All-solid-state batteries (ASSBs) possess potential performance advantages, such as high safety and high energy density, making them a strategic frontier in global power battery technology competition, which has been incorporated into the development strategies of major countries including China, the United States, Japan, South Korea, etc. Currently, the research & development of ASSBs has entered a critical breakthrough phase, with the leading enterprises such as Toyota, BYD, and CATL expecting to initiate the applications of ASSBs in electric vehicles around 2027. However, before large-scale application, comprehensive performance evaluation and failure analysis of ASSBs are still required to ensure their safe and reliable operation under complex working conditions in electric vehicles. Notably, existing research indicates that ASSBs still suffer from risks of thermal runaway and are not absolute safe, as their failure mechanisms under complex operating conditions remain inadequately understood. In light of this, this paper systematically reviews the potential safety issues of ASSBs from the perspectives of materials, interfaces, and cell design, including the intrinsic thermal stability of key materials such as cathodes, anodes, and solid state electrolytes; high-temperature thermochemical reactions at the cathode/anode-electrolyte interfaces; lithium dendrite growth and the resulting internal short circuits; and toxic gas production and environmental hazards during battery failure. Building on this analysis, the paper further outlines future research strategies for the safety of ASSBs from the perspectives of in-depth failure-mechanism analysis, optimization of key materials and interfacial stability, and system-level gas management and thermal protection, thereby offering systematic theoretical support and practical guidance for their safety assessment and engineering deployment.
