Abstract
Transmission electron microscopy (TEM) has been widely employed as an important technique for detecting morphology in various secondary battery applications. When integrated with diverse accessories, TEM could attain sub-angstrom level detection, cryogenic TEM (cryo-TEM), and other functionalities, which enables the observation and comprehension of the microstructure of secondary battery materials, as well as structural variations during battery charging and discharging processes. In this chapter, essential structures, main functions, and sample preparation methods of TEM are introduced. Additionally, applications of TEM in characterizing materials used in secondary batteries are discussed and summarized. The aim is to provide essential guidance for employing TEM and to facilitate its future development.