Dimethyl methylphosphonate (DMMP) was used as a flame retardant additive to I M LiPF6/EC + DEC system. The flammability, electrochemical stability and cycling performance of electrolyte containing DMMP were studied. The addition of DNMP to electrolytes provides a significant suppression in the flammability of the electrolyte concluded from the measurements of self-extinguish time and limited oxygen index. The totally nonflammable electrolytes can be achieved with only 10 wt.% DMMP addition-the highly efficient retardant additive. The addition of DMMP causes little damage on the cell electrochemical performance. DMMP is a promising flame retardant additive to improve the safety of lithium-ion batteries. (C) 2007 Elsevier B.V. All rights reserved.