## 3 Results and Discussion
However, as shown in Figure 2c, the Si powders were connected during the carbonization and resulted in the agglomeration. However, as shown in Figure 2c, the Si powders were connected during the carbonization and resulted in the agglomeration. However, as shown in Figure 2c, the Si powders were connected during the carbonization and resulted in the agglomeration. However, as shown in Figure 2c, the Si powders were connected during the carbonization and resulted in the agglomeration. However, as shown in Figure 2c, the Si powders were connected during the carbonization and resulted in the agglomeration. However, as shown in Figure 2c, the Si powders were connected during the carbonization and resulted in the agglomeration. However, as shown in Figure 2c, the Si powders were connected during the carbonization and resulted in the agglomeration. However, as shown in Figure 2c, the Si powders were connected during the carbonization and resulted in the agglomeration. Therefore, as shown in Figure 2c, the Si powders were connected during the carbonization and resulted in the agglomeration. Figure 1: X-ray diffraction patterns of the Si and Si/C composite powders: (**a**) Si powder; (**b**) Si/C nanocomposite powder; and (**c**) change in intensity ratio of the Si peak before and after the carbonization with respect to milling time. Figure 2d, further milling for 8 h changed the Si/C powders into very fine Si/C nanocomposite powder with comparatively more uniform distribution than that of Si/C powder without milling. The particles sizes are in the rage of 100-200 nm. This observation suggests that the hybrid process of high-energy milling and carbonization is an effective approach to synthesize the Si/C nanocomposite powders. The charge-discharge voltage curves of the Si/C nanocomposite for the 1 st, 3 rd, 10 th, 20 th, and 50 th cycles are presented in Figure 3a. The electrode delivers first cycle charge and discharge capacities of 2139 and 1658 mAh g\({}^{-1}\), respectively, corresponding to a first cycle coulombic efficiency of 77.5%. Similarly, for the 50 th cycle charge and discharge, capacities are 1267 and 1278 mAh g\({}^{-1}\) respectively, with a coulombic efficiency of 99.13%. The irreversible capacity loss of the electrode during 1 st, 3 rd, 10 th, 20 th and 50 th cycles are 22.5%, 7%, 0.9%, 0.8% and 0.87%, respectively. The first and third cycle irreversible capacity losses are higher, which could be caused by the side reactions with electrolyte and formation of a solid electrolyte interface layer on the electrode surface accompanied by the consumption of lithium [37; 38]. Therefore, coulombic efficiency after the third cycle attained \(\sim\)99% within five cycles. A long and flat discharge voltage plateau observed during the first cycle at below 0.2 V indicates the lithiation of crystalline Si transforms into amorphous Li\({}_{x}\)Si phase and the formation of SEI [39]. Figure 3b shows the discharge capacities and coulombic efficiency of Si/C nanocomposite electrode \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample Name** & **Average Particle Size (nm)** & **Standard Deviation (nm)** \\ \hline Si-8 h milling & 250 & 79 \\ Si/C composite & 350 & 138 \\ Si/C-8 h milling & 200 & 61 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Average particle size and standard deviation of the as milled Si and Si/C powders. Figure 2: FE-SEM images of the Si and Si/C composite powders: (**a**) Si raw powder; (**b**) Si milled for 8 h; (**c**) Si/C powder after carbonization; and (**d**) Si/C milled for 8 h.  
with respect to cycle number. The initial cycle discharge capacity of the electrode is 1658 mAh g\({}^{-1}\) at 0.1 C-rate. The composite electrode exhibited monotonous capacity fading, good reversible capacity and excellent capacity retention from the 5 th to 100 th cycle. However, a moderate capacity fading during the initial cycle was observed. Remarkably, the coulombic efficiencies of the electrodes after fifth cycle were steadily saturated with an efficiency of \(\sim\)99.1%.