Thermal Runaway in Lithium-ion battery: 12 stages of event
Understanding the Thermal Runaway stages is essential for creating a theoretical model and testing it during lithium ion battery development. 12 steps of thermal runaway are described comprehensively by Manh-Kien Tran et. al. in their technical paper, ‘A Review of Lithium-Ion Battery Thermal Runaway Modeling and Diagnosis Approaches’.
1. Metal Ion Dissolution
The first sign of trouble is often the dissolution of metal ions, which lasts until around 90°C. Heat disrupts the stable crystal structure of the cathode materials, causing metal ions to migrate into the electrolyte.
2. Solid Electrolyte Interface (SEI) Film Decomposition
Around the 90–180 °C mark, the SEI layer starts to decompose, releasing more heat and causing further dissolution of metal ions. The SEI is a passive film on the surface of the anode formed during the initial charging cycles and plays a crucial role in stabilizing the battery’s operation.
3. Reaction between the Lithium and Electrolyte
The lithiated carbon (anode material) starts to react with the electrolyte. This reaction is exothermic and releases heat, further accelerating the temperature rise and triggering a chain reaction of degradation processes.
4. Separator Melting
Around 130–225°C, the separator, a critical component preventing contact between the anode and cathode, starts to melt.
5. Micro Inner Short Circuit
Small internal short circuits may form as the cathode and anode come into direct contact, causing a further temperature rise.
6. Safety Venting
As the internal pressure rises due to gas formation from electrolyte decomposition, the safety vent opens, typically between 160–280°C, to slow the runaway process.
7. Separator Break Up
The separator may completely break up at around 160–250°C which leads to large-scale internal short circuits within the battery, causing a rapid surge in temperature.
8. Large Scale Inner Short Circuit
The large-scale inner short circuit results in a massive release of energy, accelerating the temperature rise and leading to the decomposition of the cathode material and electrolyte, usually at temperatures above 200°C.
9. Cathode Material Decomposition
At temp. above 200°C, cathode materials start to decompose, releasing oxygen, which reacts with the organic electrolyte, leading to combustion if the temperature is high enough.
10. Electrolyte Decomposition
Beyond the 200–230°C range, the electrolyte begins to decompose, releasing gases that can increase the internal pressure.
11. Reaction of Graphite Anode with Binder
At extremely high temperatures, the graphite anode can react with the binder material (which holds the active material onto the current collector), further increasing the temperature.
12. Combustion of Electrolyte
Finally, the volatile gases from the electrolyte can ignite, resulting in combustion, which is a catastrophic stage of thermal runaway, with temperatures often exceeding 300°C.
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