## 3 Results
### SiO2 Characterization
This phenomenon directly indicates the importance of compositing SiO\({}_{2}\) with a more stable and highly conductive material such as artificial graphite or Mesocarbon microbeads (MCMB) [17; 22]. Effect of SiO\({}_{2}\) Composition in the SiO\({}_{2}\)/C Composite on Its Structure and Coulombic Capacity  
As-prepared SiO\({}_{2}\) was mechanically milled with MCMB and heated at 500 \({}^{\circ}\)C for 30 min under flowing argon. Figure 4 shows the XRD analysis of the SiO\({}_{2}\)/C composite with various SiO\({}_{2}\) wt%. Because as-obtained SiO\({}_{2}\) is in an amorphous form, the diffraction peaks of graphite are dominant in all samples, and the SiO\({}_{2}\) peak is not detected; however, there is an increase in the peak width, specifically at 2 theta of 27\({}^{\circ}\), which may be caused by an increase in the amount of amorphous silica (SiO\({}_{2}\)). Figure 4: Electrochemical performance of SiO\({}_{2}\) in the NCA battery. Figure 3: (**a**) Charge discharge curve and (**b**) ratability of SiO\({}_{2}\) as the LiNi\({}_{0.8}\)Co\({}_{0.15}\)Al\({}_{0.05}\)O\({}_{2}\) (NCA) battery anode. The initial charge/discharge curves of the samples at different SiO\({}_{2}\) content at 1/10 C are shown in Figure 5a. It is easily observed that the specific capacity of the SiO\({}_{2}\)/C composite depends on the SiO\({}_{2}\) content in the composite. It is observed that the first capacity of the SiO\({}_{2}\)/C composite considerably increased with an increase in the SiO\({}_{2}\) content. However, when the content of SiO\({}_{2}\) was greater than 10%, the capacity was insignificantly increased. Table 2 shows that all samples have greater capacity than batteries that contain carbon materials (340 mAh g\({}^{-1}\)) (0.1 V vs. Li/Li\({}^{+}\)) [1]. Increased capacity occurs because SiO\({}_{2}\) (1961 mAh g\({}^{-1}\)) acts as an active material in composites and is responsible for increasing battery capacity. The increased capacity also indicates that SiO\({}_{2}\) used in the composite exhibits electrochemical activity [16; 17; 18]. Based on previous reports, the small amount of NaCl within silica matrices can potentially enhance the electrochemical performance of LIBs. [PERSON] et.al. claimed that 1% NaCl in electrolyte of Li-Graphite cell can improve the SEI formation on graphite surface which enhance the cycling performance. Study by [PERSON] et al. had stated that NaCl can improve the capacity of NCA cathode. Since the specific discharge capacity listed in Table 2 exceeds the capacity of pure graphite, we can conclude that the effect of a small amount of NaCl is still insignificant compared to the effect of silica composite on the graphite anode. However, the effect of NaCl additive on NCA/Graphite cell can be further studied in future research [23; 24]. Figure 5: (**a**) Initial charge/discharge curve of the samples at different SiO\({}_{2}\) content at 0.05 C; (**b**) magnified charge–discharge curve of the samples; (**c**) cycling performance of the samples at different SiO\({}_{2}\) content; (**d**) rate and cycling performance of the SiO\({}_{2}\)/C 10% composite. However, an increase in the SiO\({}_{2}\) content in the anode material will also result in a decrease in battery stability (cyclability). Figure 5c shows that the reversible capacity of SiO\({}_{2}\)/C 30% remains at 51% after 15 cycles. This is mostly due to the unstable solid electrolyte interphase (SEI) on the surface of Si [25], which causes lithium to be trapped in the active surface of Si and results in the rapid loss of irreversible capacity and low initial Coulombic efficiency (CE) [16; 17; 18]. These reactions that occur in the process can be summarized as follows:  
Figure 1:0  
Figure 1:1  
Figure 1:2  
Reactions (2) and (3) result in the generation of irreversible capacity, which leads to capacity loss. In addition, Li\({}_{4}\)SiO\({}_{4}\) compounds are reported to be electrochemically inactivated.