Magnetically triggered heat release from hydrate salt composite microchannels for low-temperature battery thermal management

While active thermal managements for Li-ion battery (LIB) consume a large amount of energy, passive one based on phase change material (PCM) fails to release thermal energy for heating as required. Thus, intelligent heat storage and release is urgently needed for utilizing PCM as passive thermal management. Herein, porous boron nitride/polyvinyl alcohol (BN/PVA) skeleton with highly ordered microchannels was fabricated to impregnate hydrate salt sodium acetate trihydrate (SAT) solution forming shape-stable SAT@BN/PVA composite with efficient thermal energy storage performance. Disturbance from magnetic trigger in the hydrate salt composite microchannels promotes nucleation and solidification, thus initiates heat release as required and remotely. Meanwhile, anisotropic heat transfer from the highly ordered microchannels can effectively enhance heat release velocity and efficiency. The magnetic triggered process is studied theoretically and experimentally, and optimized to release heat in 25 s with efficiency up to 99%. Consequently, heat release can improve temperature by 10 °C when battery pack stops working at −20 °C and enhance discharge capacity by 75% during cold-start. This research provides a new method for intelligent thermal management of LIB working in cold environment.