Advances of transmission electron microscopy research for lithium-ion batteries

Advanced transmission electron microscopy (TEM) have emerged as powerful tools for investigating the complex electrochemical processes and failure mechanisms in lithium-ion batteries at both the nanoscale and atomic levels. Advanced static TEM methods, such as electron energy loss spectroscopy (EELS), electron holography (EH), cryo-electron microscopy (cryo-EM), differential phase contrast (DPC), and four-dimensional scanning TEM (4D STEM), have provided unprecedented insights into electrode materials, solid electrolytes, and interface structures. On this foundation, multi-field in-situ TEM techniques have been developed to dynamically study the structural and chemical evolution of battery materials during electrochemical cycling in real-time. This paper reviews both static (ex-situ) studies using high-resolution electron microscopy and the recently developed dynamic (in-situ/operando) TEM techniques for battery research. We first summarize the development of advanced TEM characterization methods and their applications in lithium-ion batteries. We then focus on key findings related to lithiation/delithiation mechanisms, interface phenomena, thermal stability, mechanical degradation of battery materials in response to electrochemical cycling, as well as the effects of applied electric, thermal, and mechanical fields in-situ. This review systematically illustrates how advanced TEM characterization techniques can bridge atomic-scale observations with macroscopic battery behavior, ultimately enhancing battery performance and safety while accelerating the design and development of next-generation batteries.