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Designing potential anodes for sodium‐ion battery with both remarkable durability and high‐rate capability has captured enormous attention so far. The engineering of size and morphology is deemed as an effective manner to boost the electrochemical properties. Owing to the anisotropic self‐assembly of iron selenide, rod‐like FeSe₂ coates with nitrogen‐doped carbon is prepared through the thermal reaction of Prussian blue with selenium. Notably, the cyano groups are effectively transformed into N‐doped carbon with FeNC bonds, which uniformly coats FeSe₂, prompting Na⁺ transportations. Interestingly, the particle size is tailored by heating rates, along with increased carbon content, leading to broadened energy levels for redox reaction. Bestowed by these advantages, the FeSe₂/N‐C as Na‐storage anode delivers impressive electrochemical properties. Even at a rather high rate of 10.0 A g⁻¹, a …