Determination of Tetrafluoroborate, Perchlorate, and Hexafluorophosphate in a Simulated Electrolyte Sample from Lithium Ion Battery Production

Importance of Topic

Reliable control of anionic components in lithium-ion battery electrolytes is essential for product performance and safety. Quantitative analysis of tetrafluoroborate, perchlorate and hexafluorophosphate ensures proper electrolyte formulation and battery consistency.

Objectives and Study Overview

This work demonstrates a reagent-free ion chromatography (RFIC) method to determine three polarizable anions in simulated lithium-ion battery electrolytes. The study evaluates method accuracy, precision and applicability to complex solvent matrices.

Methodology and Instrumentation

Sample Preparation:

• Simulated electrolytes: 1 M solutions of LiBF₄ and LiClO₄ in a 1:1:1 mixture of ethylene, diethyl and propylene carbonates; LiPF₆ in water diluted with carbonate mix.
• Dilutions: 1:10,000 for BF₄^– and ClO₄^–, 1:5,000 for PF₆^–.

Chromatographic System and Conditions:

• RFIC platform: Thermo Scientific Dionex ICS-3000 with EG Eluent Generator module and Chromeleon™ software.
• Column: Dionex IonPac AS20 (4 × 250 mm) with AG20 guard (4 × 50 mm).
• Eluent: Gradient of KOH (15 mM to 80 mM over 26 min) generated in-line.
• Flow rate: 1.2 mL/min; column temperature: 35 °C; injection volume: 10 µL.
• Detection: Suppressed conductivity using Dionex ASRS 300 suppressor and CRD 200 Carbonate Removal Device in recycle mode.

Main Results and Discussion

Calibration and Separation:

• Linear response over 5–20 mg/L for all three anions with R² ≈ 1.00 and negligible offset.
• Complete resolution achieved in ~25 min; BF₄^– elutes at ~13 min, followed by ClO₄^– and PF₆^–.

Sample Analysis:

• Short-term precision (RSD) ≤0.8% for five replicate injections.
• Measured concentrations within 97–109% of expected values.
• Spike recoveries between 85% and 109%, confirming accuracy in complex matrices.

Benefits and Practical Applications

• Eliminates manual eluent preparation and use of organic modifiers.
• High-capacity AS20 column ensures sharp peaks for polarizable anions.
• Reagent-free design simplifies workflow and reduces waste.
• Suitable for routine QC in battery manufacturing and R&D labs.

Future Trends and Potential Applications

• Extension to additional anionic impurities and wider concentration ranges.
• Integration with mass spectrometry for enhanced selectivity.
• Automation and on-line monitoring for real-time electrolyte quality control.
• Faster gradients and miniaturized columns to increase throughput.

Conclusion

The RFIC method using a Dionex IonPac AS20 column offers accurate, reproducible determination of tetrafluoroborate, perchlorate and hexafluorophosphate in lithium-ion battery electrolytes. Its simplified eluent generation and robust performance make it ideal for QC and research applications.

Reference

Thunyarat Phesatcha et al., Application Note 258, Thermo Fisher Scientific (2016)