Environmental Sustainability of Liquid-Based ChemicalSynthesis of Si Nanotube as Anode for Lithium-Ion Batteries

Si nanotubes (NTs) have been widely studied as a promising anode material for next-generation lithium-ion batteries (LIBs). The potential environmental impacts of their fabrication are significant due to the involved toxic chemicals and process emissions. In this study, a scalable liquid-based synthetic method of Si NT was developed via fabrication of SiO2 NTs followed by chemical reduction in magnesium vapor to produce Si NTs. The Si NTs were then used as the anode in LIB and obtained a specific capacity of 1061 mAh/g after five cycles. The environmental emissions from the synthetic process were investigated through a series of techniques with a process-based approach. Throughout the whole synthetic process, 51.59% of Si was recovered. To synthesize 1.00 g of Si NTs, 60.09 g of C6H12, 43.66 g of Brij 58, 1.01 g of NiCl2, 2.39 g of N2H4·H2O, 3.63 g of C4H11N, 14.38 g of TEOS, 145.49 g of IPA, and 9.36 g of Mg were needed. The wastes could be categorized into three groups: gases, particles, and liquids. A ...