## 2 Results and Discussion
The CF series electrode materials were integrated into half-cell configurations and underwent a full range of electrochemical testing. Figure 4a shows the first lap charge-discharge curves of CF-25, CF-50, CF-75, and CF-100 at a current density of 100 mA g\({}^{-1}\). The first-cycle discharge capacities were 1370.35, 1237.58, 1154.05, and 1135.42 mAh g\({}^{-1}\), respectively. This was directly related to the reversible lithium-ion storage phases SiO\({}_{3}\)C and SiO\({}_{2}\)C\({}_{2}\) in the CF ceramics. For the CF-25 and CF-50 electrodes, the higher first-cycle capacity was attributed to the lower amount of free carbon and the relatively higher presence of partially reversible SiO\({}_{4}\) phases. The ICE served as a crucial metric for evaluating the efficiency of battery capacity utilization. Figure S4 shows the charge-discharge curves of CF-25, CF-50, CF-75, and CF-100 electrode materials over the first three cycles at a  
Figure 3: High-resolution XPS elemental spectra of C1s and Si 2p: (**a,e**) CF-25, (**b,f**) CF-50, (**c,g**) CF-75, and (**d,h**) CF-100. current density of 100 mA g\({}^{-1}\). The ICE values were 71.16%, 70.77%, 72.10%, and 72.18%, respectively, significantly higher than the ICE value of pure SiOC ceramic anode materials (60%) [40]. Generally, the first-cycle capacity loss is attributed to the formation of a SEI layer and to irreversible lithiation reactions, such as the formation of Li\({}_{4}\)SiO\({}_{4}\) and Li\({}_{2}\)O. Therefore, the CF-75 electrode, which had a lower amount of irreversible lithiation phases (SiO\({}_{3}\) and SiO\({}_{4}\)) and a higher carbon content, demonstrated better lithiation performance. From the charge-discharge curves of the CF-75 electrode material in Figure S5, it is evident that with increasing cycle number, the Coulombic efficiency gradually increased. The nearly overlapping curves starting from the second cycle also indicate the superior cycle stability of the electrode material. In addition, electrochemical impedance (EIS) tests were performed on the CF material in order to determine the effect of structural changes on conductivity. As shown in Figure 4b, the Nyquist diagram of the CF electrode consists of a semicircle in the high-frequency region and a slash line in the low-frequency region, which represent the charge transfer resistance (Rct) and the Warburg impedance (Wo), respectively, of Li\({}^{+}\) in the electrode material. The Rct values of 28.13 \(\Omega\), 24.83 \(\Omega\), 18.52 \(\Omega\), and 20.36 \(\Omega\) for CF-25, CF-50, CF-75, and CF-100 were obtained from the equivalent circuit fitting results, which indicated that CF-75 had the lowest charge transfer resistance and the highest conductivity. Meanwhile, CF-75 had the highest slope in the low-frequency region, indicating the lowest diffusion impedance. Therefore, with the increase in free carbon content in SiOC ceramics and Fe-catalyzed graphitization of carbon and the formation of carbon nanotubes, the enhancement of electron transport and the diffusion of Li\({}^{+}\) were facilitated. Figure 4: Electrochemical performance characterization of the CF series samples: (**a**) first-cycle charge–discharge curves at a current density of 100 mA g\({}^{-1}\), (**b**) Nyquist plots of the CF electrodes; the inset figure is the equivalent circuit for EIS data fitting, (**c**) rate performance curves, (**d**) cycle performance curves. In order to assess the potential application of the electrode materials, rate performance tests were conducted on the four CF electrode materials at different current densities, as shown in Figure 4c. CF-25 exhibited a significant decrease in capacity with increasing current density, indicating that the dense structure and low conductivity of the low-carbon CF ceramics hindered the rapid intercalation and deintercalation of lithium ions. In contrast, CF-75, with its higher graphite carbon content, achieved a capacity of 875.95 mAh g\({}^{-1}\) at a current density of 100 mA g\({}^{-1}\).