Atmospheric-pressure preparation of “tremella-like” Al2O3-SiO2 composite aerogel for battery module thermal insulation

Abuse situations such as overheating, overcharging, mechanical damage, and short circuits can lead to thermal runaway of lithium-ion batteries (LIBs). Thermal runaway propagation (TRP) in LIB modules remains a critical safety bottleneck for electric vehicles. Conventional insulation materials often fail to balance high-temperature stability, processability, and cost-effectiveness. Pure SiO₂ aerogels suffer from brittleness and sintering collapse above 600 °C, while high-performance aerogels typically rely on expensive supercritical drying. In this study, using aluminum chloride hexahydrate (AlCl 3 ·6H 2 O) and tetraethyl orthosilicate (TEOS) as raw materials (Al: Si molar ratio = 3:1), we prepared low-density, high-specific-surface-area, and thermally stable monolithic Al₂O₃- SiO₂ composite aerogels (ASA) under ambient pressure drying by optimizing the amount of propylene oxide (PO) gelling aid to 60 ml. This optimization overcomes the long-standing challenge of poor monolithic integrity in atmospheric-pressure dried aerogels while reducing production costs. Another novelty lies in the formation of stable Al-O-Si bonds in ASA, which endow the material with exceptional high-temperature resistance: the ASA maintained a high specific surface area (92.8259 m 2 /g) even after calcination at 1000 °C, far outperforming pure SiO₂ aerogels By introducing aramid fiber felt (AF) and pre-oxidized fiber felt (PF) as mechanical reinforcements, the thermal stability of the composite materials was further enhanced, forming a “nano-micro” interpenetrating structure that synergistically improves mechanical robustness and insulation performance. The thermal conductivity of ASA at 25 °C was 0.0222 W/m·K, while the PF-ASA exhibited a thermal conductivity of 0.0672 W/m·K at 500 °C and retained structural integrity after being exposed to 1200 °C, maintaining effective insulation performance. Additionally, in the thermal insulation application of battery modules, the pre-oxidized fiber insulation group demonstrates the ability to prevent heat spread, with released CO 2 and consumed O 2 reduced by 38.6% and 33.8% respectively, thereby lowering the risk of thermal runaway. The production of advanced thermal insulation materials represents a preferred solution for thermal safety protection in power batteries.