A High‐Voltage Solid State Electrolyte Based on Spinel‐Like Chloride Made of Low‐Cost and Abundant Resources

Abstract Recently, halide solid state electrolytes (SSEs) have received great attention owing to their fast ionic conductivity, high oxidation potential, and good chemical and electrochemical compatibility with high voltage cathode materials. However, most of reported halide SSEs contain rather rare and expensive elements, which hinders their sustainable utilizations in practical batteries. Here in this work, under the guidance of systematic modelling based on the density functional theory (DFT), a low‐cost alternative is developed through optimizing the lattice chemistry in a recently identified spinel‐like chloride Li₂CrCl₄ into Li_5/3Cr_1/3Zr_1/3Cl₄ for remarkably enhanced ionic conductivity and stable electrochemical window with respect to the Li‐anode. This new phase has then been synthesized successfully, delivering an ionic conductivity over 1200 times of that of the pristine phase Li₂CrCl₄, in addition to a high oxidation potential (up to 4.1 V vs Li/Li⁺) to enable outstanding interfacial compatibility with high voltage cathodes. Such a high‐voltage and fast Li‐ion conducting solid‐state electrolyte is expected to provide a highly desirable basis toward developing high energy‐density all solid‐state batteries (ASSBs) using economical and Earth‐rich elements.