Innovative GC-Based Method for Analyzing Lithium Ion Battery Electrolyte Composition

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Determining Lithium Ion Battery Electrolyte Composition
June 23, 2025
By Waldemar Weber
Publication Article Column
June 2025 Volume 21 Issue 2 Pages: 24–26

**Key Points**
– A new gas chromatography (GC)-based method allows for accurate weight percentage analysis of lithium-ion battery (LIB) electrolytes without requiring external or internal calibration.
– This method utilizes a Polyarc reactor to convert all compounds into methane, enabling flame ionization detection (FID) that is independent of the molecule type.
– The approach reduces analysis time and enhances accuracy, making it advantageous for both semi-routine and non-routine laboratories.
– Results demonstrated a high correlation with manufacturer specifications and excellent reproducibility, achieving less than 1% relative standard deviation (RSD).

To analyze the composition of organic carbonates in lithium-ion batteries, techniques such as gas chromatography–flame ionization detection (GC–FID), GC–mass spectrometry (GC–MS), liquid chromatography–mass spectrometry (LC–MS), or nuclear magnetic resonance (NMR) are typically employed. However, except for NMR, these methods provide molecule-dependent responses, necessitating the use of external calibration standards for accurate quantification.

This article introduces a GC-based method capable of determining weight percentages from a single measurement, eliminating the need for external or internal calibrations.

Electrolytes for lithium-ion batteries are produced in various locations worldwide, making it crucial to accurately assess the composition of organic carbonates for quality assurance. Variations in composition can significantly impact battery performance and safety. Precise analysis enables manufacturers to uphold consistent quality and meet the stringent industry requirements, ultimately leading to more reliable and efficient energy storage solutions.

Typically, LIB producers report weight percentages (%w) as the specified composition. To ascertain this composition, various analytical technologies are utilized, primarily including GC–FID, GC–MS, LC–MS, and NMR. Notably, all methods, except for NMR, share a common limitation: they yield molecule-dependent responses. Consequently, external calibration with standards for each anticipated compound is necessary for accurate percentage determination.

While this practice usually does not pose challenges in routine operations, it can lead to considerable time investments in semi-routine and non-routine laboratories. This article presents a GC-based method that determines weight percentages from a single measurement without requiring external or internal calibrations.

**Methodology**
The method employs the Polyarc system (Shimadzu), which features a catalytic microreactor that converts all organic compounds into methane prior to detection by the FID (Shimadzu). This conversion transforms the FID into a quantitative carbon detector (QCD). Moreover, by removing the need for calibrations, this approach significantly enhances quantification accuracy.

**Sample Preparation and Measurement**
A 25-µL sample of a LIB electrolyte containing 1M LiPF6 was diluted with 1 mL of dichloromethane and then centrifuged for 5 minutes at 8500 rpm. The centrifuged solution was transferred into a 2-mL GC glass vial and analyzed using the Nexis GC-2030 system (Shimadzu) equipped with the Polyarc reactor. The analytical hardware and software setup included:
– Main unit: Nexis GC-2030 gas chromatograph (Shimadzu)
– Accessory: AOC 30i liquid sample injector
– Main consumables: SH-I-5MS column, 30 m × 0.25 mm, 0.25-μm
– Software: LabSolutions LCGC (all Shimadzu)

**Results and Discussion**
The analysis of two different LIB electrolytes yielded the chromatograms depicted in Figure 1. The two samples exhibited slight differences in the composition of their primary carbonates and additives. Both are standard products commonly used in LIB manufacturing, with available specifications for their %w. The actual quantification may differ slightly from the original specifications due to native decomposition and rearrangement of carbonates during storage. However, as long as decomposition is minimal, it does not significantly impact the quality of the electrolytes.

Since all substances are converted to methane before detection by the FID, the method provides a molecule-independent response, simplifying the calculation of %w. The software integrates the relevant compounds (main components and additives) and computes the percentage of areas accordingly. The resulting area percentages represent the required %w of all integrated compounds.

This technology does not demand precise sample preparation; the primary goal is to avoid overloading the reactor and FID. The decomposition or purity grade can also be evaluated by comparing the sum of peak areas of the target components with those of unknown components in a percentage relationship. These two percentage areas reflect the %w between the targeted compounds and any degradation products or impurities in the electrolyte.

The calculated %w for the analyzed electrolytes, in comparison to the original specifications, is summarized in Table 1. Each electrolyte was measured three times to compute the percentage relative standard deviation (%RSD). The results in Table 1 demonstrate high accuracy in weight percentage calculations, with all components showing less than 1% RSD. The correlation between the calculated weight percentages and the manufacturers’ specifications also indicates a good agreement. Minor discrepancies are attributed to factors such as prior storage, transportation, and sample preparation. Overall, Table 1 illustrates a reliable correlation between measured values and specifications, ensuring dependable quality assurance analysis.

**Table 1: Obtained results for %w calculations.**

**Conclusion**
This article has showcased the effectiveness of a GC–MS system enhanced with a reactor for addressing common quality assurance needs in LIB electrolyte analysis. The method allows for high-accuracy results from a single measurement without additional time demands. The reactor enhancement serves as a valuable addition to traditional GC–MS analysis in this domain, where mass spectrometry is utilized for confirmation and identification, while the enhanced flame ionization detection supports reliable compositional analysis.

**About the Author**
Waldemar Weber began his studies in chemistry in 2005 at the University of Münster, Germany. After graduating, he obtained his PhD from the same university in 2011 and completed a postdoc at the Research Center for Lithium Ion Batteries ‘MEET’ in 2013. From 2015 to 2017, he worked as an application specialist at JAS in Moers, Germany. In November 2018, he joined Shimadzu Europa as Product Manager for GC–MS. Direct correspondence to: shimadzu@shimadzu.eu
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