Flux-Assisted Low-Temperature Fabrication of Highly Durable All-Oxide Solid-State Sodium-Ion Batteries

Although oxides are widely implemented in all-solid-state batteries, undesirable reactions at the electrolyte/electrode interfaces at high fabrication temperatures pose significant challenges in terms of battery fabrication. Herein, we demonstrate that premixing Na2B4O7·10H2O into an Na3.1Zr1.95Mg0.05(SiO4)2(PO4) electrolyte promotes the densification of the electrolyte layer in a symmetric battery using Na3V2(PO4)3 electrodes even at a low enough sintering temperature of 600 °C to prevent the undesirable reaction. The battery containing 10 wt % Na2B4O7·10H2O in the electrolyte exhibited 66% of the theoretical capacity and a high cycle durability (∼100% at the 99th cycle) at an operating temperature of 60 °C.