Characterization of LiCoO₂ nanoparticle suspensions by single collision events

Area of Science:

• Electrochemistry
• Materials Science
• Nanotechnology

Background:

• Lithium ion (Li ion) insertion compounds are vital for battery technology.
• Accurate characterization of nanoparticle properties is essential for optimizing battery performance.
• Existing methods for nanoparticle sizing and diffusion coefficient measurement can be complex or indirect.

Purpose of the Study:

• To develop a new, additive-free electrochemical analytical tool for Li ion insertion compounds.
• To utilize transient electrochemical experiments on nanoparticle collisions for material characterization.
• To enable simultaneous measurement of nanoparticle size and Li ion diffusion coefficients.

Main Methods:

• Transient electrochemical experiments involving collisions between LiCoO2 (LCO) nanoparticles and a polarized gold ultramicroelectrode (UME).
• Analysis of single collision events to determine nanoparticle size, suspension diffusion, and Li ion diffusion.
• Electrochemical sizing distribution measurement via charge exchange during collisions.
• Estimation of LCO nanoparticle diffusion coefficient from collision frequency versus concentration.

Main Results:

• Successfully estimated LCO nanoparticle sizes (75-450 nm) and diffusion coefficients (nanoparticle suspension: ~8 × 10⁻⁹ cm²/s; Li ion within LCO: ~1.3 × 10⁻¹¹ cm²/s).
• Demonstrated electrochemical sizing concordance with optical techniques like DLS and cryo-TEM.
• Established a correlation between charge exchanged during collision and LCO aggregate size.
• Validated the estimation of Li ion diffusion coefficient, a key factor for battery cycle life and charge rate.

Conclusions:

• The developed electrochemical collision technique offers a powerful, additive-free method for characterizing Li ion insertion nanoparticles.
• This approach provides a detailed understanding of nanoparticle properties, including size distribution and crucial Li ion diffusion kinetics.
• The findings contribute to the advancement of materials characterization for improved Li ion battery performance.