Regulating d–p Orbital Hybridized Electronic Structure via Doping Engineering for Advanced Sodium-Ion Batteries

Transition-metal selenides are promising anodes for energy storage due to their high energy density but face challenges, including volume expansion and sluggish kinetics. Herein, a doping engineering strategy is proposed to synthesize N-rich carbon-coated bimetallic zinc selenides doped with various transition metals (TM-ZnSe@NC, TM = Fe, Co, Ni) employing bimetallic zeolite imidazole frameworks as precursors through carbonization and selenization. The introduction of Fe, Co, and Ni with unpaired 3d-orbital electrons effectively reconfigures the electronic structure and crystal lattice of ZnSe. Remarkably, Fe-doped ZnSe (Fe-ZnSe@NC) demonstrates superior electrochemical performance, attributed to the redox activity of its d⁶ electronic configuration, optimal ionic radius matching with Zn²⁺, adaptable Fe-Se bonding characteristics, and low Na⁺ diffusion energy barrier. These synergistic effects enhance electronic conductivity, Na⁺ diffusion kinetics, and structural stability, achieving remarkable rate capability (215.1 mA h g^-1 at 30 A g^-1) and long-term cycling stability (423.6 mA h g^-1 after 1000 cycles at 2 A g^-1) in half-cells, as well as excellent rate performance (283.9 mA h g^-1 at 2 A g^-1) in full-cells. This doping engineering provides a feasible approach for designing high-performance electrodes for sodium-ion batteries and other energy storage systems.