Lignin-assisted exfoliation of molybdenum disulfide in aqueous media and its application in lithium ion batteries

Abstract

In this article, alkali lignin (AL)-assisted direct exfoliation of MoS₂ mineral into single-layer and few-layer nanosheets in water is reported for the first time. Under optimized conditions, the concentration of MoS₂ nanosheets in the obtained dispersion can be as high as 1.75 ± 0.08 mg mL⁻¹, which is much higher than the typical reported concentrations (<1.0 mg mL⁻¹) using synthetic polymers or compounds as surfactants. The stabilizing mechanism primarily lies in the electrostatic repulsion between negative charged AL, as suggested by zeta-potential measurements. When the exfoliated MoS₂ nanosheets are applied as electrode materials for lithium ion batteries, they show much improved electrochemical performance compared with the pristine MoS₂ mineral because of the enhanced ion and electron transfer kinetics. This facile, scalable and eco-friendly aqueous-based process in combination with renewable and ultra-low-cost lignin opens up possibilities for large-scale fabrication of MoS₂-based nanocomposites and devices. Moreover, herein we demonstrate that AL is also an excellent surfactant for exfoliation of many other types of layered materials, including graphene, tungsten disulfide and boron nitride, in water, providing rich opportunities for a wider range of applications.