SiO_<i>x</i>/C composite spheres as an anode material for high-performance lithium-ion batteries

Silicon suboxide (SiO_<i>x</i>, 0 < <i>x</i> < 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_<i>x</i> and carbon has been considered as a promising approach to mitigate these challenges, it is difficult to achieve a homogeneous distribution of SiO_<i>x</i> in carbon using standard mechanical mixing and surface coating technologies. In this study, SiO_<i>x</i>/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_<i>x</i>/C composites. The presence of strong Si-O-C bonds led to the uniform distribution of amorphous SiO_<i>x</i> particles within the carbon matrix, generating a monodisperse spherical architecture with excellent buffering properties. The resulting SiO_<i>x</i>/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_<i>x</i>/C composites in next-generation energy storage systems.