Title : Green synthesis of graphene/silicon composite and its application to lithium-ion battery
Abstract:
Lithium-ion batteries (LIBs) using silicon as the anode have a higher charge-discharge capacity than those using graphite, but the repeatability of their charge-discharge cycles is extremely low. Recently, composites of silicon with graphene have been used for LIBs, but their synthesis method is complicated and needs to be improved to realize industrial applications. Previously, we succeeded in synthesizing GO/silica composites in a simple and environmentally friendly method by simply adding tetraethyl orthosilicate (TEOS), a precursor of silica, to graphene oxide (GO), which is obtained from inexpensive natural graphite as a starting material. The GO/silica composite was then heat-treated to convert GO to reduced graphene oxide (rGO) to form rGO/silica composite, which was applied to high-strength transparent conductive films (I. Imae et al., Synthetic Metals, vol.224, pp.33-35, 2017). Furthermore, we succeeded in reducing not only GO but also silica by heat treatment of GO/silica composite in the presence of metallic magnesium, and synthesized rGO/silicon composite. The resulting composite is identified through Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. It is confirmed that the atomic ratio between silicon and carbon in the composite is consistent with that of the starting materials. Lithium-ion batteries are manufactured using the obtained composites as the anode material, and their charge/discharge properties are investigated. The manufactured batteries show a higher charge-discharge capacity than a graphene-anode-based battery as well as superior charge-discharge cycle characteristics as compared to a silicon-anode-based battery (I. Imae et al., Ceramics International, vol.48, pp.25439-25444, 2022).
