Preparation of mesoporous hard carbon anode materials by nitrogen doping of biomass to enhance the specific capacity of sodium ion adsorption

Abstract

This study synthesized a hard carbon anode material (HC-N1300) with hierarchical micro/mesoporous structure through biomass-derived nitrogen doping, aiming to explore its application in sodium-ion batteries (SIB). Structural characterization reveals that HC-N1300 possesses well-developed micro/mesopores, which significantly shorten the diffusion pathways for sodium ions (Na⁺). Compositional analysis further demonstrates an increased ratio of pyridinic-N to pyrrolic-N configurations, providing abundant electrochemically active sites. These synergistic structural and compositional advantages collectively enhance the adsorption capability in the slope region. In half-cell evaluations, the HC-N1300 delivered an initial discharge capacity of 486 mAh g⁻¹ at 0.1 A g⁻¹ with a reversible capacity of 330 mAh g⁻¹. Remarkably, it maintained 88.5 % capacity retention after 1000 cycles at 0.5 A g⁻¹. Mechanistic analysis revealed that nitrogen doping plays a crucial role in pore formation during carbonization. The hierarchical porous architecture not only increases active sites but also facilitates rapid Na⁺ diffusion, thereby effectively improving both plateau capacity and rate capability. This work provides valuable insights for designing high-performance anode materials for SIB.