Thermoformable Electrolytes for Solid-State Sodium Metal Batteries Employing Organic Cathodes

Solid-state sodium metal batteries (SSBs) are candidates for TWh-scale energy storage systems, yet remain challenged by poor processability, cracking, and interface incoherence between inorganic electrolytes and cathodes. Here, we architect thermoformable organo–ionic (ORION) electrolytes comprising controllably clustered ion aggregates within a zwitterionic matrix to create SSBs with organic cathodes. ORION electrolytes are viscoelastic liquids above 110 °C, yet they are viscoelastic solids at typical battery operating temperatures, which overcome the aforementioned challenges. We introduced ether ligands to tailor Na+-ion coordination environments and transport over 3 orders of magnitude (3.4 × 10–3 – 1.0 mS cm–1), whereupon we observed monotonic increases in Na+ mobility with increasing coordination number (up to 2.5); yet the fraction of mobile ions decreased. Thus, ligands dissociate Na+ from larger ion clusters and aggregates, prescribe what the effective mass of Na+ will be, and how Na+ will move within the zwitterionic matrix via vehicular diffusion.