Литиевые электрохимические системы

There were investigated the self-discharge dynamics in two homogeneous groups («A» and «B») of the coin lithium cells ВR2325 on the basis of superstoichiometric fluorocarbon CF1.20, selected from the uniform experimental batch of 10000 pieces. The reason of two different groups («A» and «B») appearance through 3–6 months of storage is connected with the origin of hydrogen fluoride in cathodes of group «A» cells, which will be derivated at auto catalytic hydrolysis of C-F-bonds by a moisture tracers (0.1–0.5%).

Comparative characteristic of natural and synthesized iron disulfide has been carried out. Physical, chemical and macrostructure characteristics of pyrite powders have been shown. By the methods of cyclic Vtammetry the electrochemical properties of FeS₂ – based cathodes have been investigated in non-aqueous liquid (1М LiClO₄; PC+DME) and polymer (CPVC; 1М LiClO₄; PC) electrolytes.

Major trends in cathode active material development for lithium-ion batteries have been reviewed. Statistics on all publications in «Journal of Power Sources» (from 03.2006 till 04.2007) is summarized in order to point out that the main effort in secondary batteries development is concentrated on lithium-ion batteries, especially on positive electrode study. Based on these publications the main routes for LiCoO₂ modification as well as for novel materials research have been reviewed.

It is shown that an examination of reduced galvanostatic charge-discharge curves allows making preliminary conclusion on degradation mechanism upon cycling. If such degradation is due to loss of active material all normalized curves coincide. In the case of insulating films building up normalized curves are shifted along potential axis. Various structure changes result in qualitative change of curves shape.

In this paper the possibility of applying of hydrolysis lignin as the lithium battery cathode material was demonstrated for the first time. Hydrolysis lignin features have been investigated by impedance spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Electrochemical characterization was carried out at room temperature using 1M LiBF4 in ?-butyrolacton electrolyte system. The chemical composition of cathode materials upon battery discharge down to 0.9 V was studied by the X-ray photoelectron spectroscopy and Infrared spectroscopy.

The study of the internal resistance of the lithium-ion battery designed and manufactured by JSC «Saturn» as the original, and after a long cycle life by pulse chronopotentiometry and electrochemical impedance was carried out. It is shown that the higher the hexagonal ordering of the material and the closer the degree of cation mixing to the optimal value, the less polarization resistance of the battery as original, and after a long cycle life. It was found that the less the original polarization resistance of the battery, the more its cyclic life.

On basis of analysis of literature data as well as of own experimental results we suggest some regularity for degradation of silicon electrodes upon cycling. It was shown that an electrode capacity Q at n-th cycle can be calculated from equation Q = Q₀ exp(kn+?n²/2), where Q₀ is initial capacity value, k и ? are empiric constants.

The problem of use discharge and noise characteristic of primary power sources system of thionyl chloride/lithium for definition of their operative conditions (first of all, depth of discharge) is considered. On the basis of the analysis of features of discharge curves of Li/SOCl2 cells both bobbin and wound (rolled) type, and also intensity of voltage fluctuations and power-density spectrum of electrochemical noise of above mentioned cells it is drawn a conclusion on an opportunity of carrying out their correct diagnostics.

The brief review of the processes arising in Li-ion cells in the cases of abuse is presented. The results of tests on overcharge, overdischarge, short circuit inside the cell and external short circuit for Li-ion cell having capacity of 150 A·h are shown and discussed. The recommendations to minimize the aftergrowths are suggested.

A pulse method at which a tested chemical power source is discharged by a pulse generated by constant current of special shape, and voltage on a cell is measured before and after pulse action has been developed to determine the degree of dicharge of chemical power sources. The degree of dicharge of a chemical power source is determined using a specially developed algorithm from the values of these voltages and other electrical parameters calculated.