Safe or Slow? The Illusion of Thermal Stability Under Reduced-Velocity Nail Intrusion

TL;DR

This paper explores how the speed of nail penetration affects the thermal stability of lithium-ion pouch cells, revealing that slower speeds do not cause thermal runaway but lead to self-discharge, impacting safety testing protocols.

Contribution

It demonstrates that nail penetration speed influences thermal runaway onset, offering new insights for safer battery design and testing procedures.

Findings

Lower speeds do not induce thermal runaway

Cells exhibit self-discharge with embedded nails

Penetration speed is critical for safety assessments

Abstract

This study investigates the effects of nail penetration speed on the safety outcomes of large-format automotive lithium-ion pouch cells. Through six controlled tests varying the speed of nail insertion, we observed that lower penetration speeds did not induce thermal runaway; instead, the cells exhibited self-discharge while the nail remained embedded. These findings suggest that penetration speed is a critical factor in the onset of thermal runaway, providing valuable insights for the development of safer battery systems and more effective safety testing protocols.