Scalable Synthesis of Porous Silicon by Acid Etching of Atomized Al–Si Alloy Powder for Lithium-Ion Batteries

Si anodes have attracted considerable attention for their potential application in next-generation lithium-ion batteries because of their high specific capacity (Li 15 Si 4, 3579 mAh g –1 ) and elemental abundance. However, Si anodes have not yet been practically applied in lithium-ion batteries because the volume change associated with lithiation and delithiation degrades their capacity during cycling. Instead of considering the active material, we focused on the structural design and developed a scalable process for producing Si anodes with excellent cycle characteristics while precisely controlling the morphology. Al–Si alloy powders were prepared by gas atomization, and porous Si with a skeletal structure was prepared by leaching Al using HCl. Porous Si (p-Si 12, p-Si 19 ) prepared from Al 88 Si 12 and Al 81 Si 19 comprised resinous eutectic Si, and porous Si (p-Si 25 ) prepared from Al 75 Si 25 comprised lumpy primary Si and resinous eutectic Si. The porosity of the Si anodes varied from 63% to 76%, depending on the Si composition. The p-Si 19 anode displayed the finest pore distribution (20–200 nm), excellent rate characteristics, a reversible discharge capacity of 1607 mAh g –1 after 200 cycles at a rate of 0.1 C with a Coulombic efficiency of over 97%, and high stability. The performances of the p-Si 25 and p-Si 19 electrodes began to decrease after 250 and 850 cycles, respectively, with a constant-charge capacity of 1000 mAh g –1 and at a rate of 0.2 C. In contrast, the p-Si 12 anode maintained its discharge capacity at 1000 mAh g –1 for up to 1000 cycles without degradation. Therefore, the developed manufacturing process is expected to produce porous Si as an active material in lithium-ion batteries for high capacity and long life at an industrial scale.