Powder exfoliated MoS₂ nanosheets with highly monolayer-rich structures as high-performance lithium-/sodium-ion-battery electrodes

Abstract

Due to their low yield and easy aggregation during the electrode preparation process, exfoliated MoS2 monolayers cannot fulfill the requirements of alkali-metal-ion battery tests. Hence, we have developed a facile process to fabricate powder exfoliated MoS2 nanosheets capable of large-scale production and having highly monolayer-rich structures. This process contains two steps: liquid-phase exfoliation of the edge-rich MoS2 precursor and a freeze-drying procedure. The proposed MoS2 precursors contain rich edge fractions that are easily exfoliated by this method, and the freeze-drying procedure can maintain the unique monolayer-rich structure of MoS2 in the powder phase. The electrochemical evaluations of both lithium- and sodium-ion batteries reveal that the proposed powder exfoliated monolayer-rich MoS2 electrode exhibits remarkable specific capacities and stable cyclic performances. In particular, the monolayer-rich MoS2 nanosheet electrode delivers a superior lithium-storage capacity of ∼1400 mA h g-1. The exfoliated MoS2 nanosheet electrode can withstand over 1000 cycles even at 1 A g-1. The mechanism reveals that these unique MoS2 nanosheets not only have a large surface area but also their inclusive monolayer structures exhibit much higher charge mobility than those of bulk MoS2.