Time-Temperature-Transformation (TTT) Diagram of Battery-Grade Li-Garnet Electrolytes for Low-Temperature Sustainable Synthesis

Efficient and affordable synthesis of Li⁺ functional ceramics is crucial for the scalable production of solid electrolytes for batteries. Li-garnet Li₇La₃Zr₂O_12−d (LLZO), especially its cubic phase (cLLZO), attracts attention due to its high Li⁺ conductivity and wide electrochemical stability window. However, high sintering temperatures raise concerns about the cathode interface stability, production costs, and energy consumption for scalable manufacture. We show an alternative “sinter-free” route to stabilize cLLZO as films at half of its sinter temperature. Specifically, we establish a time-temperature-transformation (TTT) diagram which captures the amorphous-to-crystalline LLZO transformation based on crystallization enthalpy analysis and confirm stabilization of thin-film cLLZO at record low temperatures of 500 °C. Our findings pave the way for low-temperature processing via TTT diagrams, which can be used for battery cell design targeting reduced carbon footprints in manufacturing.