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

Abstract

Si anodes have attracted considerable attention for their potential application in next-generation lithium-ion batteries because of their high specific capacity (Li15Si4, 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-Si12, p-Si19) prepared from Al88Si12 and Al81Si19 comprised resinous eutectic Si, and porous Si (p-Si25) prepared from Al75Si25 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-Si19 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-Si25 and p-Si19 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-Si12 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.