An attempt to formulate nonflammable lithium ion electrolytes with alkyl phosphates and phosphazenes

Using alkyl phosphates and a cyclophosphazene as cosolvents, the possibility of formulating a nonflammable electrolyte for lithium-ion batteries was explored. The emphasis was placed on determining the impact of these flame-retarding additives on the performance of the electrolyte. It was found that although the cosolvents at high contents (>10%) effectively suppress the flammability of the electrolyte, their flame-retarding effectiveness is still insufficient to render the electrolytes completely nonflammable. Furthermore, such reduction in electrolyte flammability is always realized at the expense of performance; electrochemical instability of phosphates results in severe capacity fading, while high viscosity of these cosolvents reduces both capacity utilization and power. (C) 2002 The Electrochemical Society.