Abstract
Amorphous silicon nanomaterial is isotropic on the macroscale and can effectively inhibit the expansion/contraction during lithiation/delithiation processes, which remarkably improves the cycle performance of Li-ion batteries. Bead-milling is a simple, cost-effective, and scalable method for manufacturing amorphous and/or crystalline silicon nanoparticles. In this work, the internal structure of Si nanoparticles prepared by bead-milling was found to consist of amorphous and nanocrystalline silicon as well as amorphous silicon oxide. X-ray diffraction patterns and Raman spectra are used to calculate the average crystallite size and estimate the degree of crystallization and amorphization of silicon. The quantitative analysis of amorphous silicon oxide is carried out through x-ray photoelectron spectroscopy characterization and oxygen content measuring. It was found that the average particle size (D50) and the crystallite size were reduced to 91 and 3.7 nm, respectively, from 4.06 μm and 50.6 nm before bead-milling, and the degree of amorphization and oxygen content increased to 85.7% and 7.38%, respectively, from 37.5% and 0.12% before bead-milling. It is demonstrated that the longer the milling time, the smaller the sizes of particles and crystals and the higher the ratio of the amorphous phase. However, it inversely causes side-effects such as the increase in oxidization of Si nanoparticles and the increase in content of ZrO2 impurity.
Highlights
Silicon nanomaterials are an ideal anode material for new generation high-energy density lithium-ion batteries due to their high theoretical capacity at room temperature (Li15Si4, 3578 mA h g−1, ∼10 times larger than commercial graphite), low operating voltage, environmentally benign nature, and natural abundance.1–4 the significant volume change (∼300%) of Si during lithiation/delithiation processes results in the falling apart of the electrode materials,5–7 which has prevented their uses in Li-ion batteries as the anode
The zirconium content was measured with the method of Inductively Coupled Plasma (ICP) (Optima 7300DC), and the oxygen content was tested by the Organ Element Analyzer (OEA) (Vario EL Cube)
scanning electron microscopy (SEM) can only measure several particles and the data deviate slightly from the statistic results of laser particle size analyzer (LPSA), it still clearly shows the average particle size decreasing with the increase in milling time, which is in agreement with the observation by LPSA
Summary
Silicon nanomaterials are an ideal anode material for new generation high-energy density lithium-ion batteries due to their high theoretical capacity at room temperature (Li15Si4, 3578 mA h g−1, ∼10 times larger than commercial graphite), low operating voltage (vs Li+/Li), environmentally benign nature, and natural abundance. the significant volume change (∼300%) of Si during lithiation/delithiation processes results in the falling apart of the electrode materials, which has prevented their uses in Li-ion batteries as the anode. Many nanostructures have been suggested to deal with such a problem of volume variations, such as nanoparticles, porous nanostructures, nanotubes, thin films, and nanowires.8–10 These nanosized structures have been fabricated through either chemical or physical methods. Scitation.org/journal/adv thermal reduction process assisted with magnesium powder; and Yu et al. produced Si porous nanostructures by a modified magnesiothermic reduction method with the diameter of macropores of about 200 nm These methods can prepare high-purity Si nanostructures, they are not suitable for the large-scale production because the chemical methods always involve harsh reaction conditions, complicated process, poor controllability, high cost, low yield, and so on. The Si powder dispersed uniformly in the slurry was transferred from the vat into the mill by pumping and circulated in the vat and the mill during the whole bead-milling process.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
