Synthesis of silicon-graphene composite anode via magnesiothermic reduction of silica fume for high-performance lithium-ion batteries

Abstract

Lithium-ion batteries are becoming crucial due to increasing global energy storage demands, benefiting performance and sustainability. As the world strives for a sustainable future and net-zero carbon emissions by 2050, there's a focus on energy efficiency, including transitioning away from internal combustion cars. Electric vehicles face challenges like limited range and long charging times, requiring research to enhance energy and power density. Commercially, graphite is used as the anode material for li-ion batteries but it has low capacity (372 mAh/g) while silicon has 4200 mAh/g capacity. Silicon has an enlargement problem and causes pulverization, therefore environmentally friendly materials are vital, and our study aims to synthesize a sustainable lithium-ion anode composite with silicon and graphene to boost energy and power density while contributing to sustainability. The silicon (Si) in this study was synthesized from silica fume in order to contribute to sustainability by using a waste product as the material source. Firstly, the silica fume was leached with acid and then subjected to magnesiothermic reduction to produce silicon metal because silicon has a higher specific capacity than silica. Graphene oxide (GO) was also synthesized from graphite by incorporating Modified Hummer's method. As a result of this reaction, multi-layered graphene oxide with a plate spacing of 0.852 nm was achieved. The resulting active material for battery anode was prepared with a composition of 1:1 Si:GO ratio. Characterization of graphene oxide, synthesized silicon and Si/rGO composite materials were carried out by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, Scanning electron microscope (SEM), elemental and Thermogravimetric analyzer. Electrochemical characterization for the material was also done by a half cell formation. Conducted tests were cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and cyclic charge-discharge (CCD) tests. As the result of these tests, CV analysis showed that the working voltage of the battery was in optimum condition and the fact that the lines were overlapping each other meant that the reaction was reversible. In the EIS test, it was observed that the internal resistance of the battery was as low as 55 mOhm even after 9 cycles. CCD tests revealed that the battery held its capacity at over 1200 mAh/g after 9 cycles, which is much greater than 372 mAh/g theoretical capacity of current commercial graphite anodes.