Thermal stability and safety challenges of all-solid-state batteries

All-solid-state batteries (ASSBs) are widely regarded as promising candidates for next-generation energy storage owing to their high energy density and intrinsic safety advantages. However, growing evidence indicates that ASSBs are not inherently safe. The thermal instability of key materials and interfaces can still trigger severe thermal hazards under abusive conditions. In this review, we systematically examine the thermal stability of critical components in ASSBs and elucidate the underlying safety challenges and thermal runaway mechanisms from the materials level to the full-cell and system levels. Current strategies for improving thermal stability and safety, including materials design, interface engineering, and cell-level protection, are summarized. In addition, emerging approaches based on advanced thermal characterization techniques and data-driven modeling are highlighted. This review provides a unified framework for understanding the thermal failure behavior of ASSBs and offers practical guidance for the rational design of future energy storage technologies.