Modeling of half-Heusler crystals with the chalcopyrite structure: Li<Subscript>2</Subscript>MgZn<Emphasis Type="Italic">X</Emphasis><Subscript>2</Subscript> (X = N,P, As,Sb)

A model of Li₂MgZnX ₂ half-Heusler compounds with the chalcopyrite structure is considered. The electronic structure is studied from first principles, showing that Li₂MgZnX ₂ are direct-gap crystals, except for pseudo-direct-gap Li₂MgZnP₂, with a band gap of 2.7 eV, 2.2 eV, 3.3 eV, and 2.5 eV for X = N, P, As, and Sb, respectively. The band structure and chemical bonding in the model crystals are found to be similar to those in LiMgX and LiZnX half-Heusler crystals. Total electron density and deformation electron density distributions are obtained. It is found that Mg–X and Zn–X ionic-covalent bonds are stronger than Li–X ionic bonds in Li₂MgZnX ₂ crystals, which allows Li atoms to move in the space between MgX ₄ and ZnX ₄ cation tetrahedra.     

Dodecahydro-<Emphasis Type="Italic">closo</Emphasis>-dodecaborate anion intercalation into graphite oxide

It is demonstrated by X-ray diffraction that, in the case of dodecahydro-closo-dodecaborates with small cations (H⁺, Li⁺, Na⁺, K⁺, NH ₄ ⁺ ), the intercalation of the B₁₂H ₁₂ ^2? anion into the interlayer space of graphite oxide is more favorable than the crystallization of a free salt. In the case of large cations commensurable with B₁₂H ₁₂ ^2? (e.g., Cs⁺), no intercalation takes place because these cations and the dodecaborate-closo-dodecaborate anion form stable cubic crystals as a separate phase outside the graphite oxide structure.     

Crystal Chemistry of Lithium Intermetallic Compounds: A Survey

The structural chemistry of lithium intermetallic compounds that are formed in Li–М binary systems where М = Ca, Sr, Ba, Mg, Zn, Cd, and Hg is surveyed. It is for the first time that the crystal structures of intermetallic compounds are classified in terms of polyhedral precursor metal clusters (in the program package ToposPro). The precursor metal clusters of crystal structures are identified using the algorithms of partitioning structural graphs into cluster structures and via the design of the basal 3D network of the structure in the form of a graph whose nodes correspond to the positions of the centers of precursor clusters. Tetrahedral precursor metal clusters M₄ are identified for the crystal structures LiZn₃-oC4, LiMg₃-hP2, LiCd₃-hP2, LiHg₃-hP8, (LiMg₃)(Li₂Mg₂)-tI16, Li₂Zn₂-cF16, Li₂Cd₂-cF16, Li₂Hg₂-cP2, Li₃Cd-cF4, and Li₃Hg-cF16; tetrahedral metal clusters M₄ are found for the framework structures with spacer atoms Sr(Li₂Sr₂)-tP20, Ca₂(Li₄)-cF24, and Ca₂(Li₄)-cP12; tetrahedral metal clusters M₄ and rings M₆, for framework structures Ba₃Li₂(Li₁₀)-hP30 and Ba₃Li₂(Li₄In₆)-hP30; icosahedral metal clusters M13 for the framework structure Li(Zn₁₃)-cF112; bilayer tetrahedral metal clusters 0@М₄@M₂₂ for the framework structure Li₂₃Sr₆-cF116; and deltahedra М₁₇ and deltahedra М₃₀, for framework structures Sr₄Li₁₄ [Sr(Sr₄Li₁₂)] [(Sr₂ (Sr₈Li₁₈)]-tI252 and Ba₄Li₁₄ [Ba(Ba₄Li₁₂)][(Ba₂ (Ba₈Li₁₈)]-tI252. The scenario of crystal structure self-assembly from precursor metal clusters S₃⁰ in intermetallic compounds is reconstituted as: primary chain S₃¹→ microlayer S₃²→ microframework S₃³.     

Zn selective luminescent ‘off-on’ probes derived from diaryl oxadiazole and aza-15-crown-5

New photo-induced electron transfer (PET) probes OMOX and OBOX, carrying an additional binding site in the form of ‘oxadiazole nitrogen’ have been designed to evaluate binding interactions with biologically significant Li⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, and Zn²⁺ including environmentally toxic Ba²⁺ and Cd²⁺ using optical spectral techniques. While Li⁺, Na⁺, and K⁺ did not appreciably perturb either the absorption or emission spectra, Ba²⁺, Ca²⁺, Mg²⁺, Zn²⁺, and Cd²⁺ induced slight red shifts (2-8 nm) in the UV-visible spectra as well as pronounced chelation induced enhanced fluorescence (CHEF). Both OMOX and OBOX exhibited the highest CHEF in contact with the zinc ion, whereas Ba²⁺, Ca²⁺, Mg²⁺, and Cd²⁺ induced relatively less emission enhancements. OBOX, which is a poorer emitter (Φ_f=0.0062) than OMOX (Φ_f=0.015), showed highly promising 160-fold emission enhancement in the presence of Zn²⁺. Potential, therefore is available in OBOX to function as a selective luminescent ‘off-on’ sensor for Zn²⁺ in the presence of coordinatively competing Ba²⁺, Ca²⁺, Mg²⁺, and Cd²⁺ ions.     

Electrocarboxylation of Carbon Tetrachloride in Dimethylformamide with Use of a Soluble Zinc Anode

Regularities of electrochemical carboxylation of carbon tetrachloride in conditions of galvanostatic diaphragmless electrolysis with a soluble zinc anode are studied. It is established that the generation of the CCl ₃ ^? anion at the cathode is accompanied by the discharge of salts of Zn²⁺, with the deposition of Zn⁰ at the surface. The interaction between and CCl ₃ ^? and CO₂ in experimental conditions leads to the formation of zinc trichloromethylacetate, which proves to be very unstable in the dimethylformamide environment and undergoes fragmentation with the CO₂ evolution. It is found that this process competes with currentless reduction of trichloromethylacetate under the action of Zn⁰ deposited on the cathode surface. As a result, corresponding dichloromethylacetate with a small yield of ≤5.5% forms as the sole product of electrolysis.     

X-ray diffraction and thermodynamic characteristics for tellurite of the composition Li<Subscript>2</Subscript>CeTeO<Subscript>5</Subscript>

Tellurite of the composition Li₂CeTeO₅ is synthesized by solid-phase method from cerium(IV) and tellurium(IV) oxides and lithium carbonate. The type of syngony, the unit cell parameters, and the compound’s X-ray and pycnometry densities are determined via X-ray diffraction analysis. The isobaric heat capacity of lithium–cerium tellurite is studied by means of dynamic calorimetry in the temperature range of 298.15–673 K; the results serve as the basis for deriving C _p ^° ~ f(T) dependency equations and determining the compound’s thermodynamic functions. λ-shaped anomalous effects, due probably to Type II phase transitions, are found on the C _p ^° ~ f(T) dependence.     

Electrical conductivity and ionic association of lithium and sodium perchlorates in tetrahydrofuran

The total limiting molar electrical conductivities of ions and triads of ions and the association constants of ions with the formation of ion pairs and triads of ions were calculated from the concentration dependences of the electrical conductivity of solutions of lithium and sodium perchlorates in tetrahydrofuran at 278.15–318.15 K with the use of the method specially developed earlier. The experimental total limiting electrical conductivities were used to calculate the limiting molar electrical conductivities and attraction friction factors of separate ions (Li⁺, Na⁺, ClO ₄ ^? , Li₂ClO ₄ ⁺ , Na₂ClO ₄ ⁺ , Li(ClO₄) ₂ ^? , and Na(ClO₄) ₂ ^? ). The constants of ion association into ion pairs were used to calculate the Gibbs energy of non-Coulomb interionic interaction (ΔG*_+?), and the constants of association into triads of ions, to determine the a ₃ distance parameter between the centers of the ion and the dipole of the ion pair. Positive ΔG*_+?), values and deviations of the experimental a ₃ value from the distance parameter calculated theoretically (a ₃ ⁰ ) for the triad of ions (Δa ₃ = a ₃ ? a ₃ ⁰ ) were related to non-Coulomb repulsion in the region of overlap of the solvation shells of ions and the influence of temperature and ion charge density on this repulsion.     

The enthalpy of formation of natural siderophyllite

A thermochemical study of lithium siderophyllite (K_0.75Na_0.06Rb_0.01Ca_0.11)(Li_0.11Fe _1.25 ²⁺ Mn_0.02Mg_0.66Al_0.35Fe _0.23 ³⁺ Ti_0.18)[Si_2.53Al_1.47O₁₀](OH)_1.63F_0.37 (I) and siderophyllite (Al-Fe biotite) (K_0.89Na_0.04)(Fe _1.69 ²⁺ Mn_0.03Mg_0.20Al_0.59Fe _0.14 ³⁺ Ti_0.06)[Si_2.80Al_1.20O₁₀](OH)_0.80F_1.16Cl_0.04(II) was performed on a high-temperature Tian-Calvet microcalorimeter. Their enthalpies of formation from the elements, Δ_f H _el ^° (298.15 K) = ?5724 ± 12 (I) and ?5573 ± 14 (II) kJ/mol, were determined by melt solution calorimetry. The Δ_f G _el ^° (298.15 K) = ?5359 ± 12 (I) and ?5231 ± 14 (II) kJ/mol values were calculated. An increase in the content of iron in siderophyllite increased the entropy, enthalpy, and free energy of formation from the elements.     

Enhanced lithium-ion intercalation and conduction of transparent tantalum oxide films by lithium addition with an atmospheric pressure plasma jet

An investigation is conducted on enhancing lithium-ion intercalation and conduction performance of transparent organo tantalum oxide (TaO _y C _z ) films, by addition of lithium via a fast co-synthesis onto 40 Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates at the short exposed durations of 33–34 s, using an atmospheric pressure plasma jet (APPJ) at various mixed concentrations of tantalum ethoxide [Ta(OC₂H₅)₅] and lithium tert-butoxide [(CH₃)₃COLi] precursors. Transparent organo-lithiated tantalum oxide (Li _x TaO _y C _z ) films expose noteworthy Li⁺ ion intercalation and conduction performance for 200 cycles of reversible Li⁺ ion intercalation and deintercalation in a 1 M LiClO₄-propylene carbonate electrolyte, by switching measurements with a potential sweep from ?1.25 to 1.25 V at a scan rate of 50 mV/s and a potential step at ?1.25 and 1.25 V, even after being bent 360° around a 2.5-cm diameter rod for 1000 cycles. The Li⁺ ionic diffusion coefficient and conductivity of 6.2?×?10^?10 cm²/s and 6.0?×?10^?11 S/cm for TaO _y C _z films are greatly progressed of up to 9.6?×?10^?10 cm²/s and 7.8?×?10^?9 S/cm for Li _x TaO _y C _z films by co-synthesis with an APPJ.     

Impedance spectroscopy of lithium-tin film electrodes

A method of electrochemical impedance spectroscopy was used to study the reversible lithium intercalation from nonaqueous electrolyte into tin films with the thickness of 0.1–1 μm. The impedance spectra of lithium-tin (Li _x Sn) electrodes have a complicated shape depending on the electrode state and prehistory; they reflect the occurrence of several consecutive and parallel processes, including the lithium migration, diffusion, and accumulation. The formation of a solid-electrolyte layer on the surface at Li intercalation into Sn is observed. Equivalent circuits are proposed that adequately model the experimental data on the Li _x Sn electrodes both freshly prepared and after prolonged cycling. Problems associated with the choice of equivalent circuits and determination of their parameters, the accuracy of the diffusion coefficient determination, the trends in the parameters’ variation with electrode potential (composition) are discussed.     

Comparison of Magnetic Properties between Spin Singlet and Triplet Li<Subscript>3</Subscript>Al<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> Clusters

With a second-order Møller–Plesset perturbation theory and Hartree–Fock nuclear magnetic resonance calculations, we investigated the magnetic properties of spin singlet and triplet Li₃Al ₄ ^? clusters. The obtained gauge-independent atomic orbital magnetic shielding tensors confirm the paramagnetism of singlet Li₃Al ₄ ^? and diamagnetism of the triplet. The planar rings composed of four aluminum atoms make the magnetic properties of Li₃Al ₄ ^? clusters versatile. The localized molecular orbital, low symmetry of geometric conformation and narrow gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital are found to correlate with the paramagnetism of singlet Li₃Al ₄ ^? . The origin of the paramagnetism is explained. In triplet Li₃Al ₄ ^? , the two outmost orbitals are degenerate, causing a conversion from the paramagnetism to diamagnetism.     

Bimetallic cluster cations ejected from a liquid metal ion source: Li-Na and Li-Mg

Cluster ions of alloys (Li-Na, Li-Mg) have been produced by a liquid metal ion source (LMIS), and analyzed by mass spectrometry. For the Li-Na system, bimetallic clusters with various compositions were formed, and dominant bimetallic species were Na₂Li⁺, NaLi⁺, NaLi ₂ ⁺ and NaLi ₈ ⁺ with this sequence of ion intensity. These clusters are systems containing 2 or 8 valence electrons except for NaLi⁺. For the Li-Mg, observed bimetallic clusters were limited to only three species (MgLi⁺, MgLi ₂ ⁺ and Mg₂Li⁺), but unexpectedly small multiply charged homonuclear clusters, Mg ₂ ²⁺ and Mg ₃ ²⁺ , were observed.     

Impedance spectroscopy of lithium-carbon electrodes

The methods of coulometric titration and electrode impedance spectroscopy are used in studying the behavior of carbon film electrodes free of binding and conducting additives in the course of reversible lithium intercalation from nonaqueous electrolytes. The electrodes with the high and low degrees of graphitization are studied. The measurements are performed in the frequency range from 10⁵ to 10^?2 Hz with the lithium concentration in intercalate varied from 0.025 mol/cm³ (corresponds to LiC₆) to a state free of lithium. The factors responsible for the hysteresis in charge-discharge curves, the versions of equivalent circuits (EC) suitable for modeling the impedance spectra of Li _x C₆ electrodes, the dependence of EC parameters and the lithium diffusion coefficient on the concentration are discussed. It is shown that all experimental impedance spectra can be adequately modeled by a common general EC. The concentration dependences are consistent with the earlier data of pulse methods. The diffusion coefficient varies approximately from 10^?12 to 10^?13 cm²/s.     

Electrochemical Intercalation of Lithium into Intermetallic Bismuth Compounds with Indium in Nonaqueous Solutions

Phase conversions and kinetics of electrochemical intercalation of lithium from dimethylformamide solutions of LiCl into bulk electrodes of bismuth, indium and their intermetallic compounds InBi and In₂Bi are studied using chronopotentiometry and chronoamperometry methods. The intercalation is controlled by non-steady-state lithium diffusion in the solid electrode. In the lithium–intermetallic compound systems, both components of alloys take part in the formation of compounds with lithium. Considerable volume changes, which occur during the intercalation, may lead to disintegration of lithium-containing phase constituents with a high lithium content. The extremum shape of cathodic chronoamperograms may be due successive and/or parallel reactions in which various lithium-containing compounds form. Some of these reactions are limited by solid-phase diffusion, while others involve the formation and diffusion-controlled growth of three-dimensional nuclei of a new phase.     

Electrolytic molybdenum oxides in lithium batteries

Nonstoichiometric molybdenum oxides (e-Mo_xO_y) were synthesized by cathodic reduction of aqueous ammonium and sodium molybdate solutions. Surface morphology of electrolytic (e) deposits, the chemical composition, crystal lattice structure, and the characteristics of electrochemical Li⁺ intercalation for such synthesized oxides were determined by the cation composition of molybdate solution and the conditions of deposit annealing. The electrochemical intercalation of Li⁺ ions in these Mo-oxides was investigated in thin-layer ballast-free electrodes, as a pasted mposite cathode in lithium batteries, and as an anode in lithium-ion batteries, with liquid organic and polymer electrolytes. The reversible discharge capacity of e-Mo₄O₁₁ synthesized from ammonium molybdate electrolyte in thin-layer ballast-free electrodes can exceed 225 mAh g^–1 for more than 170 cycles.     

Syntheses and crystal structures of two self-assembled dizinc(II) helicates with novel hydrazone linked polypyridyl ligands

The rationally designed polydentate ligands, L ¹ and L ² , based on the pyridinyl moiety and the hydrazone fragment have been synthesized to coordinate zinc(II) ions. We utilize pyridine as a rigid core connecting two bipyridines as ligand building blocks with a hydrozone linker for the L ¹ . The L ² has a reversed design in which a bipyridine was used as a hinging-available building block of the ligand core, connecting two pyridazine arms with a hydrazone linker. Two novel helical dizinc(II) complexes were obtained by the reaction of L ¹ and L ² with zinc(II) perchlorate in acetonitrile. The structures of both helicates were confirmed by X-ray diffractometry. Single-stranded helicate Zn ₂ L ¹ contains two zinc ions bridged by an oxygen atom. Except for the L ² ligand, no other bridging species were found between the two zinc ions in the double-stranded helicate Zn ₂ L ₂ ² . The self-assembling process of helicate Zn ₂ L ¹ in solution state was studied by UV–Vis spectrometric titration experiments. The stepwise formation constants imply a slightly positive cooperative behavior for the formation of helicates.     

Electrochemical Intercalation of Lithium into Graphite in Acetonitrile Solutions: The Effect of the Anion Nature

Effect of the anion nature on the cathodic intercalation of lithium into graphite is studied. The duration of a discharge process and the capacity of Li _x C₆ electrodes increase in the row Cl^– HSO₄ ^– < ClO₄ ^– < SCN^–. The highest negative potential of an Li _x C₆ electrode is reached when lithiating in an LiSCN non-aqueous solution. X-ray diffraction and microstructure analyses confirm the presence in the electrode's upper layers of predominantly layered compounds Li _x C₆A _y , where A is anion. In deep layers, the principal intercalation product is Li _x C₆.     

Structure of Aqueous Lithium Tetraborate Solution

The structure of aqueous lithium tetraborate solutions was investigated by species distribution calculation and synchrotron X-ray scattering. It shows that the dominant species in supersaturated solution at 298.15 K is B₄O₅(OH) ₄ ^2? and the minor species are B₃O₃(OH) ₅ ^2? , B₃O₃(OH) ₄ ^? and B(OH)₃. The ‘intramolecular’ structural parameters of B₄O₅(OH) ₄ ^2? , such as bond length and coordination number, were gives out using density function theory calculation. X-ray scattering study shows that the distance Li–O(H₂O)_I of [Li(H₂O)₄]⁺ is about 0.1983 nm with the coordination number(CN) 4 in tetrahedral configuration. The B–O(H₂O) distance in hydrated anion B₄O₅(OH)₄(OH₂) ₈ ^2? is 0.3662 nm with the CN 12. The Li⁺–B distance is about 0.3364 nm with a coordination number ~1.0. The temperature effect on solution structure was also discussed.     

Nucleophilic activity of peroxyhydrocarbonate and peroxocarbonate ions relative to 4-nitrophenyl diethyl phosphonate

Peroxocarbonate ions HCO ₄ ^? and CO ₄ ^2? , which are formed in the H₂O₂/NH₄HCO₃/HO^? system, react with 4-nitrophenyl diethyl phosphonate (I) through a nucleophilic mechanism with rate constants \(k_{HCO_4^ - } = 0.008\) and \(k_{CO_4^{2 - } } = 0.13 L/mol \cdot s\). Comparison of these constants with the corresponding constants of other inorganic anions in their reaction with I in the framework of the Brönsted equation indicates that HCO ₄ ^? and CO ₄ ^2? are typical α-nucleophiles.     

Thermodynamics of Lithium Intercalates in Carbonized Fabric

The method of quasi-equilibrium galvanostatic curves was applied to study the thermodynamics of lithium deintercalation from the system Li _x C₆ (solid phase)/Li⁺ (solution) in the interval 293-323 K and the thermodynamic characteristics (G, S, H) of lithium intercalation compounds in a carbonized fabric in relation to the degree of intercalation x.