Construction of hollow porous double-shell NSC@WS2 nanospheres for improved sodium-ion battery performance

WS2 with a layered structure is a promising anode material for sodium-ion batteries (SIBs). However, its practical application is hindered by the large stress-strain accumulation and low inherent electrical conductivity during Na+ intercalation/de-intercalation. Herein, we design and synthesize hollow porous double-shelled N/S-doped Carbon @WS2 (NSC@WS2) nanospheres using a hard template to significantly enhance structural stability, conductivity, and ion transport efficiency in SIBs. The hollow and porous structural characteristics of the NSC@WS2 composites increase the surface area available for electrochemical reactions and alleviate volume expansion during cycling, thereby enhancing the specific capacity and structural stability of electrode materials. Notably, the inner and outer shells have an average size of 5 nm, shortening the Na+ diffusion distance and accelerating Na+ diffusion kinetics. Furthermore, the N/S-doped carbon in the inner shell significantly enhances the overall conductivity and structural stability of the NSC@WS2 composite, leading to an improved electron transfer rate. As expected, the specific capacities of the NSC@WS2 anode are remarkable: 473 mAh g- 1 after 150 cycles at 0.1 A g- 1 and 428 mAh g- 1 after 400 cycles at 1 A g- 1. The long-cycle performance is impressive, with a capacity of 234.8 mAh g- 1 after 900 cycles under 5 A g- 1.