Литиевые электрохимические системы

The effect of the structure and the specific surface area of carbon materials, contained in positive electrodes, on the peculiarities of cycling of lithium-sulfur cells (the depth of electrochemical reduction of sulfur and lithium polysulfides, the changes in capacity and Coulomb efficiency of cycling) was studied.

Characterization by in situ or operando methods is very important to deeper understand the chemical and electrochemical processes, as well as the degradation processes that occur during the operation of a lithium-ion battery.

Doped lithium titanate is known to be able to reversibly cycle in the potential range from 3 to 0.01 V and this ability depends both on the nature of the dopant and the doping level. In this work Li₄Ti₅O₁₂ samples doped with Nd in the amount of 0.5 to 2.0% were studied. It was shown that while being cycled in the extended potential range, the samples with the doping level from 0.5 to 1.0% demonstrated the highest capacity.

The effect of sulfur content in positive electrodes (the surface capacity of sulfur electrodes) on the characteristics (such as the depth of sulfur electrochemical reduction, changes in capacitance and Coulomb efficiency during cycle life) of lithium-sulfur cells with electrolytes based on sulfolane was studied. It was shown that the reason for the capacitance decrease of the lithium-sulfur cells at the early stage of its cycle life is the displacement of sulfur of the porous positive electrode from the rear regions into the front ones.

The reversible insertion of lithium into electrodes based on amorphous boron has been studied. The reversible capacity upon the lithium insertion has been found to be about 750 mA⋅h/g. The most efficient in terms of specific capacity are the electrodes containing graphene as a conductive additive.

The article is devoted to the study of the possibility of creating chemical current sources with a magnesium anode. The work presents the continuation of the analysis of conventional current sources with high specific characteristics. The article describes the types of cathode-active substances that have potential possibility in making chemical current sources with a magnesium anode or an anode based on magnesium intermetallic compounds.

A modern state of developments of lithium-ion batteries, as well as their main problems and the directions of their advancing are reviewed.

A number of Li_yNi_xCo_1-xO₂ compounds were synthesised by means of solid-state annealing. The synthesis conditions (the raw components, temperature, duration) were optimized so that phases with y > 0.97 were obtained suitable for making positive electrodes for lithium-ionic batteries. The charge-discharge characteristics of such Li_yNi_xCo_1-xO₂. electrodes were studied.

The processes of thermodestruction of lithium and cobalt oxides and their mixtures have been studied. The studies using the IR-spectroscopy as well thermogravimetric analysis showed, that during the initial stage of heating the mixtures of lithium and cobalt acetates the double salts form, and only then their thermodestruction proceeds.

With the aid of chronopotentiometry, voltammetry, and potentiostatic closure, the electrochemical characteristics of lithium intercalation to polyacrylonitrile carbon fiber was determined, namely, the capacitance, kinetic currents, lithium diffusion coefficient, autocharge currents. The study was made at 298 К in 1 M solutions of LiClO₄ in some mixed organic solvents (propylene carbonate – dimethoxyethane 7:3, propylene carbonate – diethyl carbonate 3:1).