Sodium-ion conducting pseudosolid electrolyte for energy-dense, sodium-metal batteries

A liquid electrolyte based on the addition of a sodium salt in glyme solvent is encapsulated within a polymer-modified mesoporous silica matrix enabling the fabrication of a pseudosolid, sodium-ion electrolyte. This ionogel electrolyte is stable in contact with sodium metal leading to low overpotentials for sodium metal plating/stripping along with high Na+ conductivity and > 4 V electrochemical stability window. Sodium-metal batteries with sodium vanadium fluorophosphate positive electrode achieve over 400 Wh kg−1 at 0.5C.