A Scalable BaTiO ₃ Nanocoating Strategy for Cost‐Effective and Stable Sulfide‐Based All‐Solid‐State Batteries

ABSTRACT Sulfide‐based all‐solid‐state batteries (ASSBs) are promising for next‐generation energy storage due to their high energy density and intrinsic safety, yet their practical deployment is limited by the high cost of sulfide electrolytes, poor air stability, and interfacial degradation with nickel‐rich cathodes. Here, a scalable and cost‐effective BaTiO ₃ (BTO) nanocoating strategy for Li _5.5 PS _4.5 Cl _1.5 (LPSC1.5) electrolytes is presented, achieved through a rapid 10 min ball‐milling process. The uniform ∼100 nm BTO layer reduces electrolyte cost by approximately 8.1% while maintaining high ionic conductivity (8.81 mS cm ⁻¹ ). The coating significantly enhances air stability by suppressing H ₂ S evolution and preserving conductivity after exposure. Combined experimental and finite element analyses reveal that the BTO layer homogenizes charge distribution, inhibits space‐charge layer formation, and mitigates interfacial side reactions, leading to improved electrochemical and mechanical robustness. When paired with PCNCM83 cathodes, the modified electrolytes enable ASSBs with exceptional rate capability and ultralong cycling stability exceeding 10 000 cycles at 7 C. This universal nanocoating approach is compatible with various sulfide electrolytes and cathode chemistries, offering a viable pathway toward the scalable commercialization of high‐performance solid‐state batteries.