Aiding Lithium Ion Secondary Battery Electrolyte Design via UPLC-MS and APGC-MS Analysis on a Single High-Resolution Mass Spectrometer Platform

Importance of the Topic

The performance, safety and longevity of lithium-ion batteries depend critically on the chemistry of their electrolyte solutions and additives. Understanding how electrolyte composition evolves under charge–discharge cycling helps researchers and manufacturers optimize formulations, improve energy density, extend battery life and reduce degradation byproducts that can impair performance.

Objectives and Study Overview

This study presents an integrated analytical workflow to monitor changes in secondary lithium-ion battery electrolyte solutions during repeated charge–discharge cycles. By coupling ultra-high-performance liquid chromatography–mass spectrometry (UPLC-MS) and atmospheric pressure gas chromatography–mass spectrometry (APGC-MS) on a single high-resolution mass spectrometer, the protocol aims to capture both volatile and non-volatile degradation products, identify chemical markers of breakdown, and propose structural assignments for unknown impurities.

Methodology and Instrumentation

A dual-inlet approach using Waters ACQUITY UPLC I-Class PLUS and APGC on a Xevo G2-XS QTof enabled comprehensive analysis of five electrolyte extracts representing 0, 1, 40, 180 and 200 charge–discharge cycles.

• GC–MS (APGC): DB-5 MS column, gentle ionization to preserve molecular ions, He carrier, temperature gradient from 60–250 °C.
• LC–MS (ESI+): HSS T3 column, ammonium formate mobile phase, gradient to methanol, capillary voltage 2.5 kV, desolvation at 450 °C.
• Informatics: UNIFI Scientific Information System for multivariate analysis, library searching and structural elucidation.

Main Results and Discussion

Principal component analysis (PCA) of combined GC and LC data distinguished electrolyte samples according to cycle count and revealed two clusters for low (1–40) versus high (180–200) cycle numbers. Orthogonal partial least squares discriminant analysis (OPLS-DA) and s-plots pinpointed marker ions responsible for these differences. A feature at m/z 131.0336 appeared only after 40 cycles and increased at higher cycle counts. ChemSpider database matching and MassFragment confirmation suggested this compound is a decarbonylated degradation product of fluoroethyl carbonate.

Benefits and Practical Applications

The dual-inlet HRMS workflow provides a fast, untargeted means to detect and identify both volatile and non-volatile electrolyte breakdown products in a single instrument run. Identifying degradation markers informs formulation adjustments to minimize harmful byproducts, enhance additive stability and extend battery service life.

Future Trends and Potential Applications

• Integration with high-throughput cycling platforms for rapid screening of novel electrolyte additives
• Expansion of databases and machine-learning algorithms to automate structural assignments
• Application to other energy-storage systems (e.g., solid-state batteries, flow batteries)
• Real-time monitoring of electrolyte health in operational battery packs

Conclusion

A unified APGC–UPLC–MS platform coupled with multivariate informatics effectively tracks electrolyte composition changes during battery cycling, identifies key degradation markers and supports targeted improvements in lithium-ion battery design.

References

• OECD, Climate Futures: Policy Highlights, Financing Climate Futures, 2018.
• UK Parliament, Report on Electric Vehicle Adoption, 2019.
• T. M. Gür, Review of Electrical Energy Storage Technologies, Energy Environ. Sci., 2018, 11, 2696–2767.