Hybrid solid electrolyte composites based on NaNO2 and aerogel-prepared Mg-Al oxides

Abstract

Highly dispersed oxides MgO, Al₂O₃, and MgO-Al₂O₃ were synthesized via an aerogel approach and used as a heterogeneous dopant for the preparation of solid electrolyte composites based on sodium nitrite. The oxides possess a developed surface area of 300–400 m²/g. The effects of the oxide content in the composition of prepared composite materials on their textural properties and phase composition were studied using X-ray diffraction analysis and low-temperature nitrogen adsorption. A mechanism for filling pores of an ionic salt during the formation of a composite was proposed. The introduction of 30–80 mol% of highly dispersed aerogel oxides was found to increase the ionic conductivity of the composites by 3 orders of magnitude. Thus, the ionic conductivity values for pure NaNO₂ and the composite solid electrolytes at 200 °C were 1.8 × 10⁻⁶ and ∼6 × 10⁻³ S/cm, respectively. The highest ionic conductivity value of 6.45 × 10⁻³ S/cm was obtained for the composite sample containing 80 mol% of MgO.