## 3 Results
### Effect of Heat Treatment on the SiO\({}_{2}\)/C Composite  
Figure 6a shows the FTIR spectra of SiO\({}_{2}\) in the composite after heat treatment at 400, 500, and 600 \({}^{\circ}\)C. The FTIR spectra of SiO\({}_{2}\)/C show similar results at various heat treatment temperatures. The peaks at 3432, 3434, and 3433 cm\({}^{-1}\) are assigned to the -OH stretching in SiO\({}_{2}\)/C heat-treated at 400, 500, and 600 \({}^{\circ}\)C, respectively. Furthermore, the peak at approximately 1600 cm\({}^{-1}\) indicates the presence of an -OH bending band. This hydroxide group indicates the presence of water molecules [15]. It is observed that an increase in the heat treatment temperature will decrease the water content in SiO\({}_{2}\)/C (Figure 6b). The presence of SiO\({}_{2}\) is detected as the Si-O-Si stretching vibration of the sharp peak at approximately 1100 cm\({}^{-1}\)[28; 29]. SiO\({}_{2}\)/C heat-treated at 600 \({}^{\circ}\)C shows smaller transmittance than SiO\({}_{2}\)/C heat-treated at 400 and 500 \({}^{\circ}\)C, specifically for the peak at approximately 1100 cm\({}^{-1}\). On the \begin{table}
\begin{tabular}{c c c}
**Content of SiO\({}_{2}\)** & **Initial Specific Capacity Based** & **Columbic Efficiency** \\ **(wt\%)** & **on the Anode** & **(\%)** \\
0 & 340 & 85 \\
1 & 356 & 83 \\
3 & 365 & 80 \\
5 & 423 & 78 \\
10 & 541 & 76 \\
30 & 552 & 72 \\ \end{tabular}
\end{table} 
Table 2: Initial specific capacity of the SiO\({}_{2}\)/C composite. other hand, SiO\({}_{2}\)/C heat-treated at 600 \({}^{\circ}\)C has better transmittance than SiO\({}_{2}\)/C heat-treated at 400 and 500 \({}^{\circ}\)C for the peak at approximately 400 cm\({}^{-1}\). It can be concluded that heat treatment affects the SiO\({}_{2}\) surface chemistry. The FTIR spectra of graphite also show peaks at approximately 3400 and 1600 cm\({}^{-1}\), which indicates the presence of water molecules in graphite, as previously described. Figure 7 shows the XRD patterns of SiO\({}_{2}\)/C at various heat treatment temperatures. Based on the figure, all samples exhibit a graphite structure (JCPDS PDF 75-2078) owing to low content and crystallinity of silica compared to that of artificial graphite. The crystallite size of the samples, which is determined by the Scherer equation [19; 30], is affected by the heat treatment temperature; it increased along with an increase in temperature, although heat treatment was performed for only 30 min. Figure 6: (**a**) FTIR spectrum of composite SiO\({}_{2}\)/C 10% heated at 400, 500, and 600 \({}^{\circ}\)C and (**b**) Magnified zone at hydroxyl peak. Figure 7: XRD pattern of composite SiO\({}_{2}\)/C heated at 400, 500, and 600 \({}^{\circ}\)C.  
The SEM characterization of artificial graphite and SiO\({}_{2}\)/C composite heated at various temperatures is shown in Figure 8. Most graphite particles have a spherical shape with \(\sim\)27-\(\upmu\)m size. Flakes of carbon were observed between spherical particles. The abovementioned figure shows that SiO\({}_{2}\)/C has rough surface morphology, owing to the presence of 10% of SiO\({}_{2}\) aggregates. SiO\({}_{2}\) secondary particles break into micron-sized primary particles during the ball milling process. The average primary particle size of SiO\({}_{2}\) on the graphite surface heated at 400, 500, and 600 \({}^{\circ}\)C is 344, 399, and 450 nm, respectively. Moreover, with an increase in temperature, the average particle size of SiO\({}_{2}\)/C increases, owing to the agglomeration of particles [9; 31]. Table 3 shows that all samples have greater specific capacity than batteries using carbon materials. Compared to graphite, all samples have higher initial discharge capacity with an increase in temperature. Thus far, it can be concluded that with an addition of SiO\({}_{2}\) and increase in the heat treatment temperature, all of our samples exhibit high initial capacity; this improvement is achieved using an easy and simple method.