An open-access published in Nature Communications reports that the use of a novel sub-class of per- and polyfluoroalkyl substances (PFAS) in lithium-ion batteries is a growing source of pollution in air and water. Testing by the research team further found these PFAS, called bis-perfluoroalkyl sulfonimides (bis-FASIs), demonstrate environmental persistence and ecotoxicity comparable to older notorious compounds like perfluorooctanoic acid (PFOA).

Per and polyfluoroalkyl substances (PFAS) are anthropogenic compounds that have been used in numerous consumer and industrial products and processes, including non-stick coatings, industrial surfactants, and aqueous film-forming foams (AFFF). … Literature and patents also document use of PFAS as electrolytes in rechargeable, lithium (Li)-ion batteries (LiBs).

LiB electrolytes must be conductive and electrochemically stable, with low volatility and flammability. Ionic liquids, including the Li⁺ salt of bis(trifluoromethylsulfonyl)imide (bis-FMeSI, CAS 90076-65-6), are used as a primary or secondary LiB electrolyte. The Li salt of bis-FMeSI is also incorporated as an anti-static agent in polyvinylidene fluoride (PVDF) composites which are used in LiBs as electrode binders and as part of the separator between the cathode and anode. Companies that hold patents for and/or advertise production or use of bis-perfluoroalkyl sulfonimide (bis-FASI) salts including bis-FMeSI and its longer-chain homologs (e.g., bis(pentafluoroethylsulfonyl)imide; bis-FEtSI) for use as an electrolyte or polymer additive include 3M, Solvay, and Arkema. Guelfo et al.

Our results reveal a dilemma associated with manufacturing, disposal, and recycling of clean energy infrastructure. Slashing carbon dioxide emissions with innovations like electric cars is critical, but it shouldn't come with the side effect of increasing PFAS pollution. We need to facilitate technologies, manufacturing controls and recycling solutions that can fight the climate crisis without releasing highly recalcitrant pollutants.

—Jennifer Guelfo, first author

The researchers sampled air, water, snow, soil and sediment near manufacturing plants in Minnesota, Kentucky, Belgium and France. The bis-FASI concentrations in these samples were commonly at very high levels. Data also suggested air emissions of bis-FASIs may facilitate long-range transport, meaning areas far from manufacturing sites may be affected as well. Analysis of several municipal landfills in the southeastern US indicated these compounds can also enter the environment through disposal of products, including lithium-ion batteries.

Toxicity testing demonstrated concentrations of bis-FASIs similar to those found at the sampling sites can change behavior and fundamental energy metabolic processes of aquatic organisms. Bis-FASI toxicity has not yet been studied in humans, though other, more well-studied PFAS are linked to cancer, infertility and other serious health harms.

Treatability testing showed bis-FASIs did not break down during oxidation, which has also been observed for other PFAS. However, data showed concentrations of bis-FASIs in water could be reduced using granular activated carbon and ion exchange, methods already used to remove PFAS from drinking water.

These results illustrate that treatment approaches designed for PFOA and PFOS (perfluorooctanesulfonic acid) can also remove bis-FASIs. Use of these approaches is likely to increase as treatment facilities are upgraded to comply with newly enacted EPA Maximum Contaminant Levels for PFAS.

—Lee Ferguson, co-author

Resources

• Guelfo, J.L., Ferguson, P.L., Beck, J. et al. Lithium-ion battery components are at the nexus of sustainable energy and environmental release of per- and polyfluoroalkyl substances. Nat Commun 15, 5548 (2024). doi: 10.1038/s41467-024-49753-5