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 0.117mScm−1 at 0°C, and 1.20mS cm−1 at 25°C. At slightly elevated temperature ionic conductivity is on the order of 10mScm−1. The hybrid electrolyte has demonstrated reversible stability against metallic lithium at the anodic interface and >4.5V vs. Li/Li+ at the cathodic interface.