Cow leather-derived N/O codoped hard carbon as a high-performance anode material for sodium-ion batteries

Sodium-ion batteries (SIBs) have gained increasing attention owing to the abundant and cost-effective availability of sodium precursors. However, the quest for cost-effective and high-performing anode materials for SIBs remains a challenging task. In this study, we employed a straightforward pyrolysis method to fabricate nitrogen (N)-and oxygen (O)-doped hard carbon (HC) using waste cow leather, a low-cost biomass with high yield, as a carbon source. Our findings reveal that the pyrolysis temperature significantly influences the sodium storage performance of cow leather-derived HCs by modulating their microstructures and compositions. Specifically, the cow leather-derived HC pyrolyzed at 1100 degrees C exhibits a high reversible specific capacity of 207.9 mAh g-1 after 100 charge/discharge cycles at a current density of 0.1 C. Additionally, a reversible capacity of 142 mAh g-1 is maintained after 200 cycles at 1 C. Density functional theory (DFT) calculations validate that N/O codoping in HCs enhances the presence of defects and active sites and facilitates electron transfer, thereby improving sodium storage performance. This work provides insights into the sodium storage behavior of cow leather-derived HCs carbonized at different temperatures and presents a promising avenue for converting solid waste into highperformance anode materials for SIBs.