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

Abstract

Molybdenum disulfide (MoS2) 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 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 reduces 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 15000 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 could be conducive to electrode design for fast-charging batteries.