Visualizing Battery Reactions and Processes by Using In Situ and In Operando Microscopies

Based on traditional electronic, X-ray, and optical microscopies, novel tools and methodologies have been developed to monitor batteries in situ or in operando. This review surveys the recent development of several types of in situ and in operando microscopy and their utilization in studying batteries. The article is organized mainly by the in situ and in operando techniques used (X-ray microscopy, electron microscopy, scanning probe microscopy, etc.) rather than the chemical reactions that govern battery behavior. We compare different methodologies to illustrate their advantages and disadvantages in the study of different systems and problems and, at the end of the article, discuss generalized principles for the selection of methodologies and possible future directions.