Scanning Transmission Electron Microscopy Techniques for Cathode Material Analysis

Title: Phase Transitions and Ion Transport in Lithium Iron Phosphate by Atomic-Scale Analysis to Elucidate Insertion and Extraction Processes in Li-Ion Batteries
Authors: Šimic et al.,
Journal: Advanced Energy Materials Link

To fully understand the lithiation dynamics in cathode materials, atomic-scale visualization and quantification are essential. In this study, the authors applied selected area electron diffraction and scanning transmission electron microscopy (STEM) with integrated differential phase contrast imaging (iDPC) to examine the lithiation behavior in LiFePO₄ (LFP), a widely used and commercially relevant cathode material. This approach allowed the researchers to calculate local strain, crystal misfit, and estimate the lithium diffusion coefficient, revealing that lithium diffusion within the LFP lattice is constrained by multiple limiting factors.

The technique holds promise for application to other cathode systems, such as lithium nickel manganese cobalt oxides with varied nickel and manganese ratios, or manganese-doped LFP. It provides critical insights into structural features like phase relationships, strain, and distortion, as well as, to some extent, lithium kinetics—offering valuable guidance for cathode design.