461,968 research outputs found
Thermodynamic Modeling of the Li-H and Ca-H Systems
No full textThe phase diagram and thermodynamic properties of the Li-H and Ca-H systems in the literature are critically reviewed. The Gibbs energy functions of individual phases in these two systems are modeled by the CALPHAD approach. The associate solution model and substitutional model are employed to represent the thermodynamic properties of the liquid phase in the Li-H and Ca-H systems, respectively. The available experimental data are well reproduced by the present modeling. With the obtained Gibbs energy functions, the phase relationships in the Li-H and Ca-H systems at high pressures are also predicted
Electrochemical Properties and Crystal Structure of Li+/H+ Cation-Exchanged LiNiO2
No full textLiNiO2 has high energy density but easily reacts with moisture in the atmosphere and deteriorates. We performed qualitative and quantitative evaluations of the degraded phase of LiNiO2 and the influence of the structural change on the electrochemical properties of the phase. Li1-xHxNiO2 phase with cation exchange between Li+ and H+ was confirmed by thermogravimetric analysis and Karl Fischer titration measurement. As the H concentration in LiNiO2 increased, the rate capability deteriorated, especially in the low-temperature range and under low state of charge. Experimental and density functional theory (DFT) calculation results suggested that this outcome was due to increased activation energy of Li+ diffusion owing to cation exchange. Rietveld analysis of X-ray diffraction and DFT calculation confirmed that the c lattice parameter and Li-O layer reduced because of the Li+/H+ cation exchange. These results indicate that LiNiO2 modified in the atmosphere has a narrowed Li-O layer, which is the Li diffusion path, and the rate characteristics are degraded
Interfacial “Single-Atom-in-Defects” Catalysts Accelerating Li+ Desolvation Kinetics for Long-Lifespan Lithium-Metal Batteries
Full text linkThe lithium-metal anode is a promising candidate for realizing high-energy-density batteries owing to its high capacity and low potential. However, several rate-limiting kinetic obstacles, such as the desolvation of Li+ solvation structure to liberate Li+, Li0 nucleation, and atom diffusion, cause heterogeneous spatial Li-ion distribution and fractal plating morphology with dendrite formation, leading to low Coulombic efficiency and depressive electrochemical stability. Herein, differing from pore sieving effect or electrolyte engineering, atomic iron anchors to cation vacancy-rich Co1−xS embedded in 3D porous carbon (SAFe/CVRCS@3DPC) is proposed and demonstrated as catalytic kinetic promoters. Numerous free Li ions are electrocatalytically dissociated from the Li+ solvation complex structure for uniform lateral diffusion by reducing desolvation and diffusion barriers via SAFe/CVRCS@3DPC, realizing smooth dendrite-free Li morphologies, as comprehensively understood by combined in situ/ex situ characterizations. Encouraged by SAFe/CVRCS@3DPC catalytic promotor, the modified Li-metal anodes achieve smooth plating with a long lifespan (1600 h) and high Coulombic efficiency without any dendrite formation. Paired with the LiFePO4 cathode, the full cell (10.7 mg cm−2) stabilizes a capacity retention of 90.3% after 300 cycles at 0.5 C, signifying the feasibility of using interfacial catalysts for modulating Li behaviors toward practical applications
Inelastic H+Li and H
No full textRate coefficients for inelastic collisions between Li and H atoms covering all transitions between the asymptotic states Li(2s,2p,3s,3p,3d,4s,4p,4d,4f)+H(1s) and Li++H- are presented for the temperature range 2000–8000 K based on recent cross-section calculations. The data are of sufficient completeness for non-LTE modelling of the Li I 670.8 nm and 610.4 nm features in late-type stellar atmospheres. Non-LTE radiative transfer calculations in both 1D and 3D model atmospheres have been carried out for test cases of particular interest. Our detailed calculations show that the classical modified Drawin-formula for collisional excitation and de-excitation () over-estimates the cross-sections by typically several orders of magnitude and consequently that these reactions are negligible for the line formation process. However, the charge transfer reactions collisional ion-pair production and mutual neutralization () are of importance in thermalizing Li. In particular, 3D non-LTE calculations of the Li I 670.8 nm line in metal-poor halo stars suggest that 1D non-LTE results over-estimate the Li abundance by up to about 0.1 dex, aggrevating the discrepancy between the observed Li abundances and the primordial Li abundance as inferred by the WMAP analysis of the cosmic microwave background
Rate coefficients for the Li+/H- and Li-/H+ mutual neutralization reactions
No full textRate coefficients have been calculated for temperatures up to 10000 K for the mutual neutralization of Li+ and H- from cross-section calculations based on ab initio molecular potentials and couplings. Landau-Zener estimates are provided for the corresponding reaction in Li- and H+. Comparison is made with the results for the H+/H- reaction
Inelastic H+Li and H- + Li+ Collisions and non-LTE Li I Line Formtion in Stellar Atmospheres
No full textRate coefficients for inelastic collisions between Li and H atoms covering all transitions between the asymptotic states Li(2s,2p,3s,3p,3d,4s,4p,4d,4f)+H(1s) and Li++H- are presented for the temperature range 2000-8000 K based on recent cross-section calculations. The data are of sufficient completeness for non- LTE modelling of the Li I 670.8 nm and 610.4 nm features in late-type stellar atmospheres. Non-LTE radiative transfer calculations in both 1D and 3D model atmospheres have been carried out for test cases of particular interest. Our detailed calculations show that the classical modified Drawin-formula for collisional excitation and de-excitation (Li* + H ⇌ Li*′ + H) over-estimates the cross-sections by typically several orders of magnitude and consequently that these reactions are negligible for the line formation process. However, the charge transfer reactions collisional ion-pair production and mutual neutralization (Li* + H ⇌ Li+ + H-) are of importance in thermalizing Li. In particular, 3D non-LTE calculations of the Li 1670.8 nm line in metal- poor halo stars suggest that ID non-LTE results over-estimate the Li abundance by up to about 0.1 dex, aggrevating the discrepancy between the observed Li abundances and the primordial Li abundance as inferred by the WMAP analysis of the cosmic microwave background
Li3PO4-added garnet-type Li6.5La3Zr1.5Ta0.5O12 for Li-dendrite suppression
No full text
This paper proposes a strategy to stabilize the garnet/Li interface by introducing Li3PO4 as an additive in garnet-type Li6.5La3Zr1.5Ta0.5O12. The Li3PO4-added Li6.5La3Zr1.5Ta0.5O12 electrolyte exhibits a room temperature Li-ion conductivity of 1.4 x 10(-4) S cm(-1), which is less than that of the Li3PO4-free counterparts (4.6 x 10(-4) S cm(-1)). However, the presence of Li3PO4 improves the interfacial compatibility and suppresses Li-dendrite formation during Li-metal plating/stripping. The symmetric Li/garnet/Li cells with Li3PO4-added Li6.3La3Zr1.5Ta0.5O12 have been successfully cycled at a current density of 0.1 mA cm(-2) at 60 degrees C for 60 h; on contrast, the control cells with Li3PO4-free Li6.5La3Zr1.5Ta0.5O12 display noisy potential with large voltage polarization and get short-circuited completely after 33-h cycling under the same operating condition. The outstanding interface stability can be attributed to the in situ reaction of the Li flux with Li3PO4 to form a self-limiting and ion-conducting interphase, Li3P, which is confirmed experimentally. (C) 2017 Elsevier B.V. All rights reserved.</p
Finite-Time Event-Triggered H∞ Control for T-S Fuzzy Markov Jump Systems
Full text linkThis paper investigates the finite-time event-triggered H-infinity control problem for Takagi-Sugeno Markov jump fuzzy systems. Because of the sampling behaviors and the effect of network environment, the premise variables considered in this paper are subject to asynchronous constraints. The aim of this paper is to synthesize a controller via an event-triggered communication scheme such that not only the resulting closed-loop system is finite-time bounded and satisfies a prescribed H-infinity performance level, but also the communication burden is reduced. First, a sufficient condition is established for the finite-time bounded H-infinity performance analysis of the closed-loop fuzzy system with fully considering the asynchronous premises. Then, based on the derived condition, the method of the desired controller design is presented. Two illustrative examples are finally presented to demonstrate the practicability and efficacy of the proposed method
Mécanosynthèse, structure et propriétés d'hydrogénation du système Li-Mg-N-H
No full textCette thèse est consacrée à l'étude des métaux-N-H des matériaux pour le stockage d'hydrogène de solide. Le but est de caractériser la synthèse mechanochemical, structurelle et les propriétés d'hydrogénation de Li-N-H, Li-Mg-N-H et des systèmes Li-Mg-B-N-H. Premièrement, l'assimilation hydrogène pendant mechanochemistry de Li3N sous 9 MPA de H2 a été analysée au moyen de l'absorption solide-à-gaz in situ et la Diffraction de Radiographie d'ex-situ (XRD) des mesures. Deux étapes de H-sorption menant à une assimilation hydrogène globale de 9.8wt le % ont été obtenus. La première étape de réaction comprend la transformation de polymorphe-li3n (S.G.P6/mmm) dans li3n (S.G.P63/mmc) métastable la phase et la réaction du dernier avec l'hydrogène pour former lithium imide :-li3n + H2 Li2NH + LiH. La deuxième étape absorbant est lithium imide des convertis à lithium amideThis thesis is dedicated to the study of novel metal-N-H materials for solid state hydrogen storage. The aim is to characterize the mechanochemical synthesis, structural and hydrogenation properties of Li-N-H, Li-Mg-N-H and Li-Mg-B-N-H systems. Firstly, hydrogen uptake during mechanochemistry of Li3N under 9 MPa of H2 has been analyzed by means of in-situ solid-gas absorption and ex-situ X-Ray Diffraction (XRD) measurements. Two H-sorption steps leading to an overall hydrogen uptake of 9.8wt% was obtained. The first reaction step comprises the transformation of polymorph -Li3N (S.G.P6/mmm) into -Li3N (S.G.P63/mmc) metastable phase and the reaction of the latter with hydrogen to form lithium imide: -Li3N + H2 Li2NH + LiH. The second absorption step is lithium imide converts to lithium amide following the reaction scheme Li2NH + H2 LiNH2 + LiH. The assessment of reaction paths in this system as well as of the appraisal of the underlying reaction mechanisms was under taken. Secondly, reactive ball milling (RBM) under H2 of Li3N and Mg powder with a molar ratio of 2:1 was taken on to destabilize Li-N-H system and accelerate its sorption kinetics. The onset dehydrogenation temperature of the as-milled 2Li3N+Mg mixture was detected at 125°C, which is about 75°C lower than that of the Li-N-H system. The structural and phases evolution of the Li-Mg-N-H system during both the synthesis and subsequent hydrogenation/dehydrogenation cycling were characterized by combined analysis of in-situ XRD and neutron powder diffraction (NPD) measurements. It was found step wised for the both processes depending on mainly the temperature and hydrogen pressure to the system. Finally, the effect of the addition of Co-based compounds, lithium borohydides and the combination of them to Li-Mg-N-H system were systematically investigated by XRD, scanning electron microscopy (SEM), fourier transform infra-red (FTIR), differential scanning calorimetry (DSC) and hydrogen storage properties measurements with the aim to overcome the kinetic barriers and further decrease the dehydrogenation temperature. The Li-Mg-B-N-H/3wt% ZrCoH3 composite synthesized by RBM has the best hydrogen storage properties. It is shown that the activation energy was decreased and the N-H bonds were weakened, which could be the main reasons for improving the hydrogen storage properties of Li-Mg-N-H syste
Extraction relationship of Li+ and H+ using tributyl phosphate in the presence of Fe(III)
No full textDuring the extraction of lithium from high Mg-containing salt lake brines by tributyl phosphate (TBP) in the presence of Fe(III), H+ is used to stabilize Fe(III). However, the distribution ratio of H+ (D-H) is 4-6 times higher than that of Li+ (D-Li), which affects the extraction of Li+ significantly. In this study, the competition mechanism between H+ and Li+ was investigated by spectral analysis and thermodynamic equilibrium. The extracted species are determined as HFeCl4 center dot 2TBP and LiFeCl4 center dot 2TBP for H+ and Li+, respectively. The apparent equilibrium constants are K-H = 799.8 and K-Li = 120.6, respectively. Both equilibrium constants and the distribution ratios for H+ and Li+ extraction show that extraction of H+ is stronger than Li+
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