## 3 Results
### Electrochemical Characteristics of the Obtained Silicon Deposits  
The obtained silicon deposits were studied as a composite Si/C anode for a lithium-ion battery. In the first charge/discharge cycle (Figure 6), the capacity of Si/C composite prepared on the base of silicon electrodeposited from KCl-K\({}_{2}\)SiF\({}_{6}\) was between 1450 and 3000 mAh\(\cdot\)g\({}^{-1}\) during lithiation, and between 950 and 1670 mAh\(\cdot\)g\({}^{-1}\) during delithiation. Despite of the similar morphology and size of silicon fibers synthesized at different overpotentials, their energy characteristics are different. As can be seen from Figure 6, samples 2 and 3 synthesized at 0.15 and 0.25 V show similar charging times, although the initial period associated with electrolyte reduction and solid electrolyte interphase formation is quite different. Silicon synthesized at 0.1 V demonstrates 60% lower capacity, and the highest initial coulombic efficiency of 65.5%.  
After 15 cycles at 200 mA\(\cdot\)g\({}^{-1}\) (Figure 7a), the capacitance for the best sample of silicon fibers was 750 mAh\(\cdot\)g\({}^{-1}\) for sample 3 synthesized at 0.25 V overvoltage. The coulombic efficiency of the anode half-cell with silicon fibers in this case increased from 59% up to 92%. Silicon synthesized at 0.15 V (sample 2) demonstrates a similar capacity fade rate as sample 3, but a lower overall capacity. However, these samples have different coulombic efficiency during the first 10 cycles. Sample 1, while having a much lower capacity, demonstrates better capacity retention, with \(-\)50.7% of the initial capacity after 15 cycles.  
Figure 6: First charge/discharge cycle curves of Si/C composites based on electrodeposited silicon at 50 mA g\({}^{-1}\). Solid lines represent silicon deposited from molten KCl–K\({}_{2}\)SiF\({}_{6}\); dashed lines represent silicon deposited from molten KCl–K\({}_{2}\)SiF\({}_{6}\)–SiO\({}_{2}\).  
For silicon samples obtained from the KCl-K\({}_{2}\)SiF\({}_{6}\)-SiO\({}_{2}\) melt, the anode capacity was between 920 and 2430 mAh\(\cdot\)g\({}^{-1}\) for charging and between 600 and 1300 mAh\(\cdot\)g\({}^{-1}\) during discharge. As can be seen from Figure 6, the behavior of these samples is similar to the ones synthesized without the addition of SiO\({}_{2}\) to the melt, but lower capacities are achieved for all the samples. The highest capacity value was observed for the sample 5 synthesized at 0.15 V overvoltage. The initial coulombic efficiency of the silicon needles/tubes was 44-65%, lower than for the samples 1-3. Sample 4 demonstrates much higher delithiation potential than all other samples, probably due to the higher C-rate in comparison to other samples. After 15 cycles (Figure 7b), samples synthesized from the melt with SiO\({}_{2}\) addition demonstrate higher coulombic efficiency--between 93.5% and 96.1%--and better capacity retention rate. Remaining capacity of the sample 5 is 850 mAh\(\cdot\)g\({}^{-1}\), which is 74.5% of the initial capacity.  
It is probable that such a difference in capacity fade rate is caused by different silicon structures or surface layer composition; however, the reasons for drastic capacity difference among the samples with similar morphology synthesized at different deposition overpotential is not clear. The results obtained indicate that further research is promising, aimed both at optimizing the conditions for obtaining silicon deposits from the investigated molten electrolytes, and at improving the performance of a lithium-ion battery with a composite anode based on the obtained silicon.