Nanostructured MoS2 with Interlayer Controllably Regulated by Ionic Liquids/Cellulose for High-Capacity and Durable Sodium Storage Properties.

Abstract

Low intrinsic conductivity and structural instability of MoS2 as an anode of sodium-ion batteries limit the liberation of its theoretical capacity. Herein, density functional theory simulations for the first time optimize MoS2 interlayer distance between 0.80 and 1.01nm for sodium storage. 1-Butyl-3-methyl-imidazolium acetate ([BMIm]Ac) induces cellulose oligomers to intercalate MoS2 interlayers for achieving controllable distance by changing the mass ratio of cellulose to [BMIm]Ac. Based on these findings, porous carbon loading the interlayer-expanded MoS2 allowing Na+ to insert with fast kinetics is synthesized. A carbon layer derived from [BMIm]Ac and cellulose coating the composite prevents the MoS2 from contacting electrolytes, leading to less sulfur loss for a more reversible specific capacity. Meanwhile, MoS2 and carbon have a strong interfacial connection through MoN binding, contributing to enhanced structural stability. As expected, while cycling 250 times at 0.1 A g-1 , the MoS2 -porous carbon composite displays an optimal reversible capacity at 517.79 mAh g-1 as a sodium-ion batteries anode. The cyclic test of 1.0 A g-1 also shows considerable stability (310.74 mAh g-1 after 1000 cycles with 86.26% retentive capacity). This study will open up new possibilities of modifying MoS2 that serves as an applicable material as sodium-ion battery anode.