Two-level energy storage semi-interpenetrating hydrated salt gel for battery cooling and thermal runaway propagation mitigation

Hydrated salts hold great potential for battery thermal management due to their unique two-level energy storage behavior and inherent flame retardancy. However, their practical application is hampered by issues of supercooling and phase separation, which degrade thermal energy storage performance. Polymer gels, recognized for their excellent water retention and stability, present a promising solution to mitigate these problems. Their three-dimensional network also provides abundant nucleation sites, effectively suppressing supercooling. In this work, we developed a semi-interpenetrating network hydrated salt gel (SCD HSG). This gel not only improves phase change enthalpy efficiency but also exhibits two-level energy storage, covering two critical thermal management windows for lithium-ion batteries: a phase change enthalpy of 199.6 J/g for managing operational temperature rise, and a thermal decomposition enthalpy of 1954.1 J/g for the early high-temperature stage of thermal runaway, enabling safety management over a wide temperature range. Comparative analysis identified the optimal SCD HSG formulation, which exhibits negligible supercooling, only a 3.6% enthalpy loss after 50 thermal cycles, along with excellent shape stability, flexibility, and flame retardancy. Battery cooling tests showed that under 1.5C discharge (peak temperature 58.8 °C), the material's solid-liquid phase change maintained the battery temperature around 42.6 °C, demonstrating outstanding cooling capability and cycling stability. During thermal runaway, the material utilized its high endothermic reaction heat to suppress adjacent cell temperatures below 170 °C, preventing thermal propagation. The superior performance of SCD HSG offers a novel strategy for passive thermal management in energy storage systems.