NaCl‐Templated Iron Sulfide/N‐Doped Carbon Microspheres for High‐Performance Sodium‐Ion Batteries: From Nanostructural Design to Pouch Cells

ABSTRACT In this study, we report the rational design of NaCl‐templated iron sulfide/N‐doped carbon (FeS‐NaCl@NC) microspheres as high‐performance anodes for sodium‐ion batteries. A scalable spray pyrolysis process combined with subsequent sulfidation and polydopamine‐derived carbon coating enables the formation of three‐dimensional (3D) interconnected porous architectures with conformal N‐doped carbon layers. The NaCl template plays a critical role in generating internal void networks and mesoporous structures, facilitating electrolyte penetration and shortening Na + diffusion pathways, while the N‐doped carbon coating enhances electronic conductivity and interfacial stability. As a result, FeS‐NaCl@NC microspheres exhibit outstanding electrochemical performance, maintaining a high discharge capacity of 576.3 mA h g −1 after 100 cycles at 1.0 A g −1 and delivering remarkable rate capability (251.7 mA h g −1 at 10.0 A g −1 ). Notably, the improved cycling stability is rationalized by nano‐indentation results, indicating enhanced mechanical resilience against repeated volume changes. In addition, the origin of the superior rate capability is comprehensively elucidated through combined electrochemical and kinetic analyses, confirming that the designed structure enables accelerated Na + transport and charge transfer. Moreover, the practical feasibility of FeS‐NaCl@NC microspheres is validated through pouch‐type full‐cell evaluation, demonstrating its strong potential for sodium‐ion storage applications.