An battery cell, a battery cell hazard detection system, and a method for detecting a hazardous battery condition at an early stage is provided. An example battery cell may include a battery cell package defining an interior compartment of the battery cell. The battery cell may further include an anode disposed in the interior compartment of the battery cell, a cathode disposed in the interior compartment of the battery cell, and a separator positioned between the anode and the cathode. A chemical coating may be disposed on the surface of the separator, such that, in an instance in which an interior temperature within the interior compartment of the battery cell exceeds a pre-determined maximum operating temperature, the chemical coating may evaporate, forming a chemical coating vapor indicating to a sensing device the hazardous condition of the battery cell.