Mechanically Robust Thermal Insulation With High Compression Stability for Suppressing Thermal Runaway Propagation in Sodium‐Ion Battery Modules

ABSTRACT Thermal runaway propagation (TRP) in sodium‐ion batteries (SIBs) imposes severe coupled thermo‐mechanical requirements. Herein, a novel thermal insulation material with ultrahigh compressive strength and excellent cyclic compression stability is developed, representing the first demonstration of suppressing TRP in SIB modules using a dedicated thermal insulation material. Flexible silica nanofibers with outstanding thermal stability (−196°C to 1300°C) are first fabricated through electrospinning, showing a low thermal conductivity of 0.0247 W⋅m −1 ⋅K −1 . To further enhance the mechanical performance, thermally induced self‐crosslinking of poly (vinyl alcohol) is introduced, followed by the incorporation of specially modified aerogel particles to further improve the thermal insulation performance. As a result, the composite sustains compressive stresses exceeding 4.7 MPa at 80% strain, corresponding to more than 6.2 × 10 5 times its own weight, while maintaining structural integrity, and shows stable mechanical performance over 1000 compression cycles at 30% strain without obvious degradation. When applied as an interlayer in SIB modules, the insulation material effectively blocks TRP by reducing the heat transfer power from 2306.34 to 119.20 W, corresponding to a 94.83% reduction, and produces a maximum temperature difference of 778.9°C between adjacent batteries. This work establishes a generalizable framework for simultaneously achieving thermal insulation and mechanical robustness in battery safety materials, offering fundamental insights and a scalable pathway toward safer energy storage systems.