Solid Gel Electrolytes with Highly Concentrated Liquid Electrolyte in Polymer Networks and Their Physical and Electrochemical Properties and Application to Sodium Secondary Batteries

Gel polymer electrolytes consisting of sulfolane (SL)-NaN(SO 2 CF 3 ) 2 liquid electrolyte and a polyether-based host polymer were prepared, and their physicochemical and electrochemical properties were investigated. The prepared gel electrolytes generally exhibited high thermal stability regardless of the NaN(SO 2 CF 3 ) 2 concentrations. The glass transition temperature decreased with the NaN(SO 2 CF 3 ) 2 concentration owing to the strong interaction between SL and Na + . The ionic conductivities of all gel polymer electrolytes were higher than 10 −4 S cm −1 at 303.15 K as a result of the plasticizer effect of SL. Although a relatively large interfacial resistance of the electrolyte/Na metal electrode was observed owing to the high reactivity of the SL-NaN(SO 2 CF 3 ) 2 electrolyte, the fabricated [Na metal negative electrode∣gel polymer electrolyte∣sulfur-modified polyacrylonitrile positive electrode] cell, i.e., the Na-S battery, achieved reversible charge-discharge operation at 333 K and demonstrated its potential to serve as an electric power storage system capable of low-temperature operation.