Thermal runaway propagation and suppression in power Lithium-ion battery modules: an experimental comparison of module connectivity and thermal barriers

Thermal runaway propagation (TRP) in lithium-ion battery modules depends on cell chemistry, geometry, thermal boundary conditions, and intercell transport paths. This exploratory study compared an electrically connected 4-parallel/2-series (4P × 2S) module with a geometrically similar module without electrical connection (NEC) under open natural-convection conditions. Cell 2 was heated with a nominal 200 W silicone-rubber heater. Cell-surface temperatures, visible event sequences, and local multigas-sensor responses were recorded, and 3 mm silica aerogel felt (AF), microcellular polypropylene foam (MPP), and flexible flame-retardant phase change material (PCM) barriers were screened. In the representative records, the connected module developed module-wide TR within 5–6 s after Cell 2 entered TR, whereas the NEC module showed localized and delayed events. The layouts differed simultaneously in electrical continuity and nickel-strip conduction; therefore, the comparison indicates an architectural association and does not isolate Joule heating. In the equal-thickness tests, the PCM conditions produced the lowest surrounding-cell maxima (69.3–76.5 °C), and Cell 2 vented without subsequent observed ignition. The open-plume gas sensor detected early C₂H₄/H₂ responses near 38 s and broader multichannel changes near 200 s, but mixed units and uncontrolled dilution precluded quantitative composition or flammability analysis. Because heater electrical histories, matched strip controls, calibrated gas collection, barrier mass/enthalpy, and run-level replication were unavailable, causal heat partition and statistical material ranking are not claimed. The results show that module architecture and intercell barriers affect the observed propagation response under the tested conditions.