Improved cycling performances of binder-free macroporous silicon Li-ion negative electrodes using room temperature ionic liquid electrolyte

Abstract

The present article describes the innovative combination of freestanding macroporous silicon layers on copper foil collectors and room temperature ionic, liquid 1-propyl-1-methylpyrrolidinium bis(trifluosulfonyl)imide (Pyr13 FSI)-containing electrolyte (Pyr13 FSI mixed with 1 M LiTFSI) to produce highly stable negative electrodes for Li-ion batteries. A 20-μm-thick macroporous silicon layer was synthesized by anodization in hydrofluoric acid (HF)-based electrolyte followed by the deposition of a thick and mechanically stable copper layer acting as current collector. After peeling-off the parent substrate, the freestanding macroporous silicon layer was characterized as a negative electrode in a half-cell configuration. The electrode performances were determined under constant charge conditions (500, 750, and 1000 mA h g−1) and exhibited significantly higher stability for over 1800 charge and discharge cycles in 1 M LiTFSI dissolved in Pyr13 FSI.