The sealing of the battery pack, the core component of H&EVs, is crucial to the safety and operating stability of the battery system and directly impacts the safety of the whole vehicle. The output voltage of the battery pack in EVs can be as high as 300V or more. A well-sealed battery housing can eliminate the risk of water-induced short-circuiting and spontaneous combustion caused by dust ingress. When properly sealed, the battery pack will not suffer from damaged parts and decreased electric capacity resulting from the leakage of liquid from the safety valve or junction. Therefore, H&EV OEMs and battery manufacturers need to make a rigorous selection of sealing materials for battery packs to meet regulations and consumer requirements for safety and performance.