Electronic structure and chemical bonding of a graphene oxide-sulfur nanocomposite for use in superior performance lithium-sulfur cells.

We have investigated the chemical bonding and electronic structure of a graphene oxide-sulfur (GO-S) nanocomposite by X-ray Photoelectron Spectroscopy (XPS), Near-edge X-ray Absorption Fine Structure (NEXAFS), and X-ray Emission Spectroscopy (XES). The nanocomposite, synthesized by a chemical reaction-deposition approach followed by low temperature thermal treatment, is composed of a thin and uniform sulfur film anchored on a graphene oxide (GO) sheet. The GO is partially reduced during the chemical synthesis process, resulting in the appearance of a C-H bond and an increase in the ordering of GO sheets. The moderate chemical interactions between sulfur and GO can preserve the intrinsic electronic structure of GO, and on the other hand, immobilize the sulfur on the GO sheets, which should be responsible for the excellent electrochemical performance of the lithium-sulfur cells by using the GO-S nanocomposite as the cathode material.