Determination of Sulfur and Carbon in Lithium, Nickel, Manganese, and Cobalt Battery Materials

Determination of Sulfur and Carbon in Li-NMC Battery Materials — Application Note Summary

Significance of the topic:

High-performance Li-NMC (Lithium-Nickel-Manganese-Cobalt oxide) cathode materials and their complementary graphitic anodes require tight control of elemental composition. Carbon content influences electrode conductivity and electrochemical performance, while Sulfur—either as an impurity or as an intentionally added component—can strongly affect cell behavior and lifetime. Reliable, routine bulk quantification of Carbon and Sulfur at the ppm–percent scale is therefore essential for materials development, quality control, and production-release testing in the battery industry.

Objectives and study overview:

This application note demonstrates a robust macro-combustion method using the LECO SC832DR for simultaneous determination of total Carbon and total Sulfur in Li-NMC powders. The workflow covers sample preparation, instrument conditioning, blanking, calibration/drift correction, and representative analytical performance using certified reference materials and production samples. Emphasis is placed on method parameters, detection limits, and repeatability for battery-relevant matrices.

Used Instrumentation:

Key instrument and accessories used in the method:

• LECO SC832DR macro combustion Sulfur and Carbon determinator (dual-range NDIR detection for Sulfur).
• High-temperature horizontal ceramic combustion furnace operated at nominal 1450 °C in a pure Oxygen atmosphere.
• NDIR detectors for CO2 and dual-path SO2 measurement (short and long path for wide dynamic Sulfur range).
• Consumables and accessories: 528-203 ceramic combustion boats (pre-baked), 502-321 Com-Cat catalyst, 761-929 crucible tongs, 501-614 spatula.

Methodology and procedure (concise):

Analytical principle: Samples are combusted in oxygen; combustion gases are dried and analyzed by NDIR—CO2 for Carbon and SO2 for Sulfur. The dual-range SO2 cell automatically selects short or long path for optimal sensitivity across low and high Sulfur concentrations.

Sample preparation and conditioning:

• Combustion boats must be baked (1,000 °C, ≥1 h) and stored dry; handle with tongs only.
• Typical sample mass: ~0.25 g mixed with ~1.0 g Com-Cat (to promote complete combustion and matrix conversion).
• Matrix requirement: uniform powder or granular material representative of the batch.

Operational flow:

1. Instrument setup and system conditioning with three sample replicates of similar matrix.
2. Blank determination with ≥5 Com-Cat-only replicates; blank precision target: standard deviation ≤0.001 % (10 ppm) for both elements.
3. Calibration/drift correction using at least five replicates of certified reference material; verification with a second CRM.
4. Routine sample analysis—manual loading or autoloader—following the same mass and Com-Cat mixing procedure.

Typical analytical parameters (selected):

Furnace temperature: 1450 °C; nominal sample mass for analysis: 1.0000 g nominal mass listed for macro analysis but operational sample weighing was ~0.25 g with 1.0 g Com-Cat; lance-on delay 20 s. Integration timing and comparator settings differ for Sulfur and Carbon to optimize signal integration and dynamic range.

Calibration and detection approach:

Linear, forced-through-origin calibration was used for both analytes. Primary calibration standard: LECO LCRM 502-914 (1.03 % C, 1.00 % S). Calibration verification used LECO 502-964 (0.12 % C, 0.10 % S). The SC832DR automatically selects the appropriate Sulfur IR path (short/long) to extend usable dynamic range and improve low- and high-level accuracy.

Main results and discussion:

Representative results reported in the application note show two distinct sample groups:

• Group A (several Li-NMC production samples): Carbon ~1.149 % (mean), standard deviation ≈0.002 %; Sulfur measurements below the instrument lower detection limit reported as <0.0014 % (below ~14 ppm reporting threshold noted).
• Group B (another set of Li-NMC samples and BAM reference): Sulfur mean ≈0.137 ± 0.001 % and Carbon mean ≈0.075 ± 0.001 % (tight repeatability across replicates).

These results highlight the SC832DR capability to quantify Sulfur across a broad range—from sub-percent down to low-ppm detection for Carbon levels characteristic of Li-NMC materials and to provide repeatable Carbon analysis across different matrices.

Benefits and practical applications of the method:

• Single-instrument, simultaneous quantification of total Carbon and Sulfur—reduces throughput time versus separate techniques.
• Wide Sulfur dynamic range via dual-path NDIR allows measurement of both trace impurities and intentionally added Sulfur at higher concentrations.
• Robust sample preparation with Com-Cat promotes complete combustion of refractory oxide matrices typical of battery cathodes.
• Method supports routine QC, incoming materials inspection, process monitoring, and R&D evaluation of formulations and dopants.

Limitations and practical considerations:

• Detection limits: some Li-NMC samples yielded Sulfur below the stated LOD (<0.0014 %); low-ppm Sulfur determination requires strict blank control and validated LOD for specific matrix.
• Sample homogeneity and representative sampling are critical for accurate bulk results in heterogeneous powders.
• Proper conditioning of combustion boats and rigorous blanking/calibration steps are essential to achieve the quoted repeatability.

Future trends and potential applications:

• Increasing demand for lower detection limits and tighter control of trace impurities as battery chemistries evolve—driving development of more sensitive detectors, improved combustion catalysts, and enhanced contamination control.
• Greater integration of automated sample handling and laboratory information systems for high-throughput production QA/QC workflows.
• Complementary use of bulk combustion data with surface-sensitive and speciation techniques (XPS, TOF-SIMS, ICP-MS after digestion) to correlate total elemental content with chemical state and spatial distribution.
• Method adaptation for new electrode additives, novel solid-state electrolyte precursors, and recycling streams where robust total Carbon/Sulfur analysis will be required.

Conclusion:

The LECO SC832DR macro-combustion method provides a practical, repeatable approach for simultaneous total Carbon and Sulfur determination in Li-NMC cathode powders. With appropriate sample preparation (pre-baked boats, Com-Cat mixing), blank control, and CRM-based calibration, the method delivers reliable Carbon quantification and a wide dynamic Sulfur measurement capability suitable for battery materials R&D and QC. Attention to low-ppm Sulfur detection limits and sample homogeneity is required for trace-level control.

References:

• LECO Corporation. Application Note: Determination of Sulfur and Carbon in Lithium, Nickel, Manganese, and Cobalt Battery Materials. Instrument: SC832DR. Form No. 203-821-700, 2025.
• LECO Certified Reference Materials: 502-914 (LCRM Synthetic Carbon and Sulfur, 1.03 % C, 1.00 % S); 502-964 (LCRM Synthetic Carbon and Sulfur, 0.12 % C, 0.10 % S).
• LECO Consumables: 502-321 Com-Cat catalyst; 528-203 ceramic combustion boats; Manufacturer operator's instruction manual for 832 Series.