Few-layered MoS2 with expanded interplanar spacing strongly encapsulated inside compact carbon spheres by C-S interaction as ultra-stable sodium-ion batteries anode

Graphite-like metal sulfides, MoS2, is regarded as potential electrode of sodium-ion batteries (SIBs) because of its relatively large interplanar spacing (0.62 nm) and outstanding theoretical capacity (670 mA h g(-1)). However, original MoS2 electrode often suffered from shortened cycle life and poor rate capability owing to the serious volume change during sodium insertion/extraction and inferior inherent conductivity. Herein, MoS2/C compact spheres (MoS2/C CSs) with dense structure constituted by few-layered MoS2 and conductive carbon coating are successfully developed using a in-situ synthesis method. As anode of SIBs, MoS2/C CSs achieve a high capacity of 425 mA h g(-1) after 200 cycles at 0.1 A g(-1) with initial coulombic efficiency up to 84.8%. The reversible capacity is still maintained in 320 mA h g(-1) after 400 cycles at 1 A g(-1), which is three times of original MoS2 (110 mA h g(-1)). Besides, MoS2/C CSs also have considerable rate performance, reserving impressive capacity (310 mA h g(-1)) at 5.0 A g(-1). The compact and conductive carbon coating effectively inhibits volume expansion and improves electrical conductivity, meanwhile, the few-layered MoS2 nanoflakes with ampliative interplanar spacing (0.73 nm) simplify the Nat diffusion pathway and promote rapid diffusion of Nat. Furthermore, the C-S chemical bond tightly interlocks MoS2 and C, which guarantees the above mechanisms synergistically and continuously intensify the property of MoS2/C CSs anode. The above results are verified by ex-situ impedance, phase and morphology analysis. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

MoS2/C compact spheres exhibit high capacity, good cycle life, and outstanding rate performance by inhibiting volume expansion and improving electrical conductivity, while simplifying Na+ diffusion pathway and promoting rapid Na+ diffusion.