Robust and sensitive measurement of trace element impurities in LiPF6 electrolyte solutions using ICP-OES

Significance of the Topic

Lithium-ion batteries are central to modern electronics and electric vehicles. Trace metal impurities in the LiPF6 electrolyte can impact performance, safety, and longevity. Reliable, high-throughput methods for monitoring these contaminants support quality control during production, battery ageing studies, and safe end-of-life recycling processes.

Study Goals and Overview

This application note describes the development and validation of a robust ICP-OES method using the Thermo Scientific iCAP PRO XP Duo system. The aim was to achieve sensitive, fast, and reproducible quantification of 15 trace elements in LiPF6 electrolyte solutions, demonstrating full method capabilities under real-world laboratory conditions.

Methodology and Instrumentation

Samples were fresh LiPF6 dissolved in mixtures of ethylene carbonate with ethyl-methyl or diethyl carbonate. Solutions (~2 mL) were diluted in an organic diluent (5 % EMC, 20 % ethanol, balance ultrapure water). Calibration standards up to 1000 µg/L and an internal standard (5 mg/L Y) tracked matrix effects. The iCAP PRO XP ICP-OES Duo was operated in intelligent full-range mode with axial plasma viewing for enhanced sensitivity. An HF-resistant PTFE spray chamber, Burgener PEEK MiraMist nebulizer, alumina injector, and ceramic D-torch ensured chemical compatibility and stability. Key parameters included 0.3 L/min nebulizer gas, 15 L/min coolant, 1250 W RF power, 10 s exposures, and three replicates per sample.

Main Results and Discussion

• Calibration was linear (R² > 0.9991) across 0–1000 µg/L for all elements.
• Instrument detection limits were in the sub-ppb to low ppb range, adequate for strict quality control.
• Spike recoveries (50 µg/L) in fresh electrolyte ranged from 83 % to 120 %, most above 90 %, confirming method accuracy.
• Internal standard recovery remained between 85 % and 90 % over 6-hour runs, demonstrating minimal drift and effective matrix compensation.
• Continuous calibration verifications and spiked sample checks during extended sequences showed recoveries within 80–120 %, reaffirming robustness.

Benefits and Practical Applications

• High sensitivity enables detection of trace impurities at regulatory limits and below.
• Fast analysis (≈3 min per sample) with minimal downtime supports high daily throughput (>100 samples).
• Low sample volumes and simple dilution reduce reagent use and operator workload.
• Robust performance over multiple days ensures reliability in production and research labs.

Future Trends and Applications

Advances may include coupling with automated sample processors for hands-off operation, expanding the dynamic range for ageing and failure analyses, and integrating with data-analytics platforms for real-time process control. Further development could target speciation studies of degradation products and inline monitoring in battery manufacturing lines.

Conclusion

The iCAP PRO XP ICP-OES Duo method delivers fast, sensitive, and reproducible measurement of trace metals in LiPF6 electrolytes. Its robustness, broad linear range, and low detection limits make it well suited for quality control, research, and lifecycle studies in the battery industry.

References

• 1. Pistoia, G., Ed.; Lithium Batteries—New Materials, Developments and Perspectives; Elsevier Science: Amsterdam, 1994.
• 2. Scrosati, B.; Insertion Compounds for Lithium Rocking Chair Batteries. In Electrochemistry of Novel Materials; Lipkowski, J.; Ross, P. N., Eds.; VCH: New York, 1993; pp 111–140.
• 3. Wu, W.; Yang, X.; Zhang, G.; Chen, K.; Wang, S. Experimental Investigation on the Thermal Performance of Heat Pipe-Assisted Phase Change Material Based Battery Thermal Management System. Energy Conversion and Management 2017, 138, 486–492.
• 4. Chinese Standard HGT/4067-2015; Cell Liquor of Lithium Hexafluorophosphate.