Engraving Electrolyte and Ion‐Transport Tunnels in a Holey Carbon Nanosheet Array for Fast Sodium Ion Storage

Abstract 2D carbon materials are considered as attractive electrode materials for sodium ion batteries. Nevertheless, there are major hurdles for the electrolyte as well as for Na⁺ to access a wall‐like 2D structure and a serious restack of the 2D structure. Herein, we report a unique design of a holey carbon nanosheet array (HCNA) with engraved electrolyte and ion‐transport tunnels. HCNA possesses a highly continuous network of opened channels and spaces, and the restack and agglomeration are greatly suppressed. Based on electrochemical analysis, HCNA displays fast charge transfer at the electrode‐electrolyte interface and excellent sodium ion diffusion kinetics with a high Na⁺ diffusion coefficient (5.5×10⁻⁹ cm² s⁻¹). As a result, HCNA electrodes deliver excellent high‐rate performance of 197.4 mAh g⁻¹ after 1000 cycles at 500 mA g⁻¹. Such an architecture provides a promising structural platform for the fabrication of 2D carbons for highly reversible and high‐capacity sodium ion batteries and other alkali metal ion energy storage systems.