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

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.

Automated summary

In this study, a hierarchical hollow microsphere composed of heterostructured NiS/NiS2 nanoparticles confined by in situ carbon layer (H-NiS/NiS2@C) was successfully assembled by regulating the sulfidation temperature of the precursor Ni-MOFs. The ultrathin hollow spherical shells and in situ carbon layer provided rich channels for ion/electron transfer and alleviated the effects of volume change and agglomeration of the material. The resulting H-NiS/NiS2@C exhibited superb electrochemical properties, including high specific capacity, excellent rate capability, and superior cycle life.