Simultaneous Optimization of Internal Electric Fields and High-Valence Cations in Cathode Coating Microstructures

Sulfide all-solid-state lithium batteries employing cathode coatings hold significant promise as next-generation, high-safety power sources owing to their superior performance. However, the influence of the coating material's intrinsic structure on interfacial properties remains underexplored. The synergistic interaction between high-valence cations and the internal electric field induced by the coating microstructure is systematically investigated by profiling the interfacial behavior between LiNbO₃(LNO) and Li₃NbO₄ (L3NO4) coatings on LiCoO₂(LCO) cathodes in sulfide all-solid-state batteries. The highly electronegative Nb⁵⁺ cations in the LNO coating induce the formation of a precisely tuned internal electric field, which simultaneously enhances Li⁺ transport while suppressing detrimental interfacial side reactions and elemental interdiffusion, thereby ensuring outstanding cycling stability. Contrastingly, the L3NO4 coating generates low-efficiency internal electric fields with higher charge transfer barriers, leading to noticeable interface degradation and limited performance enhancement. This work highlights that synergistically optimizing cation properties and internal electric fields at the microstructural level is crucial for designing high-performance solid-state battery interfaces.