Insights Into Thermal Runaway of Li-Ion Cells by Accelerating Rate Calorimetry Coupled with External Sensors and Online Gas Analysis

Besides high energy density, fast-charging capability, and costs, safety of Li-ion batteries is fundamentally important - even after long-term usage or abusive conditions. In this paper, a new combination of accelerating rate calorimetry (ARC) coupled with a mass spectrometer (MS), as well as cell resistance and audio recording was applied to study commercial 18650-type Li-ion cells. This novel ARC-MS setup allows following the electrochemical and thermal behavior simultaneously to the evolved gases during cell venting and thermal runaway. The tested cells were (i) unaged, (ii) aged by low temperature cycling (main mechanism: Li deposition), as well as (iii) overcharged. The aged and the overcharged cells show an early onset-of-self-heating at 36 degrees C whereas the self-heating started at 96 degrees C for the unaged cells. The rank of the time until explosion of the cells is in the order of overcharged cell

Automated summary

This paper explores the safety of Li-ion batteries by studying the behavior of aged and overcharged cells, finding that they exhibit early onset of self-heating compared to unaged cells. The novel ARC-MS setup used in the study allows for tracking both electrochemical and thermal behavior simultaneously.