Beyond the thermal barrier: Coupled effects of insulating materials on runaway propagation and toxic gas emissions in lithium-ion batteries

The increasing prevalence of lithium-ion batteries (LIBs) necessitates effective thermal runaway propagation (TRP) mitigation strategies. This study comparatively evaluated four distinct thermal insulation materials (TIMs): mica plate, SiAG pre-oxidized fiber, aluminosilicate ceramic fiber, and nano SiAG felt in mitigating TRP within ternary LIB modules. An experimental platform induced thermal abuse in one cell to analyze subsequent TRP in adjacent cells. The effectiveness of each TIM was assessed by temperature profiles ( ΔT ), toxic gas emissions (CO, NO 2 , SO 2 ), and structural/thermal stability (SEM, TGA). The findings revealed a significant correlation between effective TRP mitigation and reduced toxic gas emissions. Effective TRP mitigation not only impedes inter-cell heat transfer but also suppresses secondary exothermic reactions in adjacent cells, thereby significantly reducing the generation of toxic gases. Notably, SiAG-based materials with ordered fiber structures demonstrated superior high-temperature stability and a remarkable ability to inhibit TRP, maintaining a maximum temperature difference ( ΔT TIM 1 ) of 578 °C between the triggered cell and the adjacent cell. Variations in toxic gas emission levels and types were closely linked to the thermal decomposition and adsorption characteristics of the applied TIMs. This study concludes that effective TRP mitigation substantially decreases toxic gas emissions, underscoring the critical role of TIM selection for enhanced battery safety. In contrast to mica's good thermal stability but limitations in NO 2 emissions and density, SiAG-based materials, where polar groups likely influence smoke interaction, showcased excellent insulation and structural integrity, exhibiting minimal mass loss (< 3%) at temperatures up to 817.5 °C in TGA tests. This study systematically evaluates the performance of various thermal insulation materials in suppressing thermal runaway propagation in lithium-ion batteries by analyzing their thermal, structural, and application-related properties through comprehensive experimental and analytical methods.