Surfactant-based selective assembly approach for Si-embedded silicon oxycarbide composite materials in lithium-ion batteries

High-capacity silicon anode materials have attracted significant attention for application in lithium-ion batteries (LIBs), even though the drastic volumetric changes of the silicon materials result in rapid capacity degradation. Here, an Si-embedded silicon oxycarbide (SiOC) was synthesized using a selective assembly-based method. We utilized cetrimonium bromide (CTAB), a cationic surfactant, to facilitate interfacial interactions between Si nanoparticles and silicone oil using the hydrophobic property of the CTAB tail groups. The synthesis method includes a simple pyrolysis process at 900 °C followed by the surface modification of Si nanoparticles with the CTAB surfactant to obtain a SiOC matrix with homogeneously embedded Si particles. The final composite exhibits improved electrochemical properties as a LIB anode material and displays a stable cycle life (1312 mAh·g⁻¹ for the 100th cycle at 0.5 A·g⁻¹) in addition to enhanced power characteristics (634 mAh·g⁻¹ at the high current density of 5 A·g⁻¹). The SiOC matrix effectively suppressed the volumetric change of the inner Si particles in addition to enhancing the conductivity due to the free carbon in SiOC materials.