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

Significance of the Topic

The reliable identification of solvents in lithium-ion battery (LIB) electrolytes is critical for ensuring performance, safety and consistency in battery production and development. Fast, non-destructive testing methods support quality assurance of raw materials and accelerate research and development of next-generation battery chemistries.

Objectives and Overview of the Study

This study demonstrates a streamlined workflow using the Agilent Cary 630 FTIR spectrometer with diamond ATR for rapid identification of common LIB electrolyte solvents. The goals were to build a user-generated spectral library, develop a routine identification method in Agilent MicroLab software, and validate the approach by testing four unknown commercial samples.

Methodology and Instrumentation

The core instrumentation comprised two Agilent Cary 630 FTIR spectrometers each fitted with a diamond ATR sampling module. One instrument was used to create a reference library and the second to test unknown samples. Key steps:

• Library generation: Spectra of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and ethyl acetate (EA) were acquired and stored in MicroLab.
• Operating parameters: Spectral range 4 000–650 cm–1, resolution 2 cm–1, 24 sample scans, 10 background scans, Happ–Genzel apodization, Similarity search algorithm.
• Sample handling: A drop of liquid solvent was placed on the ATR crystal, scanned, then cleaned with ethanol.

Main Results and Discussion

Four unknown solvents were analyzed and matched against the library using the Similarity algorithm. Hit quality index (HQI) values and color coding provided confidence levels:

• Sample 1 (EMC): HQI 0.9939 (green, high confidence)
• Sample 2 (EMC): HQI 0.9453 (yellow, medium confidence)
• Sample 3 (DMC): HQI 0.9782 (green, high confidence)
• Sample 4 (EA): HQI 0.9968 (green, high confidence)

The intuitive MicroLab interface displays color-coded results immediately, minimizing operator training and expediting decision-making. A medium-confidence result can trigger further investigation or alternate testing as required.

Benefits and Practical Applications

The described method offers several advantages:

• Rapid, non-destructive analysis with no sample preparation.
• Compact, portable FTIR system for lab or field use.
• User-friendly, picture-driven software reducing user errors.
• Customizable HQI thresholds and color coding for pass/fail workflows.
• Applicability to QA/QC of LIB raw materials and support for R&D efforts.

Future Trends and Potential Applications

Extensions of this approach may include:

• Expansion of spectral libraries to include additives and advanced solvent mixtures.
• Integration with automated sampling and inline process monitoring.
• Incorporation of chemometric models for quantitative impurity analysis.
• Deployment in manufacturing environments for real-time QA of battery components.

Conclusion

The Agilent Cary 630 FTIR spectrometer with ATR and MicroLab software provides a robust, rapid, and user-friendly solution for solvent identification in LIB electrolytes. The method delivers high confidence results, supports streamlined QA/QC workflows, and aids R&D teams in advancing battery technology.

Reference

• Xing J. et al. A Review of Nonaqueous Electrolytes, Binders, and Separators for Lithium-Ion Batteries. Electrochem. Energy Rev. 2022, 5, 14. doi:10.1007/s41918-022-00131-z
• Zhang J. et al. Ethers Illume Sodium-Based Battery Chemistry: Uniqueness, Surprise, and Challenges. Adv. Energy Mater. 2018, 8, 1801361. doi:10.1002/aenm.201801361
• Zonouz A. F.; Mosallanejad B. Use of Ethyl Acetate for Improving Low-Temperature Performance of Lithium-Ion Battery. Monatsh. Chem. 2019, 150, 1041–1047. doi:10.1007/s00706-019-2360-x