NASICON-PEO (Polyethylene Oxide) Polymer-in-Ceramic Composite Electrolytes: Thermal, Structural and Electrical Properties

A composite electrolyte consisting of sodium super ionic conductor (NASICON) LiSn2P3O12 (LSPO) and a polymer electrolyte (80:20 polyethylene oxide (PEO) with LiTFSI salt) was prepared using the solution casting method. The thermal stability of the composite was assessed, revealing a second-stage decomposition temperature range between 375 and 462 °C, with a glass transition temperature (Tg) of 28 °C. X-ray diffraction (XRD) analysis indicated low crystallinity in PEO-LiTFSI, with no significant structural changes, despite the emergence of a new peak at 20.7 °C. Electrochemical impedance spectroscopy (EIS) was used to investigate the electrical properties at seven different temperatures (30, 40, 50, 60, 70, 80 and 90 °C), with the highest bulk conductivity of 6.2825×10−5 S/cm observed at 50 °C. The results demonstrate that the addition of LSPO ceramic electrolyte and temperature significantly influence the thermal, structural, and electrical properties of the composite electrolyte. HIGHLIGHTS This article focused on composite electrolyte consisting of NASICON, LiSn2P3O12 (LSPO) and a polymer electrolyte (80:20 PEO with LiTFSI salt) prepared using the solution casting method. The thermal and structural properties of the material indicate good thermal stability and a predominantly crystalline structure, which are favourable characteristics for solid-state electrolyte applications. Electrochemical studies found the highest ionic conductivity of 6.2825 × 10⁻⁵ S/cm at 50 °C, highlighting the role of LSPO and temperature on electrolyte performance. These findings suggest that the LSPO–PEO composite electrolyte is a promising candidate for solid-state sodium-ion battery applications due to its enhanced thermal and electrochemical properties. GRAPHICAL ABSTRACT