Enhanced Ionic Conductivity in Planar Sodium‐β”‐Alumina Electrolyte for Electrochemical Energy Storage Applications

Abstract

Solid Na-β"-Al₂O₃ electrolyte is prepared by a simple chemical route involving a pseudo-boehmite precursor and thermal treatment. Boehmite powder is used for manufacturing the planar electrolyte with appropriate bulk density after firing at 1500 °C. The structure, morphology, and surface properties of precursor powders and sintered electrolytes are investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). As shown by XRD and TEM analyses, nanometer-sized particles are obtained for the boehmite precursor and a pure crystallographic phase is achieved for the sintered electrolyte. SEM analysis of the cross-section indicates good sintering characteristics. XPS shows a higher Na/Al atomic ratio on the surface for the planar electrolyte compared to a commercial tubular electrolyte (0.57 vs. 0.46). Energy-dispersive X-ray microanalysis (EDX) shows an Na/Al ratio in the bulk of 0.16, similar in the two samples. The ionic conductivity of the planar electrolyte is larger than that measured on a commercial tube of sodium-β"-alumina in a wide temperature range. At 350 °C, conductivity values of 0.5 S cm⁻¹ and 0.26 S cm⁻¹ are obtained for the planar electrolyte and the commercial tube, respectively. AC-impedance spectra show smaller grain boundary effects in the planar electrolyte than in the tubular electrolyte. These favorable properties may increase the perspectives for applying planar Na-β"-Al₂O₃ electrolytes in high-temperature batteries.

Solid‐State Sodium Batteries

“…In order to obtain a higher proportion of Na‐β″‐alumina for a higher ionic conductivity, various compounds, including Li 2 O, MgO, TiO 2 , ZrO 2 , Y 2 O 3 , MnO 2 , SiO 2 , Fe 2 O 3 , etc. are widely used as the stabilizers to suppress the formation of Na‐β‐alumina phase . In addition, the accommodation of excessive sodium in the interstitial sites can also promote the formation of Na‐β″‐alumina toward a higher ionic conductivity.…”

“…So far, different synthesis methods, such as solid‐state reaction, coprecipitation, sol–gel, solution combustion techniques, alkoxide hydrolysis, molecular beam epitaxy, laser chemical vapor deposition, etc. are used to synthesize this material, and some of them can effectively decrease the grain‐boundary effect leading to a higher densification . In fact, a pure Na‐β″‐alumina phase is not desirable for application due to its moisture sensitivity and a low mechanical strength .…”

Separators - Technology review: Ceramic based separators for secondary batteries

“…Due to the two-dimensional conductivity, the geometry of the material has an effect on the ion conductivity. Hence, planar alignments have higher ion conductivities than tubular ones [136]. A disadvantage of β -alumina is the requirement of higher temperatures to achieve an adequate ion conductivity.…”

An Electrochemical Study on the Cathode of the Intermediate Temperature Tubular Sodium-Sulfur (NaS) Battery

“…[12][13] The XRD results from the BASE before and after cycling (Fig. S9a) did not exhibit any new peaks suggesting no structural change in the grain boundary of the ceramic material [31][32] , having an amorphous morphology comprised of beta alumina grains with a particle size less than 5 µm. Ex-situ Raman spectroscopy of the cycled electrolyte confirmed the presence of α-Na2S5 and Na2S4 (Fig.…”