Analysis of Trigger Methods for Controlled Initiation of Thermal Runaways in Lithium-Ion Cells

Mathes J, Angerpointner L, Ringel L, Lehner S (2026)

Publication Language: English

Publication Type: Conference contribution, Abstract of a poster

Publication year: 2026

Event location: Münster DE

Abstract

This study examines the impact of different trigger methods (thermal, mechanical, and electrical) on the thermal runaway behavior of INR21700-50E lithium-ion cells. Experiments demonstrate that the trigger method significantly impacts the reaction pathway and the overall intensity of thermal runaway.

Thermal triggering is characterized by an initial phase of electrolyte evaporation, followed by hot particle ejection. In contrast, nail penetration results in an immediate release of sparks and soot; hot particle emission governs the venting behavior throughout this process. Electrical triggering, limited by internal safety devices such as the current interrupt device (CID), produces weak thermal runaway with minimal gas release, occurring only under specific overcharge conditions.

Thermal triggering experiments reveal a strong dependence on the applied heating rate. Low heating power (~0.5 W/cm²) results in less intense thermal runaway, leading to longer durations (~3.8 s), moderate mass loss (~54 %), and high surface temperatures (up to ~745 °C). High heating power (~1.5 W/cm²) produces a highly intense and rapid event with a very short duration (less than 0.1 s), significant mass ejection (~84 %), and lower peak temperatures (~433 °C). The voltage drop duration decreases drastically from approximately 625 seconds with low heating power to approximately 90 seconds with high heating power. This is accompanied by the ejection of both cell caps.

Mechanical triggering through nail penetration induces a medium-intensity thermal runaway event with moderate mass loss (~50 %) and extremely high cell surface temperatures (~787 °C). The voltage drop occurs almost instantaneously (within ~2 seconds), reflecting the immediate sequence of CID and vent activation. The temperature rise rate is two to three times higher than with thermal triggering. Variations in nail diameter have only a minor effect. No cell caps were expelled in any nail penetration scenario.

Electrical triggering via overcharge produces a significantly weaker reaction due to the CID. At moderate current levels, it leads to mild thermal runaway with low gas evolution and minimal mass loss (~2 %). However, if the cell is overcharged at high currents (> 4 C), the cell vent does not open, and no gas is released. Accordingly, the maximum temperature remains significantly lower, at approximately 87 °C, compared to 139 °C at moderate current levels. After overcharging with a high current, there is no visible external damage to the cell. With moderate current, only slight electrolyte leakage and a raised insulating ring occur after venting, and no further mechanical damage results.

Authors with CRIS profile

Jonas Mathes Lehrstuhl für Elektrochemische und Elektrische Energietechnologien Susanne Lehner Lehrstuhl für Elektrochemische und Elektrische Energietechnologien

How to cite

APA:

Mathes, J., Angerpointner, L., Ringel, L., & Lehner, S. (2026, April). Analysis of Trigger Methods for Controlled Initiation of Thermal Runaways in Lithium-Ion Cells. Poster presentation at Advanced Battery Power, Münster, DE.

MLA:

Mathes, Jonas, et al. "Analysis of Trigger Methods for Controlled Initiation of Thermal Runaways in Lithium-Ion Cells." Presented at Advanced Battery Power, Münster 2026.

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