Thermally insulating and fire?retardant bio?mimic structural composites with a negative Poisson's ratio for battery protection

Battery safety has attracted considerable attention worldwide due to the rapid development of wearable electronics and steady increase in production use electric vehicles. As battery failures are often associated with mechanical-thermal coupled behaviors, protective shielding materials excellent mechanical robustness flame-retardant properties highly desired mitigate thermal runaway. However, most insulating not strong enough protect batteries from abuse, which is one critical scenarios catastrophic consequences. Here, inspired by wood, we have developed an effective approach engineer a hierarchical nanocomposite via self-assembly calcium silicate hydrate polyvinyl alcohol polymer chains (referred as CSH wood). The versatile material wood demonstrates unprecedented combination light weight (0.018 g cm?3), high stiffness (204 MPa axial direction), negative Poisson's ratio (?0.15), remarkable toughness (6.67 × 105 J m?3), superior insulation (0.0204 W m?1 K?1 radial fire retardancy (UL94-V0). When applied cover or layer within packages, tough can resist high-impact load block heat diffusion delay spread fire, therefore significantly reducing risk property damage bodily injuries caused explosions. This work provides new pathways for fabricating advanced large scalability great potential protection electronic devices.