Determination of inorganic anions in saturated lithium carbonate solution

Importance of the topic

Lithium carbonate is a critical precursor for lithium ion and lithium polymer batteries. Characterizing inorganic anion impurities in saturated lithium carbonate solutions is vital for battery performance, manufacturing quality assurance, and recycling operations.

Objectives and Study Overview

This study demonstrates the determination of seven inorganic anions (fluoride, chloride, nitrite, bromide, nitrate, phosphate, sulfate) in saturated lithium carbonate solutions using a reagent free ion chromatography system with an anion exchange column. The approach enables quantification of trace anion impurities in both liquid and solid forms.

Methodology and Instrumentation

• Ion Chromatography system: Dionex ICS-5000+ reagent free configuration with pump module, eluent generator module, high pressure degasser, and conductivity detector module.
• Column: Thermo Scientific Dionex IonPac AG23 guard column (2×50 mm) and IonPac AS23 analytical column (2×250 mm).
• Suppressor: AERS 500 carbonate electrolytically regenerated suppressor operated in recycle mode.
• Carbonate removal device: Dionex CRD 300 operated in vacuum mode to eliminate carbonic acid background.
• Eluent: 4.5 mM potassium carbonate and 0.8 mM potassium bicarbonate generated by EGC 500 K2CO3 cartridge with EPM 500 pH modifier and mixer.
• Detection: suppressed conductivity at 8 mA, 30 °C.
• Operating conditions: flow rate 0.25 mL/min, injection volume 5 µL, column temperature 30 °C, run time 25 min.
• Sample preparation: saturated lithium carbonate solutions were filtered and diluted 1:4 with deionized water to avoid column overload; dilute spiked standards in sample matrix were used for calibration and MDL determination.

Results and Discussion

• Complete separation of seven anions achieved within 25 min with clear resolution in DI water and lithium carbonate matrices.
• Reagent free eluent generation eliminated baseline artifacts related to sulfate contamination in manual eluent preparations.
• Optimal analysis achieved at 0.33 g/100 mL lithium carbonate after 1:4 dilution to prevent column overload.
• Calibration curves showed linearity (r2 > 0.997) over the selected ranges and method detection limits of 0.02–0.22 mg/L in saturated lithium carbonate.
• Precision was demonstrated with RSDs of 1–6% and accuracy with recoveries of 95–107% in spiked samples.
• Analysis of commercial lithium carbonate samples yielded impurity levels of 0.47 mg/kg fluoride, 0.94 mg/kg chloride, and 2.9 mg/kg nitrate, confirming product specifications.

Benefits and Practical Applications

This method offers high sensitivity and reproducibility for trace anion analysis in lithium carbonate, supporting battery material quality control, supplier qualification, and recycling stream evaluation without the need for manual eluent preparation.

Future Trends and Potential Applications

Future developments may include coupling ion chromatography with mass spectrometry for enhanced specificity, integration into automated battery production workflows, extension to other battery electrolyte and active material analyses, and real time monitoring of recycling processes.

Conclusion

A reagent free ion chromatography system combined with the IonPac AS23 column, carbonate suppressor, and removal device enables robust determination of seven inorganic anions in saturated lithium carbonate solutions. The method meets rigorous sensitivity, precision, and accuracy requirements for battery industry applications.

References

1. Li Q et al. Progress in electrolytes for rechargeable Li based batteries. Green Energy & Environment. 2016;1(1):18–42.
2. Thermo Fisher Scientific. Dionex ICS-5000+ Ion Chromatography System Operator’s Manual.
3. Thermo Fisher Scientific. Dionex Eluent Generator Cartridges Product Manual.
4. Thermo Fisher Scientific. Dionex IonPac AS23 Anion Exchange Column Product Information.
5. Thermo Fisher Scientific. AERS 500 Carbonate Electrolytically Regenerated Suppressor.
6. Thermo Fisher Scientific. CRD 300 Carbonate Removal Device.
7. National Library of Medicine. PubChem. Lithium carbonate solubility data.