Semiconductive-Metallic Heterostructure Endowing Strong Built-In Electric Field for Fast and Stable Sodium Storage

Transition metal selenides have attracted much attention in the field of energy storage materials due to their high theoretical capacity and suitable working potential. However, they still suffer from slow reaction kinetics and poor stability during cycling. The construction of heterostructures is an effective strategy to improve the electrochemical performance of materials, which can improve the diffusion kinetics of ions and enhance the conductivity and structural stability of electrodes. In this paper, an in situ self-assembly strategy is proposed to encapsulate VO(acac)₂ in a customized cavity of ZIF-8 to achieve uniform dispersion of vanadium species and then to obtain ZnSe/VSe₂@NC heterostructured materials with abundant heterointerface. Based on the experimental characterization combined with density-functional theory calculations, a strong built-in electric field is induced at the interface due to the large energy band structure difference between VSe₂ and ZnSe, which promotes charge-electron transfer and achieves fast electrochemical kinetics and satisfactory reversible capacity. As an anode material for sodium-ion batteries (SIBs), ZnSe/VSe₂@NC exhibits excellent multiplicity performance (254.46 mA h g^-1 at 10 A g^-1) and long cycle stability (317.52 mA h g^-1 after 2000 cycles at 5 A g^-1). This study provides an effective strategy for the rational design of anode materials for high-performance SIBs.