Solid polymer electrolytes with sulfur based ionic liquid for lithium batteries

The electrochemical properties of a solid hybrid polymer electrolyte for lithium batteries based upon tri-ethyl sulfonium bis(trifluorosulfonyl) imide (S2TFSI), lithium TFSI, and poly(ethylene oxide) (PEO) is presented. We have synthesized homogenous freestanding films that possess low temperature ionic conductivity and wide electrochemical stability. The hybrid electrolyte has demonstrated ionic conductivity of 0.117 mS cm−1 at 0 °C, and 1.20 mS cm−1 at 25 °C. At slightly elevated temperature ionic conductivity is on the order of 10 mS cm−1. The hybrid electrolyte has demonstrated reversible stability against metallic lithium at the anodic interface and >4.5 V vs. Li/Li+ at the cathodic interface.

► First report of incorporation of a S based ionic liquid into a polymer electrolyte. ► Free standing solid hybrid polymer film with increased safety over liquid electrolytes. ► Ionic conductivity >10 mS cm−1 at 40 °C. ► Reversible stability >4.5 V vs. Li/Li+.