Determination of Elemental Impurities in Lithium Hydroxide Using ICP-OES

Significance of the topic

The rapid growth of lithium-ion batteries has driven strong demand for high-purity lithium hydroxide (LiOH) as a critical precursor chemical. Controlling trace element impurities in LiOH is essential to ensure consistent performance, safety, and longevity of battery cathode materials, especially nickel-rich chemistries.

Study objectives and overview

This application note describes the development and validation of an ICP-OES method for the simultaneous determination of 27 elemental impurities in 98% pure LiOH powder. Key aims include method robustness in high-Li matrices, calibration linearity, detection limits, spike recoveries, and long-term stability without extensive maintenance.

Methodology and instrumentation

Sample Preparation:

• Approximately 1 g of LiOH powder dissolved in 10% HNO3 and diluted to 100 mL.
• Spike experiments at 0.05 and 0.1 mg/L (5 and 10 mg/kg) for 27 elements.
• 1% Li2CO3 solutions prepared similarly for comparative stability testing.

Calibration and Standards:

• Multi-element stock solutions diluted to produce calibration standards from 0.01 to 0.5 mg/L (extended to 5 mg/L for K and Na, and 1 mg/L for Si).
• Li calibration standards at 100, 1 000, and 3 000 mg/L to quantify matrix Li.
• Continuing calibration blank (10% HNO3) and verification standards (0.1 mg/L for 27 elements, 1 000 mg/L Li) analyzed every 10–12 samples.

Background Correction and Data Processing:

• Automated Fitted Background Correction (FBC) and Fast Automated Curve-fitting Technique (FACT) for accurate interference removal.
• IntelliQuant Screening for semiquantitative element profiling and optimal wavelength selection.
• Early Maintenance Feedback (EMF) to schedule proactive instrument maintenance.

Instrumentation Used

Agilent 5800 Vertical Dual View ICP-OES equipped with:

• Advanced Valve System (AVS) 7-port switching valve for reduced sample load and inline internal standard addition.
• SeaSpray glass concentric nebulizer, double-pass cyclonic spray chamber, and quartz torch with 1.8 mm injector.
• Argon humidifier to prevent salt buildup.
• ICP Expert Pro software for instrument control, data acquisition, and processing.

Main results and discussion

Calibration and Sensitivity:

• Excellent linearity (R>0.999) for all 27 elements over working ranges.
• Limits of detection below 1 mg/kg for most elements, even in high-Li matrices.

Accuracy and Precision:

• Spike recoveries between 90% and 110% at both 5 and 10 mg/kg levels, confirming method accuracy.
• Long-term stability demonstrated over 6.8 h (290 measurements) with RSDs <5% for all elements in spiked samples; CCV measurements within ±10% of expected values.

Instrument Performance and Maintenance:

• AVS 7 reduced measurement time from 138 s to 84 s per sample and minimized torch fouling, with over 400 high-Li samples analyzed without maintenance.
• EMF alerts ensured proactive servicing, reducing downtime and consumable replacement.

Benefits and practical applications

• Reliable quality control of LiOH for battery precursor manufacturing.
• High sample throughput with reduced argon consumption and maintenance costs.
• Automated interference correction and proactive maintenance improve data confidence and laboratory efficiency.

Future trends and potential applications

As LiOH demand continues to outpace carbonate derivatives, robust analytical methods will be crucial for next-generation battery chemistries. Future developments may include real-time monitoring, integration with ICP-MS for lower detection limits, advanced chemometric tools for spectral deconvolution, and expanded application to other battery materials and process streams.

Conclusion

The Agilent 5800 VDV ICP-OES with AVS 7 and ICP Expert Pro software provides a highly accurate, precise, and robust method for determining trace elemental impurities in high-Li matrices. Automated background correction, semiquantitative screening, and proactive maintenance features deliver reliable, cost-effective quality control for LiOH and other battery precursor chemicals.

References

1. Grand View Research, Inc., “Lithium Compounds Market Size Worth $26.7 Billion by 2030,” 2023.
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4. Argus Media (AABC), “Lithium Hydroxide Demand to Overtake Carbonate,” 2019.
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6. GB/T 26008-2020, “Battery Grade Lithium Hydroxide Monohydrate,” National Standard of China.
7. GB/T 11064.16-2013, “Methods for Chemical Analysis of Li2CO3, LiOH·H2O, and LiCl by ICP-OES, Part 16,” National Standard of China.
8. ISO/AWI 16423, “Lithium Hydroxide Monohydrate—Determination of Impurities by ICP-OES,” under development.
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12. Agilent Technologies, “IntelliQuant Software: For Greater Sample Insight and Simplified Method Development,” Pub. 5994-1516EN.
13. Agilent Technologies, “IntelliQuant Screening: Smarter and Quicker Semiquantitative ICP-OES Analysis,” Pub. 5994-1518EN.
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