Rapid Analysis of Elemental Impurities in Battery Electrolyte by ICP-OES

Significance of the topic

The purity of lithium hexafluorophosphate (LiPF6) electrolyte directly affects the performance, safety, and service life of lithium-ion batteries. Trace elemental impurities can influence conductivity, accelerate degradation, and pose safety risks. Precise, reliable, and efficient multi-element analysis is therefore essential for quality control in battery manufacturing.

Objectives and overview of the study

This study aimed to develop and validate a rapid, robust ICP-OES method for the simultaneous determination of 12 elemental impurities (Al, As, Ca, Cd, Cr, Cu, Fe, Mg, Ni, Pb, S, Zn) in LiPF6 battery electrolyte. The goal was to replace labor-intensive turbidi­metric sulfate analysis and address matrix challenges posed by organic solvents.

Methodology

Sample preparation involved diluting 5 g of LiPF6 electrolyte to 100 g with a 20 % (w/w) aqueous ethanol solution, achieving a 10–20× dilution. A series of calibration standards (0.02–0.5 mg/L) was prepared in the same diluent. Each sample and standard was measured in triplicate following an 8 s stabilization period.

Used instrumentation

Analysis was performed using an Agilent 5110 vertical dual-view (VDV) ICP-OES equipped with:

• Solid-state RF generator (27 MHz) for stable plasma
• Cooled cone interface (CCI) to minimize organic interferences
• Inert sample introduction kit: OneNeb concentric nebulizer, double-pass spray chamber, Easy-fit torch, solvent-resistant tubing
• Axial plasma viewing mode for enhanced sensitivity

Background correction for Al and As was achieved via the Agilent FACT (fast automated curve-fitting technique), suppressing carbon-based spectral interferences.

Main results and discussion

Calibration curves for all 12 elements demonstrated linearity (R² > 0.999) across 0.02–0.5 mg/L. Method detection limits ranged from 0.03 mg/kg (Mg, Ni) to 0.25 mg/kg (S). Spike recovery tests at 0.025 mg/L yielded recoveries between 90 % and 110 % with RSDs below 3.1 %, confirming accuracy and precision at trace levels. Carbon buildup on the torch was effectively prevented by the CCI design.

Benefits and practical application of the method

This ICP-OES approach offers a single-run multi-element analysis—including sulfur—eliminating separate turbidi­metric assays. It delivers low detection limits, high throughput, and reduced operator dependency, making it ideal for routine quality control of LiPF6 electrolytes in battery production.

Future trends and potential applications

Potential developments include extending the method to other organic battery electrolytes, integrating inline process-monitoring tools, and applying advanced spectral deconvolution algorithms. Automation of sample handling and real-time data analysis will further enhance throughput and reliability in industrial settings.

Conclusion

The validated Agilent 5110 VDV ICP-OES method provides a reliable, high-throughput solution for monitoring elemental impurities in LiPF6 electrolyte. Its robustness against organic matrices, combined with excellent sensitivity and accuracy, supports stringent quality requirements in lithium-ion battery manufacturing.

References

• HG/T 4067-2015: Lithium hexafluorophosphate electrolyte. Chinese Standard, April 2020.