Synthesis of pyrochlore tungsten trioxide thin film and electrochemical lithium intercalation

The pyrochlore tungstate thin film has been prepared by an autoclave hydrothermal method at a temperature of 200 °C. The film was characterized by X-ray diffractometry, X-ray photoelectron spectroscopy and scanning electron micrograph measurements, showing that pure pyrochlore phase of sodium tungstate containing a small amount of water was formed by heating the film at a temperature of 350 °C. The cyclic voltammetric and galvanostic measurements revealed that a reversible electrochemical lithium intercalation into the crystal lattice of pyrochlore tungstate film takes place with charge-discharge cycling. Furthermore, the thermodynamics and kinetics of electrochemical lithium intercalation into the pyrochlore sodium tungstate film were also studied.     

The influence,on lithium electrochemical intercalation,of bond ionicity in layered chalcogenophosphates of transition metals

In the course of lithium electrochemical intercalation in the host structure of layered M∥PX₃ phases (M = V, Mn, Fe, Co, Ni, X = S, Se), it was shown that the best energy yield was obtained from low ionicity bond materials. The absorption edge energy, along with the free energy of the intercalation reactions have been correlated in a satisfactory way to the ionicity fi of the M-X bonds. These diagrams indicate which phases have to be looked at to obtain the maximum electrochemical yields.     

Magnetic properties of lithium intercalation compounds

Magnetic experiments are powerful tools to study fundamental properties and to check the qualities of samples. Temperature, stress, and impurities of materials can all affect magnetic properties and play an important role in the utilization of these materials for engineering applications. The estimation and analysis of the spontaneous magnetization can reveal ferromagnetic particles as impurities in samples. The shape of the temperature dependence of magnetization is indicative of the origin of the magnetic properties. However, it is necessary to correlate the χ _m (T) curves and isothermal M(H) plots to achieve a complete analysis of the electronic properties of the materials. Highlights of magnetic properties of lithium intercalation compounds are briefly described. Intrinsic and extrinsic properties are considered as useful parameters to determine the purity of electrode materials for rechargeable Li-ion batteries.     

Effect of diffusion on lithium intercalation in titanium dioxide

A new model of Li intercalation into rutile and anatase structured titania has been developed from first principles calculations. The model includes both thermodynamic and kinetic effects and explains the observed differences in intercalation behavior and their temperature dependence. The important role of strong local deformations of the lattice and elastic screening of interlithium interactions is demonstrated. In addition, a new phase of LiTiO2 is reported.     

Electrochemical intercalation of lithium into diamond-pyrocarbon nanocomposites

Physics of the Solid State - The electrochemical behavior of composite materials based on nanodiamond and carbal is investigated in the course of cathodic intercalation of lithium from an LiPF6...     

Electrochemical intercalation of lithium into graphitized carbons

The change of the carbon structure with electrochemical intercalation of lithium has been investigated by X-ray diffraction (XRD) method. Graphitized carbons showed the first and the second stage structures clearly during the intercalation process. However, the layer spacing corresponding to the 1st stage structure of graphitized carbon was smaller than that of graphite. This is because the first stage structure of graphitized carbon is the mixed structure of lithiated graphite crystallites and lithiated turbostratic disordered layers. The lithium is mainly intercalated into turbostratic disordered layers above 0.1 V versus Li/Li⁺, and intercalated into graphite crystallites rather than turbostratic disordered layers below 0.1 V versus Li/Li⁺.     

Effect of a rhombohedral phase on lithium intercalation capacity in graphite

Five natural graphites with different rhombohedral phase (3R phase) content have been investigated as anode materials for rechargeable lithium-ion batteries. The reversible capacity varies from 250 mA h/g to 350 mA h/g for the same intercalation conditions depending on the content of the 3R-phase. With increasing rhombohedral phase in the graphite, the intercalation capacity will be high. A peak at about 10 mV in the cyclic voltammograms (CV) of a sample with a large 3R-phase content is caused by lithium ions occupying boundaries between the rhombohedral (3R) phase and the hexagonal (2H) phase and is responsible for a capacity exceeding the theoretical value.     

Surface morphology and Raman spectroscopy of thin layers of antimony and bismuth chalcogenides

The phonon spectra in thin layers of bismuth telluride and solid solutions of Bi_2–xSb_xTe_3–ySe_y of different composition, belonging to three-dimensional topological insulators, have been investigated by micro-Raman spectroscopy, and the morphology of an interlayer van der Waals (0001) surface in them has been studied by semicontact atomic force microscopy at room temperature. The analysis of the Raman spectra and the intensity ratio of active and inactive longitudinal optical modes depending on the composition, morphology of the interlayer surface, and thickness of the layers enabled the estimation of the effect of topological surface states of Dirac fermions, associated with the strengthening of the electron–phonon interaction as a result of resonance Raman scattering, and the identification of the compositions, in which the contribution of topological surface states becomes dominant.     

Thermoelectric properties of multicomponent solid solutions based on bismuth and antimony chalcogenides with n-type conduction in the region of impurity and mixed conduction

The thermoelectric properties of Bi_2?x Sb _x Te_{3 ? y ? z} Se _y S _z solid solutions are studied in the temperature range 300–450 K. It is shown that, as the number of atoms involved in substitutions in both sublattices during the formation of a solid solution increases, the maximum in the temperature dependence of the thermopower coefficient and the minimum in the temperature dependence of the thermal conductivity shift toward higher temperatures as a result of an increase in the band gap. As the charge carrier concentration in the sample of a solid solution increases, the onset of mixed conduction shifts toward higher temperatures, which leads to an additional decrease in the thermal conductivity at a fixed temperature. The observed temperature dependences of the thermoelectric properties of the Bi_{2 ? x} Sb _x Te_{3 ? y ? z} Se _y S _z solid solutions bring about a shift of the maximum in the thermoelectric efficiency toward higher temperatures as the number of atoms involved in the substitution increases.     

Studies of lithium intercalation in 3R-WS2

The lithium intercalation into the layered dichalcogenide 3R-WS₂ has been investigated by electrochemical reduction and by chemical reaction in n-butyl lithium solution. Essential results are (a) a charge transfer of nearly 0.6e⁻/W in Li_xWS₂, (b) a small increase of the c-axis parameter of about 0.6%, and (c) a high mobility of the Li⁺-ions. The chemical diffusion coefficient of Li⁺-ions is estimated to be 8 × 10⁻⁹ cm² s⁻¹ in the composition range 0 ≤ x ≤ 0.25. The appearance of a structural transformation from 3R-WS₂ to 2H-Li_xWS₂ is interpreted on grounds of instabilities in the interlayer structure.     

Mixed-valence induced during the intercalation of lithium ions into uranium fluorides

The mixed-valence in uranium fluorides LiU₄F₁₆ and UF₄ can be induced (or eliminated) by the intercalation (deintercalation) of lithium ions into these compounds. These processes can be electrochemically performed both with LiU₄F₁₆ (or LiTh₄F₁₆) and with monoclinic UF₄ as starting materials using a liquid electrolyte composed of propylene carbonate as solvent and LiClO₄ as salt. In the cases of UF₄ and LiU₄F₁₆, the electrochemical intercalation of Li⁺ into the host matrix is reversible and a maximum of three Li⁺ ions per U₄F₁₆ unit can be reversibly intercalated. Additional experimental evidences of the mixed-valence in these fluorides are presented such as the Electron Paramagnetic Resonance characterization of the starting materials and of those electrochemically modified.     

Studies of lithium intercalation in heat-treated products obtained from molybdic acid

Several characteristics of the lithium intercalation in molybdenum trioxide hydrate, MoO₃.2/3H₂O, have been studied. The non-stoichiometric molybdenum trioxide, MoO_2.8, was obtained by dehydration and annealing treatment of molydic acid MoO₃.1H₂O. These cathode materials were tested in a lithium battery of the type Li/LiClO₄-PC/MoO_m and the electrochemical performance has been evaluated during the discharge/charge of the galvanic lithium cells.     

The effects of the lithium intercalation on the X-ray photoelectron spectra of NiPS3

Summary A detailed XPS study of the lithium-intercalated NiPS₃ specimens was performed at the 2p, 3p, 3s core levels of the nickel atoms and at the 2p core levels of the sulphur and phosphorous atoms for various lithium contents. Comparison of the Ni 2p, 3p and 3s XPS spectra corresponding to NiPS₃ and Li _x NiPS₃ systems shows some evident trends. In particular, a shift of the Ni main line towards lower binding energies, a decrease in the intensity of the Ni 3p, 2p satellite structures and a change in the full width at half maximum of the Ni 3s band with lithium content are observed. All these findings suggest a change in the 3d electron configuration for high lithium concentrations. As regards the cluster (P₂S₆)⁴⁻, with the addition of lithium, a P 2p main line shift towards higher binding energies is noted, while the S 2p peak shifts towards lower binding energies. These results are discussed in comparison with previous physical measurements concerning the nickel reduction process and the related electronic modifications. The authors of this paper have agreed to not receive the proofs for correction.     

High precision studies of lattice parameter changes in lithium intercalation compounds

We present an in situ X-ray diffraction experiment which measures lattice parameter changes resulting from lithium intercalation to a precision of one part in 10⁵. Experiments on 2H-Li_xTaS₂ demonstrate the sensitivity and reproducibility of the method. To our knowledge, these results are the most precise measurments of lattice parameter changes resulting from intercalation. We find that the c-axis of 2H-Li_xTaS₂ exhibits anomalous behaviour near $\text{x=}\text{1}\text{3}$ and $\text{x=}\text{2}\text{3}$ pr esumably because of the order-disorder transitions in the intercalated lithium.     

Electrochemical characterization on layered lithium ruthenate for electrochemical supercapacitors

Electrochemical characteristics of lithium ruthenate (Li_xRuO_2+0.5x·nH₂O) for electrochemical capacitors' electrode material were first examined in this paper by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Results show that Li_xRuO_2+0.5x·nH₂O has electrochemical capacitive characteristic within the potential range of − 0.2–0.9 V (vs. SCE) in 1 M Li₂SO₄ solution. The capacitance mainly arises from pseudo-capacitance caused by lithium ions' insertion/extraction into/out of the Li_xRuO_2+0.5x·nH₂O electrode. The specific capacitance of 391 F g^− 1 can be delivered at 1 mA charge–discharge current for Li_xRuO_2+0.5x·nH₂O electrode with an energy density of 65.7 W h kg^− 1. This material also exhibits an excellent cycling performance and there is no attenuation of capacitance over 600 cycles.     

A galvanostatic study of lithium intercalation in RuO2

The diffusion process in a host structure has been studied at constant current with the cells: RuO₂ composite/ LiClO₄PEO/Li and RuO₂ powder/LiClO₄PC/Li. The effect of grain size distribution and temperature has been investigated and the diffusion coefficient for Li in RuO₂ calculated along with the diffusion activation energy (0.52 eV). Results show no intercalation of PC at 25°C.