Thermal-Switchable, Trifunctional Ceramic–Hydrogel Nanocomposites Enable Full-Lifecycle Security in Practical Battery Systems

Thermal runaway (TR) failures of large-format lithium-ion battery systems related to fires and explosions have become a growing concern. Here, we design a smart ceramic–hydrogel nanocomposite that provides integrated thermal management, cooling, and fire insulation functionalities and enables full-lifecycle security. The glass–ceramic nanobelt sponges exhibit high mechanical flexibility with 80% reversible compressibility and high fatigue resistance, which can firmly couple with the polymer–nanoparticle hydrogels and form thermal-switchable nanocomposites. In the operating mode, the high enthalpy of the nanocomposites enables efficient thermal management, thereby preventing local temperature spikes and overheating under extremely fast charging conditions. In the case of mechanical or thermal abuse, the stored water can be immediately released, leaving behind a highly flexible ceramic matrix with low thermal conductivity (42 mW m–1 K–1 at 200 °C) and high-temperature resistance (up to 1300 °C), thus effectively cooling the TR battery and alleviating the devastating TR propagation. The versatility, self-adaptivity, environmental friendliness, and manufacturing scalability make this material highly attractive for practical safety assurance applications.