Selective synthesis of soft and hard carbons from a single precursor through tailor-made stabilization for anode in sodium-ion batteries

A major factor in classifying carbon materials is their degree of graphitization, which is defined as a structural transition from an amorphous to an ordered crystalline state. Previous studies have shown that graphitization depends on the intrinsic properties of precursors for carbon materials. Thus, these studies on graphitization have been mainly limited to modulating precursors. Herein, we demonstrate the degree of graphitization that can be governed by a stabilization process using polyethylene (PE) as a single precursor, as PE is a non-graphitizable material. PE is stabilized by e-beam irradiation and subsequent thermal oxidation or sulfuric acid treatments to investigate the effects of stabilization methods. The resulting thermally and acid-stabilized PEs are graphitized up to 2,000 degrees C, and surprisingly, they diverge from a single precursor into soft and hard carbons, respectively. We also confirm that laser desorption/ionization time-of-flight mass spectrometry is a powerful analytical tool for revealing the different structures of thermally and acid-stabilized PEs at the early stage of graphitization based on the formation patterns of carbon cluster ions. In addition, the distinct electrochemical performances of soft and hard carbons are investigated by applying them as anode materials into sodium ion batteries, respectively. We believe that this study provides fundamental insights and practical tools to develop tailor-made carbon materials from a single and common precursor.