochemical impedance spectrum. The porous Li3V2(PO4)3/C spheres exhibit better electrochemical performances than the solid ones. The spherical porous Li3V2(PO4)3/C electrode shows a high discharge capacity of 129.1 and 125.6 mAh g−1 between 3.0 and 4.3 V, and 183.8 and 160.9 mAh g−1 between 3.0 and 4.8 V at 0.2 and 1 C, respectively. Even at a charge-discharge rate of 15 C, this material can still deliver a discharge capacity of 100.5 and 121.5 mAh g−1 in the potential regions of 3.0-4.3 V and 3.0-4.8 V, respectively. The excellent electrochemical performance can be attributed to the porous structure, which can make the lithium ion diffusion and electron transfer more easily across the Li3V2(PO4)3/electrolyte interfaces, thus resulting in enhanced electrode reaction kinetics and improved electrochemical performance. 相似文献
20.
In this study, a solution method was employed to synthesize LiFePO4-based powders with Li3PO4 and Fe2P additives. The composition, crystalline structure, and morphology of the synthesized powders were investigated by using ICP-OES, XRD, TEM, and SEM, respectively. The electrochemical properties of the powders were investigated with cyclic voltammetric and capacity retention studies. The capacity retention studies were carried out with LiFePO4/Li cells and LiFePO4/MCMB cells comprised LiFePO4-based materials prepared at various temperatures from a stoichiometric precursor. Among all of the synthesized powders, the samples synthesized at 750 and 775 °C demonstrate the most promising cycling performance with C/10, C/5, C/2, and 1C rates. The sample synthesized at 775 °C shows initial discharge capacity of 155 mAh g−1 at 30 °C with C/10 rate. From the results of the cycling performance of LiFePO4/MCMB cells, it is found that 800 °C sample exhibited higher polarization growth rate than 700 °C sample, though it shows lower capacity fading rate than 700 °C sample. For Fe2P containing samples, the diffusion coefficient of Li+ ion increases with increasing amount of Fe2P, however, the sample synthesized at 900 °C shows much lower Li+ ion diffusion coefficient due to the hindrance of Fe2P layer on the surface of LiFePO4 particles. 相似文献