Qualitative and Quantitative Analysis of Carbonate Organic Solvents in Lithium Battery Electrolysis by LC/Q-TOF

Importance of the Topic

The composition of carbonate-based organic solvents in lithium battery electrolytes directly impacts ion transport, electrochemical stability, and overall battery performance. Precise analysis of these solvents is essential for quality control, formulation optimization, and ensuring long-term safety and efficiency of lithium-ion cells.

Objectives and Study Overview

This study aims to develop a reliable workflow for both qualitative and quantitative analysis of four common carbonate solvents—ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC)—in lithium battery electrolytes. Using high-resolution LC/Q-TOF mass spectrometry, the research evaluates identification confidence and constructs calibration models for EC and PC quantification in real-world samples.

Methodology and Instrumentation

Sample Preparation:

• Electrolyte samples were provided by a user and diluted with acetonitrile.
• After filtration, samples were directly injected into the LC/Q-TOF system.
• Standard curves for EC and PC were prepared by serial dilution of 100 μg/mL stock solutions to achieve 50–2000 ng/mL.

Liquid Chromatography – UHPLC Conditions:

• System: Agilent 1290 Infinity II binary pump with autosampler and column thermostat.
• Column: Agilent InfinityLab Poroshell 120 Bonus-RP, 3.0 × 100 mm, 2.7 µm.
• Mobile Phase: A = water with 0.1% formic acid; B = methanol.
• Gradient: 0–1 min (0% B), 1–8 min (0→50% B), 8–10 min (50→100% B), 10–12 min (100% B); post time 3 min.
• Flow Rate: 0.4 mL/min; Column Temp: 35 °C; Injection Volume: 2 µL.

Mass Spectrometry – Q-TOF Conditions:

• Instrument: Agilent 6546 LC/Q-TOF with Dual Agilent Jet Stream ESI source.
• Ion Mode: Positive; Capillary Voltage: 2500 V; Nozzle Voltage: 500 V.
• Drying Gas: 8 L/min at 250 °C; Sheath Gas: 12 L/min at 350 °C; Nebulizer: 45 psi.
• Fragmentor: 70 V; Mass Range: 20–1000 m/z.

Results and Discussion

Qualitative Identification:

• High-resolution full-scan and MS/MS spectra were acquired for each solvent peak.
• Compounds were matched against the Agilent PCDL database, yielding >90% match scores at 10 eV collision energy.
• MassHunter MSC software generated molecular formulas and proposed structures based on fragment correlations, confirming identification of EC, PC, DMC, and EMC.

Quantitative Analysis:

• Calibration curves for EC and PC demonstrated excellent linearity (R² > 0.99) over 50–2000 ng/mL.
• Analysis of three commercial electrolyte samples revealed EC concentrations of 2.0×10⁵–2.6×10⁵ µg/mL and PC concentrations of 5.0×10⁴–1.1×10⁵ µg/mL.

Benefits and Practical Applications

The developed LC/Q-TOF method offers high specificity, sensitivity, and throughput for routine monitoring of carbonate solvents in battery manufacturing and R&D. It supports formulation optimization by accurately determining solvent ratios and detecting trace impurities that may impact battery safety and lifespan.

Future Trends and Opportunities

Continued advances in high-resolution mass spectrometry and data-processing algorithms will enable:

• Automated screening of broader unknown compound classes.
• Integration with real-time process analytics for in-line monitoring.
• Application of machine learning to predict performance-related electrolyte properties.
• Development of greener solvent systems guided by rapid analytics.

Conclusion

This work establishes a robust UHPLC/Q-TOF MS platform for comprehensive analysis of carbonate solvents in lithium battery electrolytes, combining reliable qualitative identification with precise quantification. The approach enhances quality control and supports electrolyte design improvements.

Reference

• Wang H., Lin Z., Hu P., Li J., Pyke J. Qualitative and Quantitative Analysis of Carbonate Organic Solvents in Lithium Battery Electrolysis by LC/Q-TOF, Poster WP 306, ASMS 2023.
• Agilent Technologies. Application Note DE02091426, 2023.