Thermal Runaway Propagation in a Prismatic Lithium-Ion Battery Module with Inter-Cell Air Gaps: Large-Scale Compartment Experiments

Characterizing thermal runaway propagation (TRP) within a module and racks of modules is critical for the design of compartment-level safety systems. However, there is a dearth of large-scale experimental data. This study investigated TRP in a 14-cell, 5.5 kWh prismatic nickel–manganese–cobalt oxide module in which 94-Ah cells were not in direct contact with each other. Unlike most TRP tests, in this cell arrangement radiation is the dominant heat transfer process driving TRP. Two types of experiments were conducted: (i) single-cell failure tests in a pressure vessel and open air to estimate the generated vent-gas volume and mass loss of the cells and (ii) whole-module tests performed either on a stand without confinement or in a confined rack with dummy modules. Interior compartment temperature and heat flux data were also obtained to assess TRP-driven compartment-level response. For the single-cell testing, the average vent-gas volume per cell was 238 L at a reference condition of 300 K and 1 atm, and the average mass loss was approximately 0.9 kg during intense venting. For the module tests, although per-cell TR-onset times differed across runs by up to $$\sim$$ 300 s due to variability in the test systems, the total propagation time converged to $$\sim$$ 1000 s in all module tests. The TRP rate accelerated progressively, as an increasing number of failed cells and the module housing fire convectively and radiatively preheated the remaining cells. Complementary diagnostics including temperature, video, acoustic, and gravimetric measurements were employed to enable robust characterization of TRP.