Lithium electrochemical systems

Some problems of thin-film secondary batteries design

Specific capacity of secondary batteries with thin-film electrodes have been estimated. Notable gain in specific capacity is shown to be possible only at substitution of the both electrodes with higher capacity for traditional ones.

Dielectric qualities of lithium iron spineless doped by ion Mg+ on basis of impedance temperature researches

Cite measuring result spectrum impedance of poly crystalline samples Mg-rcplacc lithium-iron spinel structure Li0 5l;c24Mg01O4 in the frequency range И>2 105 Hz in temperature range 295 723K. Displayed, that conduct temperature dependence real part of dielectric conductivity from temperature affirm about process activation electron transition between ions of iron varied valence and accompany reorientation dipole in variable field.
At high temperatures (T> 573K) make apparent dominating contribution of electro conductivity on direct current. Activation energy of conductivity in low (295 473K) and high (473 723K) temperatures region put accordingly 0.3 and 0.4 eV. Distinction value activation energy grows with increase frequencies and form on a frequency./ 105 Hz -55%. Такса research components complex electrical module of dielectric polarization, enabling division electronic and ionic part of conductivity.

Searching for Optimal Electrolyte Compo-sitions for Chemical Sources of the Current and Heat- Accumulating Materials on the Ba-sis of Li,K||F,Cl,VO3,MoO4 Five-component Resiprocal System

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. In this paper we propose a graphical method of calculation and choice of salt composition on the basis of the study five-component reciprocal system Li,K||F,Cl,VO3,MoO4 for use as electrolytes and heat storage materials.

Corrosion and Еlectrochemical Behaviour of Magnesium and Magnesium-Lithium Alloys in Phosphoric Acid Media

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. Distinctive features of the electrochemical behavior of the magnesium-lithium alloys in comparison with pure magnesium in nitrate phosphate fluoride solutions due to their structural and phase specifics have been established.

Spectral Analysis of Nonharmonic and Polyharmonic Responses of an Electrochemical Object at Impedance Measurements

Possibilities for increasing efficiency of impedance spectral measurements are investigated. It is shown that for determination of linear electrochemical impedance a linearly changing input signal is preferable, and for the quantitative estimation of non-linearity of electrochemical impedance as an input signal it is expedient to use the cosine electric beats. The constructive diagrams of generators of such signals are offered.

On the use of ferrous oxalate FeC2O4-2H2O for the synthesis of electrode material LiFePO4

The review summarizes literature data on the thermal decomposition of ferrous oxalate with the formation of Fe, FeO, Fe2O3, Fe3O4, Fe3C, and other products. Historical evolution of views on the ways and mechanisms of oxalate thermolysis is traced. The current state of the art is analyzed from the perspective of FeC2O4·2Н2O0 compound for the synthesis of lithium iron phosphate LiFePO4, which is a promising cathode material for lithium-ion batteries.

On determination of the mechanism of the processes proceeding at syntesis of electrode material LiFePO4

The methods for the synthesis of lithium iron phosphate LiFePO4 with olivine structure have been developed. New materials based on lithium iron phosphate, including doped with metals, the «LiFePO4 + carbon» composites obtained by pyrolysis of organic compounds have been synthesized. Crystallographic characterization of the synthesized materials was carried out; their electrochemical characteristics of the extraction and intercalation of lithium have been identified. A correlation between the crystallographic and electrochemical characteristics of the materials was found. It was confirmed that an effective way to improve the electrical conductivity of LiFePO4 is to create a carbon shell of the products of pyrolysis of organic compounds on the material's particles surface. A correlation of electrical conductivity and temperature of synthesis of the material was determined. The sequence of chemical interaction between precursors for the synthesis of LiFePO4 is defined; the mechanism of solid-phase interaction is described.

Negative electrodes based on regular structured porous silicon for lithium-ion batteries

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. Electrodes thus prepared feature much higher capacity per area unit (up to 25 mA·h/cm2) than usual thin-film electrodes (about 1 mA·h/cm2).

The effect of discharge current upon battery capacity

Cycling tests of lithium-ion batteries in wide temperature and load ranges have been carried out. The existence of certain threshold discharge load corresponding abrupt decrease of discharge capacity was found.