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

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.