Scale-Up Synthesis of Porous Silicon Structures by Rotary Magnesiothermic Reduction of Silica for Advanced Energy Storage Materials

Abstract

A 1L-scale dynamic magnesiothermic reduction (DMR) of nonporous silica (1.8 μm in diameter) was conducted using a rotary reactor system to produce porous silicon (pSi) particles for lithium-ion battery (LIB) anodes. The effects of the NaCl (heat scavenger)-to-silica weight ratio (0.8, 3.0, 5.0, and 10.0) were systematically investigated in terms of (i) exothermic reduction heats (monitored in situ and estimated by enthalpy balance), (ii) porosity development in the resulting pSi particles, and (iii) electrochemical performance of the pSi/C composites, benchmarked against conventional silicon nanoparticles (SiNP, <50 nm)/C. When the NaCl/silica weight ratio was ≥5, no significant temperature spikes were observed due to effective dissipation of the exothermic heat, resulting in highly porous pSi particles. Thanks to their favorable structure, both bare pSi-1 particles (synthesized at a NaCl/silica ratio of 10.0) and the corresponding pSi-1/C composites exhibited superior cycling performance compared to bare SiNP and SiNP/C composites, respectively. In particular, the pSi/C composites derived from highly porous pSi showed enhanced cycling stability, retaining over 90.9% of their initial capacity after 270 cycles at a current density of 500 mA g^–1. It also demonstrated excellent rate capability, full-cell performance, and structural robustness, underscoring its potential as a high-capacity LIB anode material. These findings highlight the DMR of silica as a scalable and effective process for the mass production of porous silicon particles, offering a promising pathway for next-generation high-performance LIB anodes.