Regulating Interlayer Spacing and Defects on Nitrogen-Doped Hard Carbon Anodes from Waste Plastic for Sodium-Ion Batteries

Abstract

Sodium-ion batteries (SIBs) are regarded as a promising option among rechargeable batteries for energy storage systems (ESS) due to low-cost and abundant sodium source. One of the key bottleneck problems constraint their commercialization progress is the lack of suitable anode. As a potential choice, hard carbons emerge because of their unique microstructure and sustainable precursors. Nevertheless, capacity and cycling performance of hard carbons are not satisfactory for market needs. The performance of hard carbon is linked to three key microstructural parameters: interlayer spacing, pore architecture, and defect. Suitable interlayer distance enables sodium ions intercalation, while closed pores allow sodium ions fill into. Defect sites on surface facilitate the adsorption of sodium ions. Lasted researches indicate element doping affects both interlayer spacing and defect concentration in hard carbons. It is worth mentioning that waste plastics is a global issue, while these carbon-contained waste are possible to be used as hard carbon precursor. In this thesis, we employed waste polyethylene terephthalate (PET) as raw material, combining with nitrogen doping technique, synthesized nitrogen-doped hard carbon (NHC) as anode for SIBs. This hard carbon contains expanded interlayer and various defect sites, enhancing overall electrochemical performance. Using as anode, it delivers a reversible capacity of 340.4 mAh g⁻¹ at 20 mA g⁻¹. At the same time, the complex sodium storage behavior is unveiled by a series of electrochemical measurements. This research not only fulfills the demand of high-performance SIBs anodes, but also promotes a sustainable future.