Slurry-Coated LiNi_0.8Co_0.1Mn_0.1O₂–Li₃InCl₆ Composite Cathode with Enhanced Interfacial Stability for Sulfide-Based All-Solid-State Batteries

The implementation of all-solid-state lithium batteries (ASSLBs) is regarded as an important step toward the next-generation energy storage systems. The sulfide solid-state electrolyte (SSE) is a promising candidate for ASSLBs due to its high ionic conductivity and easy processability. However, the interface stability of sulfide SSEs toward high-capacity cathodes like nickel-rich layered cathodes is limited by the interfacial side reaction and narrow electrochemical window of the electrolyte. Herein, we propose introducing the halide SSE Li 3 InCl 6 (LIC) with high (electro)chemical stability and superior Li + conductivity to act as an ionic conductive additive in the Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM) cathode mixture through a slurry coating, aiming to build a stable cathode–electrolyte interface. This work demonstrates that the sulfide SSE Li 5.5 PS 4.5 Cl 1.5 (LPSCl) is chemically incompatible with the NCM cathode, and the indispensable role of the substitution of LPSCl with LIC in enhancing the interfacial compatibility and oxidation stability of the electrolyte is highlighted. Accordingly, this new configuration shows superior electrochemical performance at room temperature. It shows a high initial discharge capacity (136.3 mA h g –1 at 0.1C), cycling performance (77.4% capacity retention at the 100th cycle), and rate capability (79.3 mA h g –1 at 0.5C). This work paves the way for investigating interfacial challenges regarding high-voltage cathodes and provides new insights into possible interface engineering strategies.