480169 Synthesis of Yolk-Shell Structured Silicon-Germanium Anodes for Lithium-Ion Batteries

Monday, November 14, 2016
Grand Ballroom B (Hilton San Francisco Union Square)
Abdul-Malik Davies, Parham Rohani and Mark T. Swihart, Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, NY

The move towards a more sustainable world requires more efficient energy storage systems. New materials are needed to improve the storage capacity and other important properties of existing batteries. The lithium-ion (Li-ion) battery is an efficient energy storage system because of its relatively high energy density and low self-discharge rate (good charge retention). Silicon-Germanium (SiGe) alloy nanoparticles can potentially be used to create anodes with a much higher specific capacity than graphite, the most commonly used anode material in Li-ion batteries. However, silicon-based anodes suffer from degradation due to the repeated volume expansions and contractions resulting from the lithiation and delithiation processes that occur when the battery is charged and discharged. To address this challenge, we are preparing carbon coated SiGe anodes with a unique yolk-shell nanostructure that can accommodate the volume changes while maintaining performance. This suggested structure consists of a silicon-germanium core, carbon coated shell and a void space in between them. It is denoted as SiGe@void@C, with three distinct layers. Starting with SiGe nanoparticles obtained by reacting silane and germane gases in an oxygen free laser reactor, we are adding a sacrificial layer of silicon dioxide (silica) by using a sol-gel process to produce SiGe@SiO2. These nanoparticles are then further coated with carbon particles, followed by a careful etching process to remove the sacrificial silica layer, producing SiGe@void@C nanoparticles with the desired yolk-shell nanostructure. The void space in these nanoparticles is anticipated to accommodate the volume changes without compromising the integrity the entire yolk-shell nanostructure. We expect Li-ion batteries that incorporate the SiGe@void@C nanoparticles as an anode material, will show improvement in key performance metrics, such as the battery cycle life and capacity. Such improvements in the Li-ion battery technology can enhance the capabilities of spacecraft, medical equipment and devices, and other electronic devices that require portability.

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