1D Insertion Chains Induced Small‐Polaron Collapse in MoS₂ 2D Layers Toward Fast‐Charging Sodium‐Ion Batteries

Abstract Molybdenum disulfide (MoS₂) with high theoretical capacity is viewed as a promising anode for sodium‐ion batteries but suffers from inferior rate capability owing to the polaron‐induced slow charge transfer. Herein, a polaron collapse strategy induced by electron‐rich insertions is proposed to effectively solve the above issue. Specifically, 1D [MoS] chains are inserted into MoS₂ to break the symmetry states of 2D layers and induce small‐polaron collapse to gain fast charge transfer so that the as‐obtained thermodynamically stable Mo₂S₃ shows metallic behavior with 10⁷ times larger electrical conductivity than that of MoS₂. Theoretical calculations demonstrate that Mo₂S₃ owns highly delocalized anions, which substantially reduce the interactions of Na−S to efficiently accelerate Na⁺ diffusion, endowing Mo₂S₃ lower energy barrier (0.38 vs 0.65 eV of MoS₂). The novel Mo₂S₃ anode exhibits a high capacity of 510 mAh g⁻¹ at 0.5 C and a superior high‐rate stability of 217 mAh g⁻¹ at 40 C over 15 000 cycles. Further in situ and ex situ characterizations reveal the in‐depth reversible redox chemistry in Mo₂S₃. The proposed polaron collapse strategy for intrinsically facilitating charge transfer can be conducive to electrode design for fast‐charging batteries.