Enhanced ionic conductivity of an F−-assisted Na3Zr2Si2PO12 solid electrolyte for solid-state sodium batteries

Abstract

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.