Volume 4, Issue 9, 20 September 2023, 101542 Lithium-ion battery safety evaluation covers a broad spectrum of abuse conditions. One of the popular testing methodologies is nail penetration. However, the reproducibility of nail penetration tests is rather poor, which compromises the credibility of the results.
Nail penetration is one important mode of catastrophic failure in Li-ion batteries, and the contact resistance between a nail and electrodes is a dominant factor for heat generation. Surprisingly, previous studies always assume uniform resistance and there is no experimental measurement of contact resistance, to the best of our knowledge.
Nail tests are performed on Li-ion batteries with different nails to obtain the contact resistance–contact area curve. The curve can significantly facilitate the process of calculating an accurate localized joule heat with knowing the battery thickness and nail diameter.
It is also observed that the battery internal resistance and the nail diameter have significant influences on the thermal behaviors of Li-ion batteries during nail penetrations. In penetrations with a specific nail size, lower internal resistances will cause stronger thermal responses.
In penetrations with a specific nail size, lower internal resistances will cause stronger thermal responses. In comparison, penetration of high resistance battery with thick nails can shift the accumulated boundary heat generation to a uniform battery heat generation, which benefits the battery safety.
Nail tests were also carried out on the 0.65 Ah batteries in order to provide a check of the accuracy of the coupling model. Prior to the tests, the batteries were preconditioned under a constant current of 0.065 A between 3 V and 4.2 V for 5 cycles with finishing at charged state.