Bismuth-based materials have attracted increasing attention in the research field of sodium/potassium-ion batteries owing to the high theoretical capacity. Unfortunately, the large volume variation and poor electrical conductivity limit their electrochemical performance and applications. Herein, we report a composite of heterostructured Bi 2 S 3 /MoS 2 encapsulated in nitrogen-doped carbon shell (BMS@NC) obtained by a solvothermal reaction as a novel anode material for sodium/potassium-ion batteries. The coating of the carbon layer could effectively relieve structural strains stemmed from the large volume change and improve electrical conductivity. More importantly, by skillfully constructing the heterostructure, an internal electric field formed on the heterointerface provides a rapid diffusion of ion and charge. As a consequence, the BMS@NC composite showed an excellent electrochemical performance for both sodium-ion batteries (a capacity of 381.5 mA h g −1 achieved at a current density of 5.0 A g −1 and 412 mA h g −1 at 0.5 A g −1 after 400 cycles) and potassium-ion batteries (a high specific capacity of 382.8 mA h g −1 achieved after 100 cycles at 0.1 A g −1 ). The design of the Bi 2 S 3 /MoS 2 heterostructure provides an effective strategy to develop energy storage materials with good electrochemical properties.

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Exploring the desired anode materials to address the issues of poor structural stability tardy redox kinetics caused by large potassium ionic radius are fatal for the realization of large‐scale applications of potassium‐ion batteries. In this work, the feasibility to achieve promoted K+ storage by constructing the model of CoS2 enfolded in carbon was verified by the density functional theory calculations. And the results predicted a faster electron/potassium ion transport kinetics than bare CoS2 by increasing electron carrier density and narrowing diffusion barrier. Therefore, an interfacial engineering strategy was applied and implemented to synthesize the CoS2 nanoparticles enveloped in the S‐doped carbon (CoS2/SC) under this inspiration. The as‐prepared CoS2/SC composite exhibited a prominent rate capability and long cycling lifespan, delivering the high capacity of 375 mA h g−1 at 0.2 A g−1 at the 100th cycle and 273 mA h g−1 at 2 A g−1 over 300 cycles. The in/ex situ characterizations unraveled the converse mechanism of CoS2/SC in K+ storage, showing an eventually reversible phase transformation of within the electrochemical reactions.

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