Nanoparticle Emissions From Metal-Assisted Chemical Etching of Silicon Nanowires for Lithium Ion Batteries

As one of the most promising anode materials for high-capacity lithium ion batteries (LIBs), silicon nanowires (SiNWs) have been studied extensively. The metal-assisted chemical etching (MACE) is a low-cost and scalable method for SiNW synthesis. Nanoparticle emissions from the MACE process, however, are of grave concerns due to their hazardous effects on both occupational and public health. In this study, both airborne and aqueous nanoparticle emissions from the MACE process for SiNWs with three sizes of 90 nm, 120 nm, and 140 nm are experimentally investigated. The prepared SiNWs are used as anodes of LIB coin cells, and the experimental results reveal that the initial discharge and charge capacities of LIB electrodes are 3636 and 2721 mAh g⁻¹ with 90 nm SiNWs, 3779 and 2712 mAh g⁻¹ with 120 nm SiNWs, and 3611 and 2539 mAh g⁻¹ with 140 nm SiNWs. It is found that for 1 kW h of LIB electrodes, the MACE process for 140 nm SiNWs produces a high concentration of airborne nanoparticle emissions of 2.48 × 10⁹ particles/cm³; the process for 120 nm SiNWs produces a high mass concentration of aqueous particle emissions, with a value of 9.95 × 10⁵ mg/L. The findings in this study can provide experimental data of nanoparticle emissions from the MACE process for SiNWs for LIB applications and can help the environmental impact assessment and life cycle assessment of the technology in the future.