EAGER: Understanding Electrochemical Alloying Reaction of Nanostructured Silicon with Magnesium: Impact of Nanoscale Silicon Processing

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New forms of energy storage needed for our national prosperity requires the development of new materials and processes. This EArly-concept Grant for Exploratory Research (EAGER) will support fundamental research that will contribute to new insight on processing nanostructured silicon, which may serve as a high performance anode material for magnesium-ion batteries. Magnesium ion batteries have been suggested as a safe and inexpensive alternative to the more conventional lithium ion batteries. This research looks to overcome the fundamental barrier that restricts the storage of magnesium in nanostructured silicon, and study the relationship between the new processing route and the material performance. The surface of conventionally processed nanostructured silicon is covered with native silicon oxide, which restricts the storage of magnesium in silicon. The new processing route investigated here promises to lead to oxide-free nanostructured silicon, making it possible to reversibly store magnesium. The relationship between the size of the synthesized nanostructured silicon, the synthesis parameter, and the storage performance will be determined. Results from this research will open the way to the use of silicon -- the second most abundant element in the earth's crust, in a magnesium battery, which will benefit the US economy and society. In particular, it will lessen the concern of the material shortage in lithium and cobalt, which are currently used in rechargeable batteries.Reversible electrochemical alloying reaction of nanostructured silicon with magnesium remains a challenge. In this project, it is hypothesized that processing of oxide-free nanostructured silicon is the key to successful alloying reaction of silicon with magnesium. To verify this hypothesis, a new in situ processing route to oxide-free nanostructured silicon will be investigated. This process creates the nanostructured material in situ in a magnesium-ion battery cell when the battery is being charged and discharged. The reversible alloying reactions of silicon with magnesium will be directly investigated in the same magnesium-ion battery cell throughout charging and discharging cycles. This processing approach makes it possible to avoid any exposure of the nanostructured silicon to air, thus avoiding the formation of undesirable native silicon oxide surface films that hamper the reaction between silicon and magnesium.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.