Hard Carbon Derived from Waste Polyethylene for High‐Performance Sodium‐Ion Battery Anodes

Abstract Developing cost‐effective and high‐performance anode materials is crucial for advancing sodium‐ion batteries (SIBs) as sustainable alternatives to lithium‐ion batteries. In this study, hard carbon was synthesized from waste polyethylene (PE) via a sulfuric acid sulfonation‐assisted carbonization process, and its structural and electrochemical properties were systematically investigated. Sulfonation enhanced the carbonization process and modified the microstructure, leading to a disordered carbon structure with expanded interlayer spacing and hierarchical porosity, facilitating sodium‐ion storage. The optimized hard carbon exhibited a high reversible capacity of 312.42 mAh g −1 at 0.1 A g −1 and excellent cycling stability, retaining 243 mAh g −1 after 500 cycles at 0.5 A g −1 . These findings indicate that hard carbon derived from waste polyethylene and modified by sulfuric acid is a promising and sustainable anode material for SIBs, offering an environmentally friendly solution for energy storage applications.