Multiplatform Approach for Lithium-Ion Battery Electrolyte Compositional Analysis

Significance of the Topic

Electrolyte composition critically influences the performance, safety, and lifespan of lithium-ion batteries (LIBs). Comprehensive profiling of organic solvents, additives, and elemental impurities supports reverse engineering of commercial formulations, guides quality control, and aids in degradation studies during charge/discharge cycles.

Study Objectives and Overview

This application note presents a multiplatform analytical workflow to characterize unknown LIB electrolytes. Three commercial electrolyte samples were evaluated using complementary techniques—gas chromatography/triple quadrupole mass spectrometry (GC/TQ), liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOF/MS), and inductively coupled plasma mass spectrometry (ICP-MS)—to obtain a holistic compositional profile of volatile, nonvolatile, and elemental species.

Methodology and Instrumentation

Sample preparation involved simple dilution of electrolyte solutions in dichloromethane (for GC/TQ) or dimethyl carbonate (for ICP-MS) and reconstitution in methanol (for LC/Q-TOF). Analyses were performed as follows:

• GC/TQ: Split and splitless injections to detect abundant and trace volatile compounds.
• LC/Q-TOF/MS: Nontargeted high-resolution accurate mass analysis with chemometric processing (PCA, fold-change, hierarchical clustering, Venn diagrams) for organic additives.
• ICP-MS: QuickScan “all-element” profiling with helium cell mode, followed by FullQuant quantitation of target elements using matrix-matched calibration.

Main Results and Discussion

GC/TQ analysis identified 28 volatile compounds across the three samples. Eight common formulation components—dimethyl carbonate (DMC), diethyl carbonate (DEC), toluene, diphenyl sulfide, trimethyl phosphate, hexadecane, ethylene carbonate (EC), and N-methyl-2-pyrrolidone (NMP)—showed consistent retention times and high library match factors (>90%).

LC/Q-TOF/MS enabled separation and statistical differentiation of nonvolatile organics. PCA revealed clustering by sample, while fold-change filters and hierarchical clustering highlighted features significantly elevated compared to blanks. A Venn diagram identified unique and shared additives, and accurate-mass matching proposed chemical identities for key peaks.

ICP-MS elemental profiling via IntelliQuant heat maps showed high abundances of lithium, phosphorus, boron, sulfur, and chlorine—indicative of lithium salts LiPF6, LiBF4, and LiClO4. Quantitative results for 21 elements confirmed major electrolyte constituents and detected trace impurities (Na, K, Mg, Fe, etc.) at ppb levels in 100× diluted samples.

Benefits and Practical Applications

The integrated workflow delivers rapid, in-depth chemical characterization of unknown electrolytes. Manufacturers can apply these methods for reverse engineering, routine quality assurance, monitoring electrolyte degradation, and safeguarding battery safety and performance.

Future Trends and Opportunities

Advances may include automated data-fusion of GC, LC, and ICP datasets, high-throughput screening of novel electrolyte chemistries, deeper untargeted analysis using machine learning, and in-line process monitoring for real-time quality control.

Conclusion

A synergistic combination of GC/TQ, LC/Q-TOF/MS, and ICP-MS furnished a comprehensive compositional picture of unknown LIB electrolytes. This multidimensional approach enhances confidence in component identification and quantitation, supporting reverse engineering, quality control, and lifecycle studies.

Instrumentation Used

• Agilent 8890 GC with Agilent 7010 triple quadrupole GC/MS (high-efficiency source)
• Agilent 1290 Infinity II LC with Agilent 6545XT AdvanceBio Q-TOF
• Agilent 7900 ICP-MS with organic solvent introduction kit and helium cell mode

References

1. Springer Berlin, Heidelberg. Lithium-Ion Batteries: Basics and Applications; 2018.
2. J. Electrochem. Soc. 2017, 164(1), A5019–A5025.
3. J. Power Sources 2006, 1379–1394.
4. Agilent Technologies AN 5994-6883EN: ICP-MS Analysis of LIB Electrolyte Solvents.
5. Encyclopedia of Electrochemical Power Sources 2009, 22–27.