High-electronegativity N stabilized amorphous Mo–Se coordination via local electronic domains for boosting sodium-ion storage in hybrid capacitors

In sodium-ion hybrid capacitors (SIHCs), the high-capacity metal selenide anodes are severely limited by structural instability and polyselenide dissolution/shuttle during cycling. This study proposes an innovative strategy utilizing high-electronegativity N (χ = 3.04) to modulate local electronic domains and stabilize amorphous Mo–Se coordination (N/Mo-Se). Through self-polymerization and tunable selenization, N-doped carbon (NC) nanospheres encapsulating N-stabilized amorphous Mo-Se clusters (N/Mo-Se@NC) are successfully constructed. Theoretical and experimental analyses reveal that N-optimization effectively reconstructs the electronic distribution of Mo–Se coordination via strong covalent Mo–N bonds. This significantly enhances the covalency of Mo-Se clusters and induces localized electronic domains, thereby substantially suppressing polyselenide dissolution/shuttle during cycling. Concurrently, the amorphous N/Mo-Se clusters provide isotropic ion diffusion pathways, and together with the three-dimensional (3D) conductive networks of the NC, they jointly optimize charge transfer kinetics. The N/Mo-Se@NC anode exhibits a high reversible capacity of 328.7 mAh g−1 after 5000 cycles, even at 10.0 A g−1, with a remarkable capacity retention of 110%. The assembled N/Mo-Se@NC//AC SIHCs achieve high energy/power densities (236.1 Wh kg−1/9990 W kg−1), demonstrating superior comprehensive performance compared to most previously reported anodes. This study, through high-electronegativity atom modulation and amorphization engineering, opens new avenues for designing highly stable and high-rate Na+ storage materials.