As the world transitions towards a circular economy, the increasing demand for lithium-ion batteries (LiBs) for portable devices and electric vehicles has led to a growing volume of spent LiBs that require sustainable recycling methods. Recycling of spent and discarded LiBs may include a thermal pre-treatment step, which has proven to enhance the recovery of present valuable metals. The thermal pre-treatment of spent LiBs materials such as black mass involves subjecting the material to a controlled heating within a specified temperature range for a particular time. However, during the thermal pre-treatment gases are released due to oxidation and decomposition of components in LiBs blackmass, such as the electrolyte (LiPF6) and the binder, polyvinylidene fluoride (PVDF), which pose considerable safety issues throughout the recycling process. These issues are specifically related to emissions of hydrofluoric acid and other fluorine containing compounds, and previous studies have addressed this by lowering the decomposition temperatures and selecting the reaction medium to allow controlled decomposition of PVDF and LiPF6. However, the overall results show that it is only possible to eliminate emissions fluorine containing compounds to a limited extent. This study, therefore, aims to investigate the fluorine behaviour during thermal pre-treatment of LiBs black mass and provide insights into the effective management of fluorine evaporation during the recycling process. The black mass from spent batteries, synthetic black mass, LiPF6, and PVDF samples were individually heated to 600 °C in a thermogravimetric analyser (TGA) at a rate of 10 °C/min in an inert atmosphere of nitrogen. The gases released during the thermal treatment were analysed using a quadrupole mass spectrometer (QMS). The results indicated that PVDF is decomposed releasing HF and hydrocarbons and losing 56.6 wt.% of its mass. LiPF6 decomposed mostly at temperatures over 350 °C, losing 81.2 wt.% of its mass forming gaseous products of which LiF and PF5 was indicated by the QMS analysis. Synthetic black mass released similar gases as actual black mass, losing 3.25 wt.% of its mass. The results provide insight into the thermal behaviors of PVDF and LiPF6 during pre-treatment, offering a clear understanding of fluorine behavior during the recycling of LiBs black mass.