Stationary and pulsed electrodeposition of silicon in LiCl–KCl–CsCl–K2SiF6 melt

Abstract

Silicon and its materials are widely used in metallurgy, micro- and nano-electronics, solar energy, and are also promising materials for anodes of lithium-ion power sources with increased specific capacity. The expansion of application areas of silicon with controlled morphology necessitates the development of new energy–efficient methods of its production. In the present work, the influence of the mode as well as parameters of electrolysis of the LiCl–KCl–CsCl–K2SiF6 melt with a temperature of 545 оC on the morphology of electrolytic precipitation of silicon on glassy carbon has been studied. The galvanostatic mode of electrodeposition, widely used in industry, as well as the pulsed mode, which is actively investigated at present, were used for the electrolysis. Silicon electrodeposition was carried out by varying such parameters as cathodic current density (from 3 to 50 mA/cm2) and electrolysis duration (from 30 to 180 min) in the galvanostatic mode, as well as by varying the density and duration of the cathodic current pulse, the duration of current pauses and the total duration of electrolysis in the pulsed mode. It is shown that electrodeposition of silicon on glassy carbon is accompanied by the formation of a continuous sediments of hemispherical nuclei with a diameter of about 1 micron on the electrode surface. An increase in the cathodic current density and an increase in the cathodic current pulse pause frequency contribute to the disruption of the sediment continuity and the growth of dendrites of ordered or arbitrary shape. At the same time, the pulsed mode allows to increase the cathode current density at silicon electrodeposition (from 25–30 to 250–500 mA/cm2) and stabilize the value of the cathode potential during electrolysis.