A multi-technique approach to understanding delithiation damage in LiCoO₂ thin films

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Lithium cobalt oxide (LiCoO2) is a key material in rechargeable batteries.
• Understanding lithium extraction (delithiation) is crucial for battery performance and longevity.
• Chemical delithiation offers an alternative to electrochemical methods for studying material degradation.

Purpose of the Study:

• To investigate the structural degradation of LiCoO2 thin films during chemical delithiation using oxalic acid.
• To understand the relationship between lithium extraction and structural damage.
• To explore chemical delithiation as a simplified method for studying insertion oxides.

Main Methods:

• Multi-technique approach including synchrotron X-ray diffraction, SEM, Raman spectroscopy, XPS, and conductive AFM.
• Chemical delithiation of LiCoO2 thin films with oxalic acid.
• Analysis of structural and chemical changes at the surface and in the bulk.

Main Results:

• Identified three delithiation regimes: surface processes, bulk delithiation, and damage generation.
• Observed selective lithium extraction, affecting only a fraction of grains and causing local inhomogeneities.
• Demonstrated effective bulk delithiation that mimics electrochemical delithiation behavior.
• Ruled out the formation of cobalt oxalate during the chemical extraction process.

Conclusions:

• Chemical delithiation using oxalic acid is a viable method to study LiCoO2.
• This method avoids complications from electrolyte breakdown, simplifying in-situ measurements.
• The study provides insights into LiCoO2 structural degradation during lithium removal.