Unraveling the mechanism of ion and electron migration in composite solid-state electrolyte using conductive atomic force microscopy

Composite solid electrolytes (CSEs) which formed a flexible interface with electrodes are considered as promising electrolytes candidates for all-solid-state batteries (ASSBs). However, the role of inorganic particles and migration of Li-ions still need to be investigated. Herein, LLZO-PEO composite electrolyte is prepared with different weight ratios (0, 50, 75 wt. %) of LLZO and in-situ conductive atomic force microscopy (c-AFM) is employed to observe the changes in electrolyte topography and mechanical properties at different temperatures. Furthermore, c-AFM provides novel insights into the inhomogeneous migration of ions and electrons within the electrolyte. At high temperatures, Li-ions migrate along the amorphous PEO interphase of 0 and 50 wt. % LLZO-PEO electrolytes. With the increase of LLZO content (75 wt. %), LLZO particles form a continuous ionic network and Li-ions migrate through the LLZO particles. At low temperatures, Li-ions can only migrate along the amorphous PEO. Also, the addition of LLZO inhibits the migration of electrons and improves the insulative properties of the composite electrolyte. The current work provides novel insights into the design and development of composite electrolytes for next-generation ASSBs.