Bi-WS2 nanoflowers with expanded interlayer spacing for fast-charging sodium-ion battery anodes

Tungsten sulfide (WS 2 ) is a promising sodium-ion batteries (SIBs) anode due to its high capacity and distinctive layered structure, but its practical use is hindered by poor conductivity, large volume expansion, and particle aggregation. In the study, a bismuth-doped WS 2 (Bi-WS 2 ) nanoflower structure is developed to overcome the above limitations. The intercalation of bismuth ions expands the interlayer distance of WS 2 from 0.62 nm to 0.67 nm, thereby providing more space for Na + storage. Moreover, the incorporated bismuth ions further improve the electronic conductivity and contribute to improved structural stability. The nanoflower architecture presents ample exposed edge sites, which facilitate reversible diffusion of Na + along the edges and help to mitigate mechanical stress developed during the discharge-charge cycles. Notably, the bismuth doped tungsten disulfide nanoflowers delivers a high reversible capacity of 433.0 mAh g −1  at 0.2 A g −1 with an exceptional rate capability. Even after 2000 cycles at a high current of 10.0 A g −1 , it still delivers a capacity of 234.4 mAh g −1 , exhibiting promising electrochemical performance in comparison with previously reported anodes. Hence, Bi-WS 2 demonstrates great potential for use as a high-rate anode in future generation SIBs.