Analysis of Elemental Impurities in Lithium-Ion Secondary Battery Electrolytes Using the ICPE- 9800 Series

Significance of the Topic

Lithium-ion batteries power mobile devices, electric vehicles and hybrid cars but trace elemental impurities in the electrolyte can degrade performance, safety and lifetime. Accurate multi-element analysis of these impurities is essential for quality control and regulatory compliance under standards such as China’s HG/T4067-2015.

Objectives and Study Overview

This study evaluates the Shimadzu ICPE-9820 inductively coupled plasma atomic emission spectrometer, equipped with a hydrofluoric acid-resistant injection system and an organic solvent torch, for simultaneous determination of elemental impurities in two types of LiPF6-based electrolytes. Spike recovery and repeatability tests validate method accuracy and precision.

Methodology and Instrumentation

Sample Preparation

• Two electrolytes: 1.0 mol/L LiPF6 in ethyl methyl carbonate (EMC) and in a 50:50 (v/v) ethylene carbonate/dimethyl carbonate mix
• Ten-fold dilution with a solvent of EMC : ethanol : water (1 : 4 : 5)
• Spiking with a mixed standard of 14 elements at 0.1 mg/L (equivalent to 1 mg/kg) for recovery studies

Instrument Configuration

• ICPE-9820 spectrometer
• PFA1S nebulizer, cyclonic HF-resistant chamber, HF-resistant drain
• Quartz extension pipe and organic solvent torch
• AS-10 autosampler

Analytical Conditions

• RF power: 1.40 kW
• Plasma gas flow: 20.0 L/min, auxiliary gas: 0.70 L/min, carrier gas: 0.75 L/min
• Axial observation mode

Main Results and Discussion

Detection limits (3×σ×slope×10 dilution) for all measured elements fall below regulatory thresholds. Unspiked electrolyte analysis revealed quantifiable Al (0.21 mg/kg), Cr (0.04 mg/kg), Cu (0.02–0.01 mg/kg), Fe (0.12 mg/kg), Mg (0.017 mg/kg), Na (0.02–0.04 mg/kg) and Ni (0.09–0.07 mg/kg), with other elements below detection. Spike recovery ranged from 89 % to 107 % across both electrolytes, confirming accuracy. Ten repeat measurements of spiked EMC samples showed relative standard deviations below 6.9 %, demonstrating robust precision.

Benefits and Practical Applications

• Simultaneous multi-element detection enhances throughput
• HF-resistant components enable direct analysis of LiPF6 electrolytes without corrosion
• Organic solvent torch ensures stable plasma with high-organic-content samples
• Meets industry regulations for elemental impurities in battery electrolytes

Future Trends and Potential Uses

Advances may include extension to new battery chemistries, real-time inline monitoring in manufacturing, coupling with separation techniques for speciation, integration with machine learning for predictive quality control, and miniaturized plasma sources for on-site battery diagnostics.

Conclusion

The Shimadzu ICPE-9820 series provides a reliable, accurate and precise platform for simultaneous multi-element impurity analysis in lithium-ion battery electrolytes. Its HF-resistant injection system and organic solvent torch ensure robust operation and compliance with regulatory standards, making it a valuable tool for battery R&D and quality assurance.

Reference

1. HG/T4067-2015 Cell liquor of lithium hexafluorophosphate (February 20, 2024)