Investigation of thermal runaway propagation in NMC lithium-ion battery stacks using composite materials

• Passive materials are a promising direction for preventing thermal runaway. • New combinations of organic and inorganic components were investigated. • Four thermal barriers were tested under identical TR conditions for 12.5Ah and 2.5Ah NMC cells. • The temperature of non-triggered cells was maintained within 78–160°C (12.5 Ah) and 37–103°C (2.5 Ah). . The study evaluated the effectiveness of four thermal barriers: PyroLiq (a mixture of hollow glass spheres and liquid glass), PCM (phase change material), PCCM (composite PCM), and a liquid glass-based composite for suppressing thermal runaway in 12.5 Ah and 2.5 Ah NMC lithium-ion pouch cells. Materials 1–2 cm thick were placed between adjacent cells and tested under identical conditions to evaluate their impact on temperature behaviour, mass loss, and morphology. For 12.5 Ah cells, tests were performed in triplicate. During thermal runaway of the initiating cell (cell A), the maximum surface temperature (T max,A ) was 742 ± 71°C for PyroLiq, 722 ± 228°C for PCCM, and 523 ± 138°C for PCM. Heat transfer to the adjacent cell (B) differed significantly between materials. The maximum surface temperature of cell B (T max,B ) was 78 ± 24°C for PyroLiq, 160 ± 89°C for PCM, and 78 ± 14°C for PCCM. PyroLiq prevented TR transfer and produced the lowest heating in all tests. The composite was tested with 2.5Ah batteries with different material thicknesses (0.5-2 cm). T max,A = 674°C, T max,B was 71°C. The results obtained demonstrate that all materials studied are capable of delaying or suppressing the spread of thermal runaway. A comparison of T max , protection variability, and the post-morphological state of the materials provided quantitative guidelines for selecting inter-cell thermal barriers. These findings could be used to improve the safety of energy storage systems by optimizing the composition and dimensions of passive protection barriers.