Heterointerface Engineering of Hierarchical Bi2S3/MoS2 with Self‐Generated Rich Phase Boundaries for Superior Sodium Storage Performance

Abstract Regulating nanocrystal composition with multiphase compounds is considered an efficient approach to enhance electrochemical performance and structure stability. Nevertheless, the thorough understanding of significant reaction mechanisms and insight into the reason of enhanced performance is still urgent. In this work, the bimetallic sulfide Bi 2 S 3 /MoS 2 heterogeneous with abundant phase boundaries is successfully fabricated. The in situ investigation of Na + ‐storage mechanism confirms that enormous phase boundaries are self‐generated by composition optimization and rational structural design. More importantly, the full understanding of abundant phase boundaries on the enhanced electrochemical properties is explicitly unraveled by combining theoretical analysis and experimental results. It confirms that the interior self‐built‐in electric‐field induced by phase boundaries can enhance the reaction kinetics and boost the charge transfer. Besides, the Bi/Na 2 S interface is well‐maintained by the homogeneously distributed phase boundaries, effectively improving the conversion/alloying reversibility and keeping integrity without agglomeration and pulverization. As expected, the Bi 2 S 3 /MoS 2 composite exhibits superior rate capability and long‐cycling stability (323.4 mAh g −1 after long‐term 1200 cycles at ultrahigh rate of 10 A g −1 ). This strategy of constructing sufficient phase boundaries sheds light on the enhancement of reversibility and stability for other advanced conversion/alloying‐type anode materials.