The determination of lithium in rocks by the method of stable isotope dilution

A method is described for the determination of lithium in rocks by the method of stable isotope dilution. 50 mg to 500 mg of the sample are used for each determination. The sample is mixed with a known quantity of enriched lithium and is then decomposed by a mixture of hydrofluoric and perchloric acids. The separation of the alkali metals from iron and aluminium is based on the thermal decomposition of the perchlorates. For mass spectrometric measurements it is not necessary to separate the lithium from the other alkali metals.The values obtained for the lithium contents of two standard rocks are: G-I, 21.3 p.p. m. ; W-I, 12.6 p.p.m. Independent determinations, made using both lithium 6 and lithium 7 as tracers, have established that no significant systematic errors are caused by isotopic fractionation.Results obtained for two clay samples containing 0.1–0.3% of lithium show good agreement with spectrographic values.     

Measurement of lithium diffusion coefficient in thin metallic multilayer by neutron depth profiling

Diffusion of Li ions in thin sandwich films with copper or lead encompassing layers (obtained by ion beam sputtering deposition technique) has been studied. These metals are promising candidates for electrodes in lithium-ion batteries. It is because they exhibit an ability to store and release Li ions during charging and discharging processes. Lithium diffusion was induced in samples by thermal annealing cycles. The lithium depth profile was measured using a nondestructive neutron depth profiling technique after each thermal annealing step. The analysis of experimental data allowed to evaluate the lithium depth profiles and directly calculate the diffusion coefficients.     

Amperometric titration of calcium,strontium and barium and their mixtures in presence of large amounts of alkali metal salts

Trace amounts of alkaline earth metals are titrated with triethylenetetraaminehexaacetic acid; lead(II) is added as indicator and the current is measured by square-wave polarography. At pH 13.3, calcium, strontium and barium give a common end-point corresponding to the total content of alkaline earth ions. Copper and cadmium interfere but small concentrations of Ni, Al, Mg, Zn, Mn(II) and Fe(III) are tolerated. The alkaline earth metals can be determined in the presence of 1000-fold amounts of lithium and 10⁵- fold amounts of sodium or potassium ions.     

Effect of substituent position and lithium,sodium and potassium on the electronic structure of o-, m- and p-methoxybenzoic acids

We have studied the effect of the substituent position in the ring, and lithium, sodium and potassium ions on the electronic structure of o-, m- and p-methoxybenzoic acids (anisic acids) by the use of FT-IR, FT-Raman, Ar matrix FT-IR and ¹H NMR methods, and ab initio calculations at the B3LYP/6-311++G** level of theory. Characteristic shifts of the bands in the spectra and changes in the band intensities along the metal and ligand series were observed. On the basis of the obtained results we may answer the questions: (1) do the substituents in the benzene ring influence the electronic charge distribution in the carboxylic group of anisic acids and alkali metal anisates, (2) do the metal ions affect the electronic charge distribution in the methoxy group, (3) in what way do the alkali metals affect the electronic system of o-, m- and p-anisic acids? The substitution of lithium, sodium and potassium ions in the carboxylic group of o-, m- and p-anisic acids causes changes in the values of bond lengths and angles, and in the electronic charge distribution in the carboxylic group, methoxy group and aromatic ring. The influence of alkali metals on the electronic structure of the ligands is weaker than the effect of methoxy substituents. The effect of Li, Na and K ions on the aromatic ring of the ligands is mostly noticeable in the case of the ortho isomer. The carboxylic and methoxy groups situated in ortho positions in the ring weaken the effect of the alkali metals on the electronic charge distribution in the carboxylic anion and methoxy group.     

Probing the location and distribution of paramagnetic centers in alkali metal-loaded zeolites through (7)Li MAS NMR

The nature and surroundings of lithium cations in lithium-exchanged X and A zeolites following loading with the alkali metals Na, K, Rb, and Cs have been studied through (7)Li solid-state NMR spectroscopy. It is demonstrated that the lithium in these zeolites is stable with respect to reduction by the other alkali metals. Even though the lithium cations are not directly involved in chemical interactions with the excess electrons introduced in the doping process, the corresponding (7)Li NMR spectra are extremely sensitive to paramagnetic species that are located inside the zeolite cavities. This sensitivity makes (7)Li NMR a useful probe to study the formation, distribution, and transformation of such species.     

Electroless Formation of Hybrid Lithium Anodes for Fast Interfacial Ion Transport

Rechargeable batteries based on metallic anodes are of interest for fundamental and application‐focused studies of chemical and physical kinetics of liquids at solid interfaces. Approaches that allow facile creation of uniform coatings on these metals to prevent physical contact with liquid electrolytes, while enabling fast ion transport, are essential to address chemical instability of the anodes. Here, we report a simple electroless ion‐exchange chemistry for creating coatings of indium on lithium. By means of joint density functional theory and interfacial characterization experiments, we show that In coatings stabilize Li by multiple processes, including exceptionally fast surface diffusion of lithium ions and high chemical resistance to liquid electrolytes. Indium coatings also undergo reversible alloying reactions with lithium ions, facilitating design of high‐capacity hybrid In‐Li anodes that use both alloying and plating approaches for charge storage. By means of direct visualization, we further show that the coatings enable remarkably compact and uniform electrodeposition. The resultant In‐Li anodes are shown to exhibit minimal capacity fade in extended galvanostatic cycling when paired with commercial‐grade cathodes.     

Preparation and properties of some salts of perfluorooctanoic acid

The sodium, potassium, lithium, caesium, barium, calcium, silver, lead and ammonium salts of perfluorooctanoic acid were prepared. Their thermal stabilities, and some spectroscopic data are reported. An attempt is made to correlate some of these measurements with the properties of the metal ions or metals concerned.     

Self-diffusion of lithium in LiAlSi2O6 glasses studied using mass spectrometry

In order to improve our understanding of the transport mechanisms of lithium in glasses, we have performed diffusion and ionic conductivity studies on spodumene composition (LiAlSi(2)O(6)) glasses. In diffusion couple experiments pairs of chemically identical glasses with different lithium isotopy (natural Li vs pure (7)Li) were processed at temperatures between 482 and 732 K. Profiles of lithium isotopes were measured after the diffusion runs innovatively applying femtosecond UV laser ablation combined with inductively coupled plasma mass spectrometry (LA ICP-MS). Self-diffusion coefficients of lithium in the glasses were determined by fitting the isotope profiles. During some of the diffusion experiments the electrical conductivity of the samples was intermittently measured by impedance spectrometry. Combining ionic conductivity and self-diffusivity yields a temperature-independent correlation factor of ~0.50, indicating that motions of Li ions are strongly correlated in this type of glasses. Lithium self-diffusivity in LiAlSi(2)O(6) glass was found to be very similar to that in lithium silicate glasses although Raman spectroscopy demonstrates structural differences between these glasses; that is, the aluminosilicate is completely polymerized while the lithium silicate glasses contain large fractions of nonbridging oxygen.     

Distribution of benzo-substituted crown-ethers between chloroform and water: effects of macrocycle ring size and lithium chloride

Small size benzo-substituted crown ethers are attractive complexing agents for lithium isotope separation by solvent extraction. Low transfer of the crown ethers from solvent to water is a key point for applicability of the extractants. In the present study, 9- and 12-membered crown ethers were synthesized, and their distribution between chloroform and water was studied. Polyether ring size, benzene substituents and addition of LiCl to water were found to effect on distribution constants. Low losses of the macrocycles were observed at single-stage contact with aqueous phase. However, these losses should be taken into account in the design of multistage processes for the preparation of highly enriched lithium isotopes.     

Analytical application of 2f-wavelength modulation for isotope selective diode laser graphite furnace atomic absorption spectroscopy

Experiences in the analytical application of the 2f-wavelength modulation technique for isotope selective atomic absorption spectroscopy in a graphite furnace are reported. Experimental as well as calculated results are presented, mainly for the natural lithium isotopes. Sensitivity, linearity, and (isotope) selectivity are studied by intensity modulation and wavelength modulation. High selectivities can be attained, however, on the cost of detection power. It is shown that the method enables the measurement of lithium isotope ratios larger than 2000 by absorption in a low-pressure graphite tube atomizer.     

Lithium isotope effects in extraction of lithium chloride by benzo-15-crown-5 in the 1,1,7-trihydrododecafluoroheptanol–water system

The extraction characteristics of the 1,1,7-trihydrododecafluoroheptanol water system have been studied for lithium chloride as the salt to be extracted and benzo-15-crown-5 as the extracting agent, as well as blank extraction of lithium chloride in this system. Single-stage lithium isotope separation factors (a) have been measured at various lithium chloride concentrations in water, and the isotope effect has been multiplied by extraction chromatography. The value of a for the Li⁶–Li⁷ pair was 1.024. The light lithium isotope is concentrated in the organic phase.     

In-Situ Constructing A Heterogeneous Layer on Lithium Metal Anodes for Dendrite-Free Lithium Deposition and High Li-ion Flux

Constructing efficient artificial solid electrolyte interface (SEI) film is extremely vital for the practical application of lithium metal batteries. Herein, a dense artificial SEI film, in which lithiophilic Zn/Li_xZn_y are uniformly but nonconsecutively dispersed in the consecutive Li⁺-conductors of Li_xSiO_y, Li₂O and LiOH, is constructed via the in situ reaction of layered zinc silicate nanosheets and Li. The consecutive Li⁺-conductors can promote the desolvation process of solvated-Li⁺ and regulate the transfer of lithium ions. The nonconsecutive lithiophilic metals are polarized by the internal electric field to boost the transfer of lithium ions, and lower the nucleation barrier. Therefore, a low polarization of ≈50 mV for 750 h at 2.0 mA cm⁻² in symmetric cells, and a high capacity retention of 99.2 % in full cells with a high lithium iron phosphate areal loading of ≈13 mg cm⁻² are achieved. This work offers new sights to develop advanced alkali metal anodes for efficient energy storage.     

NMR spectroscopy of organolithium compounds. XXVI--The aggregation behaviour of methyllithium in the presence of LiBr and LiI in diethyl ether and tetrahydrofuran

1H, 6Li and 13C NMR spectroscopy were used to determine the structure of aggregates formed in mixtures of methyllithium, H3CLi, and lithium bromide and iodide in diethyl ether and tetrahydrofuran. From the chemical shifts, the signal intensity distribution and the isotope shifts observed for partially deuterated systems, it was shown that generally tetrameric structures with different halogen contents dominate. For methyllithium-lithium bromide (1:1) in THF a considerable concentration of an H3CLi-LiBr dimer was found. For the first time, deuterium-induced 6Li isotope shifts over four bonds were observed.     

Lithium-selective electrodes based on non-cyclic polyether diamide carriers in conjunction with organophosphorus solvent mediators

Series of non-cyclic polyether amides were synthesized as derivatives of pyrocatechol. Poly(vinyl chloride) membrane electrodes based on some of these carriers exhibited lithium selectivities over other alkali or alkaline-earth metal ions when dioctyl phenylphosphonate alone or mixed with o-nitrophenyl octyl ether served as plasticizer. Selectivity coefficients for lithium over sodium were up to 2.1 × 10¹, over potassium up to 1.4 × 10² and over alkaline-earth metals up to 1.5 × 10². The detection limit for lithium was 5.0 × 10⁻⁵ mol dm⁻³.     

Lithium Ion Association with Sodium Phytate and the Effects on the Conformational Equilibria. Implications in the Physiological Effects of Lithium

Abstract

³¹P NMR was employed to examine the solution interactions of lithium and potassium ions with sodium phytate. The phytate molecular conformation was found to be pH and concentration dependent. The conformational equilibria of sodium phytate in aqueous solution was not affected by the addition of potassium ions, however, it was influenced by added lithium ions and was dependent on lithium ion concentration. Furthesmore, the phytate molecule showed some selectivity for lithium ion association over potassium and sodium ions. Possible implications in the physiological effects of lithium are discussed.     

The influence of selected metals and halogens on the electronic system of benzoic acid

The influence of halogens and metals on the electronic system of the aromatic ring in lithium, sodium and potassium complexes with p-halogenobenzoic acids has been investigated by means of ¹³C and ¹H NMR, IR and Raman spectroscopy and semi-empirical calculations. It has been shown that ionic potentials and electronegativities of halogens and metals are the main factors responsible for perturbations of the electronic charge distribution in the ring.     

The influence of selected metals and halogens on the electronic system of benzoic acid

The influence of halogens and metals on the electronic system of the aromatic ring in lithium, sodium and potassium complexes with p-halogenobenzoic acids has been investigated by means of ¹³C and ¹H NMR, IR and Raman spectroscopy and semi-empirical calculations. It has been shown that ionic potentials and electronegativities of halogens and metals are the main factors responsible for perturbations of the electronic charge distribution in the ring.     

Use of a Carbon Paste Electrode Modified with Spinel‐Type Manganese Oxide as a Potentiometric Sensor for Lithium Ions in Flow Injection Analysis

A potentiometric sensor constructed from a mixture of 25% (m/m) spinel‐type manganese oxide (lambda‐MnO₂), 50% (m/m) graphite powder and 25% (m/m) mineral oil is used for the determination of lithium ions in a flow injection analysis system. Experimental parameters, such as pH of the carrier solution, flow rate, injection sample volume, and selectivity for Li⁺ against other alkali and alkaline‐earth ions and the response time of this sensor were investigated. The sensor response to lithium ions was linear in the concentration range 8.6×10^?5–1.0×10^?2 mol L^?1 with a slope 78.9±0.3 mV dec^?1 over a wide pH range 7–10 (Tris buffer), without interference of other alkali and alkaline‐earth metals. For a flow rate of 5.0 mL min^?1 and a injection sample volume of 408.6 μL, the relative standard deviation for repeated injections of a 5.0×10^?4 mol L^?1 lithium ions was 0.3%.     

Analytical application of 2f-wavelength modulation for isotope selective diode laser graphite furnace atomic absorption spectroscopy

Experiences in the analytical application of the 2f-wavelength modulation technique for isotope selective atomic absorption spectroscopy in a graphite furnace are reported. Experimental as well as calculated results are presented, mainly for the natural lithium isotopes. Sensitivity, linearity, and (isotope) selectivity are studied by intensity modulation and wavelength modulation. High selectivities can be attained, however, on the cost of detection power. It is shown that the method enables the measurement of lithium isotope ratios larger than 2000 by absorption in a low-pressure graphite tube atomizer. Received: 26 April 1999 / Revised: 25 June 1999 / Accepted: 30 June 1999