The impact of internal wound and stacked structures of lithium-ion batteries on its thermal runaway behavior

• The thermal runaway behaviors in LFP batteries with wound and stacked internal structures are compared. • The internal thermal propagation rates in both battery structures is discussed. • Combustion stability and thermal hazard potential in both battery designs are evaluated by HRR and THR measurements. With the growing application of lithium iron phosphate (LFP) batteries in energy storage systems, their thermal safety has attracted increasing attention. The internal structural configuration of cells, as a critical structural factor, remains insufficiently clarified in terms of its impact on thermal runaway (TR) behavior. In this study, two LFP batteries with identical capacities and electrode materials but distinct internal structures were subjected to external heating to induce TR. A comparative analysis was conducted focusing on TR triggering mechanisms, temperature evolution, voltage response, and heat release characteristics. Results show that the stacked cell exhibits significantly lower TR onset temperature ( T TR ) of 81.7±1.4°C and shorter triggering time ( t TR ) of 642±3 s, indicating weaker thermal stability compared to the wound cell, which shows higher T TR of 104.5±2.4°C and longer t TR of 1336±111 s. Additionally, the internal TR propagation rate of the wound cell reaches 1.19 mm/s, much faster than the 0.29 mm/s observed in the stacked cell. Upon venting, the stacked cell produces intense lateral gas jetting that causes flame detachment and blow-off, preventing sustained combustion and leading to incomplete measurement of heat release rate (HRR) and total heat release (THR). In contrast, the wound cell maintains stable combustion and continuous heat release throughout the TR, reflecting its superior thermal resilience and controllability. These findings elucidate the intrinsic influence of internal cell structure on TR characteristics and provide critical insights for optimizing the balance between energy density and thermal safety in battery design for stationary storage applications.