[MoS] Insertion Chains Induced Small-Polaron Collapse in MoS2 2D Layers: A Novel Mo2S3 Anode for Ultrafast Sodium Storage

Abstract Molybdenum disulfide (MoS 2 ) with high theoretical capacity has been viewed as a promising anode for sodium-ion batteries, but suffers from inferior rate capability owing to the polaron-induced slow charge transfer. Herein, we proposed a polaron collapse strategy induced by electron-rich insertions to effectively solve the above issue. Specifically, 1D [MoS] chains are inserted into MoS 2 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 2 S 3 shows metallic behavior with 10 7 times larger electrical conductivity than that of MoS 2 . Theoretical calculations demonstrate that Mo 2 S 3 owns highly delocalized anions, which substantially reduces the interactions of Na − S to efficiently accelerate Na + diffusion, endowing Mo 2 S 3 lower energy barrier (0.38 vs 0.65 eV of MoS 2 ). The novel Mo 2 S 3 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 15000 cycles. Further in situ and ex situ characterizations reveal the in-depth reversible redox chemistry in Mo 2 S 3 . The proposed polaron collapse strategy for intrinsically facilitating charge transfer could be conducive to electrode design for fast-charging batteries.