Analysis of Elemental Impurities in Anode Materials for Lithium-Ion Secondary Batteries Using the ICPE- 9820

Importance of the Topic

High-purity anode materials are critical for the performance, safety, and longevity of lithium-ion secondary batteries. Trace elemental contaminants in graphite can impact charge/discharge efficiency and induce unwanted side reactions. Therefore, reliable methods for quantifying a wide range of metallic and non-metallic impurities are essential for quality control in battery manufacturing.

Study Objectives and Overview

This application note describes the use of the ICPE-9820 inductively coupled plasma atomic emission spectrometer (ICP-AES) to:

• Quantify elemental impurities (Al, B, Co, Cr, Cu, Fe, Li, Mn, Mo, Na, Ni, P, S, Zn, Zr) in graphite anode material.
• Validate analytical accuracy via spike recovery tests.
• Demonstrate the “Acquisition for All Wavelength” feature for post-analysis identification of unexpected impurities (e.g., Ca, Mg, Si, Sr).

Materials and Methods

Sample preparation followed the GB/T 24533-2019 protocol:

• 0.5 g graphite was digested with 3 mL HNO₃ and 9 mL HCl in a microwave system at 200 °C for 30 min.
• After cooling, the digest was filtered (0.45 μm PTFE) and diluted to 50 mL. The resulting solution was further diluted two-fold (200× total).
• Method blanks and spike-fortified samples were prepared in parallel.

Instrumentation

The ICPE-9820 system configuration:

• Nebulizer: 10UES
• Spray chamber: Cyclone HE
• Torch: Mini-torch (reduced argon consumption)
• Auto-sampler: AS-10
• RF power: 1.20 kW
• Plasma gas: 10.0 L/min; Auxiliary gas: 0.60 L/min; Carrier gas: 0.70 L/min
• Detection views: Axial (high sensitivity) and radial (improved linearity at higher concentrations)

Results and Discussion

Detection limits for most elements were in the low µg/L range. Calibration curves used seven standards (0–2.5 mg/L for most elements). Key findings:

• Quantitative results showed impurity levels ranging from below detection limit to tens of mg/kg.
• Spike recoveries for all elements fell between 96 % and 102 %, confirming method accuracy.
• Axial view provided superior sensitivity for trace-level alkali metals (Na, K), while radial view ensured linear response at higher concentrations.
• Post-analysis qualitative scanning identified additional impurities (Ca, Mg, Si, Sr) without rerunning samples, leveraging the “Acquisition for All Wavelength” feature.

Benefits and Practical Applications

The ICPE-9820 method offers:

• Comprehensive multi-element screening in a single run.
• Flexibility to add wavelengths post-acquisition for unexpected elements.
• Cost savings via a mini-torch design that lowers argon consumption.
• Regulatory compliance with GB/T 24533-2019 for anode material testing.

Future Trends and Potential Applications

Advances in battery research will drive demand for even lower detection limits, faster throughput, and wider spectral coverage. Potential developments include:

• Integration of collision/reaction cell technology to further reduce interferences.
• Automated data-processing algorithms for real-time impurity profiling.
• Extended wavelength libraries for emerging anode materials beyond graphite (e.g., silicon composites).

Conclusion

The ICPE-9820 ICP-AES system demonstrates robust performance for analyzing elemental impurities in lithium-ion battery anode materials. High sensitivity, excellent accuracy, and the ability to detect unplanned contaminants post-analysis make it a powerful tool for quality assurance in battery manufacturing.

References

• GB/T 24533-2019. Graphite negative electrode materials for lithium-ion batteries. Standards Press of China, 2019.