Extending the Self-Templating Strategy to Micron-Sized Stöber Silica: A Critical Temperature Threshold for...

Silicon anodes are a promising high-capacity alternative to graphite for next-generation lithium-ion batteries, yet their practical application faces challenges due to significant volume changes during cycling. Introducing porous structures can effectively alleviate mechanical stress and enhance cycling stability, which can be realized via magnesiothermic reduction of silica based on a self-templating mechanism. Nevertheless, extending it to solid, monodisperse Stöber silica spheres >500 nm presents a major challenge, wherein elongated magnesium diffusion paths cause incomplete conversion and fragmentation, inhibiting the formation of the well-defined 3D macro/mesoporous networks derived from smaller silica templates. Here, we overcome this limitation by identifying 900 °C as the critical minimum temperature that enables the self-templating mechanism for 730 nm Stöber silica. The enhanced magnesium vapor diffusion and silicon sintering kinetics at this temperature overcome diffusion barriers, generating a well-defined macro/mesoporous network. This optimized porous silicon anode achieves improved cycling stability and rate performance over commercial microsized silicon and lower-temperature samples, maintaining a reversible capacity of 655 mAh g^-1 after 300 cycles at 0.2C and delivering 656 mAh g^-1 at 1C. This study reveals temperature as the decisive factor in achieving a diffusion-sintering balance, enabling the successful fabrication of robust, well-defined 3D macro/mesoporous networks from large solid Stöber silica via self-templating.