Institute of High-temperature Electrochemistry of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia:

Yu. P. Zaykov, Professor, Director, e-mail: dir@ihte.uran.ru

A. V. Isakov, Junior Researcher

A. P. Apisarov, Researcher

O. V. Chemezov, Senior Researcher

Nowadays, silicon is widely used in electronic industry and metallurgy. Silicon nanomaterials can provide significant increasing of efficiency of anodes for lithium-ion electrochemical cells and photovoltaic cells. The main method of obtaining of high-purity silicon and silicon-based nanomaterials is a gas phase deposition. This method has a relatively high specific energy consumption and complex apparatus design. Therefore, it is urgent to develop new methods of silicon production. Electrolysis of molten salts is a promising method for production of silicon and silicon-based nanomaterials. Relatively cheap materials, such as K₂SiF₆ and SiO₂, can be used in this case as raw materials. Solutions of potassium hexafluorosilicate or silica dioxide in the mixture of alkali metal halides are promising electrolytes. In this paper, electrolytic deposition of silicon from the KF – KCl – K₂SiF₆ and KF – KCl – K₂SiF₆ – SiO₂ melts was investigated depending on the temperature, cathode current density and electrolyte composition. The process of silicon electrolysis was carried out in a laboratory scale cell with a high cathodic current yield (up to 93%). The composition and structure of the resulting deposits were studied, using scanning electron microscopy, X-ray diffraction and X-ray analysis. This paper represents the results of the silicon electrolysis in molten KF – KCl – K₂SiF₆ and KF – KCl – K₂SiF₆ – SiO₂. Solid layers and silicon nanowires were obtained by the electrolysis of halide and oxide halide melts. Electron microscopy data and X-ray analysis revealed the influence of oxygen on the silicon cathode structure. There was found that addition of silica to molten KF – KCl – K₂SiF₆ reduces the average grain size.

This work was carried out with the financial support of the project of presidium of Russian Academy of Sciences (2012-2014) “Development of electrochemical method of obtaining of solar silicon from molten salts and creation of new silicon-based materials” (Project No. 12-P-3-1039 (12-П-3-1039).

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