Enhanced ionic conductivity of an F^--assisted Na₃Zr₂Si₂PO₁₂solid electrolyte for solid-state sodium batteries

Na3Zr2Si2PO12 (NZSP) is considered to be one of the most promising solid electrolytes for solid-state sodium batteries. However, the low ionic conductivity of NZSP is one of the main challenges for its practical application. Herein, an F- assisting strategy to improve the ionic conductivity of NZSP is proposed. The F- assisting in NZSP electrolyte promotes the formation of a microstructure with large grains, low grain boundary concentration and high relative density, which is favorable to obtain high ionic conductivity. Consequently, the F-assisted NZSP solid electrolyte exhibits a high ionic conductivity of 1.41 × 10-3 S cm-1 at 27 °C, which is about six times that of the un-assisted NZSP electrolyte (2.32 × 10-4 S cm-1). Moreover, the Na/Na3V2(PO4)3 solid-state sodium battery with the F-assisted NZSP electrolyte exhibits an excellent cyclability with 97.8% capacity retention (85.9 mA h g-1) after 100 cycles at 0.5C at 40 °C. This F- assisting strategy provides a new way for the development of other classes of ceramic solid electrolytes for solid-state batteries.