Low-Level UV-Vis Haze Detection for Improved Reliability of Li-Ion Battery Electrolytes

Significance of the Topic

The purity and stability of lithium-ion battery electrolytes critically influence battery performance, safety, and lifetime. Trace particulate contaminants, often invisible to the naked eye, can lead to reduced ion transport, compromised safety, and overall performance loss. Rapid, sensitive detection of low-level haze in electrolyte solutions addresses a key quality control gap in battery manufacturing and storage.

Study Objectives and Overview

This application note demonstrates a UV-Vis spectroscopy–based approach for low-level haze detection in lithium-ion battery electrolytes using an integrating sphere accessory. The objectives are to:

• Develop a rapid, reproducible method for assessing haze in electrolyte solutions.
• Compare haze levels in fresh and aged samples of LiPF6 in EC/DMC and EC/EMC mixtures.
• Highlight instrumentation advantages for manufacturing quality control.

Methodology and Instruments

Electrolytes tested were 1.0 M LiPF6 in EC/EMC (50/50 v/v) and 1.0 M LiPF6 in EC/DMC (50/50 v/v). Samples were stored in sealed vials at room temperature and analyzed fresh, after 1 day, and after 6 months. Haze measurements were performed by:

• Transferring 3 mL of sample into a standard 10 mm quartz cuvette.
• Employing diffuse transmission measurements from 380 to 780 nm with 1 nm intervals, 1.5 nm bandwidth, and 0.1 s signal averaging.
• Using the ASTM D1003 method (“Haze as per D1003”) in Cary WinUV Color software.

Instrumentation Used

• Agilent Cary 60 UV-Vis spectrophotometer.
• Agilent diffuse reflectance accessory (integrating sphere).
• Agilent Cary WinUV Color software for haze calculations (CIE A illuminant, 2° observer angle).

Main Results and Discussion

Fresh electrolyte solutions exhibited very low haze values (0.59 % for EC/DMC and 0.20 % for EC/EMC), indicating high clarity. After 24 hours of storage, haze rose to 2.15 % (EC/DMC) and 1.06 % (EC/EMC) without visible turbidity. Six-month–old samples showed pronounced degradation (haze of 9.73 % and 13.39 %), accompanied by yellowish discoloration. The integrating sphere captured scattered light that conventional transmission measurements may miss, demonstrating the method’s sensitivity to early-stage particulate formation.

Benefits and Practical Applications

This UV-Vis haze detection technique offers:

• High sensitivity to low-level turbidity in electrolyte solutions.
• Rapid, non-destructive analysis suitable for inline or at-line quality control.
• Automated reporting and haze calculations via Cary WinUV Color software.
• Enhanced reliability in battery production, storage, and transportation monitoring.

Future Trends and Potential Applications

Advances in integrating sphere design and spectral analysis may further lower detection limits and enable real-time monitoring. Combining haze data with chemometric models could predict electrolyte degradation pathways. This methodology could extend to other sensitive battery chemistries and high-purity solvent systems across pharmaceutical and specialty chemical industries.

Conclusion

The Agilent Cary 60 UV-Vis spectrophotometer with diffuse reflectance accessory provides a robust, sensitive method for detecting low-level haze in lithium-ion battery electrolytes. Early identification of particulate contamination supports improved safety, performance, and lifecycle management of batteries. Integration of automated haze calculations and reporting streamlines quality control workflows.

References

• Alwan W. Low-Level UV-Vis Haze Detection for Improved Reliability of Li-Ion Battery Electrolytes; Application Note 5994-8446EN; Agilent Technologies: 2025.
• ASTM D1003. Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics; ASTM International.