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

Significance of the Topic

Accurate identification of solvents in lithium-ion battery (LIB) electrolytes underpins battery performance, safety, and reliability. As demand grows for portable electronics, electric vehicles, and grid energy storage, ensuring raw materials meet strict quality requirements is essential for manufacturers and researchers alike.

Objectives and Overview

This study demonstrates a streamlined approach for fast and reliable solvent identification using the Agilent Cary 630 FTIR spectrometer with Attenuated Total Reflectance (ATR). Key objectives include:

• Creating a reference spectral library of common LIB electrolyte solvents.
• Developing a routine identification method using Agilent MicroLab software.
• Validating the method by identifying blind solvent samples.

Methodology and Instrumentation

The protocol leverages non-destructive FTIR-ATR analysis to capture characteristic chemical fingerprints without sample preparation. A reference library was built from standard solvents, and user-defined hit-quality thresholds were applied for pass/fail identification.

Used Instrumentation

• Agilent Cary 630 FTIR spectrometer with diamond ATR module.
• Agilent MicroLab software for instrument control, library creation, and spectral search.
• Sample handling: Direct application of a droplet onto the ATR crystal; cleaning with ethanol after each measurement.

Main Results and Discussion

Four commercially labeled “unknown” solvents were analyzed against the custom library using a similarity search algorithm. The hit quality index (HQI) values obtained were:

• Unknown 1: Ethyl methyl carbonate (EMC), HQI 0.9939 (high confidence)
• Unknown 2: Ethyl methyl carbonate (EMC), HQI 0.9453 (medium confidence)
• Unknown 3: Dimethyl carbonate (DMC), HQI 0.9782 (high confidence)
• Unknown 4: Ethyl acetate (EA), HQI 0.9968 (high confidence)

Color-coding of results (green >0.95, yellow 0.90–0.95) provided an intuitive display for rapid decision-making. One sample flagged at medium confidence illustrates the value of user-defined thresholds for further investigation.

Benefits and Practical Applications

The described workflow offers:

• Rapid, on-site verification of LIB solvent identity for quality assurance.
• Minimal training requirements due to pictorial software interface.
• Non-destructive testing, preserving sample integrity.
• Easy expansion and maintenance of the spectral library to include new materials.

Future Trends and Opportunities

Advances in battery chemistries and increased solvent diversity will drive the need for larger, AI-assisted spectral libraries. Integration of cloud-based data management and machine-learning algorithms can further enhance identification speed and confidence levels. Portable FTIR platforms may enable in-line monitoring during raw material intake.

Conclusion

The Agilent Cary 630 FTIR spectrometer with ATR and MicroLab software delivers a straightforward, reliable solution for solvent identification in LIB electrolyte production and R&D. High hit-quality indices and intuitive color-coded results streamline quality control workflows, ensuring material compliance and accelerating battery development.

References

1. Xing, J. et al. A Review of Nonaqueous Electrolytes, Binders, and Separators for Lithium-Ion Batteries. Electrochem. Energy Rev. 2022, 5, 14.
2. Zhang, J. et al. Ethers Illume Sodium-Based Battery Chemistry: Uniqueness, Surprise, and Challenges. Adv. Energy Mater. 2018, 8, 1801361.
3. Zonouz, A. F.; Mosallanejad, B. Use of Ethyl Acetate for Improving Low-Temperature Performance of Lithium-Ion Battery. Monatsh Chem. 2019, 150, 1041–1047.