We synthesized and investigated (2-chloro-4-methoxy)-phenoxy pentafluorocyclotriphosphazene (2-C1-4-MPPFPP) as a safety additive for lithium-ion batteries. Experimental results demonstrate that the addition of 2-C1-4-MPPEPP into the base electrolyte reduces electrolyte flammability. Moreover, 2-CI-4MPPFPP, which is electro-polymerized at 4.5 V (vs. Li/Li+), is demonstrated to protect LiMn2O4/Li cells from voltage runaway at overcharge. A 5 vol% concentration of 2-C1-4-MPPEPP in the electrolyte was shown to have a negligible effect on the cycling and lower discharge rate performances of LiMn2O4/Li cells. (C) 2017 Elsevier B.V. All rights reserved.