Quantifying Transport, Geometrical, and Morphological Parameters in Li-Ion Cathode Phases Using X-ray Microtomography

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Lithium-ion cathode performance depends on meso-scale geometry and constituent properties (active material, binder, conductive additive, pore).
• Electrode processing significantly impacts cathode structure and properties, influencing battery performance.
• Correlating processing techniques with charge/discharge behavior is key to enhancing battery performance.

Purpose of the Study:

• To investigate the relationship between electrode processing methods and the resulting morphology of lithium-ion cathodes.
• To characterize the geometrical and morphological differences in Li(Ni1/3Mn1/3Co1/3)O2 (NMC) cathodes processed via distinct techniques.
• To demonstrate how X-ray microtomography can elucidate these processing-morphology relationships for improved battery design.

Main Methods:

• Utilized X-ray microtomography to image pristine NMC cathode samples subjected to different processing approaches.
• Employed two sample preparation methods: epoxy casting (isolating active material) and Kapton tape encapsulation (enabling phase contrast for segmentation).
• Analyzed geometrical and morphological details of active material and secondary phases (carbon/binder, pore) using phase contrast imaging.

Main Results:

• Calendered and ball-milled samples showed distinct differences in active material geometry and morphology.
• Drying modes influenced the distribution of secondary phases and pore structures.
• Phase contrast imaging effectively segmented active material from binder, conductive additive, and pore regions, revealing processing-induced structural variations.

Conclusions:

• Electrode processing techniques significantly alter cathode morphology at the meso-scale.
• Understanding the processing-morphology relationship through advanced imaging like X-ray microtomography is crucial for optimizing lithium-ion battery performance.
• Phase contrast X-ray microtomography offers valuable insights into multi-phase cathode structures, enabling targeted improvements in battery design and function.