Polydopamine‐Derived Carbon‐Coated Sn/SnO ₂ Anodes for High‐Performance Sodium‐Ion Batteries

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Tin dioxide (SnO 2 ) has attracted significant attention as an anode material for sodium‐ion batteries (SIBs), primarily due to its high theoretical capacity and the abundance of its constituent elements. However, its poor electronic conductivity and significant volume changes during repeated sodium‐ion insertion/extraction severely limit its practical application. This study successfully synthesized a series of polydopamine (PDA)‐derived carbon‐coated Sn/SnO 2 composites (Sn/SnO 2 @C) through a hydrothermal method combined with carbonization treatment. By adjusting the usage of PDA, the carbon content and structural disorder can be precisely controlled. Structural and compositional analysis indicates that Sn/SnO 2 nanoparticles are uniformly encapsulated by a continuous nitrogen‐doped amorphous carbon layer, forming a stable core–shell structure. Electrochemical evaluations demonstrate that the optimized Sn/SnO 2 @C‐1 electrode delivers a high reversible capacity of 251.5 mAh g −1 after 300 cycles at 0.1 A g −1 , long‐term cycling stability with 159.0 mAh g −1 at 0.5 A g −1 and 143.5 mAh g −1 at 1.0 A g −1 after 800 cycles, also exhibits excellent rate capability. This study highlights the pivotal role of PDA‐derived carbon structures in optimizing tin dioxide anodes, providing significant insights for the rational design of high‐performance SIBs.