Synergistic effect of boron and nitrogen co-doping on anthracite-based hard carbon anode toward enhanced sodium storage

Anthracite-based carbon materials are widely regarded as practical anode materials for sodium-ion batteries due to their abundant resources, cost-effectiveness, high carbon yield, and excellent chemical stability. However, their widespread applications are hindered by issues such as poor cycling performance, limited storage capacity, and low coulombic efficiency. Herein, we propose an innovative “construction-release-repair” design strategy that leverages the synergistic effect of B/N co-doping to address these challenges. By constructing B–N bonds, releasing unstable heteroatoms, and repairing defect sites on carbon layers, this strategy significantly enhances the microstructure and surface engineering of anthracite-based hard carbon. The optimized hard carbon anode delivers high specific capacity of 344.2 mAh g -1 at 0.03 A g -1 with an initial coulombic efficiency of 85.3%, and excellent cycle retention of 88.2% after 500 cycles at 0.2 A g -1 . In-situ Raman spectroscopy and density functional theory calculations reveal that the B/N synergistic effect enhances the sodium-ion adsorption, reduces the diffusion barrier, and enhances reaction activity, facilitating more efficient intercalation and nanopore filling in the low-voltage plateau region. This work offers valuable insights into microstructure regulation and the design of high-performance anode for sodium-ion materials. This work proposes a "construction-release-repair" design strategy, utilizing the synergistic effect of B/N co-doping to enhance the microstructure and surface engineering of anthracite, resulting in coal-based hard carbon with high initial coulombic efficiency and capacity. DFT calculations demonstrate that the synergistic effect improves sodium ion adsorption, reduces diffusion barriers, and significantly enhances anode reaction activity.