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Zhang et al. Energy Mater 2024;4:400043 https://dx.doi.org/10.20517/energymater.2023.102 Page 5 of 12

Figure 2. (A) XRD results, (B) Raman and (C) FTIR spectrum of SiO /G/C, SiO /G and SiO /C composites; (D) XPS spectrum of SiO x
x
x
x
/G/C, SiO /G, and SiO /C; SiO /G/C’s XPS spectrum of (E) O 1s and (F) Si 2p. XRD: X-ray diffraction; FTIR: Fourier transform infrared
x
x
x
spectroscopy; XPS: X-ray photoelectron spectroscopy.
[25]
CNTs [23,24] . Additionally, a broad diffraction peak around 22.3° was indexed to the amorphous SiO in
x
SiO /C. Raman spectra shown in Supplementary Figure 3 confirmed the low crystallinity SiO with a broad
x
x
peak at 459 cm -1[26] , consistent with XRD data. The presence of carbonaceous materials in the three
-1
previously mentioned samples was confirmed by D and G bands at approximately 1,324 and 1,564 cm ,
respectively, [Figure 2B]. The intensity ratio of the D-and G-Raman peaks (I /I value) of SiO /G/C
D
x
G
composites of 0.34 suggested a high degree of graphitization, beneficial for the performances of SiO -carbon
x
anodes [27,28] . The FTIR spectrum [Figure 2C] exhibited two peaks in SiO /G/C at 1,630 and 1,677 cm ,
-1
x
corresponding to the C=O and C=C bonds, similar to those peaks observed in SiO /C and SiO /G, indicative
x
x
of sp carbon hybridization . Peaks located at 1,103, 808, and 470 cm were attributed to bending and
[29]
-1
2
asymmetric stretching vibrations of SiO . Comparison of FTIR spectra between SiO nanoparticles
[30]
x
x
(derived from ball milling micro SiO) and SiO /G/C [Supplementary Figure 4] confirmed the formation of
x
C–O–Si bonds. The disappearance of the broad peak located at 3,435 cm , assigned to the vibration of the
-1
–OH bond in SiO , in SiO /G/C suggests that the -OH of SiO might combine with the dual-carbon network
x
x
x
to form C–O–Si covalent bonds. Si–O–Si bonds in SiO and SiO /G/C are located at 1,086 and 1,103 cm ,
-1
x
x
respectively. The shift in these two peaks is attributed to the C–O–Si bond formation at 1,230 cm in
-1
[31]
SiO /G/C, consistent with previous reports . XPS spectra of SiO /G/C, SiO /G, and SiO /C are depicted in
x
x
x
x
Figure 2D, with similar peaks around 533, 284, 155, and 104 cm assigned to O 1s, C 1s, Si 2s, and Si 2p,
-1
respectively. Further insights into electronic structure of the SiO /G/C composite were obtained from the O
x
1s, Si 2p, and C 1s XPS spectra, as shown in Figures 2E and F, and Supplementary Figure 5, respectively.
The O 1s spectrum in Figure 2E contains three peaks corresponding to C–O–Si, C–O–C, and Si–O–Si
bonds , confirming the effect of ball milling in promoting the formation of a C–O–Si bond in the
[32]
SiO /G/C. The Si 2p spectrum [Figure 2F] exhibits three peaks: Si–O (105.1 eV), Si–C (104.4 eV), and Si–Si
x
(103.7 eV) . Analysis of the C 1s spectrum [Supplementary Figure 5] reveals peaks at 285.1, 284.2, and
[33]
283.8 eV, attributed to C=O, C–O, and C–C/C=C bonds, respectively . These findings confirm the creation
[34]