Phase Transformation of 1T′-MoS₂ Induced by Electrochemical Prelithiation for Lithium-Ion Storage

Abstract

Two-dimensional (2D) MoS2 is one of the most representative materials of the transition metal dichalcogenide (TMD) family, which is mostly studied in the semiconductor 2H and metal 1T phases. However, the properties of the metalloid 1T′ phase remain unclear because of its immature preparation process and thermodynamic instability (metastable state). Herein, this study used theoretical calculations to discover the relationship and conditions for MoS2 to transition between the 2H, 1T, and 1T′ phases. Meanwhile, charge and discharge voltages and current density were controlled by ion insertion technology, and then 1T′-MoS2 with large size and definite morphology (the whole process was called “phase transition engineering”) was prepared. The prepared 1T′-MoS2 was used as the anode material for lithium-ion batteries. Compared with 2H-MoS2, the cyclic stability and specific capacity of 1T′-MoS2 were greatly improved. In addition, phase transformation of natural molybdenite (2H-MoS2) by phase transition engineering also yielded promising electrochemical properties. Consequently, phase transition engineering not only provided an opportunity for the phase transformation of TMDs of natural sulfide metals such as molybdenite but also offered an effective method to investigate the properties of 2D metastable polymorphic materials.