Analysis of electrolyte components of lithium-ion batteries using gas chromatography-mass spectrometry

Importance of the topic

The composition of the electrolyte in lithium-ion batteries critically controls ion transport, viscosity, dielectric properties and therefore affects battery performance, safety and lifetime. Reliable, fast and sensitive analytical methods for identifying and quantifying common carbonate-based solvents and additives are essential for quality control of battery manufacturing, failure analysis, and research into formulation and degradation mechanisms.

Objectives and study overview

This application note describes the development and validation of a straightforward gas chromatography–mass spectrometry (GC–MS) method for qualitative and quantitative analysis of common ester and carbonate components in lithium-ion battery electrolytes. Goals were to produce a sensitive, rapid and easily implemented protocol for routine screening and quantitation with direct injection following simple dilution.

Methodology

- Sample preparation: direct dilution of electrolyte in ethyl acetate (solvent selection tested vs. acetone, hexane, toluene, ethanol and chloroform). Ethyl acetate provided acceptable solubility and was selected as the dilution medium. - Calibration: five calibration levels prepared from a certified standard mixture (nominally ≥97% purity) in ethyl acetate at 4, 10, 20, 50 and 100 mg/L. Linear response evaluated across 4–100 mg/L. - Acquisition: full-scan EI GC–MS (40–200 m/z) used for screening; authors note that Selected Ion Monitoring (SIM) can improve limits of detection by 1–2 orders of magnitude when needed.

Used instrumentation

- Gas chromatograph: Thermo Scientific TRACE 1310 GC with liquid autosampler AS1310. - Mass spectrometer: Thermo Scientific ISQ 7000 single quadrupole MS with electron ionization (EI). - Column: Thermo Scientific TraceGOLD TG-5MS, 30 m × 0.25 mm i.d., 0.25 µm film. - Key GC–MS conditions: split injection 50:1, injection volume 1 µL, SSL injector at 280 °C; oven program 50 °C (3 min), ramp 10 °C/min to 240 °C (3 min); helium carrier at 1.0 mL/min; ion source 300 °C; transfer line 280 °C; full-scan acquisition 40–200 m/z.

Main results and discussion

- Analytes covered: ethyl methyl carbonate (EMC), vinylene carbonate (VC), diethyl carbonate (DEC), n-propyl propionate (PP), fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC) and 1,3-propane sultone (PS). - Chromatographic performance: baseline separation achieved under the described oven program with retention times spanning ~2.7 to ~11.0 min for the target esters. - Linearity: excellent linear calibration across 4–100 mg/L for all targets with correlation coefficients R2 > 0.999. - Limits of detection (extrapolated at S/N = 3, full-scan): generally low µg/L range. Representative LODs reported: EMC ~3 µg/L; DEC ~4 µg/L; PP ~4.5 µg/L; VC ~9 µg/L; PC ~19 µg/L; PS ~25 µg/L; FEC ~28 µg/L; EC ~32 µg/L. Using SIM mode can reduce these LODs by 1–2 orders of magnitude when higher sensitivity is required. - Accuracy and precision: recovery of the 20 mg/L spike into a diluted electrolyte matrix ranged between ~92.4% and 105.3% across analytes, with repeatability (n = 6) expressed as RSD ≤ 4.16%. - Solvent choice: ethyl acetate selected after comparison due to superior solubility of the target carbonates/esters and compatibility with direct GC injection.

Benefits and practical applications of the method

- Simplicity and throughput: minimal sample preparation (single-step dilution) enables rapid turnaround for routine QC and formulation checks. - Robust quantitative performance: wide linear range (4–100 mg/L), low µg/L detection capability (full-scan), and strong recoveries with low RSD support reliable quantitation in production and R&D settings. - Flexibility: full-scan acquisition allows non-target screening; switching to SIM increases sensitivity for trace-level determinations when required. - Use cases: electrolyte composition verification, additive monitoring, batch release testing, stability/degradation studies, and failure analysis.

Future trends and potential applications

- Enhanced sensitivity and selectivity: adoption of SIM routinely for trace analytes, and integration of tandem MS or high-resolution MS for improved identification of unknown degradation products. - Alternative sampling approaches: incorporation of headspace or solid‑phase microextraction (HS-SPME) for volatile components or to reduce matrix effects and solvent use. - Broader analyte scope: combining GC–MS for volatile/semivolatile electrolytes with LC–MS workflows to capture non-volatile salts, ionic species and polar additives. - Automation and data analytics: automated sample handling and chemometric analysis to support large-scale QC and formulation optimization. - Method adaptation for aged/degraded samples: targeted workflows to detect decomposition products and to monitor safety-relevant species at trace levels.

Conclusion

The described single-quadrupole GC–MS method is a pragmatic, validated approach for rapid qualitative and quantitative analysis of common carbonate-based solvents and additives in lithium-ion battery electrolytes. It provides strong linearity, low µg/L detection limits (with potential for further improvement via SIM), high recoveries and good repeatability following a simple dilution in ethyl acetate. The method is suitable for routine QC, formulation assessment and electrolyte screening in research and manufacturing environments.

References

1. Lei, Y. Study on the effects of electrolyte properties; Central South University. Some organic additives are positive for the full-molytan liquid flow battery.
2. Sun, S. Research on sub-liquid electrolytes; Harbin University of Technology. New separation for lithium-ion batteries.