Intercalative Motifs‐Induced Space Confinement and Bonding Covalency Enhancement Enable Ultrafast and Large Sodium Storage

Abstract Alloying‐type metal sulfides with high theoretical capacities are promising anodes for sodium‐ion batteries, but suffer from sluggish sodiation kinetics and huge volume expansion. Introducing intercalative motifs into alloying‐type metal sulfides is an efficient strategy to solve the above issues. Herein, robust intercalative InS motifs are grafted to high‐capacity layered Bi₂S₃ to form a cation‐disordered (BiIn)₂S₃, synergistically realizing high‐rate and large‐capacity sodium storage. The InS motif with strong bonding serves as a space‐confinement unit to buffer the volume expansion, maintaining superior structural stability. Moreover, the grafted high‐metallicity Indium increases the bonding covalency of BiS, realizing controllable reconstruction of BiS bond during cycling to effectively prevent the migration and aggregation of atomic Bi. The novel (BiIn)₂S₃ anode delivers a high capacity of 537 mAh g⁻¹ at 0.4 C and a superior high‐rate stability of 247 mAh g⁻¹ at 40 C over 10000 cycles. Further in situ and ex situ characterizations reveal the in‐depth reaction mechanism and the breakage and formation of reversible BiS bonds. The proposed space confinement and bonding covalency enhancement strategy via grafting intercalative motifs can be conducive to developing novel high‐rate and large‐capacity anodes.