Advanced Technologies for Characterizing and Detecting Battery Thermal Failure: A Review

ABSTRACT Energy storage is essential in accelerating the global transition toward clean and sustainable energy across various sectors. Lithium‐ion batteries (LIBs) have become increasingly significant for energy storage due to their high energy density, low maintenance, and high coulombic efficiency. However, a challenge arises from the risk of thermal failure across all cell formats and chemistries, particularly under harsh electrochemical and thermal conditions and mechanical stress. In severe cases, such failures have led to catastrophic fires or explosions, posing substantial safety risks and environmental concerns due to gas emissions and toxic discharge. Therefore, an understanding of thermal failure mechanisms is essential for ensuring the safe deployment of batteries across various applications. This review first examines the causes and consequences of thermal failure, providing didactic mechanistic insights. It then compares recent progress in thermal and electrochemical failure analysis using advanced characterization techniques, including X‐ray imaging, optical sensing, acoustic field imaging, and spectroscopy, to study the thermal runaway (TR) mechanism and reveal how thermal failures develop and propagate in batteries. It further examines how these advanced characterization tools can inform battery management systems and industrial practice and concludes by outlining future challenges and perspectives for achieving safe energy storage systems.