Environmental Emissions from Chemical Etching Synthesis of Silicon Nanotube for Lithium Ion Battery Applications

Abstract

Silicon nanotubes (SiNTs) have been researched as a promising anode material to replace graphite in next-generation lithium ion batteries. Chemical etching synthesis of SiNTs is a simple, controllable and scalable process for SiNT fabrication, but the environmental emissions are of grave concern. In this paper, the process emissions from chemical etching synthesis of SiNTs as anode for lithium ion batteries is studied through experimental techniques, considering the categories of aqueous wastes, gaseous emissions, aqueous nano-particle emissions, and gaseous aerosol emissions. The synthesized SiNTs are measured at 10 µm length and 1-2.2 µm diameter, and can maintain a specific capacity of over 800 mAh/g after 100 cycles in battery testing. In aqueous waste, the chemical compositions of all elements participating in the chemical etching are experimentally determined, with AgNO 3 and Co(NO 3 ) 2 identified as the major pollutants. The only gaseous emission generated from the chemical etching synthesis process is H 2 , with 0.0088 ± 0.0002 mol H 2 generated to produce 1.0 mg SiNTs. The aqueous nanoparticle sizes are found to be between 250 nm and 1540 nm. A large number of aerosol nanoparticle emissions of up to 2.96 × 10 7 particles/cm 3 are detected through in situ experimental measurement.

Review of silicon-based alloys for lithium-ion battery anodes

“…Repeated expansion and contraction during cycling could increase the exposure of fresh surfaces to the electrolyte, thereby leading to the repeated formation of a solid electrolyte interphase (SEI). Consequently, the electrolyte is gradually consumed, and the coulombic efficiency (CE) of the material decreases [15][16]. Second, repeated discharging/charging could cause the mechanical fracture of Si particles and lead to the pulverization and exfoliation of the active material from the current collector.…”

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

“…With a high specific capacity of 4200 mAh/g and advantages such as low average delithiation potential, low cost, and nontoxicity, Si has been recognized as one of the most promising anode materials to replace graphite in LIBs. , However, bulk Si in LIB anode suffers from large volume expansion, causing a series of problems including electrode cracking, material pulverization, electrical contract loss, voltage cutoff, and severe capacity fading. , To overcome these drawbacks, nanostructured Si materials are being developed. − Among the various types of Si nanostructured materials, Si nanotubes (NTs) have been found as a promising anode material structure since the NT structure can accommodate certain volume expansion and meanwhile provide a larger surface area to promote lithium diffusion. , In the literature, a high and stable 1670 mAh/g gravitational specific capacity has been reported for the Si NT-based battery . According to past studies, Si NTs can be fabricated by various methods, such as chemical vapor deposition (CVD), ,, liquid-phase etching, and chemical reduction . As the fabrication of Si NTs typically involves heavy metals (e.g., Ni), toxic organic chemicals (e.g., hydrazine, diethylamine, and tetraethyl orthosilicate), and significant amounts of emissions (e.g., PM 10), the potential environmental impacts of Si NT production at an industrial scale would be significant.…”