Quick and Easy Material Identification of Salts Used in Lithium-Ion Batteries by FTIR

Importance of the Topic

Reliable identification of electrolyte salts is essential for ensuring performance, safety, and consistency in lithium-ion battery production and research. Rapid material confirmation helps prevent costly errors in manufacturing and accelerates the development of novel, high-performance electrolytes.

Objectives and Overview of the Study

This application note demonstrates how the Agilent Cary 630 FTIR spectrometer with ATR sampling and MicroLab software can be used to build a custom spectral library and rapidly verify the identity of common lithium-ion battery electrolyte salts, even under moisture-controlled glove box conditions.

Methodology and Instrumentation

The study employed a compact FTIR-ATR system equipped with a diamond crystal module. Seven reference salts (Li2CO3, LiCl·H2O, LiCl, LiFePO4, LiTFSI, LiPF6, LiBF4) were measured to create a user-generated library in seconds. Unknown samples were then analyzed without sample preparation by pressing the solid directly on the ATR crystal. Spectra were collected over 4000–650 cm–1 at 4 cm–1 resolution (32 background and sample scans) under argon purge. The MicroLab software controlled instrument parameters, guided the workflow with pictorial prompts, and applied a Similarity search algorithm to match unknowns against the custom library.

Main Results and Discussion

All four blind samples were correctly identified with hit quality indices above 0.98. Color-coded confidence levels (green >0.95) provided clear, immediate feedback and minimized operator interpretation. The workflow proved robust in a glove box, showing no compromise in spectral quality when handling moisture-sensitive lithium salts.

Benefits and Practical Applications

• No sample preparation or consumables required, enabling truly nondestructive testing.
• Ultracompact, lightweight FTIR design suitable for confined glove box environments.
• Rapid library creation and automated analysis reduce training needs and user error.
• Color-coded results streamline decision making for QA/QC and R&D laboratories.

Future Trends and Opportunities

Integration of FTIR-ATR with inline or at-line monitoring could support real-time quality control in battery assembly. Expanding spectral libraries to include novel electrolyte formulations and degradants will aid in accelerated development of next-generation batteries. Combining FTIR data with chemometric models or complementary techniques (e.g., Raman, NMR) may yield deeper insights into electrolyte stability and safety.

Conclusion

The Agilent Cary 630 FTIR spectrometer, paired with intuitive MicroLab software, offers a fast, reliable, and user-friendly tool for material identification of LIB electrolyte salts. Its glove box compatibility and automated library search capability make it ideal for both manufacturing quality control and research environments.

References

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• Szczuka C. et al. Identification of LiPF6 Decomposition Products in Li-Ion Batteries with Endogenous Vanadyl Sensors Using Pulse EPR and DFT. Adv. Energy Sustainability Res. 2021, 2, 2100121.
• Larsson F. et al. Toxic Fluoride Gas Emissions from Lithium-Ion Battery Fires. Sci. Rep. 2017, 7, 10018.
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• GB/T 19282-2014. Analytic Method for Lithium Hexafluorophosphate. National Standard of the PRC.
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