Blend-based polymer electrolytes of poly(ethylene oxide) and hyperbranched poly[bis(triethylene glycol)benzoate] with terminal acetyl groups

Blend-based polymer electrolytes, with favorable mechanical strength, consisting of a linear poly(ethylene oxide) (PEO), a hyperbranched polymer (poly[bis(triethylene glycol)benzoate] with terminal acetyl groups), and LiN(CF3SO2)2 salt, were prepared by the solvent casting technique. Thermal properties, ionic conductivity, electrochemical stability window, lithium ion transference number, and cyclic voltammetric behavior of the blend-based polymer electrolytes were all evaluated and discussed. In comparison with polymer electrolytes based on PEO, the blend-based polymer electrolytes exhibited improved lithium ionic conductivity and lithium/electrolyte interfacial performance. Blend-based polymer electrolyte with a hyperbranched polymer/PEO ratio of 20/80 in wt% and [LiN(CF3SO2)2]0.125 exhibited ionic conductivities as high as 8.1×10−4 S cm−1 at 80°C and 3.8×10−5 S cm−1 at room temperature. The electrochemical stability window was about 4.9 V. It was also demonstrated that crystallinity of the blend-based polymer electrolytes depends significantly on the hyperbranched polymer/PEO weight ratio as well as the lithium salt content.