Optimized architectural engineering and interface modulation in metallic-phase selenide for exceptional sodium-storage performance

Transition metal selenides (TMSs) exhibit promise as anode materials for sodium-ion batteries (SIBs) due to their high specific capacity and diverse electronic properties. However, practical implementation faces challenges such as structural deterioration, solid-electrolyte interphase (SEI) instability, and diminished coulombic efficiency, especially at the nanoscale. Here, we introduce a novel approach that combines surface engineering of Fe3Se4 with an interface engineering strategy (Fe3Se4@NC) to effectively address these issues. By incorporating engineered void spaces and an electrolyte-blocking layer within micrometer-sized secondary clusters, Fe3Se4 nanoparticles gain the ability to expand and contract freely during cycling, thereby preserving interparticle connections and enhancing the structural integrity. The synergy of surface engineering with a nitrogen-doped carbon layer and interface engineering through electrolyte modulation leads to an outstanding 95.1 % initial Coulombic efficiency in the Fe3Se4@NC electrode. Even after 2000 cycles at 5 A g−1, the electrode retains over 89.2 % of its initial capacity with an average specific capacity of 450 mAh g−1. In situ transmission electron microscopy (TEM) and in situ X-ray diffraction (XRD) analysis shed light on the structural evolution and sodiation dynamics during charge/discharge process. Experimental investigations and DFT calculations provide a comprehensive understanding of the SEI composition and the structural stability of the composite. [Display omitted] •Micrometer-sized Secondary Clusters for Controlled SEI Formation.•Defects-Repairing Induced Catalytic Bonds for Enhanced Coulombic Efficiency.•Comprehensive Understanding through Multiscale Characterizations and Theoretical Simulations.•Exceptionally Fast Na+ Ion Transport and Long-Term Stability.