Safety of Sodium‐Ion Batteries: Evaluation and Perspective from Component Materials to Cells, Modules, and Packs

ABSTRACT Sodium‐ion batteries (SIBs) are gaining mounting attention as they begin to enter early stages of demonstration/commercialization. To accelerate their safe and reliable deployment, especially in large‐scale energy storage applications, systematic and timely investigations into the safety of SIBs are essential. This review, understanding battery safety starts with materials and involves systematic engineering of degradation and failure across scales with balanced consideration of performance and cost, offers a comprehensive analysis and perspective of SIB safety after a bottom‐up evaluation of component materials, cell designs, and module/pack assemblies. The discussion starts with understanding degradation mechanisms at the material‐level and focuses on the responses of electrodes, electrolytes, separators, and current collectors to thermal, electrical, and mechanical abuses. Engineering approaches are introduced to mitigate risks across scales, from cell‐level thermal runaway to pack‐level propagation. Cell‐level strategies, including electrode properties, manufacturing factors, and auxiliary devices that relieve heat and pressure, are intended to manage material‐induced instability and support cell safety under stress. At the module/pack‐level, insulation, spatial configuration, and management systems are emphasized for their roles in preventing local failures from spreading into system‐wide incidents. By linking safety phenomena across hierarchical levels, this review provides a guideline for diagnosing safety vulnerabilities in advancing SIB technologies.