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 Li La Zr O (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.