A Novel Phosphate-Based Flame Retardant and Film-Forming Electrolyte Additive for Lithium Ion Batteries

Bis(2-methoxyethoxy)methylallylphosphonate (BMEMAP) was synthesized as bi-functional additive of flame retardant and film former in electrolytes of ethylene carbonate (EC) and dimethyl carbonate (DMC). The flame retardancy of the additive was characterized by measuring the self-extinguishing time of electrolytes. It is shown that adding 10 vol.% BMEMAP in 1 M LiPF6/EC + DMC (1:1, v/v) can effectively inhibit the burning of electrolytes and provide a wide electrochemical window. Further evaluation indicates that the additive hardly affect the conductivity of electrolyte. The electrochemical tests reveal that the electrolytes with and without BMEMAP have similar electrochemical behavior with LiFePO4 electrode and natural graphite.