LiCrS2 and LiMnS2 Cathodes with Extraordinary Mixed Electron-Ion Conductivities and Favorable Interfacial Compatibilities with Sulfide Electrolyte.

Sulfide-type solid-state electrolytes for all-solid-state lithium ion batteries are capturing more and more attention. However, the electronegativity difference between the oxygen and the sulfur element makes sulfide-type solid-state electrolytes chemically incompatible with the conventional LiCoO2 cathode. In this work, we proposed a series of chalcopyrite-structured sulfide-type materials and systematically assessed their performances as the cathode materials in all-solid-state lithium ion batteries by first-principle calculations. All the five metallic LiMS2 (M = Cr, Mn, Fe, Co, and Ni) materials are superionic conductors with extremely small lithium ion migration barriers in the range from 43 to 99 meV, much lower than most oxide- and even sulfide-type cathodes. Voltage and volume calculations indicate that only LiCrS2 and LiMnS2 cathodes are structurally stable during cycling with the stable voltage plateaus at ∼3 V, much higher than that of the P3m1-LiTiS2 cathode. For the first time, we studied the interfacial lithium transport resistance from a new perspective of charge transfer and redistribution at the electrode/solid-state electrolyte interface. LiCrS2 and LiMnS2 cathodes exhibit favorable interfacial compatibilities with Li3PS4 electrolyte. Our investigations demonstrate that the metallic LiCrS2 and LiMnS2 superionic conductors would possess excellent rate capability, high energy density, good structural stability during cycling, and favorable interfacial compatibility with Li3PS4 electrolyte in all-solid-state lithium ion batteries.