Clarifying the lithium storage behavior of MoS2 with in situ electrochemical impedance spectroscopy

Abstract

MoS₂ is considered a potential electrode material for lithium-ion batteries because of its high energy density. However, it has not been commercialized owing to its poor cycle stability. To explore the reasons for its poor cycle stability, in situ X-ray diffraction, in situ transmission electron microscopy, and other characterization methods were used to explore the lithium storage mechanism and the phase transitions of MoS₂ during lithium storage. Because MoS₂ forms an amorphous structure during cycling, these physical methods have difficulty distinguishing between the various electrochemical stages of the reaction in detail. In this work, in situ electrochemical impedance spectroscopy (EIS) was adopted to record the change in the impedance of the MoS₂ electrode during the discharging and charging processes. The results show that the first discharging and charging process of MoS₂ can be further divided into six stages and five stages, respectively. In addition, a program based on Python was used to batch-process EIS data, which promotes the further application of in situ EIS. This study can help researchers analyze the lithium storage process of MoS₂ in more detail than was previously possible, and this method can also be applied to mechanistic research on other electrode materials.