Exfoliation of MoS₂ Nanosheets Enabled by a Redox-Potential-Matched Chemical Lithiation Reaction

Ion intercalation assisted exfoliation is the oldest and most popular method for the scalable synthesis of molybdenum disulfide (MoS₂) nanosheets. The commonly used organolithium reagents for Li⁺ intercalation are n-butyllithium (n-BuLi) and naphthalenide lithium (Nap-Li); however, the highly pyrophoric nature of n-BuLi and the overly reducing power of Nap-Li hinder their extensive application. Here, a novel organolithium reagent, pyrene lithium (Py-Li), which has intrinsic safe properties and a well-matched redox potential, is reported for the intercalation and exfoliation of MoS₂. The redox potential of Py-Li (0.86 V vs Li⁺/Li) is located just between the intercalation (1.13 V) and decomposition (0.55 V) potentials of bulk MoS₂, thus allowing precise Li⁺ intercalation to form a lamellar LiMoS₂ compound without undesirable structural damage. The lithiation reaction can be accomplished within 1 h at room temperature and the exfoliated nanosheets are almost single layer. This method also offers the advantages of low cost, high repeatability, and ease in realizing large-scale production.