Environmental Sustainability of Metal-Assisted Chemical Etching of Silicon Nanowires for Lithium-Ion Battery Anode

Abstract

Silicon nanowires (SiNWs) with three different average diameters of 90, 120, and 140 nm were synthesized by a metal-assisted chemical etching (MACE) method. Environmental sustainability of the MACE process was studied by investigating material consumptions, gas emissions, and silver nanoparticle concentrations in nitric acid solutions for 1 g of SiNWs and 1 kW h of lithium-ion battery (LIB) electrodes. It was found that the process for 90 nm SiNWs has the best sustainability performance compared with the other two processes. Specifically, in this study for 1 g of 90 nm SiNWs, 8.845 g of Si wafer is consumed, 1.09 g of H2 and 1.04 g of NO are produced, and 54.807 mg of Ag nanoparticles are found in the HNO3 solution. Additionally, for 1 kW h of LIB electrodes, the process for 90 nm SiNWs results in 1.943 kg of Si wafer consumption, 239.455 g of H2 and 239.455 g of NO emissions, and 12.040 g of Ag nanoparticles concentrations. By quantitatively investigating the material consumptions and emissions, this study assesses the sustainability performance of the MACE process for synthesizing SiNWs for use in LIBs, and thus it provides process data for the analysis and the development of sustainable production methods for SiNWs and similar anode materials for next-generation LIBs.

Prospective LCA of Next-Generation Cells for Electric Vehicle Applications

“…The wide interest in introducing silicon content into typical graphite anodes is due to the higher specific capacity of silicon (4200 mAh/g) compared to that of graphite (372 mAh/g) [9]. Nevertheless, silicon suffers from drastic volume change (up to 400%) during the charging and discharging process, which is the main barrier to its use in anodes [10]. A well-studied approach to reduce the above-mentioned issue consists of submitting the bulk silicon particles to dedicated chemical processes (e.g., metal deposition, chemical and metal-assisted chemical etching) to get multi-dimensional nanostructured silicon so that the final morphology is composed of Silicon NanoWires (SiNWs) [9], [11], [12].…”

“…Generation 4 cells include the batteries with solid electrolytes, called Solid-State Batteries (SSBs), which are categorized into three types: sulfide-, oxide-, and, more recently, polymer-type. Because the solid electrolyte facilitates the coupling with a lithium metal anode, which as a specific capacity of 3860 mAh/g [10], SSBs nearly double the energy density of the best-performing Li-ion chemistry, resulting in a smaller and lighter battery pack [14]. Moreover, the absence of flammable liquid electrolytes in SSBs ensures increased safety [14].…”

“…In the literature, several conventional LCAs have been performed focused on EV batteries, some of them, i.e., [5], [9], [10], [12], [14], [17]- [23], addressing the environmental impacts of next-generation cells. In [12], the life cycle environmental impacts of a SiNWs battery pack are compared with those of a current Li-ion battery pack.…”

“…The environmental impacts of two next-generation cells are compared with those of a current Li-ion cell in [9], where the dependence of energy consumption on production volume is taken into account. In [10], the environmental impacts of two next-generation battery packs (i.e., Silicon NanoTubes (SiNTs) and SiNWs batteries) are compared with those of a current Li-ion battery pack. Nevertheless, for both SiNTs and SiNWs batteries, no industrial scale up is performed.…”

Distinctive conductivity improvement by embedding Cu nanoparticles in the carbon shell of submicron Si@C anode materials for LIBs

“…1,8 In the past decade, many efforts have been made in the research and development of Si scale-down, [9][10][11] hybridization, 12 and novel structural design. 13,14 Typically, volume change and damage to Si anodes could be effectively relieved by minimizing the particle size, 15,16 such as Si nanoparticles, 17,18 nanowires, [19][20][21] nanotubes, 22,23 thin lms, and skeletons. 13,24,25 Based on our previous studies, 17,18 a lamellar submicron Si was also feasible as the anode for LIBs.…”