Enhancing sodium ionic conductivity: An interface bridging strategy for Na3Zr2Si2PO12 solid-state electrolyte

Abstract

For the solid-state electrolyte (SSE), a key issue needs to be solved urgently is that the sodium ionic transport among the Na₃Zr₂Si₂PO₁₂ (NZSP) particles is interrupted by the presence of impurities and pores. Herein, we propose an interface bridging strategy to enhance sodium ion conductivity through preparing NZSP/zeolitic imidazolate frameworks-8 (ZIF-8)/poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) SSEs (NZSP/ZIF/PH). Firstly, the Zn-NZSP particles without impurities prepared by Zn-doping, providing Zn connection sites for ZIF and NZSP. Secondly, the effective interface interaction between NZSP and ZIF is achieved through in-situ growth of ZIF on the surface of NZSP particles. Finally, a seamless interface bridging structure is established via the compatibility between ZIF and PVDF-HFP in NZSP/ZIF/PH SSE. Consequently, the optimized NZSP/ZIF/PH-C SSE exhibits an inter-particle ionic conductivity of 3.67 mS cm⁻¹ (0.048 mS cm⁻¹ of NZSP) and a total ionic conductivity of 1.34 mS cm⁻¹ (0.036 mS cm⁻¹ of NZSP). Moreover, the symmetrical Na/SSE/Na cell using NZSP/ZIF/PH-C demonstrates a prolonged cycle life exceeding 1600 h with the charge-discharge voltages of ±0.15 V at a current density of 1 mA cm⁻². This research introduces an innovative interface bridging strategy to connect NZSP particles, thereby enhancing the ionic transport performance of SSEs in solid-state batteries.