Enhanced ionic conductivity via oxygen-vacancies-enriched Na3Zr2Si2PO12 for PEO-based composite solid electrolytes

The high ionic conductivity and cycling stability of solid electrolytes are crucial for the application of all-solid-state sodium batteries (ASSSBs). In this study, a PEO-based composite polymer solid electrolyte (CPE) with improved ionic conductivity was prepared by incorporating oxygen-vacancy-enriched Na₃Zr₂Si₂PO₁₂ (OVNZSP). It was discovered that the presence of oxygen vacancies on the surface of the NZSP filler can promote the dissociation of sodium salts in the electrolyte and decrease the crystallinity of PEO, resulting in the effective conduction of Na⁺. Consequently, there is a significant enhancement in the ionic conductivity of the electrolyte, reaching 5.28 × 10⁻⁴ S cm⁻¹ at 60 °C. Furthermore, the substantially optimized Na⁺ transport facilitates the CPE maintaining superior electrochemical performance at high current densities. The ASSSBs assembled using OVNZSP-incorporated CPE exhibit excellent cycle stability, with a capacity retention of 85 % at a current density of 1C after 800 cycles. This method offers a promising strategy for enhancing the ionic conductivity of solid-state electrolyte and optimizing ASSSBs.