Confident Identification of Battery Solvent Impurities Using Complementary GC-MS Techniques

Dimethyl carbonate (DMC) plays a critical role in lithium-ion battery electrolytes, where solvent purity directly impacts performance, safety, and lifetime. Even trace-level impurities can contribute to degradation of solid electrolyte interfaces, consumption of lithium ions, or gas formation—effects that compromise both efficiency and safety.

As battery materials continue to evolve, analytical approaches must provide both high sensitivity and high-confidence identification. A recent LECO application study demonstrates how combining two GC-MS platforms enables a more complete characterization of DMC impurities than either approach alone.

Why Impurity Characterization in DMC Is Challenging

Battery-grade solvents demand detection of contaminants across a wide concentration range, starting from major byproducts to trace-level species. In DMC, impurities may include oxygenated compounds, hydrocarbons, and nitriles, many of which arise from synthesis or handling processes.

These compounds can co-elute or exist at levels below typical detection thresholds, making comprehensive analysis difficult with a single analytical technique. In addition, electron ionization (EI) spectra do not always provide a clear molecular ion, complicating compound confirmation.

A Complementary Analytical Strategy: Sensitivity + Confidence

The application note demonstrates a combined workflow using the approach:

• Pegasus BTX (GC-TOFMS) for high-sensitivity detection
• Pegasus HRT (high-resolution GC-MS) for accurate mass confirmation

The Pegasus BTX enables detection of impurities at below parts-per-billion levels, ensuring that even low-abundance analytes are captured.

Following detection, the Pegasus HRT provides high-resolution, accurate mass data in both EI and positive chemical ionization (PCI) modes. PCI is particularly valuable when EI spectra lack a clear molecular ion, allowing confirmation through common adduct species such as protonated molecular ions [M+H]⁺.

Because both ionization modes can be accessed without hardware changes, the workflow supports efficient, multi-dimensional confirmation of analyte identity.

Observations

Using this combined approach, multiple classes of impurities were identified in the DMC sample. These included:

• Oxygenated reaction byproducts
• Alcohols, carbonates, and ethers
• Hydrocarbons and aromatic species
• Additional low-level analytes detected with high library match scores

Importantly, the high sensitivity of the Pegasus BTX revealed a broader set of low-concentration compounds, while the Pegasus HRT increased confidence in compound identification through accurate mass measurements and confirmation of molecular formulas.  

The study also highlights cases where co-eluting compounds were successfully deconvoluted, allowing individual components to be identified even without complete chromatographic separation.

Why This Matters for Battery Materials Analysis

This work illustrates a key principle for advanced materials characterization: detection and identification are distinct challenges that often require complementary solutions.

• Detection alone is insufficient without confident identification
• High-resolution confirmation is limited if low-level species are not first detected

By combining these capabilities, laboratories can gain deeper insight into solvent purity, production processes, and potential performance risks in battery systems.

Explore the Complete Study

This short overview highlights only a portion of the findings. The full application note provides:

• Detailed acquisition parameters and workflows
• Chromatographic and spectral data examples
• Confirmed impurity lists with retention times and similarity scores
• Examples demonstrating EI/PCI complementarity and accurate mass confirmation

To better understand how complementary GC-MS techniques can improve confidence in battery solvent analysis, download the full application note: “Battery Solvent Characterization: Identifying Impurities in Dimethyl Carbonate”.