A New Class of Phosphates as Co-Solvents for Nonflammable Lithium Ion Batteries Electrolytes

The two new phosphates, DMMEMP and DEMEMP containing ethylene oxide (EO) have been synthesized and used as co-solvents respectively mixed with ethylene carbonate (EC) and dimethyl carbonate (DMC). The flammability of the new ternary electrolytes was examined by measuring the self-extinguishing time of electrolytes. As the content of DMMEMP or DEMEMP in the mixture reaches 30 wt%, no flammability is observed. The electrochemical test results indicate that the ternary electrolytes dissolving 1.0 M lithium bis(trifluoromethanesulfonyl)imide(LiTFSI) have good thermal stabilities, wide electrochemical windows and high conductivities. The Li/LiFePO4 half-cells using the electrolyte show good charge-discharge performances and cycle stabilities.