Study of Solid-Solid Interface in All-Solid-State Batteries: Atomic Structures and Ion Conductivities at Interfaces

Abstract

All-solid-state lithium batteries are expected to become the next generation of batteries. One of the major drawbacks for the practical use of all-solid-state batteries is their large interface resistance at the solid electrolyte and electrode interface. We have been investing electrolyte/electrode interfaces using all-solid-state thin-film batteries. In this study, we report an extremely low resistance of 8.6 Ωcm² at a solid electrolyte (Li₃PO₄) and electrode (LiCoO₂) interface. This value is an order of magnitude smaller than those presented in previous reports on all-solid-state batteries. Using synchrotron surface X-ray diffraction, we investigated the atomic structure of the Li₃PO₄/LiCoO₂ interfaces; the low-resistance interface exhibited a flat and well-ordered atomic arrangement at the electrode surface, whereas the high-resistance interface showed a disordered interface. These results indicate that the crystallinity of LiCoO₂ at the interface has a significant impact on interface resistance.