Rapid Processing of Uniform, Thin, Robust, and Large‐Area Garnet Solid Electrolyte by Atmospheric Plasma Spraying

All‐solid‐state batteries (ASSBs) are rapidly moving toward commercialization as a promising high‐performance energy storage device for portable electronics and electric vehicles. One of the most challenging problems hindering the industrialization of ASSBs is the lack of technologies for cost‐effective and large‐scale manufacturing of high‐quality solid‐state electrolytes (SSEs) with about the same thickness as the polymer separators in conventional lithium‐ion batteries. Herein, atmospheric plasma spraying (APS) is adopted as a practical route to process large‐scale, uniform, and thin SSEs to conduct Li‐ions and further to manufacture ASSBs. Garnet‐type Li₇La₃Zr₂O₁₂ (LLZO) films with thicknesses ranging from 30 to 300 µm are successfully manufactured with direct APS technique followed with a post annealing treatment. The electrolyte reaches a high Li‐ion conductivity of 3.82 × 10⁻⁵ S cm⁻¹ at room temperature (25 °C). Additionally, the LLZO film with a thickness of 300 µm shows a flexural strength of 157 MPa. Li/LLZO/Li and Li/LLZO/LiFePO₄ cells are assembled with the films, both showing stable cycling performance. The APS method shows scalability in solid‐state electrolyte film production, and most importantly, such a process is highly compatible with the current battery industry.