High‐Throughput Screening and Characterization of Non‐Flammable Na‐Cl Solid Electrolytes

ABSTRACT Non‐flammable solid electrolytes are key materials in all‐solid‐state batteries. Chloride solid electrolytes exhibit high ionic conductivities derived from weak Coulomb interactions with carrier ions. However, not all chlorides are stable, and a limited number of Na‐Cl‐based materials exhibit ionic conductivities above 10 −4 S cm −1 . Herein, the ionic conductivities of Na‐Cl compounds in a structural database (Materials Project) are comprehensively calculated through force field molecular dynamics and density functional theory calculations. The results predict that Na 3 La 5 Cl 18 (mp‐1173723) is thermodynamically stable with a high ionic conductivity (1.5 × 10 −2 S cm −1 ) at 298 K. Moreover, the 1D conduction pathway along the c ‐axis of Na 3 La 5 Cl 18 is confirmed. Nuclear magnetic resonance measurements confirm the high ionic conductivity (>10 −4 S cm −1 at 298 K) of synthesized Na 3 La 5 Cl 18 . Analysis of characterization results reveals that the ionic conductivity of Na 3 La 5 Cl 18 can be further improved by suppressing La mixing in the 1D conduction pathway, while impedance measurements and relaxation time analysis show that conductivity is enhanced by reducing the large crystallite grain boundary resistance. Na 3 La 5 Cl 18 has a higher ignition temperature (>800°C) compared to the sulfide electrolyte Na 3 PS 4 (∼300°C). The results of this study enable the realization of ASSBs with improved safety.