Lithium battery thermal runaway early warning system and method based on cavity ring-down spectroscopy technology

The invention discloses a lithium battery thermal runaway early warning system and method based on a cavity ring-down spectroscopy technology. The system comprises an intermediate infrared quantum cascade laser, an optical isolator, a collimating lens, an optical resonant cavity, a focusing mirror, a photoelectric detector and a main control unit. The quantum cascade laser outputs laser with characteristic gas absorption wavelength, and the laser passes through the optical isolator, is adjusted and coupled by the collimating lens and enters the measuring cavity; after multiple times of reflection, resonance is generated, and a laser beam is output and reaches a photoelectric detector after being focused by a focusing mirror; when the photoelectric detector detects the laser with the set intensity, the main control unit turns off the optical isolator, and the concentration of the detected characteristic gas is calculated by detecting the time interval of the output laser attenuating to the set intensity. The s