All‐Solid‐State Sodium Batteries with a Polyethylene Glycol Diacrylate–Na3Zr2Si2PO12 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 Na3Zr2Si2PO12 are integrated. The PEGDA polymeric phase of the composite can maintain an amiable ionic interface between the solid‐state electrolyte and electrodes. The Na3Zr2Si2PO12 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‐Na3Zr2Si2PO12‐NaClO4 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‐NaClO4‐Na3Zr2Si2PO12 composite electrolyte are fabricated by coupling a Na2MnFe(CN)6 positive electrode to a Na‐metal negative electrode. The resulting Na ‖ PEGDA‐SCN‐NaClO4‐Na3Zr2Si2PO12 ‖ Na2MnFe(CN)6 cells show remarkable cycling stability.