Improving Battery Production Yield, Performance, and Stability Using FTIR

Significance of the Topic

The accelerating shift to electric vehicles and large‐scale energy storage demands robust quality control for lithium‐ion battery materials. Lithium hexafluorophosphate (LiPF6), the principal salt in commercial electrolytes, is highly reactive and prone to moisture‐induced decomposition, generating corrosive hydrogen fluoride. Uncontrolled degradation negatively impacts battery safety, performance, and manufacturing yield.

Objectives and Study Overview

This application note demonstrates a streamlined FTIR‐ATR workflow for rapid quality assessment of battery‐grade LiPF6. Using the Agilent Cary 630 FTIR spectrometer and MicroLab software, the study evaluates salt integrity under varied storage and handling conditions, establishing pass/fail criteria based on a library match quality index (HQI).

Materials, Methodology and Instrumentation

• Instrument: Agilent Cary 630 FTIR spectrometer with diamond ATR module
• Software: Agilent MicroLab FTIR with user‐generated LiPF6 library
• Acquisition parameters: 4000–650 cm–1 spectral range, 32 background and sample scans, 4 cm–1 resolution, no zero fill, Happ‐Genzel apodization, Mertz phase correction
• Library search: similarity algorithm, HQI thresholds—green >0.95, orange 0.90–0.95, red <0.90
• Samples: three LiPF6 bottles—new unopened, opened eight months ago (moisture‐controlled), and opened eight months ago (measured in ambient air)

Key Results and Discussion

• Sample 1 (new, moisture‐free): HQI 0.9939 (high confidence)
• Sample 2 (opened, stored dry): HQI 0.9136 (medium confidence)
• Sample 3 (opened, measured in air): HQI 0.7915 (low confidence)

Time‐resolved ATR spectra of Sample 3 revealed progressive attenuation of the 803 cm–1 band over 10 minutes, confirming moisture‐driven degradation. Color‐coded HQI results enable immediate pass/fail decisions, underlining the need for dry handling of opened LiPF6.

Benefits and Practical Applications

• Non‐destructive, rapid fingerprinting of reactive salts
• Minimal operator training via intuitive graphical interface
• Compact design suitable for bench and glovebox use
• Real‐time quality decisions for manufacturing QC and research and development

Future Trends and Applications

• Integration of FTIR QC into automated production lines for inline monitoring
• Expansion of spectral libraries to cover diverse battery chemistries
• At‐line and in‐process analysis to reduce downtime and waste
• Predictive maintenance and lifetime assessment based on spectral degradation markers

Conclusion

The combination of the Agilent Cary 630 FTIR and HQI‐based MicroLab software offers a straightforward, robust solution for assessing LiPF6 degradation. Its ease of use and compact footprint make it an invaluable tool for enhancing battery production yield, performance, and safety in both industrial and laboratory environments.

References

1. Larsson F. et al. Toxic Fluoride Gas Emissions from Lithium‐Ion Battery Fires. Sci. Rep. 2017, 7(1), 10018.
2. Han J.Y.; 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 B.W. 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.