A thermal battery works by using an inactive, solid electrolyte that becomes conductive only when heated to its operating temperature, typically through an internal pyrotechnic heat source.
Here's a breakdown of the process:
-
Inactive State: At room temperature, the electrolyte is non-conductive, preventing any electrochemical reactions. This gives the battery a very long shelf life.
-
Activation: An electrical pulse is sent to a squib, which ignites a pyrotechnic heat source, often containing heat pellets. This heat source is strategically located within the battery cell.
-
Electrolyte Melting: The heat generated by the pyrotechnic source melts the solid electrolyte. Once molten, the electrolyte becomes highly conductive, allowing ions to flow freely between the electrodes.
-
Electrochemical Reaction: With the electrolyte now conductive, the electrochemical reaction between the anode and cathode begins, generating electricity. The battery provides power until the electrolyte cools down and solidifies again, or until the reactants are consumed.
-
Heat Train: The "heat train" is a critical part of the activation process. It is composed of center-hole and side heat strips that facilitate the rapid and even distribution of heat throughout the battery cells, ensuring uniform activation.
In summary, a thermal battery remains inactive until heat is applied to melt its solid electrolyte, initiating an electrochemical reaction and providing power.
