Tuning the Mesopore Structure of Polyethylene Glycol Terephthalate (PET)-Derived Hard Carbon for High-Capacity Sodium-Ion Batteries

Hard carbon (HC) is considered to be a highly promising anode material for sodium-ion batteries. However, the synthesis conditions and pore structure regulation are still challenging for high-capacity sodium-ion storage. In this study, HCs using polyethylene glycol terephthalate (PET) as a carbon resource and ZnO as a nanopore template were synthesized and systematically investigated. By optimizing the additive amount of zinc gluconate, the starting material for ZnO, PET-derived HCs with a proper mesoporous structure were obtained. The as-prepared hard carbon demonstrated a high reversible capacity of 389.42 mAh·g^-1 at 20 mA·g^-1, with the plateau capacity accounting for 68%. After 75 cycles, the discharge capacity stabilized at 367.73 mAh·g^-1 with a retention ratio of 89.4%. The rate performance test indicated that a proper mesopore structure helped to improve the sodium-ion diffusion coefficient, effectively enhancing the charge-storage kinetics. This work provides a promising strategy for converting PET into valuable carbon materials for application in the field of renewable energy technology.