All‐Solid‐State Sodium Batteries with a Polyethylene Glycol Diacrylate–Na 3 Zr 2 Si 2 PO 12 Composite Electrolyte

A novel sodium‐ion conducting polymer–ceramic solid‐state composite electrolyte is developed for ambient‐temperature sodium batteries. Polyethylene glycol diacrylate (PEGDA) is used as a polymeric matrix into which ceramic nanoparticles of NASICON‐type Na 3 Zr 2 Si 2 PO 12 are integrated. The PEGDA polymeric phase of the composite can maintain an amiable ionic interface between the solid‐state electrolyte and electrodes. The Na 3 Zr 2 Si 2 PO 12 ceramic phase not only enhances the sodium‐ion conductivity of the composite but also can suppress the Na dendrites from penetrating through the electrolyte membrane. To optimize the Na + ‐ion conductivity, a succinonitrile (SCN) plasticizer is also incorporated. The composite solid electrolyte membranes are fabricated with an ultraviolet (UV) curing process. Through proper management of the composition, the PEGDA‐SCN‐Na 3 Zr 2 Si 2 PO 12 ‐NaClO 4 composite solid electrolyte delivers an ionic conductivity of 4.5 × 10 −4  S cm −1 at room temperature. All‐solid‐state Na cells with the PEGDA‐SCN‐NaClO 4 ‐Na 3 Zr 2 Si 2 PO 12 composite electrolyte are fabricated by coupling a Na 2 MnFe(CN) 6 positive electrode to a Na‐metal negative electrode. The resulting Na ‖ PEGDA‐SCN‐NaClO 4 ‐Na 3 Zr 2 Si 2 PO 12 ‖ Na 2 MnFe(CN) 6 cells show remarkable cycling stability.