Pure Si powder used as an anode material can enhance the capacity of lithium ion batteries. However, repeated charging and discharging can cause significant volume expansion, thereby reducing the durability and battery life cycles. Using round-shape, nanoscale Si powder, which can be fabricated by a reduction process of spherical SiO₂ powder, can relieve this problem. This reduction method results in the formation of SiO_x including Si structure. In particular, approaches such as using nano powder as a starting material or employing a high-energy milling process to produce nano powder have been extensively explored in recent research. In the present study, nano-sized SiO_x powder containing Si was fabricated by using 100 nm synthetic, spherical SiO₂ powder and commercial Si powder as the starting material. The materials were mixed by a high-energy milling process using an attrition mill and then subjected to magnesiothermic reduction heat treatment. In particular, NaCl was used during the heat treatment to inhibit the formation of Mg₂SiO₄ reactant. The crystallinity and the Si-O-Si bonding state of the final SiO_x powder, obtained after acid treatment and DI water washing, were examined by characterization using X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy.

Keywords: Spherical silica, Nano silicon, Attrition milling, Magnesiothermic reduction, SiO_x powder.