An Experimental Study on the Thermal Runaway Characteristics of Single and Multiple Lithium-Ion Cells

This study experimentally investigated thermal runaway in NCA-type 18650 lithium-ion cells under single- and multiple-cell configurations. In single-cell tests, thermal runaway began at an average surface temperature of 186.9 ℃, with a maximum heat release rate (HRR) of 7.6 ± 0.8 kW, showing high reproducibility. In multiple-cell tests, the onset temperatures of the 2nd and 3rd cells rose to 207.8 ℃ and 211.9 ℃, influenced by thermal contact and heating rate, with propagation times of 54.7 s and 87.0 s. HRR data showed three distinct peaks during propagation, indicating that multiple-cell behavior cannot be explained by simply summing single-cell results. The severity of thermal runaway was strongly affected by venting duration and heating rate.