Synergistic Coupling of a Chitosan‐Modified Sepiolite Rigid Framework With N/S Co‐Doped Carbon for the Construction of a High‐Performance Sodium Metal Anode Interface

Sodium metal batteries (SMBs) have emerged as strong candidates for next‐generation large‐scale energy storage technologies due to their low cost and high energy density. However, the instability of the solid electrolyte interphase (SEI), inevitable volume expansion, and uncontrollable dendrite growth hinder the practical application of sodium metal anodes (SMAs). Herein, a synergistic CSMB@C protective layer was rationally constructed by integrating a chitosan‐modified sepiolite framework with methylene‐blue‐derived N/S co‐doped carbon, designed to stabilize the sodium metal anode interface. The resulting architecture integrates a mechanically robust sepiolite scaffold, adhesive chitosan, and an N/S co‐doped carbon layer, thereby facilitating Na ⁺ transport and homogenizing sodium deposition. Consequently, the CSMB@C@Na composite electrode exhibits superior cycling performance and a long cycle life exceeding 3000 h in a symmetric cell. When paired with Na ₃ V ₂ (PO ₄ ) ₃ , the full cell delivers 104.37 mAh g ⁻¹ at 5 C and retains 69.29% of capacity after 2000 cycles. This work demonstrates a practical strategy for stabilizing SMAs using natural clay‐derived materials.