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 theirpotentialapplication in next-generation lithium-ion batteries because of theirhigh specific capacity (Li15Si4, 3579 mAh g(-1)) and elemental abundance. However, Si anodes havenot yet been practically applied in lithium-ion batteries becausethe volume change associated with lithiation and delithiation degradestheir capacity during cycling. Instead of considering the active material,we focused on the structural design and developed a scalable processfor producing Si anodes with excellent cycle characteristics whileprecisely controlling the morphology. Al-Si alloy powders wereprepared by gas atomization, and porous Si with a skeletal structurewas prepared by leaching Al using HCl. Porous Si (p-Si-12, p-Si-19) prepared from Al88Si12 and Al81Si19 comprised resinous eutectic Si,and porous Si (p-Si-25) prepared from Al75Si25 comprised lumpy primary Si and resinous eutectic Si. Theporosity of the Si anodes varied from 63% to 76%, depending on theSi composition. The p-Si-19 anode displayed the finest poredistribution (20-200 nm), excellent rate characteristics, areversible discharge capacity of 1607 mAh g(-1) after200 cycles at a rate of 0.1 C with a Coulombic efficiency of over97%, and high stability. The performances of the p-Si-25 and p-Si-19 electrodes began to decrease after 250 and850 cycles, respectively, with a constant-charge capacity of 1000mAh g(-1) and at a rate of 0.2 C. In contrast, thep-Si-12 anode maintained its discharge capacity at 1000mAh g(-1) for up to 1000 cycles without degradation.Therefore, the developed manufacturing process is expected to produceporous Si as an active material in lithium-ion batteries for highcapacity and long life at an industrial scale.

Automated summary

A scalable process for producing Si anodes with excellent cycle characteristics was developed, by controlling their morphology and structure. The porous Si anodes prepared from Al-Si alloy powders exhibited reversible discharge capacity of 1607 mAh g(-1) after 200 cycles at a rate of 0.1 C with high stability and Coulombic efficiency. This manufacturing process shows great potential for producing high-capacity and long-life lithium-ion batteries.