N, S Codoped Carbon Nanosheet Arrays with Enlarged Interlayer Spacing for Ultrafast and Durable Sodium Storage

The development of advanced carbon anodes is pivotal for enabling high-performance sodium-ion batteries (SIBs). However, their reaction dynamics and cycling stability remain a formidable challenge. In this work, we report a novel three-dimensional (3D) carbon framework anode (S-CNS@CNF), featuring engineered carbon nanosheet arrays coupled with a sulfur and nitrogen codoping strategy. Specifically, nickel hydroxide is employed as a structural inducer to facilitate the vertical anchoring of carbon nanosheet arrays onto porous carbon nanofibers, thereby constructing an interconnected 3D porous architecture. This hierarchical structure affords a wealth of active sites for Na⁺ adsorption while simultaneously facilitating highly efficient pathways for electron transport. Furthermore, N, S codoping introduces a high density of defect sites and enlarges the interlayer spacing of the carbon nanosheets. Experimental findings combined with theoretical calculations reveal that the incorporation of sulfur into the carbon further enhances the Na⁺ storage kinetics and increases Na⁺ adsorption energy. Benefiting from the synergistic effects between interconnected 3D porous architectures and N, S doping, the as-prepared anode delivers a high reversible capacity of 399.5 mAh g^-1 at 0.1 A g^-1 and outstanding rate capability, retaining 146.7 mAh g^-1 at 20 A g^-1. When Na₃V₂(PO₄)₃ (NVP) is employed as the cathode, the NVP//S-CNS@CNF full cell outputs a specific capacity of 117.6 mAh g^-1 at 2 A g^-1.