Defect-engineered WS_xSe_2-x nanocrystals anchored on selenized polyacrylonitrile fibers toward high-performance sodium/potassium-ion batteries with a wide working temperature range

Sodium/potassium ion batteries (SIBs/PIBs) are attractive energy storage devices that offer greater sustainability and economic efficiency compared to their lithium-ion battery (LIB) counterparts. However, conventional electrode materials with satisfactory cycling stability and rate capacity are still lacking, due to intrinsic low electronic conductivity, sluggish intrinsic ion/electron kinetics and unsatisfactory structural stability. Herein, a well-designed two-step electrospinning/annealing strategy has been employed to fabricate defect-rich WSxSe2-x nanocrystals within selenized polyacrylonitrile fibers (designated as WSSe-Se@PAN). By tuning the Se-doping into the PAN fibers and forming defect-rich WSxSe2-x nanocrystals, the synergistic coupling of S-vacancy regulation can enhance the active sites, expand the interlayer spacing, and accelerate Na+/K+ diffusion kinetics, simultaneously. The WSSe-Se@PAN electrode, serving as the anode, delivers a superior sodium storage performance (467 mA h g(-1) at 2.0 A g(-1) after 700 cycles), and shows a reversible discharge capacity of 299 mA h g(-1) at 0.5 A g(-1) after 60 cycles with 99.8% capacity retention for the sodium ion full batteries. Encouragingly, it displays excellent feasibility in a wide working temperature range between -15 and 50 degrees C for SIBs. Furthermore, it exhibits high-rate capability and robust cycling life (139 mA h g(-1) at 1.0 A g(-1) after 1000 cycles) for PIBs. This work demonstrates that defect engineering of metal chalcogenides by anion doping is a feasible strategy to achieve high-performance anode materials for alkali metal ion batteries.