PET Waste-Derived Hard Carbon with Superior Rate Capability for Sodium-Ion Battery Anodes

Sodium-ion batteries (SIBs) are considered a promising alternative to lithium-ion systems, with hard carbon (HC) being the most suitable anode material due to its disordered structure and increased interlayer distance. At the same time, the recycling of polyethylene terephthalate (PET), whose waste volumes are constantly growing, remains a pressing issue. In this work, recycled PET is used as a precursor for obtaining HC by direct carbonization at temperatures of 900–1400 °C. It is shown that the carbonization temperature significantly affects the structure and electrochemical properties of the obtained materials. The best characteristics were demonstrated by samples PET_1000 and PET_1100, which provided a high reversible capacity of 275–280 mAh g−1 at a current density of 20 mA g−1 in sodium-ion half-cells. The results confirm that controlled carbonization of recycled PET is an effective approach for obtaining highly efficient anode materials for SIBs and, at the same time, represents a promising way to utilize plastic waste.