Analysis of electrode materials for lithium ion batteries

Significance of the topic

The performance and lifetime of lithium-ion batteries depend critically on electrode surface chemistry and interphase layers formed during cycling. Characterizing these air-sensitive surfaces with high fidelity is essential to guide materials development and improve energy density, cycle life, and safety.

Objectives and study overview

• Demonstrate X-ray photoelectron spectroscopy (XPS) analysis of pristine and cycled Li(NiMnCo)O₂ cathodes.
• Assess surface composition changes, particularly lithium content, after cell charging.
• Preserve electrode surfaces during transfer from inert environment to the spectrometer.

Methodology and Instrumentation

To prevent sample exposure to air, electrode specimens were prepared in a glove box and transferred in a Thermo Scientific Vacuum Transfer Module (VTM) compatible with the Nexsa XPS System. The VTM was evacuated in the glove box antechamber, ensuring inert transport into the spectrometer load-lock. Survey spectra were acquired on pristine and multiple-cycle charged cathodes to quantify element-specific signals.

Instrumentation:

• Thermo Scientific Nexsa XPS System
• Vacuum Transfer Module for inert sample handling
• Glove box for sample preparation under inert atmosphere

Main Results and Discussion

• The pristine cathode showed significant binder residue composed of fluorine- and oxygen-containing polymers, which may influence early cycling behavior.
• The cycled cathode retained binder signals and exhibited additional electrolyte decomposition products on its surface.
• Quantitative analysis of Ni, Mn, and Co in Li(NiMnCo)O₂ remained consistent between samples, while lithium intensity dropped to approximately 40% in the charged state, reflecting expected lithium migration away from the cathode during charging.

Benefits and Practical Applications

• Inert transfer preserves true surface chemistry for accurate XPS analysis of air-sensitive battery electrodes.
• Quantitative insights into binder residues and electrolyte decomposition guide electrode formulation and processing optimization.
• Monitoring lithium depletion supports validation of charge-discharge mechanisms and quality control in battery manufacturing.

Future Trends and Opportunities

• Integration of in situ and operando XPS to observe electrode reactions under realistic operating conditions.
• Advanced depth profiling approaches to map solid-electrolyte interphase (SEI) layer composition and growth dynamics.
• Expansion to novel cathode chemistries, including high-nickel and multi-element oxide systems.
• Combination with complementary techniques (e.g., ToF-SIMS, TEM) for multidimensional surface characterization.

Conclusion

The application of a vacuum transfer module coupled with Nexsa XPS enables reliable analysis of lithium-ion battery electrodes without ambient exposure. Observed changes in binder presence and lithium concentration between pristine and charged cathodes validate the approach for studying electrode surface phenomena, providing valuable feedback for battery material development.

Reference

• Thermo Fisher Scientific. Application Note AN52615: Analysis of electrode materials for lithium ion batteries. 2018.