ELECTRODEPOSITION OF SILICON ON SILVER IN LiCl-KCl-CsCl-KSiF MELT

Silicon is widely used in various fields, including microelectronics as well as in modern high-power lithium-ion batteries. The latter require silicon in the form of nanoscale and submicron particles, or in the form of thin continuous films. The previously obtained results of the casting of electrodeposited silicon films on glass carbon indicate the need to select a substrate for silicon precipitation. A silver substrate with which silicon does not interact can be considered as a model substrate. In this work, the kinetics and mechanism of the cathode process on a silver substrate in a low-melting LiCl-KCl-CsCl-KSiF melt with a temperature of 550°C have been studied using voltage measurements. As a result of the research, it is shown that the process under study proceeds in two stages, the kinetics of which are characterized by cathode peaks at a potential of about 0 V and at a potential of less than −0.15 V relative to the potential of the silicon quasi-electrode of comparison. Based on diagnostic criteria, it is shown that the process under study is irreversible. From the voltage dependences according to the equation for an irreversible electrochemical process, the diffusion coefficient of electroactive ions was estimated, which for the second peak was 1.2·10 cm/s. Based on voltage measurements, the parameters were selected and electrodeposition of silicon onto silver substrates was carried out in galvanostatic, potentiostatic and galvanopulse modes. Discontinuous precipitation consisting of spherical particles up to 500 nm in diameter was obtained in the galvanostatic mode. In the potentiostatic and galvanopulse modes, volumetric precipitation was obtained, consisting of the same particles completely covering the silver substrate, on which dendrites of a certain geometric shape then grew. X-ray phase and micro-X-ray spectral analysis confirmed that there are no silver silicide phases in the silicon precipitate, however, elements contained in the electrolyte, as well as a small amount of oxygen, are present on the silicon surface. The results obtained are necessary to find conditions for obtaining silicon precipitates in the form of thin films and in the form of sediments with a developed surface.