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What is Lithium Battery Thermal Runaway？
2026-08-28
From smartphones to electric vehicles, lithium batteries have become an indispensable energy source in modern life. As the scale of Lithium Battery applications continues to expand, thermal runaway has emerged as the most critical safety concern in the industry.
1. What Is Lithium Battery Thermal Runaway?
Lithium battery thermal runaway is a self-accelerating exothermic reaction triggered by internal or external factors. When a battery is subjected to conditions such as overcharge, impact, high temperature, or internal defects, the internal temperature rises rapidly. The SEI (Solid Electrolyte Interphase) protective film breaks down, the separator melts, and an internal short circuit occurs—continuously releasing massive heat and flammable gases, ultimately resulting in swelling, jet flames, or even explosion.
2. What Causes Battery Thermal Runaway?
Electrical Abuse
Overcharge/over-discharge, charger mismatch, BMS protection failure; cell-to-cell consistency degradation in Battery Packs, with individual cells experiencing overcharge that triggers thermal runaway.
Overcharge/over-discharge, charger mismatch, BMS protection failure; cell-to-cell consistency degradation in Battery Packs, with individual cells experiencing overcharge that triggers thermal runaway.
Mechanical Damage
Drops, crush, or puncture causing separator rupture, direct contact between positive and negative electrodes forming an internal short circuit, instantly releasing large amounts of heat.
Thermal Abuse
High-temperature environments, poor heat dissipation, or sustained high-current discharge causing internal heat accumulation that cannot dissipate, triggering SEI film decomposition.
Manufacturing Defects
Metal contamination introduced during production, separator imperfections, leading to latent internal short circuits that gradually develop during use.
3. The Thermal Runaway Process in Lithium Batteries
Self-Heating Stage
The SEI film on the battery anode breaks down. The SEI film decomposes at elevated temperatures, releasing heat and consuming active lithium.
The SEI film on the battery anode breaks down. The SEI film decomposes at elevated temperatures, releasing heat and consuming active lithium.
Runaway Stage
Large-area separator melting occurs, triggering massive internal short circuits; the cathode and electrolyte decompose violently, generating large volumes of gas. The battery swells, and temperature spikes dramatically. Heat conducts to adjacent cells, causing cascading propagation.
Large-area separator melting occurs, triggering massive internal short circuits; the cathode and electrolyte decompose violently, generating large volumes of gas. The battery swells, and temperature spikes dramatically. Heat conducts to adjacent cells, causing cascading propagation.
Termination Stage
Combustion and heat release only cease when all internal reactive materials are fully consumed. Conventional fire extinguishers struggle to suppress the internal chain reaction, providing only external cooling.
Combustion and heat release only cease when all internal reactive materials are fully consumed. Conventional fire extinguishers struggle to suppress the internal chain reaction, providing only external cooling.
4. How to Prevent Lithium-Ion Thermal Runaway?
Product Design Level
1.Select cell materials with good thermal stability, paired with a BMS (Battery Management System) that monitors voltage, current, and temperature in real time, rapidly disconnecting the circuit upon detecting anomalies.
2.Implement effective thermal management and heat dissipation design to maintain battery operating temperature within a reasonable range.
Usage and Maintenance Level
1.Use original manufacturer-matched chargers; eliminate overcharge and never mix with substandard power supplies.
2.Avoid dropping, crushing, or puncturing batteries; keep away from high-temperature heat sources. Discontinue use and isolate immediately upon detecting swelling, abnormal heating, or odor.
3.Conduct regular inspections of battery fleets; promptly retire aged cells with degraded consistency. Do not mix new and old cells.
5. Conclusion
Thermal runaway is triggered by multiple factors—electrical, mechanical, thermal, and manufacturing defects. Through material optimization, intelligent BMS monitoring, and thermal insulation/explosion-proof structural design, incident probability can be significantly reduced.
With advances in materials science, improvements in BMS technology, and optimization of thermal management solutions, lithium battery safety is continuously improving. Adhering to safe charging practices, avoiding extreme operating conditions, and performing regular inspections and maintenance is a responsibility to oneself and others.