Fluorinated Lithium Salts: A Significant Class of Environmental Pollutants of Emerging Concern from Spent Lithium-Ion Battery Recycling

Fluorinated lithium (Li) salts are essential constituents of Li-ion battery (LIB) electrolytes, yet their environmental emissions during the rapidly expanding recycling of retired LIBs remain unexplored. Herein, we established a targeted screening list of 11 commonly used fluorinated Li salts and reported their first identification in dust and recycled black mass (BM; a powder-like primary form of crushed spent LIBs after pyrolysis) from a typical spent LIB recycling plant in China. Nine and seven fluorinated Li salts were detected in the dust and BM samples, respectively, with lithium hexafluorophosphate as the dominant compound, followed by lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide. Total concentrations of fluorinated Li salts (∑F-Li salts) exhibited high levels ranging from 581 to 47,500 ng/g (median: 12,100 ng/g) in ambient dust, with significantly higher levels in LIB dismantling areas than in nondismantling areas. By contrast, ∑F-Li salts in BM samples were much lower (<LOD-1800 ng/g; median: 17.8 ng/g), indicating that fugitive emissions to the environment or the transformation/decomposition of fluorinated Li salts occurred during high-temperature pyrolysis. Our findings demonstrate that spent LIB recycling contributes to substantial emissions of fluorinated Li salts into the surrounding environment, highlighting the need for further evaluation of their environmental impacts.