Bridging thermal abuse mechanisms, diagnostic parameters, and safety standards: A critical review of lithium-ion battery risk assessment

Thermal runaway (TR) remains a major safety concern for lithium-ion batteries (LIBs) under high-temperature conditions. Many reviews discuss reaction steps, warning signals, or testing standards separately, which makes it difficult to see how internal failures relate to measurable signs or to certification practices. This review describes the main reactions that occur as temperature rises, including Solid Electrolyte Interphase (SEI) breakdown, reactions between the anode and electrolyte, separator failure, oxygen release from cathode materials, and electrolyte vaporization. The typical temperature ranges and conditions that trigger each reaction are summarized. The review then compares four common diagnostic signals used in early warning systems: temperature, voltage, impedance, and gas emission. Their response speed, delays, and practical limitations are discussed. Finally, major international thermal abuse standards for cells, modules, and battery systems are compared, highlighting differences in test methods and acceptance criteria. Putting these aspects together helps clarify how battery behavior, measurable indicators, and safety testing relate, and points to where more realistic evaluation methods could improve safety.