Interface Engineering of Metal-coated Si-nanostructured Thin Films for High-capacity Li-ion Battery Anode

Abstract

Si is a promising anode material for Li-ion batteries due to its high specific capacity; however, the pulverization during the lithiation/de-lithiation reduces the Coulombic efficiency and cycle stability. Si nanostructures with an increased surface-to-volume ratio, such as porous Si (PS) and Si nanowires (SiNWs), improve the electrochemical performance of the cell. Further, metal coating on the nanostructures increases the current density to improve cyclic stability. The work demonstrates the sputtered Ag and Cu coating (~ 4 nm to 30 nm) on PS and SiNW thin films fabricated by electrochemical anodization and metal-assisted chemical etching for the anode. The morphology of the ultra-thin metal coatings was investigated by an electron microscope equipped with a focused ion beam. X-ray photoelectron spectroscopy detects changes in the Si electronic configuration due to the metal coating and the interface engineering. X-ray diffraction system with critical angle measurement through reflectivity fringes analyzes the thickness and metal phase. The work explains the plausible mechanism for metal-coated PS and SiNW thin films to be the preferred anode materials for current density improvement