Abstract:

 Lithium sulfur (Li/S) is a promising candidate of next generation of rechargeable batteries because of its extremely high specific capacity and abundant natural resources. However, the safety issue might be one of the most important factors which hinder their practical applications. Here a highly effective flame-retarding additive, ethoxypentafluorocyclotriphosphazene (PFPN), is firstly applied in Li/S batteries to improve their thermal safety properties. The addition of about 5% (weight ratio) PFPN makes the highly flammable liquid electrolyte totally nonflammable. Furthermore, the addition of PFPN simultaneously reduces the polarization voltage and obviously enhances the rate capability of sulfur-based composite materials. All these results indicate that PFPN is a favorable flame inhibiting additive in conventional liquid electrolytes for rechargeable lithium sulfur batteries.

Key words: flame retardant, PFPN, functional electrolyte, lithium sulfur batteries, composite cathode