Ultrafast sintering of Na3Zr2Si2PO12 solid electrolyte for long lifespan solid-state sodium ion batteries

•Na3Zr2Si2PO12 solid electrolyte is fabricated using ultrafast high-temperature sintering (UHS) in seconds to significantly suppress the Na loss and impurity formation.•The prepared Na3Zr2Si2PO12 exhibits the high ionic conductivity of 2.62 × 10−4 S cm−1, low activation energy of 0.28 eV and high relative densities of 93 %.•The corresponding solid-state Na3V2(PO4)3 cell delivers a capacity retention of 89 % after 800 cycles with the areal NVP loading of 4.5 mg cm−2 at room temperature.