Phosphorus FRs for battery electrolytes

Review underlines benefits and potential of phosphorus-based FRs to improve fire safety of organic battery electrolytes. Organic electrolytes offer high ionic conductivity and electrochemical stability making them a key component of batteries, in particular for e-mobility and energy storage. They are however flammable. Fluorine-based FRs used in electrolytes today increase battery fire toxicity and require high concentrations, with both cost and battery performance impacts.  This review summarises around 150 studies of phosphorus-based FRs tested in battery electrolytes, concluding that they can offer reduced toxicity, lower smoke, and electrical and thermal stability. Phosphate, phosphonate, phosphinate, phosphine oxide, cyclophosphazenes, and P(3+) / phosphite based compounds are considered. The review concludes that studies are carried out in different types of batteries with different test parameters measured making comparison of results difficult, that FRs must be adapted to specific battery electrolyte and electrode chemical compositions and that phosphorus FRs for electrolytes offer potential for development to improve battery fire safety.

“Phosphorus-Based Flame-Retardant Electrolytes for Lithium Batteries”, J-H. Kim et al., Adv. Energy Mater. 2025, 15, 2500587, DOI: https://doi.org/10.1002/aenm.202500587