Abstract: The high-temperature ejecta generated by thermal runaway in aviation lithium batteries can cause the failure of the battery pack’s top structure, leading to the rapid spread of flames to surrounding equipment, which poses a significant safety hazard to aircraft. This study investigates the impact of thermal runaway on the battery pack’s top plate under different states of charge (SOC) using a self-constructed battery thermal shock containment platform. Specifically, the study focuses on the high-temperature and shock effects on the battery pack top plate. It further compares and analyzes the protective effects of organic and inorganic fire-retardant coatings against thermal shock damage and the lightweighting effects of coating application on the battery pack’s structural design. The experimental results show that, under 100% SOC conditions, a 1.0 mm thick aluminum plate develops perforations when subjected to thermal runaway-induced shock, while a 1.5 mm thick aluminum plate remains intact and effectively contained. When 1 mm thick battery pack top plates were coated with 0.5 mm thick organic coatings (E85S15B3, E80S20) and an inorganic coating (APB3), the coated plates maintained their structural integrity under thermal runaway shock, with peak surface temperatures reduced by 93.8%, 90.7%, and 90.0%, respectively, compared to uncoated samples. Additionally, a 1 mm thick top plate with a 0.5 mm thick E85S15B3 coating exhibited similar protection against high-temperature damage as a 3 mm thick uncoated top plate, while reducing the weight by 62.95%, effectively achieving lightweighting.These results demonstrate that fire-retardant coatings significantly enhance the safety of battery packs by improving thermal runaway tolerance and reducing the risk of fire spread. Moreover, they offer a practical solution for the lightweight design of battery packs. Both organic and inorganic coatings show excellent thermal protection performance, underscoring the potential of fire-retardant coatings in improving the safety of aviation lithium batteries. This study provides valuable insights into the development of safety protection technologies for lithium batteries, particularly in high-performance applications such as electric aircraft, emphasizing the importance of considering thermal protection and structural integrity in these systems.