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

Importance of the Topic

Maintaining high purity and clarity in lithium-ion battery electrolytes is critical for performance, safety, and cycle life. Trace particulates generated by moisture-induced degradation can impede ion transport, accelerate side reactions, and compromise overall battery reliability. Rapid detection of low-level haze provides an effective quality control measure to identify early signs of electrolyte deterioration that are not visible to the naked eye.

Objectives and Study Overview

This application note evaluates a new UV-Vis spectroscopy approach using the Agilent Cary 60 spectrophotometer with a diffuse reflectance accessory (DRA) to quantify haze in battery-grade electrolytes. Two common formulations (1.0 M LiPF₆ in EC/DMC and EC/EMC) were monitored over time to demonstrate the method’s sensitivity in detecting particulate contamination and degradation under standard storage conditions.

Methodology and Instrumentation

Five-milliliter aliquots of each electrolyte were stored in sealed glass vials at room temperature and sampled fresh, after one day, and after six months. Three milliliters were transferred to 10 mm quartz cuvettes for analysis. Haze measurements followed ASTM D1003 using four integrating-sphere scan modes (baseline, sample + white reference, blank, and sample alone). Key instrument settings:

• Scan range: 380–780 nm, 1 nm interval
• Spectral bandwidth: 1.5 nm
• Signal averaging: 0.1 s
• CIE illuminant A, 2° observer
• Calculation mode: “Haze as per D1003”

Used Instrumentation:

• Agilent Cary 60 UV-Vis Spectrophotometer
• Diffuse Reflectance Accessory (DRA) with integrating sphere
• Cary WinUV Color software for haze calculations and reporting

Main Results and Discussion

Fresh samples exhibited very low haze values (0.20% for EC/EMC, 0.59% for EC/DMC), indicating high clarity. After one day, haze rose to 1.06% (EC/EMC) and 2.15% (EC/DMC) without visible turbidity. Six-month storage produced haze levels of 13.39% and 9.73%, respectively, accompanied by yellowish discoloration. These findings confirm that the integrating-sphere method captures early particulate formation and moisture-related breakdown more effectively than standard transmission measurements.

Benefits and Practical Applications

• Early detection of sub-visible particulates ensures tighter quality control in electrolyte production.
• Non-destructive, rapid analysis with automated reporting accelerates routine screening.
• Improved light collection efficiency minimizes measurement errors in low-scattering samples.
• Supports storage and transport monitoring to prevent compromised battery performance.

Future Trends and Opportunities

Expanding haze analysis to a broader range of electrolyte chemistries and additives could further optimize battery manufacturing workflows. Integration with inline process monitoring and AI-driven predictive maintenance systems may enable real-time quality assurance. Advances in miniaturized integrating-sphere accessories could facilitate portable field testing for on-site diagnostics.

Conclusion

The Agilent Cary 60 UV-Vis spectrophotometer with DRA offers a sensitive and reliable approach for low-level haze detection in lithium-ion battery electrolytes. By capturing scattered light from sub-visible particulates, this method uncovers early degradation events, enhances quality control, and contributes to the development of safer, higher-performing batteries.

References

• Agilent Technologies, Cary 60 UV-Vis Spectrophotometer Documentation
• Cary WinUV Color Software User Guide
• ASTM D1003 Standard Test Method for Haze and Luminous Transmittance