Homologous Heterostructured NiS/NiS₂@C Hollow Ultrathin Microspheres with Interfacial Electron Redistribution for High‐Performance Sodium Storage

Abstract

Nickel sulfides with high theoretical capacity are considered as promising anode materials for sodium‐ion batteries (SIBs); however, their intrinsic poor electric conductivity, large volume change during charging/discharging, and easy sulfur dissolution result in inferior electrochemical performance for sodium storage. Herein, a hierarchical hollow microsphere is assembled from heterostructured NiS/NiS₂ nanoparticles confined by in situ carbon layer (H‐NiS/NiS₂@C) via regulating the sulfidation temperature of the precursor Ni‐MOFs. The morphology of ultrathin hollow spherical shells and confinement of in situ carbon layer to active materials provide rich channels for ion/electron transfer and alleviate the effects of volume change and agglomeration of the material. Consequently, the as‐prepared H‐NiS/NiS₂@C exhibit superb electrochemical properties, satisfactory initial specific capacity of 953.0 mA h g⁻¹ at 0.1 A g⁻¹, excellent rate capability of 509.9 mA h g⁻¹ at 2 A g⁻¹, and superior longtime cycling life with 433.4 mA h g⁻¹ after 4500 cycles at 10 A g⁻¹. Density functional theory calculation shows that heterogenous interfaces with electron redistribution lead to charge transfer from NiS to NiS₂, and thus favor interfacial electron transport and reduce ion‐diffusion barrier. This work provides an innovative idea for the synthesis of homologous heterostructures for high‐efficiency SIB electrode materials.