Defect‐Free Transfer Principles for Scalable, Thin Garnet‐Based Hybrid Solid Electrolytes in Solid‐State Batteries

ABSTRACT

The scalable fabrication of thin, uniform, and defect‐free hybrid solid electrolytes (HSEs) remains a critical challenge for solid‐state batteries due to the lack of quantitative design principles governing interfacial interactions during coating, transfer, and impregnation. Here, we establish thermodynamic criteria for Li ₆ . ₇₅ La ₃ Zr ₁ . ₇₅ Ta ₀ . ₂₅ O ₁₂ ‐based hybrid layers (LLZTO‐HLs) fabrication using Hansen solubility parameters to correlate interfacial compatibility with process behavior. Uniform coating requires sufficiently high slurry–substrate compatibility, whereas clean transfer demands low binder–substrate adhesion. Furthermore, binder–polymer electrolyte compatibility governs impregnation behavior, enabling rational combination selection. Based on this framework, defect‐free, 15 µm‐thin LLZTO‐HLs are fabricated over large areas (120 cm ² ) via transfer printing and integrated into transfer‐printed HSEs (THSEs). Compared with direct coating, transfer printing enables uniform electrolyte layers and electrode interfacial stability owing to the absence of slurry infiltration into the porous anode. Consequently, THSEs exhibit enhanced Li ⁺ transport, superior rate capability, and improved cycling stability in coin‐type hybrid solid‐state batteries. Notably, comparable cycling performance is retained in pouch‐type cells despite increased cell area, highlighting the excellent uniformity and scalability of the THSE. The THSE demonstrates superior thermal stability under elevated temperatures. The thermodynamic design principles established herein provide a generalizable framework for scalable manufacturing of high‐performance HSEs.