Thermal-Induced Structure Evolution at the Interface between Cathode and Solid-State Electrolyte

The interfaces between the electrode and solid-state electrolyte play a decisive role in the performance of all-solid-state batteries. For example, the formation of the interphase between cathode and solid-state electrolyte can affect interfacial impedance and thus the rate capability. Herein, the thermal stability at the solid-solid interface between LiMn2O4 cathode and garnet electrolyte LLZTO via combined in situ techniques is studied, including in situ X-Ray diffraction, in situ transmission electron microscopy, and in situ Raman. The dynamic process of interfacial reaction at different scales is elucidated. Starting from 300 degrees C, Mn ions from LiMn2O4 would migrate into the solid-state electrolyte, accompanied with the formation of LiMn3O4 interphase. As the temperature increases to 500 degrees C, the LiMn3O4 interphase transforms to MnO structure which hinders Li-ion transportation and therefore increases the interfacial impedance. Although both LiMn2O4 and LLZTO could withstand continuous heating, their interface is inherently thermally unstable at relatively low temperature, which requires special attention during thermal treatment for practical fabrication. Findings provide mechanistic insights into the interfacial reaction which serves as a guidance for the design and manufacturing of all-solid-state batteries. The interface between cathode and solid-state electrolyte is crucial to the performance of all-solid-state battery. In situ heating transmission electron microscopy is used to explore the thermal stabilization character of LiMn2O4 and LLZTO interface. With temperature increase, Mn ions gradually accumulate at the interface accompanied by irreversible phase transition, which suggests the thermal instability of LMn2O4 and LLZTO interface.image (c) 2023 WILEY-VCH GmbH