Mg2+/F− Synergy to Enhance the Ionic Conductivity of Na3Zr2Si2PO12 Solid Electrolyte for Solid‐State Sodium Batteries

Abstract Na super ion conductor (NASICON) Na 3 Zr 2 Si 2 PO 12 (NZSP) is considered to be one of the most promising solid electrolytes for solid‐state sodium batteries. However, low ionic conductivity is one of the main challenges for its practical application. Herein, we report a novel Mg 2+ /F − co‐assisting strategy to synthesize NZSP solid electrolyte with enhanced ionic conductivity. Mg 2+ /F ‐ co‐assisting leads to a significant increase in the particle size and a reduction in the concentration of grain boundary. A dense microstructure is also formed with co‐assisting. Consequently, high ionic conductivity of 2.21 mS cm −1 at 300 K, low electronic conductivity of 1.76×10 −5 mS cm −1 at 300 K and low activation energy of ∼0.27 eV are achieved for the optimized Mg 2+ /F − co‐assisted NZSP solid electrolyte. Finally, a Na/Na 3 V 2 (PO 4 ) 3 solid‐state sodium battery employing Mg 2+ /F − co‐assisted NZSP solid electrolyte exhibits an excellent electrochemical performance. High discharge specific capacity of 71.5 mAh g −1 is displayed at 1 C at 300 K, with 96 % retention after 100 cycles. Therefore, this cation/anion co‐assisting strategy provides inspiration for the development of other classes of ceramic solid electrolytes for solid‐state sodium batteries.