Visualizing Electrochemical Reactions in Rechargeable Battery Anodes via In Situ Transmission Electron Microscopy...

Rechargeable batteries are increasingly constrained by performance and safety limitations originating from anode degradation, including lithium dendrite-induced short circuits, bulk phase transformations, and interfacial SEI evolution. These processes are highly dynamic, strongly coupled, and span multiple spatial and temporal scales, complicating the establishment of direct structure-property correlations and impeding the rational design of next-generation anodes. Transmission electron microscopy (TEM), particularly in situ modalities, overcomes these limitations by combining sub-ångström resolution with multimodal capabilities-including real-space imaging, diffraction, and spectroscopy-to directly visualize morphology, structural, and chemical in real time. This review summarizes mechanistic insights obtained through analytical TEM across three hierarchical domains: (1) electrode surfaces, revealing deposition/stripping kinetics and dendrite nucleation; (2) bulk phases, tracking phase transformations, volumetric changes, and ion transport; and (3) electrode-electrolyte interfaces, elucidating SEI formation, evolution. Methodological challenges, such as electron-beam-induced artifacts, lithium's low atomic number, and liquid-phase confinement, are critically assessed, alongside emerging solutions including cryogenic TEM, low-dose imaging, and advanced liquid-cell designs. By integrating materials science with state-of-the-art electron microscopy, this review establishes a framework for leveraging in situ TEM to accelerate the development of durable, high-performance, and safe battery anodes.