Deterioration Evaluation of Lithium-Ion Battery Components Using Infrared/Raman Microscope and Airtight Cells

Significance of the Topic

Lithium-ion batteries power a wide range of applications from portable electronics to electric vehicles. Their performance degrades over repeated charge–discharge cycles due to structural and chemical changes in key components. Understanding these changes under realistic, inert conditions is critical for extending battery life and ensuring safety.

Objectives and Overview of the Study

This work applied an integrated infrared/Raman microscope (AIRsight) combined with airtight sample cells to evaluate deterioration in lithium-ion battery components. The study compared virgin and cycled samples of positive electrode, negative electrode, and separator materials after 100 charge–discharge cycles under controlled temperature and voltage.

Methodology and Instrumentation

A model cell was assembled using LiFePO4 (positive electrode), graphite (negative electrode), polypropylene separator, and a standard carbonate electrolyte. Two sample sets were prepared: a pristine cell and one subjected to 100 cycles at 4.8 V and 40 °C. Components were disassembled in a glovebox, cleaned, and sealed in CaF2-window airtight cells. Measurements were conducted with the AIRsight infrared/Raman microscope under the following conditions:

• Infrared reflection mode: 4000–880 cm-1 range, 8 cm-1 resolution, 100 accumulations for electrodes and 40 for separators
• Raman mode: 4000–150 cm-1 range, 10 accumulations, 10 s exposure, 50× objective, 532 nm excitation

Key Results and Discussion

Infrared spectra of LiFePO4 revealed a phosphate stretching band at 1230 cm-1. After cycling, a band near 1075 cm-1 shifted to higher wavenumbers, indicating lithium deintercalation and FePO4 formation. Raman analysis of graphite showed an increase in the disorder-related D band relative to the G band, with the ID/IG ratio rising from 0.21 to 0.32, reflecting increased structural defects. Polypropylene separator spectra remained unchanged, demonstrating stability under the test conditions.

Benefits and Practical Applications

Combining infrared and Raman techniques in a single instrument minimizes sample transfer and spatial misalignment, while airtight cells preserve air-sensitive materials for up to two weeks. This approach enables more accurate, correlated analyses of battery components and simplifies comparative studies.

Future Trends and Potential Applications

Advancements may include in situ monitoring during cycling, high-resolution mapping of degradation pathways, and application to emerging battery chemistries. Integration with machine learning could facilitate predictive models for performance and lifetime.

Conclusion

The AIRsight infrared/Raman microscope with airtight cells proved effective for assessing structural and chemical changes in lithium-ion battery components under inert conditions. It successfully identified electrode degradation mechanisms while confirming separator stability, offering a valuable tool for battery research and quality control.

References

1. A Ait Salah, P Jozwiak, K Zaghib, J Garbarczyk, F Gendron, A Mauger, C M Julien FTIR features of lithium-iron phosphates as electrode materials for rechargeable lithium batteries Spectrochimica Acta Part A 65 1007–1013 2006
2. Gen Katagiri Raman Spectroscopy of Graphite and Carbon Materials and Its Recent Application TANSO Journal of The Carbon Society of Japan No 175 304–313 1996