Stable and Safe Lithium Metal Batteries with Ni-Rich Cathodes Enabled by a High Efficiency Flame Retardant Additive

A novel electrolyte additive−(trifluoroethoxy)pentafluorocyclotriphosphazene (TFPN) is synthesized and tested as flame retardant additives for lithium metal batteries. Flame test reveals that 5 wt% TFPN addition can enable electrolyte non-flammable. Moreover, it is found that TFPN addition could form a LiF-rich solid electrolyte layer (SEI) on lithium metal and suppress the growth of lithium dendrites. With 5 wt% TFPN added electrolyte, the Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811)/Li full cells show a high reversible capacity and a much improved capacity retention. These results suggest that TFPN may be used as a promising multifunctional additive for lithium metal batteries. These findings may also be useful for the design of other nonaqueous batteries.