Simple and efficient synthesis methods for fabricating anode materials of sodium-ion batteries and their sodium-ion storage mechanism study

Hard carbon (HC) is the most promising anode material for sodium-ion batteries (SIBs). However, the unclear storage mechanism of HC anode materials, especially in the low-potential plateau region, hinders the design and development of high-performance SIBs. In this paper, waste plastic with rich ester bonds, polyterephthalate (PET), is selected as the precursor to synthesize HC anode materials with different micromorphologies via low-temperature pyrolysis strategies. The relationship between the microstructure and sodium-ion storage behavior is evaluated. By combining theoretical calculations with Matlab, in situ X-ray diffraction (XRD), in situ Raman spectroscopy (Raman) and ex situ X-ray photoelectron spectroscopy (XPS), this study reveals that the sodium-ion storage capacity in the low-potential plateau region of the prepared HC materials is contributed by "interlayer intercalation" and "closed hole filling". An adsorption-intercalation- and pore-filling-based sodium-ion storage mechanism is proposed, which provides guidance for building high-performance and sustainable energy storage materials.