Determination of tetrafluoroborate, perchlorate, and hexafluorophosphate in an electrolyte sample for lithium-ion battery production

Importance of the Topic

Precise quantitation of anions in lithium-ion battery electrolytes is critical for ensuring battery performance, safety, and energy density in consumer electronics and electric vehicles. Ion chromatography (IC) offers a robust means to monitor concentrations of key lithium salts such as tetrafluoroborate, perchlorate, and hexafluorophosphate in non-aqueous electrolyte mixtures.

Objectives and Overview

This study aims to update a previous method (AN258) by integrating modern RFIC equipment and miniaturized Dionex IonPac AS20 columns. The goal is to efficiently separate and quantify LiBF4, LiClO4, and LiPF6 in simulated battery electrolytes with reduced eluent consumption and improved peak resolution.

Methodology and Instrumentation

Reagent-free ion chromatography was performed on a Thermo Scientific Dionex ICS-6000 dual-channel HPIC system with RFIC-EG module and suppressed conductivity detection. A KOH gradient was generated using an EGC 500 cartridge coupled to a CR-ATC 600 trap column and high-pressure degasser. Separation employed 2 mm Dionex IonPac AG20 guard and AS20 analytical columns (2 × 50 mm and 2 × 250 mm). The eluent gradient (0–15 min: 15 mM KOH; 10–13 min: 80 mM; 13–26 min: 80 mM; 26–30 min: 15 mM) at 0.3 mL/min, 30 °C column temperature, and 70 mA suppressor current afforded baseline separation. Calibration standards (1–40 mg/L) and simulated samples of LiBF4, LiClO4, and LiPF6 in carbonate solvent mixtures were prepared and analyzed with 10 µL injections.

Main Results and Discussion

The method achieved clear separation with retention times of 11.8, 17.5, and 22.6 min for BF4–, ClO4–, and PF6–, respectively, with no interference from eluent shifts. Calibration curves were linear (r2 = 1.000) over 1–40 mg/L. Interday precision RSDs were below 1.8% for BF4–, 0.8% for ClO4–, and 4.5% for PF6–. Recoveries ranged from 94 to 112%, confirming method accuracy. The 2 mm column format reduced flow rate fourfold (from 1.2 to 0.3 mL/min), decreasing eluent usage and waste generation proportionally.

Applications and Practical Benefits

This IC method provides a reliable QA/QC tool for battery manufacturers to verify electrolyte composition, ensuring consistent energy density and safety. The lower eluent consumption reduces operating costs and extends cartridge life, while the improved peak resolution enhances quantification confidence.

Future Trends and Opportunities

Emerging directions include further miniaturization of IC systems, integration with mass spectrometry for structural confirmation, real-time online monitoring of production lines, and development of greener eluent generation strategies to minimize environmental impact.

Conclusion

The updated RFIC method with 2 mm Dionex IonPac AS20 columns offers a precise, accurate, and resource-efficient approach for simultaneous determination of tetrafluoroborate, perchlorate, and hexafluorophosphate in lithium-ion battery electrolytes, aligning with industry needs for high-throughput and sustainable analytics.

References

• Qi Li et al. Progress in electrolytes for rechargeable Li-based batteries and beyond. Green Energy & Environment. 2016;1(1):18–42.
• Thermo Fisher Scientific. Determination of Tetrafluoroborate, Perchlorate, and Hexafluorophosphate in a Simulated Electrolyte Sample from Lithium-Ion Battery Production. Application Note 258, 2010.
• Thermo Fisher Scientific. Dionex IonPac AS20 IC Columns Product Manual. Thermo Fisher Scientific.