Recent progress on in situ characterizations of electrochemically intercalated transition metal dichalcogenides

Layered transition metal dichalcogenides (TMDCs) have been extensively studied owing to their unique physical and chemical properties. Weak van der Waals (vdW) interactions between the stacking layers of TMDCs allow intercalation of various species including monovalent alkali, divalent alkaline earth and multivalent metal ions, zero-valent transition metals, as well as organic molecules, all of which can drastically alter fundamental properties of the TMDCs. The urge to understand the phenomena and the desire to exploit them for applications have inspired a great deal of investigations. A large portion of the mystery has been unveiled over the past decade of intense research; however, many questions remain open and require further explorations. This review is concerned with investigations on structural and electronic evolution of TMDCs driven by electrochemically controlled intercalations. Herein, we aim to survey the recent advances and experimental platforms for monitoring the intercalation processes in situ by utilizing nanodevices. In addition, several inquiries and prospects are outlined in a broader context for future avenues of studies.