Magnesiothermic Reduction of Structured Silica As Anode for Lithium Ion Batteries
Through using structured silica precursors, the goal is to reduce the silica to silicon while maintaining its structure and porosity and thus mitigate the degradation during cycling. Two types of silicon oxide precursor materials that meet these requirements have been evaluated, among them hollow silica microspheres from 3M and silica aerogel from Aspen Aerogels. The major steps including silica synthesis and magnesium vapor reduction will be discussed.
Preparation of Si precursor materials has been performed by magnesium reduction followed by the removal of unnecessary impurities such as magnesium oxide and silica by washing the material in 1M HCl followed by 1% HF. Preliminary data from XRD confirms Si formation from the magnesiothermic reduction. SEM, TEM, EDS, BET, XRD, and Raman spectroscopy will be presented to analyze the structure and morphology of the materials. Structure dependent electrochemical properties such as cyclic voltammetry, cycleability, galvanostatic discharge, and cycle stability will be discussed.
Fig. 1: (A) TGA for 3M silica microspheres (iM30K) and (B) TGA for Aspen Aerogels’ SiO2 aerogel with Mg with the corresponding SEM images (C) 3M microspheres and (D) Silica aerogel precursors. (E) XRD for reduced SiO2 aerogel: top profile is fully washed reduced Si, middle profile is after reduction but before washing, and bottom profile is for a Si nanopowder reference to vindicate successful Si reduction from SiO2.
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