## 2 SiOC-Based Anode Materials  
SiOC is a kind of silicon-based anode material, which is an amorphous ceramic material composed of Si, O and C elements bonded to each other, generally through the precursor conversion method. The silicon-containing polymer (polysiloxane, polycarbosilane and sesquisilane, etc.) is transformed into amorphous SiOC ceramic material after cross-linking and subsequent pyrolysis [28; 29]. [PERSON] et al. [30] studied the pyrolysis behavior of PMPS and PPSSO and characterized the products. They found that the pyrolysis products are amorphous structures and can reversibly intercalate lithium. Interestingly, the ceramics can achieve good reversible capacity at relatively low voltages, which opened the boom of research on SiOC anode materials [13]. Furthermore, [PERSON] et al. [30] discovered reversible lithium-ion intercalation in SiOC materials at potentials below 1 V, achieving a specific capacity of near 600 mAh-g\({}^{-1}\). By utilizing siloxane units with varying functional groups and employing diverse synthesis methods, the team synthesized over 60 SiOC anode variants (Figure 4). The numbers represent the reversible capacity of the SiOC anode material as a function of its composition. The highest capacity values are observed in compositions that contain mixed Si bonds (grey area), where silicon is tetrahedrally bonded to both oxygen and carbon [3]. Two proposed models illustrate the microstructure of polymer-derived SiOC ceramics (Figure 5). Monomers of commercially available polysiloxanes and organosilicon polymers can be used as precursors, both of which contain Si-O-Si bonds in their molecular structures, and the groups of the side chains can be volatilized during pyrolysis, which facilitates the introduction of C atoms into the side chains. SiOC is composed of an amorphous SiO\({}_{X}\)C\({}_{(4-x)}\) (\(0<x\leq 4\)) glass phase and a free carbon phase. The glass phase contains four phase structures: SiO\({}_{3}\)C, SiO\({}_{2}\)C\({}_{2}\), SiO\({}_{3}\) and SiO\({}_{4}\), which are formed by different numbers of C atoms replacing the O atoms in the SiO\({}_{2}\) tetrahedral structure, in which the C atoms are  
Figure 4: SiOC compositional triangle. The numbers reflect composition-dependent reversible capacity in SiOC anodes, with maxima occurring in mixed-bond regimes (grey region) characterized by tetrahedral Si-O-C coordination Copied with permission from Springer Nature [27]. sp\({}^{3}\) hybridized. Free carbon, on the other hand, is free in the whole phase structure in the form of sp\({}^{2}\) hybridization, and is used as a framework to support the whole structure [13]. Figure 5: Two proposed models illustrating the microstructure of polymer-derived SiOC ceramics. Copied with permission from Springer Nature [27]. (**a**) a classic model featuring a microstructure with clusters of silica tetrahedra, a monolayer of SiC\({}_{x}\)O\({}_{4-x}\) mixed bonds, and a graphene cage-like network that encapsulates the silica nanodomains; (**b**) Model 2 with an isolated carbon-rich SiO\({}_{x}\)C\({}_{4-x}\) interface; and (**c**) Model 2 with an interconnected carbon-rich SiO\({}_{x}\)C\({}_{4-x}\) interface in carbon-rich SiOC ceramics [2]. In recent research, [PERSON] et al. [31] prepared SiOC materials by pyrolysis using pre-ceramic polymers and crosslinkers such as 1,3,5,7-tetramethyl1,3,5,7-tetravinylcyclotetrasiloxane or divinylbenzene, and the obtained SiOC anode showed a lithium storage capacity of up to about 1300 mAh\(\cdot\)g\({}^{-1}\), but there was an irreversible capacity loss during the first charge and discharge. After optimizing the balance between silicon-oxycarbon-silicon and free-carbon phases, the high-carbon SiOC material has a measured reversible capacity of 650 mAh\(\cdot\)g\({}^{-1}\) and exhibits excellent cycling stability and high charge/discharge rate performance, with a reversible capacity of approximately 200 mAh\(\cdot\)g\({}^{-1}\) at 2C.