Analysis of Hexafluorophosphate Ion in Electrolytic Solution for Lithium-Ion Rechargeable Batteries by Ion Chromatography

Importance of the topic

Accurate determination of the hexafluorophosphate (PF6−) ion is essential for controlling the quality and performance of lithium-ion battery electrolytes. As LiPF6 can hydrolyze and generate impurities that affect battery life and safety, robust analytical techniques are vital for both industrial manufacturing and research.

Objectives and Study Overview

This work presents an ion chromatography (IC) method using a suppressor-type system to quantify PF6−. The study aims to demonstrate chromatographic separation, evaluate calibration linearity and repeatability, and apply the method to a commercial lithium-ion battery electrolyte.

Methodology

Sample preparation and chromatographic conditions were optimized as follows:

• Dilution: Electrolyte diluted 1,000‐fold with pure water and filtered through a membrane.
• Column: Shim-pack IC-SA2 (10 mm L × 4.6 mm I.D.) with Shim-pack IC-SA2(G) guard to handle strong PF6− retention.
• Mobile phase: 12 mmol/L NaHCO3 and 0.6 mmol/L Na2CO3, flow rate 1.0 mL/min.
• Injection volume: 10 µL; column temperature: 30 °C.

Used Instrumentation

• Shimadzu Prominence HIC-SP suppressor-type ion chromatograph.
• CDD-10A SP conductivity detector with chemical suppressor.
• Shim-pack IC-SA2 analytical column and matching guard column.

Key Results and Discussion

Analysis of PF6− standard solutions (2.5–250 mg/L) yielded a linear calibration (R2 > 0.999). Repeatability tests at 100 mg/L showed retention time RSD of 0.16 % and peak area RSD of 0.86 %. The method quantified PF6− in a commercial electrolyte labeled as 1 mol/L, obtaining 1.00 mol/L (144.6 mg/L) with no significant hydrolysis effects under the chosen conditions.

Benefits and Practical Applications

The described IC method delivers high sensitivity, precision and robustness for PF6− analysis, supporting quality control in battery manufacturing and research labs. Using potassium hexafluorophosphate as a standard simplifies handling and improves safety.

Future Trends and Potential Applications

Advancements may include coupling IC with mass spectrometry for impurity profiling, faster high-throughput columns, green mobile phases, and inline monitoring systems in battery production. Expanding the method to detect degradation products and other electrolyte salts can further enhance battery diagnostics.

Conclusion

The presented suppressor-type IC approach enables reliable quantitation of PF6− in both standards and commercial lithium-ion battery electrolytes, offering excellent linearity, repeatability and applicability for industrial quality assurance.

Reference

• Tasaki K., Kanda K., Nakamura S., Ue M.: Journal of The Electrochemical Society, 150(12) A1628–A1636 (2003).