Tailored Crosslinking of Poly(Ethylene Oxide) Enables Mechanical Robustness and Improved Sodium-Ion Conductivity

Sodium-based energy storage systems are promising candidates for electric vehicles and grid-level energy storage applications. The advancement of sodium-based energy storage systems relies on the development of high performance sodium-ion conducting electrolytes and membranes that exhibit high ionic conductivity and mechanical stability. A crosslinked poly(ethylene oxide) based polymer electrolyte was developed that demonstrates high ionic conductivity, as well as excellent mechanical stability over a wide temperature range. Ionic conductivities up to 2.0 × 10−4 S/cm at 20 °C and 7.1 × 10−4 S/cm at 70 °C are achieved for the plasticized membrane, almost four orders of magnitude greater than that of the non-plasticized membrane. The membranes are mechanically robust, and the storage modulus of the membrane is maintained at ∼1 MPa from −20 to 180 °C even with the addition of plasticizer. This study provides a synthesis approach towards the design of highly ion conducting, mechanically robust gel polymer electrolytes for Na-ion batteries, non-aqueous flow batteries, and many other applications.