Silicon prepared by electro-reduction in molten salts as new energy materials

Silicon has a large impact on the energy supply and economy in the modern world. In industry, high purity silicon is firstly prepared by carbothermic reduction of silica with the produced raw silicon being further refined by a modified Siemens method. This process suffers from the disadvantages of high cost and contaminant release and emission. As an alternative, the molten salt electrolysis approach, particularly the FFC Cambridge Process (FFC: Fray-Farthing-Chen), could realize high purity silicon products with morphology-controllable nanostructures at low or mild temperatures (generally 650–900 °C). In this article, we review the development, reaction mechanisms, and electrolysis conditions of silicon production by the FFC Cambridge Process. Applications of the silicon products from electrolysis in molten salts are also discussed in terms of energy applications, including using them as the photovoltaic element in solar cells and as the charge storage phase in the negative electrode (negatrode) of lithium ion batteries.