High-throughput screening of M-based layered compounds as solid-state electrolytes for chloride-ion batteries

The development of solid-state electrolytes (SSEs) for chloride-ion batteries (CIBs) has lagged significantly behind that of electrode materials, primarily due to the difficulty in simultaneously achieving high structural stability, electronic insulation, and fast Cl^- diffusion kinetics at room temperature. Drawing inspiration from the structural analogy between electrode materials and SSEs in cationic battery systems, this study adopts a materials design strategy that transforms layered CIB electrode materials into SSE candidates by substituting transition metals (TM) with equivalent non-transition main group metals (M). Through comprehensive first-principles high-throughput screening based on thermal, kinetic, and thermodynamic stability, we identify O-GaOCl (Pmmn space group) and Ca₂GaO₃Cl as the most promising SSE materials. Our analysis of electronic structures reveals that replacing TM³⁺ with M³⁺ eliminates partially filled d-orbitals near the Fermi level, resulting in wide bandgaps of 3.78 eV for O-GaOCl and 3.34 eV for Ca₂GaO₃Cl, satisfying the stringent insulation requirements for electrolytes. Evaluation of Cl^- diffusion kinetics demonstrates that O-GaOCl exhibits an exceptionally low migration barrier of 0.25 eV, attributed to a concerted migration mechanism where two Cl^- ions move simultaneously, reducing electrostatic repulsion. Ca₂GaO₃Cl shows a moderate barrier of 0.44 eV. Electrochemical window calculations indicate that O-GaOCl and Ca₂GaO₃Cl possess stable windows of 1.60 V and 3.28 V, respectively. These findings establish a viable pathway for designing CIB SSEs and position O-GaOCl and Ca₂GaO₃Cl as compelling candidates for enabling all-solid-state CIB technology.