Defect-rich WS2–SPAN nanofibers for sodium/potassium-ion batteries: ultralong lifespans and wide-temperature workability

Abstract

Currently, the investigation of two-dimensional (2D) crystalline materials, notably transition metal tungsten-based sulfides, is scarcely reported in the wide-temperature field. Thus, tungsten sulphide encapsulated in a sulphurized polyacrylonitrile composite (WS₂–SPAN) was prepared using an electrospinning technology combined with a sulphuration process. By virtue of the abundant S vacancies and in situ N doping, the WS₂–SPAN composite shows an impressively ultralong lifespan and stable circulation capacity over a wide temperature range (−15–50 °C). For sodium storage, the WS₂–SPAN-2 composite delivers optimized high-rate performance and ultrastable cycling properties (464 mA h g⁻¹/450 cycles at 0.5 A g⁻¹; 354 mA h g⁻¹/1400 cycles at 2 A g⁻¹, 190 mA h g⁻¹/12 000 cycles at 5 A g⁻¹; 129 mA h g⁻¹/18 000 cycles at 10 A g⁻¹, surpassing previously reported WS₂-based anodes for SIBs). This is paired with an Na₃V₂(PO₄)₃ cathode, which exhibits excellent storage capacity (241 mA h g⁻¹/200 cycles at 0.5 A g⁻¹). Potassium storage also demonstrates admirable performance (362 mA h g⁻¹/100 cycles at 0.1 A g⁻¹; 278 mA h g⁻¹/3000 cycles at 1 A g⁻¹). In addition, a detailed illustration of the electrochemical storage mechanism of WS₂–SPAN composites is presented through theoretical calculations and electrochemical dynamics. Thus, the present investigation provides new insights into the preparation of novel WS₂-based anodes for sodium/potassium-ion batteries with ultralong lifespans and wide-temperature workability.