Preparation of porous silicon using magnesiothermic reduction of porous silica glass and electrode characteristics for lithium-ion batteries

Magnesiothermic reduction was applied to porous silica glass grains with a characteristically interconnected pore structure. The prepared porous silicon maintained the morphology with pore size of approximately 30–40 nm, which was derived from the nanostructure of the starting silica glass. Medium-sized grains of the silica glass produced the largest silicon yield. This result could be explained based on the diffusion-controlled reaction mechanism, involving the reaction of SiO₂ with Mg₂Si to produce silicon. The electrochemical behavior was investigated using a coin-type cell composed of the prepared porous silicon–carbon mixtures and lithium foil electrodes. The initial charge and discharge capacities reached 1382 and 1187 mAh g⁻¹, respectively, which were close to the theoretical value (1329 mAh g⁻¹). After 50 charge/discharge cycles, 80% of the initial capacity is maintained. These results indicate that porous silicon derived from porous silica glass can be employed as an anode material for lithium-ion batteries.