Choice of the Composition of the Chloride Melts for the Electrochemical Synthesis of Silicon

The work is aimed at studying the kinetics of silicon electrodeposition from different chloride melts in order to select both optimal melt compositions and their electrolysis parameters. The study was carried out in KCl, KCl-CsCl and LiCl–KCl-CsCl melts with the addition of K 2 SiF 6 at different temperatures depending on the melting point of each system. The optimal deposition potentials and current densities for electrolysis were determined by voltammetry. The LiCl–KCl-CsCl based melts are characterized by the highest silicon electrodeposition rates. Moreover, lowering lithium chloride content increase electrodeposition rates at the same other conditions. In LiCl–KCl-CsCl melt containing lithium chloride, the electrodeposition rate is highest in an electrolyte with a reduced LiCl content due to the lowest decomposition rate of the additive. Galvanostatic and potentiostatic electrolysis was carried out in the melts with different composition that have the highest rate of electrodeposition. It was found that continuous deposits occur in the LiCl–KCl-CsCl melt, while in other melts silicon is deposited in the form of fibers and dendrites. Fibers with a diameter of up to 0.7 μm were obtained in LiCl-free melts, and films consisting mainly of spherical grains with a diameter of up to 1 μm were obtained in a melt with lithium chloride.