Potassium-ion　batteries　(PIBs)　are　regarded　as　promising　candidates　in　next-generation　energy　storage　technology;　however,　the　electrode　materials　in　PIBs　are　usually　restricted　by　the　shortcomings　of　large　volume　expansion　and　poor　cycling　stability　stemming　from　a　high　resistance　towards　diffusion　and　insertion　of　large-sized　K　ions.　In　this　study,　BiSbSx　nanocrystals　are　rationally　integrated　with　sulfurized　polyacrylonitrile　(SPAN)　fibres　through　electrospinning　technology　with　an　annealing　process.　Such　a　unique　structure,　in　which　BiSbSx　nanocrystals　are　embedded　inside　the　SPAN　fibre,　affords　multiple　binding　sites　and　a　short　diffusion　length　for　K+　to　realize　fast　kinetics.　In　addition,　the　molecular　structure　of　SPAN　features　robust　chemical　interactions　for　stationary　diffluent　discharge　products.　Thus,　the　electrode　demonstrates　a　superior　potassium　storage　performance　with　an　excellent　reversible　capacity　of　790　mAh　g−1　(at　0.1　A　g−1　after　50　cycles)　and　472　mAh　g−1　(at　1　A　g−1　after　2000　cycles).　It＇s　one　of　the　best　performances　for　metal　dichalcogenides　anodes　for　PIBs　to　date.　The　unusual　performance　of　the　BiSbSx@SPAN　composite　is　attributed　to　the　synergistic　effects　of　the　judicious　nanostructure　engineering　of　BiSbSx　nanocrystals　as　well　as　the　chemical　interaction　and　confinement　of　SPAN　fibers.　©　2022　Wiley-VCH　GmbH.