Ambient‐Temperature All‐Solid‐State Sodium Batteries with a Laminated Composite Electrolyte

This study presents a sodium‐ion conductive laminated polymer/ceramic‐polymer solid‐state electrolyte for the development of room‐temperature all‐solid‐state sodium batteries. At the negative electrode side, a negative‐electrode‐benign poly(ethylene oxide) (PEO) is used as a polymer matrix into which succinonitrile (SN) is integrated to improve the room‐temperature Na + ‐ion conductivity. At the positive electrode side, a cathode‐friendly poly(acrylonitrile) (PAN) serves as a polymer matrix into which a NASICON‐type ceramic solid‐electrolyte (Na 3 Zr 2 Si 2 PO 12 ) powder is incorporated toward both the enhancement of Na + ‐ion conductivity and the prevention of Na dendrite from penetrating through the electrolyte membrane. Through a strategical management of composition, the PAN‐Na 3 Zr 2 Si 2 PO 12 ‐NaClO 4 composite and the PEO‐SN‐NaClO 4 polymer deliver a balanced Na + ‐ion conductivity. Combining the two electrolyte layers, the laminated PEO‐SN‐NaClO 4 /PAN‐Na 3 Zr 2 Si 2 PO 12 ‐NaClO 4 solid electrolyte provides a Na + ‐ion conductivity of 1.36 × 10 −4 S cm −1 at room temperature. With respect to the anodic friendly feature of the PEO‐SN‐NaClO 4 layer and the cathodic friendly feature of the PAN‐Na 3 Zr 2 Si 2 PO 12 ‐NaClO 4 layer, the laminated solid electrolyte presents a stable electrochemical window of 0–4.8 V. Room‐temperature all‐solid‐state sodium batteries fabricated with the laminated solid electrolyte, a Na‐metal negative electrode, and a Na 2 MnFe(CN) 6 positive electrode exhibit remarkably stable cyclability.