Hydrogen fluoride emissions from lithium-ion batteries during induced thermal runaway via in situ laser spectroscopy

Improved understanding of hydrogen fluoride (HF) emissions from lithium-ion battery fires, including the temporal dynamics, is needed to optimize fire response and protection. Due to the high polarity of HF and its associated surface adsorption and reactivity, most traditional sensing methods are prone to error and slow response due to issues with sampling or surface interactions. To address these limitations, an in situ tunable diode laser absorption spectrometer is developed to achieve real-time measurements of HF emissions during dynamic battery fires with a temporal resolution of milliseconds, and with detection limits of single parts per million along with several orders of magnitude of dynamic range. The laser spectrometer is used in situ to perform measurements near the fire source so that the fire dynamics and the transient behavior of HF emissions can be more accurately characterized. Thermal runaway and fire/explosion conditions of model 18650 lithium-ion batteries are simulated in a conical radiative heater, and HF measurements are performed online via an optical access port in the effluent exhaust. By varying the radiative heating flux of the conical heater and the initial state of charge of the batteries, different characteristics of the safety venting and thermal runaway behavior of lithium-ion batteries and the corresponding emissions of toxic HF gas are measured. These findings provide valuable insights into the dynamics of lithium-ion battery fires and will aid in the development of strategies to mitigate their associated risks.