Aircraft Battery Systems having Heat Activated Thermal Barriers

A battery system includes a plurality of battery modules each formed from a plurality of battery cells. A shared cooling structure is thermally coupled to each of the battery modules. The shared cooling structure is configured to conduct heat relative to the battery modules. A thermal interface is disposed between the battery cells of each battery module and the shared cooling structure. Each thermal interface is configured to transition from a first thermal conductivity state to a second thermal conductivity state when heat generated by the respective battery cells exceeds a threshold level. The second thermal conductivity state is lower than the first thermal conductivity state such that after one of the thermal interfaces has transitioned from the first thermal conductivity state to the second thermal conductivity state, heat transfer from the respective battery cells to the shared cooling structure is reduced.