Lawrence Berkeley National Laboratory

NASICON-structured solid-state electrolytes (SSEs) are highly promising materials for sodium solid-state metal batteries (NaSMBs). However, the current synthesis methods are often labor-intensive and inefficient, consuming a significant amount of energy and time. Here, an ultrafast high-temperature synthesis (UHS) technique is successfully demonstrated to directly synthesize NASICON-type SSEs from mixed precursor powders, reducing the synthesis time from hours to merely seconds. The intermediate with a Na3PO4 structure plays a critical role in the rapid synthesis of NASICON-type SSEs, ultimately leading to the formation of the final NASICON phase. Moreover, the UHS-synthesizes NASICON-type Na3.3Zr1.7Lu0.3Si2PO12 (NZLSP) exhibits high room temperature ionic conductivity of 7.7 × 10−4 S cm−1, approximately three times that of the undoped Na3Zr2Si2PO12 (NZSP). The Na|NZLSP|Na symmetric cell can sustain highly stable cycling for over 4800 h. This study provides a novel insight and validation in the precise and targeted synthesis of complex oxide solid-state electrolytes.