Determination of Oxygen in Lithium Battery Materials

Importance of the topic

The oxygen content of lithium-ion battery cathode materials (e.g., LiFePO4, Li-NMC, Li-NMO) is a critical compositional attribute that directly affects crystal structure, electrochemical performance, thermal stability and safety. Accurate, routine measurement of oxygen enables manufacturers and researchers to detect oxygen loss or nonstoichiometry that would reduce capacity, alter voltage profiles, and increase risk during cycling and abuse. Reliable oxygen analysis is therefore essential for quality control, process optimization and research into next-generation cathode chemistries.

Objectives and overview of the application note

This application note demonstrates a validated procedure for determining total oxygen in lithium battery materials using the LECO ONH836 series impulse furnace analyzer. It presents the analytical approach, recommended sample preparation and handling, key operating parameters, calibration strategy, typical results for common cathode powders, and practical considerations for implementation in QC or research laboratories.

Methodology

The method is based on high-temperature combustion of a pre-weighed powdered sample in a graphite crucible inside an impulse furnace. Oxygen in the sample reacts with the graphite to form CO and CO2. An inert carrier gas (helium) transports the evolved gases through a mass flow controller and sequential non-dispersive infrared (NDIR) detectors. CO is oxidized to CO2 in a heated reagent and the total CO2 signal is used for oxygen quantitation. Calibration is performed using certified reference materials and verified with independent standards.

Instrumentation Used

• LECO ONH836 series impulse furnace analyzer (O836 model) with graphite crucible combustion.
• Helium carrier gas (argon not suitable).
• NDIR detector sequence for CO and CO2 with inline oxidation reagent.
• Automated sample introduction (automated sample drop) and optional electrode cleaning.
• Accessories: 776-247 graphite crucibles, 502-040 tin capsules for sample containment, lower electrode tips (with/without automation), crucible and sample tweezers, five-place balance for low-mass weighing.

Sample preparation and practical details

Samples should be representative, homogeneous powders or granules and can be analyzed as received. Due to high oxygen content and dust generation, recommended sample masses are small (approximately 0.005–0.01 g) to avoid NDIR saturation and excessive dust accumulation. When weighing sub-0.05 g masses, a five-place balance is required. Tin capsules are used to transfer weighed samples into the loading head while avoiding trapping atmospheric gases (leave capsules open). Reference materials (LECO LCRM/LRM, NIST or equivalent) are used for calibration and drift correction.

Key method parameters (summary)

Analyses use an automated sample drop with a short analysis delay (~30 s). Helium is the carrier gas. Furnace operation uses staged/ramped heating with high-power steps (reported power up to several kilowatts, adjustable with line voltage), short outgas cycles, and surface oxide removal routines disabled for this application. Integration times are long to capture the complete signal (example integration ~200 s) and baseline windows are applied. Specific power, time and cycle settings should be adapted to local line voltage and crucible longevity to balance recovery and crucible burn-through.

Calibration and quality control

Calibration was performed using a BAM-SO14 Li-NMC cathode material (34.0% O) with a linear calibration forced through the origin and verified using LECO iron powder reference (1.10% O). Procedure includes multiple blank replicates to determine instrument blank, multiple calibration replicates for each standard, and verification of calibration with independent standards. Cleaning of electrodes between runs and routine blank checks are emphasized to maintain data quality.

Main results and discussion

Typical results reported in the note (mean ± s) demonstrate the method's capability for common cathode powders:

• LiFePO4 (MSE Supplies PO0127): mean O ≈ 40.2% (s ≈ 0.5) for sample masses ~0.0047–0.0050 g.
• Li-NMC (Sigma Aldrich 761001): mean O ≈ 33.7% (s ≈ 1.2) for masses ~0.0098–0.0102 g.
• Li-NMO (Sigma Aldrich 915432): mean O ≈ 33.5% (s ≈ 0.6) for masses ~0.0100–0.0101 g.

The reported precision is adequate for routine QC given appropriate sample handling and low sample masses. The larger standard deviation observed for one Li-NMC dataset highlights sensitivity to sample heterogeneity, weighing precision, or operational factors; users should verify repeatability for their specific materials and instrument configuration.

Benefits and practical applications

• Direct quantitation of total oxygen provides actionable information on cathode stoichiometry and oxidation state that correlates with electrochemical performance and safety.
• Low sample mass requirement enables analysis of limited or valuable material batches and reduces waste.
• The technique is suitable for laboratory QC, incoming materials inspection, production batch verification and R&D studies of material stability and synthesis optimization.
• Use of certified reference materials and routine blanks supports traceability and regulatory-compliant quality systems.

Future trends and potential applications

• Integration with automated sample handling and higher-throughput workflows to support production-scale quality control.
• Development of inline or near-line sensors and miniaturized combustion systems for real-time monitoring during material synthesis and electrode coating.
• Improved sample introduction and dust-management strategies to reduce detector contamination and extend maintenance intervals.
• Combination of oxygen analysis with complementary techniques (XRD, ICP, TGA, XPS) to correlate oxygen stoichiometry with crystal structure, impurity levels and surface chemistry.
• Standardization of calibration materials and interlaboratory comparisons specific to battery cathode chemistries to tighten method reproducibility across suppliers.

Conclusion

The ONH836 impulse furnace method provides a robust, traceable approach for measuring total oxygen in lithium battery cathode powders. With appropriate low-mass sampling, certified reference materials, and careful instrument operation, laboratories can obtain reproducible oxygen determinations that support product quality, safety assessments and materials development. Attention to sample homogeneity, detector saturation risks and calibration verification is essential to maintain accuracy.

References

• LECO Corporation. Application Note: Determination of Oxygen in Lithium Battery Materials. O836 Series. Form No. 203-821-723. 2026.
• LECO certified reference materials (LCRM, LRM) and suggested standards (BAM-SO14 Li-NMC cathode material, LECO 502-702 Iron Powder LCRM) as used for calibration and verification in the application note.