Литиевые электрохимические системы

This paper represents performance of air-hydrogen free-breathing Fuel Cell (FC) in limited volume conditions. Research work was carried out with thin two-cell stacks related to use in prototype of particular power source system, which includes aluminium-water microgenerator of hydrogen. In small current densities field (<200 mA/cm²) it was established, that after FC had been confined within the small volume, characteristics of FC became better than in non-limited-volume conditions due to self humidification.

Reversible lithium intercalation from a non-aqueous electrolyte into thin films of tin (0.1–1 mcm) and carbon (-3 mcm) was studied by means of electrode impedance spectroscopy. The measurements were made within a frequency range of 10⁵–10^-2 Hz at a varying lithium concentration in the matrix. The paper discusses several versions of electrical equivalent circuits to simulate the experimental impedance spectra, and the concentration dependence of the lithium diffusion coefficient.

At present LiCoO₂ is commercially available material for positive electrodes of lithium-ion batteries. For further improvement of its properties a number of doped samples of lithium cobaltite were synthesized. Mg and Ti were used as dopants. Crystal structure of LiCo_{1 – x – y}Mg_xTi_yO₂ was studied with XRD, whereas chemical composition was determined with atomic absorption spectroscopy, complexometric titration as well as inductively-bonded plasma. The average initial discharge capacity amounted to 145 to 150 mA·h/g.

Cell with electrochemical system «lithium – fluorinated carbon» intended for electrical pacemakers have been developed. Their significant advantages over traditional lithium – iodine cells for pacemakers are shown. Discharges characteristics, a shelf-life, and reliability, as well as an effect of various additives in fluorinated carbon cathode on discharge characteristics have been studied.

The electrode behavior of various fluorinated graphite materials and different conductive additives in various electrolytes are studied. Fluorocarbon materials based on graphite fibers are shown to have the best discharge characteristics. The advantage of thin cathodes based on fluorinated nanomaterials with a solid polymer electrolyte in comparison with the similar electrodes with traditional fluorocarbon active material is demonstrated. The use of fluorinated nanomaterials results in increased discharge characteristics of the cells.

Possibility of ultradispersed TiO₂2 (anatase modification) using as the base of the lithium power sources cathode material obtained by chloride-acid hydrolysis of titanium tetrachloride has been studied. The researches of Li+ ions electrochemical intercalation kinetics and phasic model of the process was suggested. The cathode material phase composition changes during discharge were fixed and interpreted.

Silicon electrodes with regular porous structure were prepared by the photoelectrochemical etching of single-crystal n-type silicon wafers, followed by the removal of the substrate. Electrodes with pores having circular and square section were studied. The porosity was increased via additional oxidation with the subsequent etching of oxide. The electrochemical characteristics of anodes were found to depend on porosity, electrodes with porosity 60-70% possessing maximal capacity for lithium reversible insertion.

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In modem technological processes increase used molten multicomponent solt mixtures. Determination of the composition and melting temperature are important in application of the compositions, identification of patterns processes occurring during melting and solidification of alloys, as well as the phases in equilibrium at a given thermodynamic conditions, possibly in the study of phase diagrams.

The corrosion and electrochemical behavior of magnesium and the MA 21 magnesium-lithium alloys in solutions of moderately acidic phosphates with various additives was studied. The inhibiting effect of nitrate and fluoride ions on the anode dissolution of these objects was revealed. Features of the electrochemical dissolution of magnesium and the magnesium-lithium alloys in nitrate phosphate solutions with fluoride ions caused by their activation-passivation competition have been noted.