Spatial‐Temporal Scanning Kelvin Probe Microscopy for Evaluating Ionic Velocity in Solid‐State Electrolytes

Solid-state electrolytes (SSEs) with high ionic conductivity are crucial for the development of high-performance all-solid-state batteries. While a growing number of strategies based on nanoengineering are emerging to enhance the ionic conductivity of SSEs, understanding nanoscale ionic transport remains a nontrivial challenge. In this work, a simple yet effective approach is developed for in situ measuring microscopic ionic velocity in SSEs. Ionic transport under an electric field is directly captured using spatial-temporal scanning Kelvin probe microscopy (SKPM). This method reliably quantifies the microscopic ionic conductivity of SSEs, consistent with the results of macroscopic electrochemical impedance spectra, while providing nanoscale spatial resolution that is essential for comprehending ionic migration in nanostructured systems. The spatial-temporal SKPM, validated on LiZr₂(PO₄)₃ and Li_1.05Zr_1.95Fe_0.05(PO₄)₃, can be further extended to other SSEs for direct visualization of ionic migration dynamics. This work contributes to the understanding of ionic transport mechanisms and paves the way for advancements in the ionic conductivity of SSEs.