Two‐Dimensional Ultrathin C₂N Nanosheets for High‐Performance Sodium‐Ion Storage

Abstract In this study, we have created and investigated ultrathin, large‐size two‐dimensional C₂N nanosheets, which serve as promising anode materials for sodium ion batteries. Those ultrathin C₂N nanosheets were produced through a chemical vapor deposition process, involving the polymerization of the precursor molecule HAT‐CN on sodium chloride templates. Notably, these nanosheets inherit an abundance of nitrogen sites from the precursor molecules, which are highly advantageous for sodium ion storage. In addition, the ultrathin nature of these nanosheets leads to significantly shorter ion transport pathways, enhancing their capacity for rapid ion storage compared to C₂N particles. As a result, the anode constructed using C₂N nanosheets demonstrates a notably higher capacity of 335.1 mAh g⁻¹ at 0.5 A g⁻¹, outperforming the 211.5 mAh g⁻¹ of C₂N particles. Furthermore, it exhibits outstanding rate performance, achieving 255.4 mAh g⁻¹ at a current density of 2.0 A g⁻¹, along with excellent cycle stability, maintaining a reversible capacity retention of 92.9 % over 1500 cycles at 2.0 A g⁻¹. This research introduces a novel approach to developing high‐capacity anode materials for sodium storage by utilizing carbon nitride materials.