Novel Na3Zr2Si2PO12–polymer hybrid composites with high ionic conductivity for solid-state ionic devices

•Na3Zr2Si2PO12 (NZSP)–polymer nanocomposite hybrids have been synthesized.•High ionic conductivity of ~10−4 Ω−1 cm−1 and stability window of ~4.64 V have been reported.•Conductivity mechanism has been proposed.•Composites exhibit reversible σ–T cycles at least upto 100 °C. Incorporation of PEO based Na+ ion polymer electrolyte in Na3Zr2Si2PO12 (NZSP) NASICON results into novel hybrid composite formation with high ionic conductivity of ~10−4 Ω−1 cm−1 at room temperature. Thus compositions 63NZSP-37(PEO1−xNaIx) for x = 0.03–0.13 have been prepared. The ionic transport mechanism investigated using impedance and X-ray absorption near edge structure spectroscopy suggests decoupling of Na+ ions from the polymer matrix, and significant role of NASICON crystallites in providing pathways for ionic conduction. Compositions with large salt content exhibit reversible conductivity-temperature cycles at least upto 100 °C. The best conducting composite (x = 0.13) exhibits appreciable electrochemical stability window of 4.64 V vs Na/Na+.