Research review discusses flame retardants for electrolytes in current and possible future battery technologies. Current lithium ion battery technologies use liquid organic electrolytes, which are flammable and can react with cathodes, as well as polymer separator membranes. PIN flame retardants can improve fire safety. Various phosphorus (e.g. PBMP, ADP = AlPi, DMMP, TMP, TEP, vinyl benzyl phosphonates, …), nitrogen (e.g. PBI, adiponitrile), nitrogen-phosphorus (e.g. HT) and inorganic PIN FRs are discussed, and also fluorinated phosphorus FRs (e.g. TFEP, fluorinated cyclic phosphates) because current electrolytes are generally organo-fluoride based). Auxiliary solvents can be used to avoid reactions between the graphite anode and phosphorus FRs in the electrolyte (e.g. vinylene carbonate VC or fluoroethylene carbonate FEC). PIN compounds are also being researched to produce flame retardant solid electrolytes.
PBMP = poly(bis(4-phenoxyl)propane methylphosphonate)
ADP = AlPi = aluminium (Al) diethyl hypophosphite
DMMP = dimethyl methyl phosphonate
TMP = trimethyl phosphate
TEP = triethyl phosphate
TFEP = tris(2,2,2-trifluoromethyl) phosphate
PBI = polybenzimidazole
HT = hexaphenoxycyclotriphosphazene
“Glory of Fire Retardants in Li-Ion Batteries: Could They Be Intrinsically Safer?”, R. Mishra et al., Adv. Sustainable Syst. 2024, 2400273 https://doi.org/110.1002/adsu.202400273