Quality Control of Lithium-Ion Battery Electrolytes Using LC/MS

Significance of the Topic

The quality of lithium-ion battery electrolytes influences battery efficiency, safety, and lifespan. Degradation of organic carbonate solvents through moisture or thermal stress generates oligomers that impair performance and accelerate aging. Robust analytical methods are essential for routine quality control and research in battery development.

Objectives and Study Overview

This study demonstrates an HPLC-MS approach for simultaneous separation and quantification of common electrolyte solvents—ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate (PC), ethyl methyl carbonate (EMC)—and their degradation products dimethyl 2,5-dioxahexanedioate (DMDOHC) and diethyl 2,5-dioxahexanedioate (DEDOHC). The method targets detection limits below 30 ppm for main components and below 5 ppb for degradation products.

Methodology

A reversed-phase gradient from 2 percent to 95 percent acetonitrile over 14 minutes was applied at a flow rate of 0.4 mL/min. Sample injections of 1 µL in feed injection mode prevented peak distortion from strong solvents. Quantitative detection employed positive-ion SIM mode monitoring of selected fragment ions. Calibration curves spanned 0.01–10 ppm for EC, PC, DMDOHC, DEDOHC and 10–10 000 ppm for DMC, DEC, EMC with 1/x weighting.

Used Instrumentation

• Agilent 1260 Infinity II Flexible Pump (G7104C)
• Agilent 1260 Infinity II Hybrid Multisampler (G7167C)
• Agilent 1260 Infinity II Multicolumn Thermostat (G7116A)
• Agilent 1260 Infinity II Diode Array Detector WR (G7115A)
• Agilent InfinityLab LC/MSD iQ Single Quadrupole (G6160A)
• Poroshell 120 EC-C18 Column, 2.1×250 mm, 4 µm

Main Results and Discussion

All seven analytes were separated within 14 minutes with excellent peak shape. Calibration linearity (R²>0.996) and LOQs between 0.011 and 94 ppm were achieved. In fresh electrolyte, DMC and DEC accounted for ~32.6 percent and ~40.5 percent, while EC exceeded calibration limits. Degradation products appeared at 0.007 ppm (DMDOHC) and 0.45 ppm (DEDOHC). After one-week aging at 40 °C, DMC and DEC levels decreased and oligomer concentrations rose to 12.3 ppm and 32.6 ppm.

Benefits and Practical Applications

The method offers rapid, sensitive analysis for routine QC of electrolyte formulations. It enables battery manufacturers and research laboratories to monitor solvent purity and early-stage degradation, supporting improvements in performance and shelf life.

Future Trends and Potential Uses

Extending the method to additional oligomeric degradation products or trace impurities via high-resolution or tandem MS can enhance structural insights. Coupling with automated sample preparation and online elemental analysis may support high-throughput screening in battery research and production.

Conclusion

The presented LC/MS method provides a fast, reliable, and sensitive approach for quality control of lithium-ion battery electrolytes. It quantifies key solvents and degradation products at trace levels, facilitating performance monitoring and stress-testing applications.

References

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2. Rapid Analysis of Elemental Impurities in Battery Electrolyte by ICP-OES. Agilent Technologies application note, 5994-1937EN, 2020.
3. Quick and Easy Material Identification of Salts Used in Lithium-Ion Batteries by FTIR. Agilent Technologies application note, 5994-6243EN, 2023.
4. Schultz C.; Vedder S.; Streipert B.; Winter M.; Nowak S. Quantitative Investigation of the Decomposition of Organic Lithium Ion Battery Electrolytes with LC-MS/MS. RSC Adv. 2017, 7(45), 27853–27862.