Tailoring Rod‐Like FeSe2 Coated with Nitrogen‐Doped Carbon for High‐Performance Sodium Storage

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 considerable capacity of 308 mAh g^?1 is yielded over 10 000 loops. Supported by the detailed analysis of kinetic features, reduced size of particles could bring about the enhanced contributions of pseudocapacitive and quickening rate of ions transferring. The phase evolutions are further investigated by in situ EIS and ex‐situ technologies. The work is expected to provide a new strategy to prepare metal‐selenide with controllable size and induce the faster kinetic of high‐rate materials.