Mixture Of LiCl Research Articles

Preparation of Mg-Li-Sm alloys by electrocodeposition in molten salt

Electrocodeposition of Mg-Li-Sm alloys was investigated in molten KCl-LiCl-MgCl 2-SmCl 3-KF system. The effects of electrolytic temperature and cathodic current density on current efficiency were studied and optimal electrolysis parameters were obtained. The optimum electrolysis condition was a molten salt mixture of LiCl: KCl =50:50 (wt.%), electrolytic temperature: 660 °C, cathode current density: 9.5 A/cm 2 and electrolysis time of 40 min. The current efficiency reached 77.3%. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses of the deposits indicated that Mg-Li-Sm alloys, having Mg, βLi and Mg 41Sm 5 phases, were obtained by electrocodeposition in molten system. The content and distribution of elements in Mg-Li-Sm alloys were analyzed by ICP-MS and EPMA, respectively. The results showed that the distribution of Mg and Sm was homogeneous in the alloys. ICP analyses of samples obtained by electrolysis showed that lithium contents in Mg-Li-Sm alloys could be controlled by MgCl 2 concentration and electrochemical parameters. It was proved that preparation of Mg-Li-Sm alloys by electrocodeposition in molten salt was feasible.

Synthesis of LiMn2O4 by molten salt technique

Lithium manganese oxide powders have been successfully prepared by a molten salt synthesis using eutectic mixture of LiCl and MnO2 salt at 900 °C. The synthesis was performed in open atmosphere. The crystalline powders were characterized for their phase identification using X-ray diffraction analysis. The physicochemical properties of the lithium manganese oxide powders are investigated by thermal analysis (thermo gravimetric analysis/ differential thermal analysis), Fourier transform infrared spectroscopy, Raman spectroscopy, atomic absorption spectroscopy, electron spin resonance spectroscopy, and scanning electron microscopy. This work shows the feasibility for obtaining lithium manganese oxide at low-temperature molten salt flux method.

Influence of composite LiCl–KCl molten salt on microstructure and electrochemical performance of spinel Li4Ti5O12

Abstract A series of spinel Li4Ti5O12 samples were synthesized via a composite molten-salt method (CMSM) using the mixtures of LiCl and KCl with different L values (L is defined as the molar ratio of LiCl:KCl) as the reaction media. It is found that the melting point of the composite molten salt can effectively influence the formation of particles, and leads to different electrochemical performances of the as-prepare Li4Ti5O12. The investigations of X-ray diffraction (XRD), particle size distribution (PSD), Brunauer–Emmet–Teller (BET) surface area, and scanning electron microscopy (SEM) indicate that the as-prepared Li4Ti5O12 with L = 1.5 is a pure phase, and has uniform homogeneous octahedral shape particles, rather narrow PSD, and high BET surface area. Electrochemical tests show that the optimized Li4Ti5O12 with L = 1.5 has an initial discharge capacity of 169 mAh g−1 and an initial charge–discharge efficiency of 94% at 0.2 C rate, and achieves good rate performances from 0.2 C to 5 C.

Coagulation of tobacco mosaic virus in alcohol–water–LiCl solutions

The coagulation and colloidal stability of tobacco mosaic virus (TMV) in alcohol–water–LiCl solutions were studied. Without the addition of LiCl salt, the coagulation was promoted by the increase of hydrophobicity of the alcohols that is proportional to their alkyl chain length and concentration. Addition of the LiCl salt reduced the electrostatic repulsion between TMV particles resulting in coagulation in methanol–water and ethanol–water solutions. In water–alcohol–LiCl mixture, the coagulation of TMV was driven by both the hydrophobic interaction of the solution and the screening effect of the salt simultaneously. To understand the particle–particle interaction during the coagulation, the interaction energy was calculated using DLVO theory. Considering the electrostatic repulsive energy, van der Waals attractive energy, and hydrophobic interaction energy, the total energy profiles were obtained. The experiment and model calculation results indicated that the increase of alcohol concentration would increase hydrophobic attraction energy so that the coagulation is promoted. These results provide the fundamental understanding on the coagulation of biomolecular macromolecules.

Vacuum distillation of a mixture of LiCl–KCl eutectic salts and RE oxidative precipitates and a dechlorination and oxidation of RE oxychlorides

In this study, a vacuum distillation of a mixture of LiCl–KCl eutectic salt and rare-earth oxidative precipitates was performed to separate a pure LiCl–KCl eutectic salt from the mixture. Also, a dechlorination and oxidation of the rare-earth oxychlorides was carried out to stabilize a final waste form. The mixture was distilled under a range of 710–759.5 Torr of a reduced pressure at a fixed heating rate of 4 °C/min and the LiCl–KCl eutectic salt was completely separated from the mixture. The required time for the salt distillation and the starting temperature for the salt vaporization were lowered with a reduction in the pressure. Dechlorination and oxidation of the rare-earth oxychlorides was completed at a temperature below 1300 °C and this was dependent on the partial pressure of O 2. The rare-earth oxychlorides (NdOCl/PrOCl) were transformed to oxides (Nd 2O 3/PrO 2) during the dechlorination and oxidation process. These results will be utilized to design a concept for a process for recycling the waste salt from an electrorefining process.

The Surface Adsorption of Hydride Ions and Hydrogen Atoms on Zn Studied by Electrochemical Impedance Spectroscopy with a Non-Equilibrium Thermodynamic Formulation

We show that non-equilibrium thermodynamics theory for surfaces combined with electrochemical impedance spectroscopy can be used to derive the excess surface concentrations of reactants and products of an electrochemical reaction at an electrode. We predict the equivalent circuit for a postulated reaction using this theory, and derive expressions for the excess surface concentrations. The method is illustrated with experimental data for the following hydride reaction to hydrogen at a Zn anode in a molten eutectic mixture of LiCl and KCl at 673 K: The results support a two-step mechanism for hydrogen evolution via the hydrogen atom. We calculate the excess surface concentrations of the hydride ions and the hydrogen atoms at the metal surface, and find that the hydride ions cover a fraction of the surface while the hydrogen atoms are present in large excess. The excess surface concentration of the hydride ions varies largely with the polarized state of the surface, and so does its mean activity coefficient at the surface. The results contribute to a better understanding of the system in question. The method is general and is expected to give similar information for other electrodes.

Non-monotonic systematic variation of the thermodynamic properties of lanthanide metals in liquid bismuth

In a system consisting of molten eutectic mixture of LiCl, KCl, and liquid bismuth, the excess enthalpy changes of Ce, Pr, Nd and Ho in liquid bismuth were evaluated in a temperature range from 850 K to 1100 K by electromotive force measurement. The newly determined values were compared with those previously determined for La, Gd, Tb, and Dy, and the systematic variation of these values along the lanthanide series was discussed. As a result, it was found that the excess enthalpy changes of lanthanides show non-monotonic variation as a function of 2/3 power of molar volumes, which does not agree with the linear trend of variation which is anticipated by the semi-empirical rule. Instead of the conventional definition of the excess enthalpy changes standardized to the metallic states, those standardized to the hypothetical metallic vapor states were adapted and their systematics were discussed.

Membrane transport characteristics of binary cation systems with Li + and alkali metal cations in perfluorosulfonated ionomer

Nafion ionomer membranes were exchanged with series of pair of cation mixtures between Li + and other alkali metal cations, and investigated for equilibrium and transport characteristics of ion and water. Samples were prepared by equilibrating the membranes in the mixtures of LiCl and alkali chloride in aqueous solutions of various mixing ratios. The alkali metal cations, especially those of larger atomic number, revealed higher affinity to sulfonic acid groups than Li +, but less water content and higher density of the membrane. It was found that the mobility of cations followed the order of Li + < Na + > K +, Rb + > Cs +. Concentration of sulfonic acid group increased, when Li + was exchanged with other cations, but ionic mobility of each cation was affected differently by the other cations in the mixed state. The interaction between Li + and alkali metal cation appeared to be larger for Li/Rb and Li/Cs systems than for Li/Na and Li/K systems, but as long as the ionic transference numbers are concerned, a pair of cations moved independent of each other. The water transference coefficient (electro-osmosis drag coefficient) of Li + was ca. 15, but decreased to 10 for Na + and even less when other alkali metal cations existed. In the mixed systems, Li + and alkali metal cations showed tendency to drag more water molecules than in the individual ions, which indicated that ionic conductivity decreases when cations are coexisting in the membrane.

Electrochemical Studies on Lanthanum Ions in Molten LiCl-KCl-eutectic Mixture

We have investigated the electrochemical behaviour of lanthanum ions in a eutectic molten mixture of LiCl and KCl, using linear sweep voltammetry, as well as semi-integration and semi-differentiation of cyclic voltammograms. It was found that the reduction of La3+ is quasi-reversible, and that the obtained diffusion coefficient of La3+ is consistent with that estimated from thermodynamic data. The electrochemical reduction, diffusion of La3+ in LiCl-KCl, and the structure and stability of the complex ion are discussed.

Corrosion of intermetallic compound Fe40Al in molten LiCl and LiCl-Li2O

A lithium reduction technique has been developed for the spent nuclear fuel management [1]. In this process the oxide (UO2) is reduced to metallic form by the reaction with lithium dissolved in the molten LiCl at 750 ◦C. The strong basic Li2O formed during the reduction process is soluble in salt. Thus, the accelerated corrosion of alloys resulting form the Li2O in molten LiCl cause a serious problem in containment materials, resulting in the delay of the application of the new technique. To date, only a few reports have been published on the corrosion of materials in molten LiCl-Li2O, with the main objective to find a material that can be used to improve the vessel longevity for this new technology [1– 3]. In these studies, corrosion behaviors of many ironbase and nickel-base alloys with good high-temperature oxidation resistance have been investigated in molten LiCl-Li2O under air. Unfortunately, all these alloys experience serious corrosion in the melt. Fe40(at%)Al-base intermetallics in presence of molten salts present better corrosion resistance when comparing them with common alloys [4]. Accordingly, this work was conducted to investigate the corrosion behavior of Fe40Al in molten LiCl and LiClLi2O mixture by immersion experiments. Fe40Al was prepared by vacuum induction melting and casting into an ingot. The ingot was cut into specimens of 10 mm × 8 mm × 2 mm. All the specimens were finely ground and polished. Immersion experiments were carried out at 750 ◦C in molten LiCl or LiCl-3 wt%Li2O. The concentration of Li2O in the molten mixture was chosen to be 3 wt% which corresponded to approximately 100% theoretical UO2 reduction [1]. LiCl and the mixture of LiCl and Li2O, contained in alumina crucibles were dried at 350 ◦C for 24 h, and then held in the molten state at 750 ◦C. For every group of experiments, 25 g salt was contained in an alumina crucible of 25 ml. After a selected period of time, the corroded specimens were rinsed with distilled water, dipped in a solution containing hydrochloric acid and tetrabutylammonium iodide to strip corrosion products, dried and weighted by microbalance. Fig. 1 shows the weight loss curves for the corrosion of Fe40Al in molten LiCl and LiCl-Li2O at 750 ◦C in air. The presence of Li2O significantly accelerates the corrosion of Fe40Al. In molten LiCl, the weight loss increased linearly with test time in the initial stage, and then increased parabolically after about 5 h. Similarly, in molten LiCl-Li2O, a large weight loss is first obtained at short exposure times (about 1 h), and then the 0 5 10 15 20 25 0 20 40 60 80 100 120

Ion mobilities and microscopic dynamics in liquid (Li,K)Cl.

The dynamical properties of ionic melts formed from mixtures of LiCl and KCl have been studied across the full composition range in computer simulations of sufficient length to enable reliable values for such collective transport coefficients as the viscosity, conductivity, and internal mobilities to be determined reliably. Interest centers on the nontrivial concentration dependence exhibited by these transport coefficients, which agrees well with that observed experimentally, and in relating this to the strength of the association between an ion and its first coordination shell. The relationships between the various transport coefficients, such as those between the diffusion coefficient and the viscosity (Stokes-Einstein) and the conductivity (Nernst-Einstein) also exhibit composition dependences that reflect this association. The connection between the internal mobility and two measures of the coordination shell dynamics (the cage relaxation time and the self-exchange velocity) is explored; it is shown that the self-exchange velocity follows the composition and temperature dependence of the internal mobility very well. Finally, it is shown that allowing for anion polarization in the interaction model increases the mobility of all species without changing the structure of the melt discernibly, with the largest effect being found for the Li(+) ion.

Molten salt synthesis of LiNi 0.5Mn 1.5O 4 spinel for 5 V class cathode material of Li-ion secondary battery

Well-ordered high crystalline LiNi 0.5Mn 1.5O 4 spinel has been readily synthesized by a molten salt method using a mixture of LiCl and LiOH salts. Synthetic variables on the synthesis of LiNi 0.5Mn 1.5O 4, such as synthetic atmosphere, LiCl salt amount, synthetic temperature, and synthetic time, were intensively investigated. X-ray diffraction (XRD) patterns and scanning electron microscopic (SEM) images showed that LiNi 0.5Mn 1.5O 4 synthesized at 900 and 950 °C have cubic spinel structure ( Fd 3 ̄ m ) with clear octahedral dimension. LiNi 0.5Mn 1.5O 4 spinel phase began to decompose at around 1000 °C accompanied with structural and morphological degradation. LiNi 0.5Mn 1.5O 4 powders synthesized at 900 °C for 3 h delivered an initial discharge capacity of 139 mAh/g with excellent capacity retention rate more than 99% after 50 cycles.

Electronic Absorption Spectra of Lanthanides in a Molten Chloride. Part 1. Molar Absorptivity Measurement of Neodymium(III) in Molten Eutectic Mixture of LiCl—KCl.

Electronic Absorption Spectra of Lanthanides in a Molten Chloride. Part 1. Molar Absorptivity Measurement of Neodymium(III) in Molten Eutectic Mixture of LiCl—KCl.

An electrochemical hydrogen meter for measuring hydrogen in sodium using a ternary electrolyte mixture

An electrochemical sensor for measuring hydrogen concentration in liquid sodium that is based on a ternary mixture of LiCl, CaCl 2 and CaHCl as the electrolyte has been developed. DSC experiments showed the eutectic temperature of this ternary system to be ∼725 K. Impedance spectroscopic analysis of the electrolyte indicated ionic conduction through a molten phase at ∼725 K. Two electrochemical hydrogen sensors were constructed using the ternary electrolyte of composition 70 mol% LiCl:16 mol% CaHCl:14 mol% CaCl 2 and tested at 723 K in a mini sodium loop and at hydrogen levels of 60–250 ppb in sodium. The sensors show linear response in this concentration range and are capable of detecting a change of 10 ppb hydrogen in sodium over a background level of 60 ppb. Identification of this electrolyte system and its use in a sensor for measuring hydrogen in sodium are described in this paper.

Densities of Eutectic Mixtures of Molten Alkali Chlorides below 673 K

Densities of eutectic mixtures of LiCl + KCl, LiCl + CsCl and LiCl + KCl + CsCl melts have been measured by the Archimedean method using an electronic balance. Densities of LiCl + CsCl and LiCl + KCl + CsCl melts have been measured at temperature below 673 K.

Lithium-Ion Conductors of the System LiCo1−xFexO2, Preparation and Structural Investigation

Layered structure oxides of the system NaCo1−xFexO2 were prepared for 0≤x≤1 by solid-state reaction. Vegard-like behavior was proved for these compounds by X-ray analysis, indicating mixed transition metal layers and sodium layers without cation disorder. By ion-exchange of these compounds in a molten eutectic mixture of LiCl and LiNO3 at 260°C the system LiCo1−xFexO2 was prepared for the whole composition range and characterized by chemical analysis, X-ray diffraction and FTIR spectroscopy. Atomic absorption spectroscopy showed almost complete ion-exchange from sodium to lithium. The members of this system are shown to crystallize, as the sodium compounds, in the rhombohedral space group R3m (α-NaFeO2-type). X-ray diffraction, considerations based on the intensity ratio R101=I101/I104 and Rietveld refinement give evidence for increasing cation disorder with increasing iron content, that reaches the value of LiFeO2 (4.5%) already at an iron content of x=0.4.

Effect of Cobalt on the Magnetic Properties of the LiFe1−xCoxO2 Layered System (0≤x≤1)

Layered LiFe1−xCoxO2 was prepared in the whole composition range by ion-exchange reaction in a molten eutectic mixture of LiCl and LiNO3 at 260°C. The magnetic properties were studied by means of magnetic susceptibility and high-field magnetization measurements. Layered LiFeO2 exhibits a Néel temperature of TN=20 K. Some cationic disorder is present but seems to have no effect on the magnetic properties. The saturation magnetization and the number of effective Bohr magnetons are consistent with the high spin state (S=52) of the Fe3+ ion. A two sublattice model consisting of antiferromagnetic order between ferromagnetic layers is proposed with an estimation of the ferro- and antiferromagnetic interactions. Replacing iron by cobalt leads to an increase of the Weiss temperature θ up to x=0.4 but at the same time the antiferromagnetic long-range order is destroyed. The effect of cobalt on the superexchange interactions is also discussed.

Synthesis and electrochemical properties of lithium cobalt oxides prepared by molten-salt synthesis using the eutectic mixture of LiCl–Li 2CO 3

Lithium cobalt oxide powders have been successfully prepared by a molten-salt synthesis (MSS) method using a eutectic mixture of LiCl and Li 2CO 3 salts. The physico-chemical properties of the lithium cobalt oxide powders are investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), particle-size analysis and charge–discharge cycling. A lower temperature and a shorter time (∼700°C and 1 h) in the Li:Co=7 system are sufficient to prepare single-phase HT-LiCoO 2 powders by the MSS method, compared with the solid-state reaction method. Charge–discharge tests show that the lithium cobalt oxide prepared at 800°C has an initial discharge capacity as high as 140 mA h g −1, and 100 mA h g −1 after 40 cycles. The dependence of the synthetic conditions of HT-LiCoO 2 on the reaction temperature, time and amount of flux with respect to starting oxides is extensively investigated.

Electrochemical Behavior of Impurity Elements in Magnesium Electrolysis

Electrochemical behavior of some metallic elements in molten salt systems has been investigated as a fundamental study for purification of Mg metal. A mixture of MgCl 2 , CaCl 2 and NaCI was mainly used as an electrolytic bath, and a eutectic mixture of LiCl and KCl including MgCl 2 was also used. The electrochemical behavior of Li, Cr, Fe and Ni was examined by voltammetry, and their cathodic reactions were discussed. The results indicated that the electrochemical separation of the elements from Mg metal was possible in the molten salt systems. Potentio-static electrolysis was carried out below the melting point of Mg metal, and Mg metal was obtained. However, the deposit consisted of small Mg metal particle, and the surface of the particle was oxidized during rinsing with water.

Preparation and polymerization of new organic molten salts; N-alkylimidazolium salt derivatives

N-vinylimidazolium tetrafluoroborate (VyImBF 4) was prepared by the neutralization and polymerized to obtain a model of molten salt polymers. After polymerization, obtained P(VyImBF 4) showed much lower ionic conductivity (2.0×10 −9 S cm −1 at 30°C) than the corresponding monomeric VyImBF 4 (1.0×10 −4 S cm −1 at 30°C). The conductivity increased with the increase of lithium salts (LiTFSI and LiBF 4) concentration up to 25 mol% to Im + unit. However, the ionic conductivity was decreased once at the concentration of 50 mol%. Then the conductivity increased again about one order at 60 mol% addition and reached a constant value for highly concentrated samples. All the samples were turbid when approximately more than 60 mol% salt was added, suggesting phase separation. The microscopic phase separation was effective to keep the ionic conductivity high in P(VyImBF 4). When LiCl was added to P(VyImBF 4), the maximum conductivity was found at 50 mol%. P(VyImBF 4)/LiCl mixture showed lower ionic conductivity than other mixtures did for any salt concentration. The salt having low lattice energy led to high ionic conductivity of the polymer salt.