SiO_x/C composite spheres as an anode material for high-performance lithium-ion batteries

Silicon suboxide (SiO_x, 0 < x < 2) is a promising anode candidate for lithium-ion batteries because of its high capacity; however, the significant volume expansion during cycling significantly restricts its practical application. Although combining SiO_x and carbon has been considered as a promising approach to mitigate these challenges, it is difficult to achieve a homogeneous distribution of SiO_x in carbon using standard mechanical mixing and surface coating technologies. In this study, SiO_x/C composites were fabricated using a sol-gel approach. More specifically, vinyltriethoxysilane and resorcinol/formaldehyde were selected as the silicon and carbon precursors, respectively, to synthesize uniform spherical porous SiO_x/C composites. The presence of strong Si-O-C bonds led to the uniform distribution of amorphous SiO_x particles within the carbon matrix, generating a monodisperse spherical architecture with excellent buffering properties. The resulting SiO_x/C electrode demonstrated an outstanding electrochemical performance and cycling stability, maintaining a reversible discharge capacity of 660.2 mA h g^-1 at 2 A g^-1 after 200 cycles. Moreover, after 200 charge/discharge cycles, the electrode volume increased by only 17.7%, effectively mitigating the issue of volume expansion. Consequently, this study paves the way for the practical application of SiO_x/C composites in next-generation energy storage systems.