Lotus rhizome-like S/N–C with embedded WS2 for superior sodium storage

Abstract

Sodium-ion batteries (SIBs) hold great promise as power sources because of their low cost and decent electrochemical behavior. Nevertheless, the poor rate performance and long-term cycling capability of anode materials in SIBs still impede their practical application in smart grids and electric vehicles. Herein, we design a delicate method to embed WS₂ nanosheets into lotus rhizome-like heteroatom-doped carbon nanofibers with abundant hierarchical tubes inside, forming WS₂@sulfur and nitrogen-doped carbon nanofibers (WS₂@S/N–C). The WS₂@S/N–C nanofibers exhibit a large discharge capacity of 381 mA h g⁻¹ at 100 mA g⁻¹, excellent rate capacity of 108 mA h g⁻¹ at 30 A g⁻¹, and a superior capacity of 175 mA h g⁻¹ at 5 A g⁻¹ after 1000 cycles. The excellent performance of WS₂@S/N–C is ascribed to the synergistic effects of WS₂ nanosheets, contributing to larger interlayer spacing, and the stable lotus rhizome-like S/N–C nanofiber frameworks which alleviate the mechanical stress. Moreover, the WS₂@S/N–C electrode shows obvious pseudocapacitive properties at 1 mV s⁻¹ with a capacitive contribution of 86.5%. In addition, density functional theory calculations further indicate that the WS₂@S/N–C electrode is very favorable for Na storage. This novel synthetic strategy is a promising method for synthesizing other electrode materials for rechargeable batteries in the future.