High ionic conductive sodium β-alumina (SBA) and SBA-NaPF₆ composite solid electrolytes prepared by cold sintering process

Sodium β-alumina (SBA) electrolytes are among the most excellent candidates for all-solid-state batteries due to their high electrochemical performances and low cost of sodium resources. However, thermally sintering at above 1400 °C is required to fabricate high dense SBA electrolytes, thus giving rise to a huge energy consumption. Here, dense SBA electrolytes and (1-x)SBA-xNaPF₆ (x = 5, 10, 15, 20 wt%) composites were fabricated using cold sintering process (CSP) below 300 °C with 2 mol/L NaOH solution as transient chemistry. The ionic conductivity of SBA electrolytes is significantly enhanced from 5.53×10^-6 S cm^-1 to 5.91 × 10⁻⁴ S cm⁻¹ as 15 wt% NaPF₆ was introduced to the composite, which is comparable with the SBA sintered above 1400 °C. CSP may provide a promising approach for the fabrication of solid-state electrolytes by avoiding the detrimental impact of high temperature heat treatment.