Enhancing thermal safety of lithium-ion battery modules via optimized insulation layout and advanced composite phase change material

The thermal safety of lithium-ion batteries (LIBs) remains an unresolved challenge. In this study, a series of thermal runaway propagation (TRP) tests were conducted on ternary LIBs. Aerogel layers were inserted between each battery or every two batteries to construct individual insulation module (IIM) and spacer insulation module (SIM), respectively. In the IIM, 2 mm and 3 mm aerogel layers only delayed TRP, while 4 mm aerogel confined TR to the second battery, with the third battery reaching peak front and back temperatures of 194.1 °C and 130.2 °C, respectively. When configured as the SIM, protection improved further: under 4 mm aerogel, the protected battery's peak temperatures decreased to 199.5 °C and 107.7 °C, respectively. Energy-flow analysis revealed that insulation layout optimization enhanced safety far more effectively than increasing thickness. A variable thermal conductivity composite phase change material (VTPCM) was also developed, exhibiting a high latent heat of 1227 J·g -1 . Its thermal conductivity reached 1.96 W·m -1 ·K -1 at room temperature but dropped to 0.0387 W·m -1 ·K -1 at elevated temperature, yielding a switching ratio of 50.6. TRP test demonstrated that 3 mm VTPCM completely blocked TRP, limiting the protected battery's peak temperatures to 183 °C and 76.6 °C, respectively, while reducing the heat transfer power from 3839.38 W to 68.26 W, achieving a 98.2% reduction. This study provides a solid theoretical foundation and practical pathway to alleviate the spatial conflict between insulation materials and battery energy density, and to reconcile the functional contradiction between thermal management and thermal insulation.