Quantifying redox heterogeneity in single-crystalline LiCoO₂ cathode particles

Area of Science:

• Materials Science
• Electrochemistry
• Synchrotron Radiation Physics

Background:

• Active cathode particles, like lithium cobalt oxide (LCO), are critical for Li-ion battery performance.
• The microstructure of LCO particles significantly impacts electrochemical behavior and cell-level performance.
• Despite assumptions of homogeneity in crystalline LCO, sub-particle charge inhomogeneity is a known challenge.

Purpose of the Study:

• To revisit and address the challenge of sub-particle level charge inhomogeneity in LCO particles.
• To develop a robust methodology for accurately analyzing local spectroscopic fingerprints in single-crystalline LCO.
• To reveal the mesoscale chemical complexity within LCO particles with improved fidelity.

Main Methods:

• Utilized X-ray absorption spectra on single-crystalline LCO particles with anisotropic lattice structures.
• Addressed the ambiguity caused by X-ray polarization sensitivity in spectral analysis.
• Developed a novel method extracting white-line peak energy from X-ray absorption near-edge structure (XANES) spectra as a key attribute for local state-of-charge representation.

Main Results:

• Demonstrated that X-ray absorption spectra are sensitive to incident X-ray polarization, impacting analysis.
• The developed methodology significantly improves the accuracy of local state-of-charge determination in LCO.
• Revealed mesoscale chemical complexity within LCO particles with enhanced fidelity.

Conclusions:

• The new XANES-based method accurately quantifies local charge distribution in LCO particles.
• Highlights the importance of particle engineering for optimizing LCO cathode performance.
• The methodology has broad applicability for spectro-microscopic studies of single-crystalline materials at synchrotron facilities.