Bio-Inspired Intumescent Nanocomposite Aerogel Liners for Active Fire Suppression and Thermal-Runaway Containment in Structural Battery Modules of Electric Vehicles

Thermal-runaway (TR) propagation is a critical safety bottleneck for high-energy lithium-ion battery packs. In this study, a millimeter-scale intumescent nanocomposite aerogel liner that merges passive super-insulation with active flame suppression and load sharing was presented. The liner is fabricated in two steps: (i) gelation and ambient-pressure drying of a hexamethyl-disilazane (HMDS)-silylated SiO2–boehmite wet gel to yield a crack-free backbone; (ii) vacuum infiltration of a 10 wt % aqueous slurry containing chitosan/phytic-acid–ammonium-polyphosphate (APP) microcapsules (d50 ≈ 3.5 µm), followed by freeze-drying, achieving a 40 wt % capsule loading while retaining 93% open porosity. Characterization confirms structural integrity: FE-SEM shows homogeneous capsule dispersion; XRD displays an amorphous SiO2 halo plus 6 nm γ-AlOOH crystallites; FT-IR identifies Si–CH3 (1272 cm−1) and p=O (1246 cm−1) bands; N2 sorption and helium pycnometry verify the preserved pore network. The liner delivers an in-plane thermal conductivity of 0.026 ± 0.001 W m−1 K−1 at 25°C and 0.040 ± 0.002 W m−1 K−1 at 200°C. TGA-DSC reveals intumescence onset at 225°C, an exotherm at 308°C, and a residual char of 56 ± 2 wt %. Under cone calorimetry (35 kW m−2), the liner cuts the peak heat-release rate (PHRR) by 73% (95 ± 10 vs. 350 ± 20 kW m−2), more than doubles time-to-ignition (14 ± 2 s), and expands 3.9 ± 0.2×, achieving a UL-94 V-0 rating. Compressive modulus was found to be 1.45 ± 0.10 MPa at 23°C and 1.02 ± 0.07 MPa at 200°C, surpassing the 0.5 MPa threshold for shear-transfer panels. In a nail-penetration test of a four-cell 21,700 module, the liner limited neighboring-cell temperature to <130°C, whereas an unprotected module surpassed 650°C and ignited within 50 s. Adding <4 kg to a 70 kWh pack and containing no halogens, this capsule-loaded silica/boehmite aerogel offers a scalable, roll-to-roll route to lightweight, regulation-compliant TR barriers.