7439-93-2

Lithium deposition is observed in situ using a microfluidic test cell. The microfluidic device rapidly sets up a steady concentration gradient and minimizes ohmic potential loss, minimizes electrolyte usage, and shows good repeatability. Dendrite growth is observed at different current densities for electrolytes containing lithium hexafluorophosphate or lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) in mixtures of propylene carbonate (PC) and dimethyl carbonate. Dendrites are formed at shorter times in electrolytes containing LiTFSI and high amounts of PC. The time to first observed dendrites increases linearly (for all electrolyte compositions) with a resistance given by the Tafel slope of the lithium reduction polarization curve.

Tungsten microelectrodes (diam = 25 μm) have been used to study the deposition and stripping behavior of Li/Li+ and Bi/Bi3+ in the LiCl:KCl eutectic at 400°C. The Li deposition current can be simulated assuming the growth of a single hemisphere of liquid metal on the microelectrode. High stripping current densities were observed and quantitated using standard electrochemical equipment. An inverted microscope assembly was employed for in situ observation of the Li/Li+ deposition and stripping processes at the microelectrode. A precipitate appears to form in the melt surrounding the electrode during Li deposition.

The electrochemical formation of Sm-Ni alloys was investigated in a molten LiCl-KCl-SmCl3 (0.5 mol%) system at 723 K. The cyclic voltammogram for a Mo electrode showed the reduction wave from Sm(III) to Sm(II) at 1.60 V (vs Li+/Li), but no reduction wave from Sm(II) to Sm metal. For a Ni electrode, small cathodic currents were observed at potentials more negative than 0.10 V, which indicated the formation of Sm-Ni alloy. The formation of an SmNi2 phase was confirmed by XRD analysis of a sample prepared at 0.10 V for 72 h. The thickness of the SmNi2 film was estimated to be approximately 100 nm. A much thicker SmNi2 film (～20 μm) was obtained by cathodic galvanostatic electrolysis at 50 mA cm-2 in a time period as short as 1 h. Since Li metal was codepositing during the electrolysis and the SmNi2 film was rapidly formed, this electrochemical formation method was termed the 'Li codeposition method'. The formed SmNi2 film was changed to other alloy phases by anodic potentiostatic electrolysis. The formation potentials of SmNi5, SmNi3 and SmNi2 were found to be 1.20, 0.65 and 0.29 V, respectively.

Electrochemical properties of Li7La3Zr2 O12 (LLZ) were investigated to reveal its availability as a solid electrolyte for all-solid-state rechargeable batteries with a Li metal anode. After calcination at 1230°C, a well-sintered LLZ pellet with a garnet-like structure was obtained, and its conductivity was 1.8 × 10-4 S cm-1 at room temperature. The cyclic voltammogram of the Li/LLZ/Li cell showed that the dissolution and deposition reactions of lithium occurred reversibly without any reaction with LLZ. This indicates that a Li metal anode can be applied for an LLZ system. A full cell composed of a LiCoO2 /LLZ/Li configuration was also operated successfully at expected voltage estimated from the redox potential of Li metal and LiCoO2. Simultaneously, an irreversible behavior was observed at the first discharge and charge cycle due to an interfacial problem between LiCoO2 and LLZ. The discharge capacity of the full cell was 15 μA h cm-2. These results reveal that LLZ is available for all-solid-state lithium batteries.

The present vapor-phase optical (atomic) absorption measurements study the escape dynamics of Li atoms from a LiNbO3 target surface upon laser ablation in vacuum. The objective is to understand the low-Li content of LiNbO3 films prepared by pulsed laser deposition. A primary result is a delayed release of Li atoms, 2-20 μs after the laser pulse; they eject with a velocity of 6 × 105 cms-1, which is consistent with an electronic ejection mechanism. The long emission period means there are almost no intraplume Li collisions in the gas phase and no forward focusing of the delayed released atoms. This appears to explain the low-Li content usually found in films grown in the normal direction.

Metallic grey Li//3NaSi//6 is formed by heating the elements in stoichiometric amounts. The compound is the only stable ternary phase in the Li-Na-Si system, and does not belong to the tetrasilatetrahedrane derivatives. The novel complex layer structure is characterized by two-dimensional infinite polyanions showing polymerized tube-like structural units which are known from Hittorf's violet phosphorus and GeAs//2 respectively. The alkali metal atoms are inserted between the respective polyanionic layers Li//3NaSi//6 is a diamagnetic semiconductor with a molar susceptibility chi //m//o//l of minus 243 multiplied by 10** minus **6 emu mol** minus **1, R(300 K) equals 50 OMEGA and R(2 K) equals 3 multiplied by 10**3 OMEGA . Li//3NaSi//6 reacts with protic solvents as well as with benzophenone (in tetrahydrofuran) topotactically yielding a new metastable silicon modification, namely allo-Si.

The effects of some film-forming organic additives, fluoroethylene carbonate (FEC), vinylene carbonate (VC), and ethylene sulfite (ES), on lithium deposition and dissolution were investigated in 1 M LiClO4 dissolved in propylene carbonate (PC) as a base solution. When 5 wt % FEC was added, the cycling efficiency was improved. On the contrary, addition of 5 wt% VC or ES significantly lowered the cycling efficiency. The surface morphology of lithium deposited in each electrolyte solution was observed by in situ atomic force microscopy (AFM). In PC + FEC, the surface was covered with a uniform and closely packed layer of particle-like deposits of about 100-150 nm diam. The surface film seemed to be more solid in PC + VC, and inhomogeneous in PC + ES. From ac impedance measurements, it was revealed that the surface film formed in PC + FEC has a lower resistance than that in the additive-free solution, whereas that formed in PC + VC or PC + ES has a higher resistance. Large volume changes during lithium deposition and dissolution require that the surface film should be elastic (or soft) and be self-repairable when being damaged. In addition, a nonuniform current distribution is liable to cause dendrite formation, which requires that the surface film should be uniform and its resistance should be as low as possible. PC + FEC gave a surface film that satisfies all these requirements, and therefore only FEC was effective as an additive for deposition and dissolution of lithium metal.

The electrochemical deposition of lithium on an Ni substrate was conducted in propylene carbonate (PC) containing 1.0 mol dm-3 LiClO4 (LiClO4/PC). The morphology of the lithium deposited on the Ni substrate had the typical dendrite form. The electrodeposition of lithium was then performed in LiClO4/PC containing 5 × 10-3 mol dm-3 HF. The lithium deposited on the Ni substrate in this electrolyte had a hemispherical form, and irregular shapes were not observed. The color of the Ni electrode surface turned to brilliant blue during the electrodeposition of lithium. This indicates that the lithium surface is very smooth and uniform. After five discharge and charge cycles, there were no lithium dendrites on the electrode surface. From these results, it can be concluded that the addition of a small amount of HF to the electrolyte is significantly effective for the suppression to the lithium dendrite formation.

During Li metal electrodeposition from a 0.5 M LiP F6 -PC electrolyte solution onto a horizontal Li metal electrode, the refractive index profile corresponding to the concentration profile of Li+ ion near the cathode was measured in situ by holographic interferometry. The Li+ concentration gradient around the rapidly growing dendrite arms is steeper than at the cathode plane, clearly reflecting the local current density convergence at the dendrite tips and arms. As in a LiCl O4 -PC solution, an incubation period was observed between the start of current passage and the onset of the refractive index fringe shift. It increases with decreasing applied current density. The incubation period in LiP F6 -PC is shorter than that in LiCl O4 -PC at current densities greater than 1.0 mA cm-2; however, at 0.5 mA cm-2 in LiP F6 -PC electrolyte solution it is appreciably longer than in LiCl O4 -PC. This complicated behavior is apparently due to the solution chemistry of LiP F6 -PC electrolyte, which produces HF and oxyfluoride impurities that are lacking in the LiCl O4 -PC system. Thus, the different current dependence of the incubation time in these two systems may yield clues for an elucidation of the dynamics of solid electrolyte interphase formation.

We present experimental results on the nucleation of nanoscale metallic lithium colloids, of well-controlled diameter (2-5 nm), in MeV electron-irradiated LiF single crystals. Conduction electron spin resonance experiments show a clear-cut quantum effect in these colloids: the spin susceptibility follows a mixed Curie-Pauli law, characteristic for tiny metallic particles in which the mean level spacing is comparable to kT. The behavior of the spin relaxation times (T1 and T2) is presented and a discussion of quantum size effect in small metallic particles is proposed.

Solid solutions of lithium in Ag and Cu in the form of balls, wires, or strips are convenient sources for depositing lithium films as getters on the walls of vacuum vessels. Measurement of the O2, CO and CO2 sorption characteristics have shown that these films - e.g. those generated electrothermally from Ag/Li solid solutions - excel the best getters of the Ba-film type or the high porosity getters based on Ti, V and Zr alloys. It has been found that tight lithium films passivate as a sorption depth of approximately 100 ? is reached. Methods for further improvement of the sorption behavior of lithium coatings are discussed.

A new dehydrogenation mechanism for LiBH4-MgH2 mixtures revealed that magnesium destabilised the LiBH4 resulting in complete dehydrogenation of the borohydride phase and the formation of a Li-Mg alloy. The Royal Society of Chemistry 2006.

Preliminary investigations of the electrochemical behavior of Li-Al/LiCl, KCl/Co//3O//4 and Li-Al/LiCl, KCl/CoO cells are reported. At an operating temperature of 420 degree C, maximum discharge capacities of up to 546 mA-h per gram of cobalt oxide were r

Kinetic data for the electroreduction of alkali metal cations in dimethylformamide and acetonitrile are reported at a variety of indium amalgam electrodes and at a gallium-indium electrode (eutectic composition).The kinetic parameters were found to depend markedly on the nature of the electrode material in which the product alkali metal is soluble.The data are discussed on the basis of a model in which adsorption of metal cation on the electrode and transfer of the cation from the solution phase to the metal phase are assumed to be the rate-controlling steps.This model provides an excellent description of the variation in the kinetic parparameters with electrode composition and potential.

The formation and the morphological change of surface film on a Au(111) electrode in propylene carbonate solution containing 0.1 M LiClO4 in the potential region between 0.8 and 2.5 V (Li/Li+) were studied by in situ scanning tunneling microscopy. The surface film was observed on a gold electrode at potentials more negative than 1.5 V (Li/Li+), and many nuclei appeared on the flat terrace of the electrode at potentials more negative than 0.9 V, where underpotential deposition of lithium on gold was started. Many holes on the surface film were observed after the dissolution of lithium and were thought to be formed as a result of breakdown of the film in nanometer order. The deposition and dissolution of the submonolayer lithium affected the surface morphology in nanometer order.

The lithium cycling efficiencies of the lithium anode in the ethylene carbonate (EC)-based electrolytes were improved by adding vinylene carbonate (VC) to the electrolyte. We analyzed the surface films of deposited lithium on a nickel substrate in a VC-containing electrolyte with scanning electron microscopy, Fourier transform infrared spectroscopy, two-dimensional nuclear magnetic resonance, gel permeation chromatography, and X-ray photoelectron spectroscopy. The corresponding surface films comprise various polymeric species including poly-(vinylene carbonate) [poly-(VC)], oligomeric VC, and a ring-opened polymer of VC. Furthermore, the surface film of carbon double bonds (C = C-O) and lithium carboxylate (RCOOLi) as reduction products of VC were formed on deposited lithium. These structures of the surface film on the lithium anode were similar to those on the graphite anode. At elevated temperatures, the VC-containing electrolyte led to the formation of surface films comprising poly(VC). The VC-derived polymeric surface film, which exhibited gel-like morphology, could prevent the deleterious reaction which occurs between deposited lithium and the electrolyte, resulting in an enhanced lithium cycling efficiency. 2004 The Electrochemical Society.

The kinetics of lithium evaporation from Ag-Li wire has been studied experimentally in the temperature interval 520-630 °C. The initial stage of the process takes place in the kinetic regime and finishes with the formation of a thin layer of silver on the surface of the alloy. Then the process moves to the diffusion region where the evaporation flow and the mass of the deposited film can be described quantitatively with the help of simple analytical expressions.

Hydrogen production via thermochemical water-splitting by lithium redox reactions was investigated as energy conversion technique. The reaction system consists of three reactions, which are hydrogen generation by the reaction of lithium and lithium hydrox

Disclosed herein is an improved method for regenerating materials from a desulfurization/demetallation reaction. The desulfurization/demetallation reaction preferably has products including one or more of an alkali sulfide, polysulfide or hydrosulfide, or alkali earth sulfide, polysulfide, or hydrosulfide. The method includes the steps of reacting the desulfurization/demetallation products with a halogen, liberating and removing sulfur from the product, and then electrolyzing the halogenated products to separate the halogen from the alkali metal or alkali earth metal.

LiMSnO4 (M=Fe, In) compounds were synthesized by high temperature solid-state reaction method and the electrochemical studies were carried out vs. lithium metal. Lithium is reversibly intercalated and deintercalated in LiFeSnO4 with a constant capacity of ～90 mAh/g. In situ X-ray diffraction data show that ramsdellite structure is stable for lithium intercalation and deintercalation in LiFeSnO4. Galvanostatic discharge/charge of LiFeSnO4 in the voltage window 0.05-2.0 V shows a reversible capacity of ～100 mAh/g. The observed capacity in LiFeSnO 4 is due to the two processes involving alloying/dealloying of Li4.4Sn and formation/decomposition of Li2O. In contrast, the new isotypic oxide LiInSnO4 does not exhibit any lithium intercalation due to the absence of mixed valence for indium. Its reversible capacity is strongly dependent on the voltage window. LiInSnO4 exhibits severe capacity fading on cycling in the voltage window 0.05-2.0 V, but shows a stable capacity of ～90 mAh/g in the voltage range 0.75-2.0 V. In situ XRD patterns of LixFeSnO4 (1≤x≤2) at various Li contents during initial lithium intercalation and deintercalation.

The present invention concerns a new general process for asymetric hemisynthesis of harringtonines and their analogs, that are alcaloids used in chimiotherapy. This process comprises direct esterification of a natural cephalotaxine with an acylating compound constituted of a side chain precursor which backbone and fonctionalization are entirely preformed.

The present invention concerns a new general process for asymetric hemisynthesis of harringtonines and their analogs, that are alcalo?ds used in chimiotherapy. This process comprises direct esterification of a natural cephalotaxine with an acylating compound constituted of a side chain precursor which backbone and fonctionalization are entirely preformed.

The thermal behavior of dilithium-tetrahydridoberyllate Li2BeH4 has been studied up to 825 K by simultaneous DSC-TGA measurements. A solid-solid transition between the hexagonal phenakite form (Be2SiO4) previously described and a possible high-temperature cubic form (Li2SO4-HT) occurs at 536±2 K. In addition the thermal decomposition has been characterized by measuring the mass of gas released during heating up to 1075 K. Two distinct steps in the temperature ranges 545-575 K and 905-935 K indicate a total loss of two moles of hydrogen per mole of hydride. The variation of specific heat against temperature has been measured in the 180-420 K range by differential microcalorimetry. A weak but reproducible and reversible anomaly can be detected in the 320-350 K range. This anomaly is marked by a change in the slope of the Cp vs. T curve. The change in the slope clearly corresponds to a maximum in the vicinity of 340 K on the Cp/T vs T representation. This thermodynamic behavior could be interpreted as a superconductivity criterion when correlated with magnetic irreversibilities previously observed for the same compound. Thus, LiBe2H4 could appear like a type-II superconductor with a critical temperature Tc=(340±10) K. However this remarkable potential property requires resistivity measurements to be definitely established.

LiBC is a new compound composed only from light main group elements. LiBC is synthesized from the elements in sealed niobium ampoules at 770 K, and short annealing at 1770 K, forming hexagonal platelets with golden lustre. According to Li(1+)(BC)(1-), boron an carbon form planar heterographite layers of the isoelectronic hexagonal boron nitride type. The inter-layer regions are completely filled by lithium (P63/MMC; a=275.2 pm; c=705.8 pm; hP6; ZrBeSi type). The deformation density of the valence electrons prove the π character of the B-C bonds, as well as a polarization according to (BC)(1-). Chemical and physical properties indicate a certain range of homogeneity x(Li)a mechanism similar to that of graphite.

We present an investigation of the recombination reaction between lithium atoms and O2 in the presence of both N2 and He as bath gases.Lithium atoms were produced by the pulsed photolysis of either LiI, LiOH, or LiO2 molecules in the presence of an excess of O2 and the bath gas.The Li atom concentration was then monitored by laser-induced fluorescence of the metal atoms at λ = 670.7 nm using a pulsed nitrogen-pumped dye laser and boxcar integration of the fluorescence signal.Termolecular behavior was demontstrated in the case of both bath gases, and absolute third-order rate constants were obtained over the temperature range 267-1100 K.A fit of these data to the form AT-n yields k(M = N2) = (4.30 +/- 1.36) * 10-30(T/300 K)-(1.02 +/- 0.06) cm6 molecule-2 s-1 and k(M = He) = (1.25 +/- 0.48) * 10-30(T/300 K)-(0.38 +/- 0.08) cm6 molecule-2 s-1.It is demontstrated that these measurements are essentially in the low-pressure limit; the rate coefficients are then extrapolated from the experimental temperature range to ambient mesospheric temperatures ( 140 K a satisfactory fit to the Troe formalism.

The UV photolysis of powdered LiAlH4 has been investigated isothermally between room temperature and 150 deg C.For temperatures below 110 deg C, similar-shaped decelaratory evolved pressure vs. time curves are obtained with the amount of evolved gas increasing with increasing temperature.These curves can be resolved, with respect to time, into two saturating exponential components and one linear term.The activation energies for the short and long exponential and the linear periods were found to be 3.5+/-1.3, 1.0+/-0.6, and 11.6+/-1.4 kcal/mol respectively.Above 110 deg C, the photolysis curves are sigmoidal, and faster than the thermal-only decomposition curve.The induction, acceleratory, and decay periods' rate constants show a first order dependence on relative UV light intensity. (The main effect of the UV photolysis is seen as generating additional nuclei on the exposed external surfaces of the solid.) γ-Ray pre-irradiation was found to shift the entire co-irradiated p,t curve to shorter times.This effect has been attributed to the formation of additional decomposition sites in the bulk of the sample by γ radiation.

The fast decomposition of trialkylstannyllithiums, R3SnLi (R=Me, Et and Bu), in the presence of hexaalkyldistannanes, R3SnSnR3, was observed, and its mechanism was investigated kinetically.Partial dissociation of R3SnLi into a complex in a solvent cage is suggested to occur in the initial step.The RLi in the complex can be trapped instantaneously by R3SnSnR3 to afford R4Sn and R3SnLi, and the counterpart R2Sn: by R3SnLi giving R3SnR2SnLi.The decomposition of R3SnLi followed first-order kinetics within 3.5 h, corresponding well to the rate of disappearance of R3SnSnR3 and of appearance of R4Sn.The partial dissociation rate constant (k1) of Me3SnLi into the complex was determined as 2.0*10-3 min-1.The values of k1 are about 100 times those of rate constants (k') for decomposition of R3SnLi in the absence of R3SnSnR3.Reformation of R3SnLi from the complex is highly significant.

The results of an investigation of uranium interaction with alkali metal fluorides at 1273 K and above under nonequilibrium conditions are presented. The processes are accompanied by evaluation of alkali metal vapors and formation of uranium tetra and tri