Flame retardant(FR) properties were investigated with tricredyl phosphate(TCP) and tris(pentafluorophenyl)phosphine(TFPP) as additives for lithium-ion batteries. Thermal stability was improved with additives in $Li/LiNifrac{1}{3}Mnfrac{1}{3}Cofrac{1}{3}O_2$ cells comparing to non-additive electrolytes. Oxygen evolution reaction of the cathode material was delayed to up $55^{circ}C$, from $275^{circ}C;to;330^{circ}C$. Electrolytes with the 1 wt.% additives provided good FR properties while the resonable battery performance is maintained.