An Atomic View of Cation Diffusion Pathways from Single-Crystal Topochemical Transformations.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Understanding lithium-ion diffusion in battery cathodes is crucial for improving Li-ion battery performance.
• Current methods often rely on computational models or lower-resolution imaging, limiting atomistic understanding.
• Experimental visualization of ion diffusion at the atomic scale remains a significant challenge.

Purpose of the Study:

• To experimentally image lithium-ion diffusion pathways at the atomistic level within a cathode material.
• To provide an angstrom-level 3D picture of ion diffusion in kinetic states.
• To validate computational models with experimental data for Li-ion battery materials.

Main Methods:

• Utilized topochemical lithium-ion insertion/extraction to induce single-crystal-to-single-crystal transformations in V₂O₅.
• Employed operando powder X-ray diffraction and single-crystal X-ray diffraction.
• Generated electron density maps to visualize ion diffusion in metastable phases.

Main Results:

• Identified the preferred lattice interstitial sites for lithium ions during insertion to high depths of discharge.
• Created a snapshot of ion diffusion dynamics in a metastable phase of the V₂O₅ polymorph.
• Achieved atomistic-level imaging of lithium-ion diffusion, providing experimental validation for theoretical predictions.

Conclusions:

• Developed an experimental approach for atomistic imaging of ion diffusion in battery materials.
• The study provides unprecedented experimental insight into lithium-ion transport mechanisms.
• This work paves the way for designing more efficient cathode materials for next-generation batteries.