Flexible solvent-free polymer electrolytes for solid-state Na batteries

Post-lithium batteries, based on alkaline and alkaline earth elements, are cheaper technologies with the potential to produce disruptive changes in the transition towards cleaner and sustainable energy sources less dependent on fossil fuels. This contribution deals with the development and characterization of sodium-conducting solvent-free polymer electrolytes towards the attainment of Sodium Polymer Batteries. Obtained via the polycondensation of α, ω-dihydroxy-oligo(oxyethylene) with an unsaturated dihalide, whose further curing leads to amorphous networked electrolyte films. Using NaClO₄ and NaCF₃SO₃ at different O/Na ratios, the best polymer electrolyte reaches a cationic conductivity (σ⁺) exceeding 1 mS cm^-1 at 90 °C whereas maintaining mechanical integrity up to at least 120 °C.