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 FeSe 2 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 FeSe 2 , 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 FeSe 2 /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.

No abstract

No abstract

As a result of its high‐energy density, metal–selenides have demanded attention as a potential energy‐storage material. But they suffer from volume expansion, dissolved poly‐selenides and sluggish kinetics. Herein, utilizing' thermal selenization via the Kirkendall effect, microspheres of NiSe2 confined by carbon are successfully obtained from the self‐assembly of Ni‐precursor/PPy. The derived hierarchical hollow architecture increases the active defects for sodium storage, while the existing double N‐doped carbon layers significantly alleviate the volume swelling. As a result, it shows ultrafast rate capability, delivering a stable capacity of 374 mAh g−1, even after 3000 loops at 10.0 A g−1. These remarkable results may be ascribed to the NiOC bonds on the interface of NiSe2 and the carbon film, which leads to the faster transfer of ions, the effective trapping of poly‐selenide, and the highly reversible conversion reaction. The kinetic analysis of cyclic voltammetry (CV) demonstrates that the electrochemical process is mainly dominated by pseudocapacitive behaviors. Supported by the results of electrochemical impedance spectroscopy (EIS), it is confirmed that the solid–electrolyte interface films are reversibly formed/decomposed during cycling. Given this, this elaborate work might open up a potential avenue for the rational design of metal‐sulfur/selenide anodes for advanced battery systems.

No abstract