Electrochemical Lithiation Mechanism of Two-Dimensional Transition-Metal Dichalcogenide Anode Materials: Intercalation versus Conversion Reactions

The fundamental understanding of electrochemical lithiation mechanism in two-dimensional layered transition-metal dichalco-genides (TMDs) is essential for the development of high-performance TMD-based anodes for lithium-ion batteries (LIBs). Here, we perform systematic density functional theory calculations to reveal the thermodynamic stability and lithiation dynamics of TMD electrode materials. The calculated results show that there exist two different lithiation mechanisms: one is the reversible intercalation reaction mechanism in which TMD electrodes represented by NbS2 and ZrS2 can maintain their layered structures without significant structural distortions in the lithiation process. The other is the irreversible conversion reaction mechanism where the Li intercalation induces a layer-by-layer structural dissociation of TMD electrodes represented by MoS2 and SnS2 into Li2S and metal nanoparticles. Two contrasting lithiation mechanisms are attributed to a delicate competition between the Li-TMD interaction and metal-chalcogen bonding interaction. Furthermore, we develop a general guiding principle to predict the Li intercalation mechanism of TMD anodes for LIBs.