The silicon electrodeposition from the KF-KCl-(10 mol%) K2SiF6 melt at 943–1103 K has been studied. The polycrystalline continuous single-phase silicon coatings (∼99.9 wt% Si) have been obtained on the graphite, glassy carbon, silver, and tungsten substrates. The Raman spectroscopic study of the Si/C and Si/Ag interfaces has proved an absence of the intermediate phases. Two phases (Si and Ni2Si) were formed during the silicon electrodeposition on nickel.
Silicon electrodeposition on glassy carbon from the KF-KCl-K2SiF6,
KF-KCl-K2SiF6-KOH and KF-KCl-K2SiF6-SiO2 melts was studied by the cyclic
voltammetry. ?he electroreduction of Si(IV) to metallic Si was observed as a
single 4-electron wave under all considered conditions. The reactions of
cathode reduction of silicon from fluoride and oxyfluoride complexes were
suggested. It was shown that the process can be controlled by the preliminary
transformation of SiO44- to SiF62- and SiOxFyz-. The influence of the current
density on structure and morphology of silicon deposits obtained during
galvanostatic electrolysis of the KF-KCl-K2SiF6-SiO2 melt was studied.
Currently, silicon and silicon-based composite materials are widely used in microelectronics and solar energy devices. At the same time, silicon in the form of nanoscale fibers and various particles morphology is required for lithium-ion batteries with increased capacity. In this work, we studied the electrolytic production of nanosized silicon from low-fluoride KCl–K2SiF6 and KCl–K2SiF6–SiO2 melts. The effect of SiO2 addition on the morphology and composition of electrolytic silicon deposits was studied under the conditions of potentiostatic electrolysis (cathode overvoltage of 0.1, 0.15, and 0.25 V vs. the potential of a quasi-reference electrode). The obtained silicon deposits were separated from the electrolyte residues, analyzed by scanning electron microscopy and spectral analysis, and then used to fabricate a composite Si/C anode for a lithium-ion battery. The energy characteristics of the manufactured anode half-cells were measured by the galvanostatic cycling method. Cycling revealed better capacity retention and higher coulombic efficiency of the Si/C composite based on silicon synthesized from KCl–K2SiF6–SiO2 melt. After 15 cycles at 200 mA·g−1, material obtained at 0.15 V overvoltage demonstrates capacity of 850 mAh·g−1.
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