Phosphated cyclic carbonates as flame retardant additives for lithium batteries

Lithium-ion batteries (LIBs) are extensively used in modern electronics due to their high energy and power densities. However, important safety concerns persist due to the flammability of conventional electrolytes such as lithium hexafluorophosphate solution (LiPF 6 ) in ethylene carbonate (EC) and dimethyl carbonate (DMC). In this work, we synthesize molecules bearing a phosphate group and one or two 5-membered cyclic carbonate groups and investigate them as flame-retardant additives in electrolyte for lithium batteries. At 2 wt%, the series of cyclic phosphate additives exhibit promising multifunctional behavior in lithium-ion battery electrolytes. These additives expand the electrochemical stability window and improve initial discharge capacities, while also significantly enhancing flame retardancy. For instance, (2-oxo-1,3-dioxolan-4-yl)methyl diphenyl phosphate increases the initial discharge capacity to 89 mAh g −1 at 1C, although with some reduction in long-term capacity retention. Overall, the molecules demonstrate strong potential as non-flammable electrolyte additives that balance electrochemical performance and thermal safety. Post-cycling surface characterization of the NMC cathode reveals the formation of a more uniform and compact cathode–electrolyte interphase (CEI) compared to conventional organic electrolytes (1 M LiPF 6 in EC/DMC). The CEI is enriched with phosphate- and LiF-containing species and exhibits fewer decomposition products. These findings highlight these compounds as promising candidates for safer LIB formulations, balancing electrochemical performance with enhanced thermal stability. • A series of new phosphated cyclic carbonates were synthesized as additives for batteries electrolytes. • The phosphated cyclic carbonates offered strong flame-retardant performances at low concentrations. • The additives formed a stable LiF-rich cathode–electrolyte interphase and improved high-voltage stability.