Representative Sampling of NMC and Nickel-Rich Cathode Powders

Introduction

When making lithium-ion batteries, manufacturers pick different cathode materials based on how well the battery needs to perform, how much it costs, how safe it is, and where the materials come from. For electric cars, two main types are used right now : lithium iron phosphate (LFP) and nickel-based ones, mostly nickel manganese cobalt oxide (NMC) and nickel cobalt aluminum oxide (NCA).

NMC and NCA cathodes are generally selected when high energy density is a priority. Increasing the nickel content can increase the amount of energy stored, but it can also make the cathode material more reactive and more sensitive to its handling and storage conditions.

Common NMC compositions include NMC 111, NMC 532, NMC 622 and NMC 811. These numbers indicate the relative proportions of nickel, manganese and cobalt. NMC 811, for example, contains a higher proportion of nickel than NMC 622. However, the exact properties of a cathode powder also depend on its manufacturing process, particle morphology, surface treatment and storage conditions.

Compared with LFP, nickel-based cathodes have historically been more widely used in Europe and North America, particularly in electric vehicles requiring a longer driving range. LFP has a stronger position in China, although its use is also expanding in other regions. Battery chemistry choices continue to evolve according to vehicle design, cost and supply-chain strategy.

For NMC and nickel-rich cathode powders, exposure to air and moisture can modify the material surface and affect subsequent electrode processing. The level of sensitivity is not identical for every NMC grade. It must therefore be assessed according to the specific composition and the supplier’s material requirements.

Sampling can create a point of exposure if the process is opened or if the powder is transferred manually into an unsuitable container. It can also introduce foreign particles or metallic contamination that may affect laboratory results.

A representative sampling system must therefore do more than collect the required quantity of powder. It should preserve the condition of the material, limit uncontrolled atmospheric exposure and reduce contamination risks between the process and the laboratory.

This application case study examines how NMC and nickel-rich cathode powders can be sampled directly from closed process equipment while maintaining sample integrity and protecting the operator.

Sources : Yu et al., Nature Communications, 15 July 2025, International Energy Agency, regional battery chemistry data, updated 8 April 2025, Journal of Electrochemical Energy Conversion and Storage, 2021

The Application

NMC cathode active material is produced through several processing stages that may include precursor preparation, lithiation, calcination, milling, classification, coating, blending and final packaging. The exact sequence depends on the cathode composition and the manufacturer’s production method.

For this application scenario, the finished NMC or nickel-rich cathode powder is transferred from a final blender or storage vessel towards the packaging system. Quality-control samples are required before the batch is released or supplied to the electrode manufacturing process.

The laboratory analyses may include:

Because the powder may be sensitive to atmospheric exposure, the sampling operation must preserve the condition of the material between the process and the laboratory.

Opening a vessel or manually transferring the powder can expose the sample to ambient moisture and carbon dioxide. It can also introduce contamination from sampling tools, containers or the surrounding environment.

For this application, the proposed sampling system is installed directly on closed process equipment. Depending on the production layout, the sampling point may be located:

• Below the final blender
• On an intermediate storage hopper
• Along a gravity transfer line
• Before the final packaging station

The sample is collected in a defined-volume chamber and discharged into a suitable closed container. Where required by the material specification, the sample recovery arrangement may also be designed for operation under a controlled or inert atmosphere.

The final sampling configuration must be based on the actual NMC grade, process conditions, required analyses and permitted level of atmospheric exposure. It should not be selected solely from the material’s commercial designation.

💡Engineering Insight
“NMC powder” does not describe one uniform material. Composition, nickel content, particle structure and surface treatment can all influence how the powder must be sampled and protected.

The Sampling Challenge

Representative sampling of NMC and nickel-rich cathode powder requires control of both the material collected and the environment in which it is collected. Several factors might influence sample integrity:

Moisture and Air Exposure

NMC powders can react with components of the surrounding atmosphere. The degree of sensitivity varies according to nickel content, particle structure, surface treatment and storage conditions.

Opening the process during sampling may expose the powder to humidity and carbon dioxide. This exposure can modify the surface condition of the sample before it reaches the laboratory.

The permitted exposure time and atmospheric conditions must therefore be defined for the specific material.

Differences Between NMC Grades

NMC 111, NMC 532, NMC 622 and NMC 811 do not have identical characteristics. Increasing the nickel content changes the chemistry and can increase the material’s sensitivity to handling conditions.

The sampling procedure used for one NMC grade should not automatically be applied to another without reviewing the product specification.

Particle Segregation

Differences in particle size, density or morphology may cause segregation during blending, transfer, hopper discharge or packaging.

A sample collected from a stagnant zone or only one part of the powder stream may not accurately represent the complete batch.

Metallic and Cross-Contamination

Trace contamination can be important when evaluating cathode active materials. Potential sources include:

• Unsuitable product-contact materials
• Wear particles
• Residues from previous batches
• Sampling tools
• Open containers
• The surrounding production environment

The materials and surface condition of the sampling equipment must be compatible with the producer’s impurity limits.

Powder Retention

Fine powder can remain inside the sampling chamber, around seals or within the sample discharge path. Residual material may affect the next sample or create carryover between different NMC grades.

The equipment must therefore allow appropriate inspection and cleaning.

Operator Exposure

Manual sampling can release fine cathode powder into the working environment. A closed sampling and container connection can reduce direct handling, but the required containment level must be determined through the site’s risk assessment.

💡Engineering Insight
For nickel-rich cathode materials, representative sampling and sample protection are closely connected. A representative sample can lose its value if its condition changes before laboratory analysis.

Controlled-Atmosphere Sampling Concept

When NMC powder is stored or transferred under a controlled atmosphere, the sampling operation should preserve those conditions as far as required by the material specification.

Installing a sampling valve on closed process equipment reduces open handling. However, a closed system is not necessarily free from ambient air. Air may remain inside:

• The sampling chamber
• The discharge outlet
• The connection between the valve and the container
• The empty sample container

These volumes must be considered when defining the sampling procedure.

Standard Closed Sampling

A standard closed arrangement may be sufficient when brief atmospheric exposure is acceptable.

The sample is collected directly from the process and discharged into a connected container, limiting powder release and manual handling. The container is then closed and transferred to the laboratory.

Inert-Gas-Assisted Sampling

When stricter atmospheric control is required, the sampling container, discharge connection or receiving container may need to be purged with a compatible inert gas before the sample is collected.

A possible operating sequence is:

1. connect the prepared sample container
2. purge the relevant internal volumes
3. isolate or stop the purge according to the validated procedure
4. fill the sampling chamber from the process
5. move the chamber to the discharge position
6. release the sample into the container
7. close or isolate the container before removal

The exact sequence depends on the valve configuration, process pressure and required level of atmospheric protection.

Defining the Required Protection

The cathode-material manufacturer should specify:

• Maximum permitted moisture exposure
• Acceptable oxygen and carbon dioxide levels
• Permitted exposure duration
• Required inert gas
• Sample-container preparation
• Sealing and transport conditions

Without these values, it is not possible to determine whether standard closed sampling is sufficient or whether inert-gas-assisted sampling is necessary.

💡Engineering Insight
The appropriate sampling atmosphere must be based on the material specification. Adding an inert-gas purge without defined acceptance criteria does not by itself prove that the sample has been protected.

Purging the Sampling Chamber and Container

If you need to keep the powder from being exposed to the atmosphere, purging can help. It clears out the ambient air sitting in the sampling path before the powder even reaches the chamber or receiving container.

Just keep in mind : the purge system has to work around the entire sampling assembly, not just the valve by itself.

Areas to Be Considered

The volumes potentially requiring purging include:

• the sampling chamber
• the discharge cavity
• the connection between the valve and container
• the empty receiving container
• any flexible hose or adapter used for sample recovery

If one of these volumes remains open to the surrounding atmosphere, the expected protection may not be achieved.

Purge Gas

The gas must be compatible with the powder, process and laboratory analysis. Nitrogen or argon may be considered, but the appropriate gas must be selected and approved by the material manufacturer.

The purge gas should meet the required limits for:

• moisture
• oxygen
• particles
• oil or other contaminants
• pressure and flow stability

Purging Sequence

A possible sequence consists of connecting the sample container, purging the enclosed volume and then operating the sampling valve.

The required purge duration or number of volume exchanges cannot be defined without knowing:

• the internal volume of the system
• gas flow rate
• connection geometry
• initial atmospheric conditions
• permitted residual moisture and oxygen levels

These parameters should be established during qualification.

Pressure Management

The purge must not create an uncontrolled pressure increase inside the sample container or discharge connection.

The design may require a controlled gas outlet, pressure limitation or verified vent path. Any discharged gas and entrained powder must be handled according to the site’s safety and containment requirements.

Sealing the Sample

After collection, the container should be isolated from the sampling system without exposing its contents to ambient air.

Depending on the application, this may involve:

• a closable bottle
• a sealed sampling receiver
• an isolation valve
• a prepared container transferred to a glovebox
• another validated closed-transfer arrangement

💡Engineering Insight
Purging is effective only when gas flow, internal volume, outlet path and acceptance criteria are defined. Purge time alone does not demonstrate atmospheric control.

Standard Closed Sampling vs Inert-Gas Sampling

The appropriate sampling arrangement depends on the sensitivity of the NMC powder and the purpose of the laboratory analysis.

A standard closed system may be adequate for some materials, while nickel-rich or specially treated cathode powders may require stricter atmospheric control.

Selection Criteria

Before choosing between the two arrangements, the manufacturer should determine:

• which NMC grade is being sampled
• whether the material is stored under an inert atmosphere
• which properties will be analysed
• the permitted moisture, oxygen and carbon dioxide exposure
• the time between sampling and analysis
• the required sample quantity and frequency
• whether the laboratory can preserve the same conditions

Using an inert-gas system is not automatically necessary for every NMC powder. Conversely, a standard closed sampler should not be assumed sufficient when atmospheric limits are critical.

💡Engineering Insight
The sampling system should not provide a lower level of atmospheric control than the process and laboratory procedures surrounding it.

Selecting Contact Materials and Seals

All surfaces exposed to the NMC powder can become a potential source of contamination or product retention. Material selection must therefore reflect the cathode producer’s impurity limits, cleaning procedure and process conditions.

Metallic Contact Surfaces

Stainless steel may be suitable for many applications, but the required grade and surface finish must be approved by the material manufacturer.

The assessment should consider:

• permitted metallic impurities
• corrosion resistance
• abrasion and wear
• surface roughness
• cleaning compatibility
• inspection requirements

If the powder is abrasive, wear at moving interfaces should also be evaluated. Even small quantities of material released from product-contact components may influence sensitive trace-element analyses.

Surface Finish

A controlled surface finish can reduce irregularities where fine powder may accumulate. However, surface finish alone does not guarantee complete cleanability.

The complete geometry should be reviewed for:

• gaps
• recesses
• sharp transitions
• inaccessible cavities
• areas around the sampling chamber
• potential compression of powder between moving parts

Seal Selection

Seal materials must be compatible with the process temperature, powder, cleaning agents and inert gas, where used.

The seal arrangement should also minimise:

• powder trapping
• abrasion
• particle generation
• leakage of ambient air
• carryover between batches

The appropriate seal material cannot be selected without the actual operating conditions and chemical compatibility requirements.

Lubrication

If lubrication is required, its location and potential contact with the powder must be assessed. Any lubricant used near the product zone should be compatible with the producer’s contamination-control requirements.

Material Traceability

For quality-critical applications, the manufacturer may require documentation for product-contact components, such as:

• material certificates
• surface-finish records
• seal specifications
• cleaning declarations
• inspection or maintenance records

💡Engineering Insight
Material compatibility is not limited to corrosion resistance. Wear, particle generation and trace contamination must also be considered when sampling cathode powders.

Preventing Cross-Contamination Between NMC Grades

A production facility may handle several cathode materials, such as NMC 622, NMC 811 or surface-treated variants. Residues remaining in the sampling system can affect the next sample and potentially distort laboratory results.

Cross-contamination control must therefore form part of both the equipment design and the sampling procedure.

Potential Retention Areas

Powder may accumulate in:

• the sampling chamber
• the discharge cavity
• gaps around moving components
• seals
• container adapters
• purge connections
• flexible hoses or transfer accessories

These areas should be accessible for inspection or addressed through a validated cleaning method.

Cleaning Between Products

The required cleaning procedure depends on the acceptable carryover between grades. Possible approaches include:

• dry manual cleaning
• vacuum cleaning with suitable equipment
• disassembly of product-contact components
• purging with a compatible gas
• wet cleaning when permitted by the equipment and process
• collection of one or more discard samples before the quality-control sample

A gas purge may remove loose particles, but it should not be assumed to clean adhered or compacted powder completely.

Cleaning Verification

The manufacturer should define:

• acceptable carryover limits
• critical contaminants
• sampling or swabbing locations
• analytical method
• inspection criteria
• cleaning frequency
• conditions requiring disassembly

The verification method must be sensitive enough to detect residues at the required acceptance level.

Dedicated or Shared Equipment

Dedicated sampling equipment may be considered when contamination limits are particularly strict or when cleaning between materials is difficult to validate.

Shared equipment may remain suitable when:

• the sampling path is accessible
• retained powder can be removed reliably
• the cleaning method is documented
• compliance with the carryover limit can be demonstrated

Sample Sequence

When several samples are collected from the same batch, the first operation may contain residual material from the sampling chamber or dead space.

If the quality system permits, an initial sample may be discarded or analysed separately. This decision must be defined in the approved sampling procedure rather than left to the operator.

💡Engineering Insight
A visually clean sampling chamber is not necessarily free from analytically significant residues. Cleaning acceptance must reflect the impurity limits applied to the cathode material.

Proposed FAMAT Sampling Configuration

For this application, a FAMAT volumetric sampling valve can be installed directly on the blender, storage vessel or transfer line. The configuration should be adapted to the NMC grade, process atmosphere and laboratory requirements.

Defined-Volume Sampling Chamber

The piston contains a chamber designed to collect a defined nominal volume of powder. The required chamber size should be selected according to:

• the sample mass required by the laboratory
• the powder’s bulk density
• its flow behaviour
• the number of increments required
• the available installation geometry

The actual sample mass must be verified with the powder because the chamber may not fill identically under all process conditions.

Closed Sample Recovery

The discharge side can be connected to a suitable sample container before the valve is operated. This limits manual handling and keeps the powder within a controlled path.

The connection should allow the container to be isolated or closed before it is removed from the sampling system.

Controlled-Atmosphere Option

Where required, the sampling arrangement may incorporate connections for a compatible purge gas. The proposed design could allow the discharge path and receiving container to be purged before the powder is released.

The purge circuit must include a defined inlet and outlet path. Its pressure, flow rate and operating sequence must be established during engineering and qualification.

Valve Actuation

The valve may be manually operated for occasional sampling or fitted with an actuator for integration into an automated sequence.

Automated operation may be appropriate when:

• several increments are required during batch transfer
• the sampling time must be repeatable
• the process operates within a closed or restricted area
• sampling events must be recorded by the control system

Installation Orientation

The valve orientation should support reliable chamber filling and complete discharge. A slight inclination may assist gravity discharge in some installations.

The final position must be confirmed from the process geometry and testing with the actual powder.

Cleaning and Inspection

The configuration should permit inspection of critical product-contact areas and cleaning according to the site procedure.

Particular attention should be given to:

• the sampling chamber
• the discharge path
• seals and moving interfaces
• purge connections
• the container adapter

💡Engineering Insight
For NMC powder, the valve, purge circuit and sample container should be engineered as one system. Evaluating these components separately may leave uncontrolled exposure points between the process and laboratory.

Validation Points

Before routine use, the complete sampling arrangement should be tested under representative process conditions. The validation should include the valve, purge system, sample container and operating procedure.

Sample Quantity and Repeatability

Repeated sampling operations should confirm:

• consistent chamber filling
• acceptable variation in collected mass
• complete discharge into the container
• absence of unacceptable powder retention
• repeatability across the expected process conditions

The acceptance limits must be defined according to the sampling plan and analytical requirements.

Atmospheric Protection

If inert-gas-assisted sampling is used, testing should verify that the required conditions are achieved throughout the sampling path.

Depending on the material specification, this may include measurement of:

• residual oxygen
• residual moisture or dew point
• purge pressure
• gas flow rate
• purge duration
• container conditions after sealing

The measurement location is important. Values recorded only at the gas supply do not demonstrate the conditions inside the sampling chamber or receiving container.

Sample Integrity

Where relevant, comparative analysis may be performed between samples collected using the proposed system and samples prepared under established controlled conditions.

The comparison may include:

• moisture content
• surface-related parameters
• residual lithium compounds
• chemical impurities
• particle size distribution

The appropriate tests must be selected by the cathode-material manufacturer.

Containment

The complete sampling sequence should be assessed for powder leakage during:

• connection of the container
• valve operation
• sample discharge
• container removal
• cleaning and maintenance

Any containment performance claim should be supported by an appropriate test method and documented results.

Cleaning and Carryover

Cleaning verification should demonstrate that residues from the previous batch or NMC grade remain below the defined acceptance limit.

Testing should include the areas most likely to retain powder rather than only the most accessible surfaces.

Operating Sequence

The procedure should clearly define:

1. preparation of the sample container
2. connection to the sampling system
3. purge sequence, where required
4. valve operation
5. sample isolation
6. container removal
7. identification and transport
8. cleaning or preparation for the next sample

💡Engineering Insight
Validation should test the complete sampling sequence under real operating conditions. Testing the valve alone does not demonstrate that the sample remains representative and protected until it reaches the laboratory.

Conclusion

Representative sampling of NMC and nickel-rich cathode powders requires control of both the quantity collected and the environment surrounding the sample.

A valve installed directly on closed process equipment can reduce open handling and provide a consistent sampling point. However, when atmospheric exposure is critical, the sampling chamber, discharge connection and receiving container must be considered together.

The main engineering points include:

• the specific NMC composition and nickel content
• permitted exposure to moisture, oxygen and carbon dioxide
• powder flow and chamber-filling behaviour
• sample quantity and number of increments
• product-contact materials and seals
• metallic and cross-contamination limits
• purge-gas quality and operating sequence
• container preparation and closure
• cleaning and carryover verification
• validation under representative process conditions

A standard closed sampling arrangement may be sufficient when limited atmospheric exposure is acceptable. When the material specification requires stricter control, an inert-gas-assisted configuration may be considered.

The required protection level must be defined by the cathode-material manufacturer. It cannot be determined solely from a designation such as NMC 622 or NMC 811.

Testing with the actual powder and complete sample-recovery arrangement is recommended before routine operation.

Discuss Your NMC Powder Sampling Application

FAMAT Sampling can review your application according to:

• NMC grade and powder characteristics
• process atmosphere
• sampling location
• required sample quantity
• contamination limits
• sample-container interface
• manual or automated operation
• cleaning and validation requirements

Contact FAMAT Sampling to discuss a sampling configuration adapted to your NMC or nickel-rich cathode powder process.