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 Na_3.1Zr_1.95Mg_0.05(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.