Flat–Zigzag Interface Design of Chalcogenide Heterostructure toward Ultralow Volume Expansion for High‐Performance Potassium Storage

Abstract Heterostructure construction of layered metal chalcogenides can boost their alkali‐metal storage performance, where the charge transfer kinetics can be promoted by the built‐in electric fields. However, these heterostructures usually undergo interface separation due to severe layer expansion, especially for large‐size potassium accommodation, resulting in the deconstruction of heterostructures and battery performance fading. Herein, first a stable interface design strategy where two metal chalcogenides with totally different layer‐morphologies are stacked to form large K⁺ transport channels, rendering ultralow interlayer expansion, is presented. As a proof of concept, the flat–zigzag MoS₂/Bi₂S₃ heterostructures stacked with zigzag‐morphology Bi₂S₃ and flat‐morphology MoS₂ present an ultralow expansion ratio (1.98%) versus MoS₂ (9.66%) and Bi₂S₃ (9.61%), which deliver an ultrahigh potassium storage capacity of above 600 mAh g⁻¹ and capacity retention of 76% after 500 cycles, together with the built‐in electric field of heterostructures. Once the heterostructures are used as an anode for potassium‐based dual‐ion batteries (K‐DIBs), it achieves a superior full‐cell capacity of ≈166 mAh g⁻¹ with a capacity retention of 71% after 400 cycles, which is an outstanding performance among the reported K‐DIBs. This proposed interface stacking strategy may offer a new way toward stable heterostructure design for metal ions storage and transport applications.