Improving Battery Production Yield, Performance, and Stability Using FTIR

Importance of the Topic

This application note highlights the critical need for reliable quality control of lithium hexafluorophosphate (LiPF6), the principal electrolyte salt in lithium-ion batteries. Due to its high reactivity with moisture and potential to generate corrosive and toxic by-products, stringent monitoring is essential to ensure battery performance, longevity, and safety.

Objectives and Study Overview

• Demonstrate a streamlined QA/QC workflow for LiPF6 using FTIR spectroscopy in manufacturing environments
• Compare degradation status of samples subjected to different storage and environmental conditions
• Evaluate the impact of moisture exposure on material identification confidence

Methodology and Instrumentation

The study employs the Agilent Cary 630 FTIR spectrometer equipped with a diamond ATR module to perform rapid, non-destructive chemical fingerprinting. Spectral data were acquired from 4000 to 650 cm–1 at 4 cm–1 resolution, collecting 32 background and sample scans. A user-generated spectral library and similarity search algorithm yield a hit quality index (HQI) for material confirmation.

Instrumentation Used

• Agilent Cary 630 FTIR spectrometer
• Diamond ATR module suitable for glovebox and bench applications
• Agilent MicroLab FTIR software with library management and color-coded confidence indicators

Results and Discussion

Three LiPF6 samples were analyzed under different conditions:

• Sample 1 (new bottle, moisture-free environment): HQI 0.9939 (high confidence)
• Sample 2 (opened eight months earlier, moisture-free environment): HQI 0.9137 (medium confidence)
• Sample 3 (opened eight months earlier, ambient air): HQI 0.7915 (low confidence), indicating significant degradation

The time-resolved monitoring of sample 3 over ten minutes revealed progressive changes in absorption peaks around 803 cm–1, confirming ongoing decomposition in the presence of moisture.

Benefits and Practical Applications

• Enables fast pass/fail assessment of LiPF6 quality in production and research settings
• Provides intuitive, color-coded confidence levels for immediate decision making
• Compact and robust design for integration in gloveboxes and field laboratories

Future Trends and Opportunities

• Integration of machine learning and advanced chemometric tools for enhanced spectral analysis
• Expansion of spectral libraries to cover additional battery salts and degradation products
• Development of real-time monitoring systems for electrolyte health during cell assembly and cycling

Conclusion

The combination of the Cary 630 FTIR spectrometer and MicroLab software offers a straightforward, reliable approach to assess LiPF6 integrity. Leveraging HQI-based pass/fail criteria and user-friendly software guidance empowers manufacturers and researchers to safeguard battery quality, performance, and safety.

References

1. Larsson F et al. Toxic Fluoride Gas Emissions from Lithium-Ion Battery Fires. Sci Rep 2017;7(1):10018.
2. Han JY, Jung S. Thermal Stability and the Effect of Water on Hydrogen Fluoride Generation in Lithium-Ion Battery Electrolytes Containing LiPF6. Batteries 2022;8(7):61.
3. Juba BW et al. Lessons Learned Fluoride Exposure and Response. Journal of Chemical Health and Safety 2021;28(2).
4. Kraft V et al. Ion Chromatography Electrospray Ionization Mass Spectrometry Method Development and Investigation of Lithium Hexafluorophosphate-Based Organic Electrolytes and Their Thermal Decomposition Products. J Chromatogr A 2014;1354:92–100.