Bis(2,2,2-trifluoroethyl) methylphosphonate: An Novel Flame-retardant Additive for Safe Lithium-ion Battery

• PFMP was synthesized as a flame-retardant additive.
• The SET value of the electrolyte containing 20% TFMP shows the reduction of 86%.
• The 20% TFMP electrolyte exhibits excellent electrochemical compatibility on the anode and cathode.

A novel fluorinated alkyl phosphonate - bis(2,2,2-trifluoroethyl) methylphosphonate (TFMP) were synthesized as flame retardant to reduce the flammability of the electrolyte with minimal impact on the electrochemical performance of the electrode. The flammability and electrochemical properties of TFMP with various contents were evaluated using self-extinguishing time (SET), conductivity test, cyclic voltammetry (CV) and glavanostatic charge and discharge test. The experimental results demonstrated that the addition of 20 vol% TFMP can make the electrolyte be hardly flammable, exhibiting high-efficiency flame retardant. Moreover, the 20 vol% TFMP-containing electrolyte also exhibited insignificant influence on graphite anode with high initial capacity of 346 mAh g−1 and excellent capacity retention of 93% over 100 cycles. For LiFePO4 cathode, the excellent electrochemical performance was observed including gradually increasing reversible capacity from 128 to 139 mAh g−1 over 100 cycles in the 20 vol% TFMP-containing electrolyte. The results imply that TFMP is a promising option as highly flame-retardant and electrochemically compatible electrolyte additive for safe lithium-ion batteries.

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