Reduction kinetics of porous silicon synthesis for lithium battery anodes

Porous silicon (pSi) microparticles can be favorably employed as the high-capacity and stable anode materials in all formats of lithium-based batteries. Magnesiothermic reduction reaction (MRR) of low-cost silica produces pSi structures at relatively low temperatures; however, yield and reduction selectivity are currently limited. Herein, we conduct MRR kinetic studies using the Ginstling-Brounstein (GB) and Jander diffusion models under dynamic (via reactor rotation) and static conditions (D-MRR and S-MRR, respectively) at various reduction temperatures and times. The reduction rate and nominal kinetic constants for the D-MRR are found to be more than three times greater than those for the S-MRR, possibly because of the enhanced mass transfer rate in the D-MRR. D-MRR results in superior precursor conversion and pSi yield than S-MRR. The apparent activation energy for D-MRR is approximately 180 kJ mol-1 by GB model. The pSi microparticles are mesoporous (pore size = 23.7 nm, pore volume = 0.30 cm3 g-1) and comprise interconnected primary silicon nanoparticles (SiNPs) (diameter = 30 nm). Therefore, a pSi/C composite anode demonstrates significantly enhanced cycling stability compared with conventional solid SiNP/C composites. Overall, D-MRR is a highly efficient and scalable production process for pSi microparticles for use in high-capacity anodes for advanced lithium-based batteries.

Automated summary

According to the kinetic studies, the magnesiothermic reduction reaction (MRR) of silica for producing porous silicon (pSi) microparticles shows better precursor conversion and pSi yield under dynamic conditions compared to static conditions. The pSi microparticles, which are mesoporous and composed of interconnected primary silicon nanoparticles, exhibit significantly enhanced cycling stability when used as anode materials in lithium-based batteries. Therefore, the dynamic MRR (D-MRR) is a highly efficient and scalable production process for pSi microparticles for advanced lithium-based batteries.