Electrodeposition of ordered silicon fibers from the KI–KF–KCl–K₂SiF₆ melt for lithium-ion power sources

The possibility of using silicon-based anodes in lithium-ion power sources is actively investigated due to the increased lithium capacitance of silicon. This work reports the preparation of submicron silicon fibers on glassy carbon in KI–KF–KCl–K₂SiF₆ melt at 720°C. For this purpose, the parameters of silicon electrodeposition in the form of fibers were determined by cyclic voltammetry, experimental batches of ordered silicon fibers with an average diameter from 0.1 to 0.3 μm were obtained under galvanostatic electrolysis conditions, and using the obtained silicon fibers, anode half-cells of lithium-ion current sources were fabricated and their electrochemical behavior and behavior under multiple lithiation and delithiation were studied. By means of voltammetric studies, it is observed that charging and discharging of the anode based on the obtained silicon fibers occurs at potentials from 0.2 to 0.05 V and from 0.2 to 0.5 V, respectively. Cycling of electrodeposited silicon fibers in anode half-cells of lithium-ion power source was carried out. Depending on the charge current, the discharge capacity ranged from 200 to 500 mAh/g at Coulomb efficiency of 98–100 %. Also, multiple cycling of the sample of lithium-ion power source with a lithium counter electrode was performed. In the course of 800 cycling with current 0.5C, the discharge capacity of the sample decreased from 165 to 65 mAh/g. Scanning electron microscopy shows the volumetric expansion of the of silicon fibers during cycling.