Theoretical Designof High-Performance Solid-StateElectrolyte Na₃La₃Gd₁Sm₁Cl₁₈

Leveraging density functional theory, deep potential model, and grand potential phase diagram analysis, we have developed a promising solid-state electrolyte based on sodium chloride, Na₃La₃GdSmCl₁₈ (NLGSC). This material demonstrates outstanding stability in thermal, dynamical, mechanical, and thermodynamic aspects, complemented by a wide band gap of 5.6 eV and excellent ductility with a Pugh’s ratio of 2.30. Importantly, NLGSC achieves a high ionic conductivity of 3.00 mS/cm at 300 K, a low activation energy of 0.24 eV, and a migration barrier of only 0.20 eV along the crystallographic <i>c</i>-axis. Furthermore, it displays a broad electrochemical stability window spanning 0.65 to 3.78 V and superior chemical compatibility with high-voltage cathode materials such as Na₂FePO₄F, Na₃V₂(PO₄)₃, and Na₃V₂P₂O₈F₃. These findings establish NLGSC as a promising solid-state electrolyte for Na-ion batteries, further expanding the applications of the recently synthesized chloride superionic conductors [<i>Nature</i> <b>2023</b>, 616, and 77].