Dense homogeneous hetero-interfacial coupling between amorphous Mo–N and crystalline Mo2N for enhanced sodium-ion storage

Optimizing the interfacial environments of electrodes has emerged as an effective strategy to improve their electrochemical properties. Amorphous/crystalline interfacial coupling can effectively utilize the advantages of amorphous materials to optimize the interfacial structure for efficient Na⁺ storage. Herein, the dense homologous amorphous/crystalline heterointerfaces are in situ achieved in N-doped carbon nanobundles via self-polymerization and precise nitriding (Mo–N/Mo₂N@C). The amorphous Mo–N rich in unsaturated vacancy defects provides abundant active sites with isotropic ion-transport channels, and can effectively alleviate structural stress from crystalline Mo₂N. Meanwhile, the conductive Mo₂N can facilitate effective electron transfer, augmented further by the carbon encapsulation. Theoretical calculations reveal that the dense heterointerfaces can optimize the electronic structure and shift the d-p orbital centers of Mo and N upward, thereby enhancing the adsorption and mobility of Na⁺, and ultimately improving the charge transport and storage efficiency of the electrode. The Mo–N/Mo₂N@C as an anode delivers a 46.9% increase in reversible capacity over Mo₂N@C, reaching 461.1 mAh·g^–1 at 0.1 A·g^–1, along with improved rate capability and cycling stability, underlining its practical utility. These results suggest that the homologous interfacial coupling can boost the storage properties of nitrides, providing a valuable reference for improving the properties of electrodes with low theoretical capacities.

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