Lithiation Capabilities of Bulk Silicon at Elevated Temperature

Abstract

Pure silicon, despite its high intrinsic capacity for lithium storage, is not typically utilized in Li-based battery systems due to severe swelling and subsequent fracturing of the material associated with the lithiation/delithiation process. This phenomenon, known as pulverization, significantly limits the capacity of the material over multiple cycles. Typical routes to overcome pulverization require nanostructured high aspect ratio wires or compositing with carbon. We present a differing approach reliant on elevated temperature operation to demonstrate lithiation in bulk silicon at elevated temperature. The move to elevated temperature shows the effect of increased thermal energy on Si structural stability during alloying and de-alloying processes. A fully functioning Swagelok half-cell of lithium versus silicon has been fabricated and tested at 250°C using a molten salt (LiTFSI) electrolyte, demonstrating the lithiation and delithiation of bulk Si at an elevated temperature. Results show increased reversible lithium capacity in bulk silicon, which may be of interest in applications where inexpensive, commodity electrode materials are favored.