Avoid Thermal Runaway by Monitoring Battery Swell Gas and Electrolyte Degradation

Importance of Topic

Lithium-ion battery safety is critical for preventing thermal runaway and ensuring reliable performance. Monitoring gas evolution and electrolyte degradation provides early warning of cell failure and supports quality control in manufacturing and research.

Objectives and Study Overview

This application note presents a valve-free gas chromatography (GC) approach to analyze three key aspects of battery safety:

• Hydrocarbon composition in battery swell gas
• Hydrogen monitoring as an indicator of cell degradation
• Electrolyte solvent and additive profiling

The goal is to achieve sensitive, reproducible detection and to identify both known and unknown species using a single dual‐detector GC system.

Instrumentation Used

The analytical setup includes an Agilent 8890 GC configured with:

• An Agilent 5977B GC/MSD for mass‐selective detection and compound identification
• A thermal conductivity detector (TCD) for hydrogen and permanent gas analysis
• A valve‐free QuickSwap capillary flow module for rapid column changes without venting
• CTC PAL3 Series 2 RTC headspace autosampler for electrolyte injection

Methodology

Three complementary GC methods were developed:

• Swell gas profiling on a GS-GasPro column via gas-tight syringe injection
• Hydrogen quantification on a CP-Molsieve 5Å column with TCD detection
• Electrolyte headspace analysis on a DB-1701 column

Heated headspace sampling minimizes inlet and column contamination by nonvolatile salts. Calibration employs standard gas mixtures, an Agilent regulator for gas-phase standards, and NIST library matching for unknowns.

Main Results and Discussion

• Swell gas analysis resolved C1–C6 hydrocarbons, CO, CO₂ and detected over 30 components including fluorinated degradation products via deconvolution software.
• Coeluting sulfuryl fluoride and phosphorus trifluoride were accurately quantified using extracted ion monitoring.
• Hydrogen detection by TCD demonstrated a linear response from 0.06 % to 5 % with clear separation from nitrogen and oxygen.
• Electrolyte headspace analysis achieved good linearity (10–500 mg/L) for 15 target additives, with instrument detection limits below 1.3 mg/L and improved robustness over direct liquid injection.

Practical Benefits and Applications

This valve-free GC configuration offers:

• Comprehensive quality control for battery production and failure analysis
• Reduced maintenance and downtime by eliminating sample valves
• Robust detection and identification of known and unknown gas and liquid species
• Quick column switching without MS venting for flexible method development

Future Trends and Opportunities

• Integration of high-resolution MS for enhanced unknown identification
• Machine learning–driven data analysis for real-time failure prediction
• Adaptation to emerging battery chemistries and solid-state systems
• Development of portable GC platforms for on-site safety diagnostics

Conclusion

The valve-free dual‐detector GC system provides a powerful and adaptable solution for battery safety testing. By combining GC/MSD and TCD detection with headspace sampling, the method delivers sensitive, reproducible analysis of both gas evolution and electrolyte composition, supporting robust quality assurance and early failure detection in lithium-ion battery applications.

References

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