1D Insertion Chains Induced Small-Polaron Collapse in MoS 2D Layers Toward Fast-Charging Sodium-Ion Batteries.

Molybdenum disulfide (MoS ) 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 MoS 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 Mo S shows metallic behavior with 10 times larger electrical conductivity than that of MoS . Theoretical calculations demonstrate that Mo S owns highly delocalized anions, which substantially reduce the interactions of Na-S to efficiently accelerate Na diffusion, endowing Mo S lower energy barrier (0.38 vs 0.65 eV of MoS ). The novel Mo S anode exhibits a high capacity of 510 mAh g at 0.5 C and a superior high-rate stability of 217 mAh g at 40 C over 15 000 cycles. Further in situ and ex situ characterizations reveal the in-depth reversible redox chemistry in Mo S . The proposed polaron collapse strategy for intrinsically facilitating charge transfer can be conducive to electrode design for fast-charging batteries.