Time‐Temperature‐Transformation (TTT) Diagram of Battery‐Grade Li‐Garnet Electrolytes for Low‐Temperature Sustainable Synthesis
Abstract
Efficient and affordable synthesis of Li + functional ceramics is crucial for the scalable production of solid electrolytes for batteries. Li‐garnet Li 7 La 3 Zr 2 O 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.
Y.Z. acknowledges financial support from the MIT Energy Initiative fellowship offered by ExxonMobil. J.L.M.R. thanks the Thomas Lord Foundation for financial support. The SEM images were collected at the Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Coordinated Infrastructure Network (NNCI), supported by the National Science Foundation under NSF award no. 1541959. CNS is part of Harvard University. The authors thank Prof. Christopher A. Schuh's lab at MIT for offering access to equipment and providing support for the DSC experiments. Y.Z. thanks Zachary D. Hood, Lincoln J. Miara, and Christopher Eschler for fruitful discussions on the crystallization kinetics at the early stage of this study.
