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).
LFP batteries don’t have nickel or cobalt in their cathode material. They’re usually chosen because they’re more stable when heated, last for many charging cycles, and cost less. Nickel-based cathodes are often used when the battery needs to store more energy. The U.S. Department of Energy says that LFP and NMC are still the main types of lithium-ion batteries. LFP is known for being safer, while NMC is known for having a higher energy density.
Where these batteries are used also varies by region. LFP batteries are particularly common in China, while nickel-based batteries have historically been more popular in Europe and North America. But this difference is becoming smaller as LFP batteries are being used more outside of China. Data from the International Energy Agency in 2024 shows that the types of cathode materials used are still strongly linked to the car markets and manufacturing plans in different regions.
No matter the type of material, how well the cathode performs depends on having very specific material qualities. For LFP powder, things like the size of the particles, the exact chemical makeup, how much moisture is in it, how much it packs down, and whether each batch is consistent can all be part of how quality is checked. A lab test only matters if the sample taken actually represents the material being used in production.
So, taking a good sample is an important part of the production and quality control process. Where the sample is taken from, how the powder flows, how much powder is collected, the design of the equipment, and the conditions during sampling can all impact how accurate the sample is. This study looks at how a system for sampling LFP cathode powder can be part of a closed production process, while also dealing with issues like material separating, getting contaminated, and keeping workers safe.
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
The process for making LFP cathode active material involves several steps: synthesis, heat treatment, milling, sorting, mixing, and handling. How it’s done depends on the company and the specific powder properties needed.
In this case, the finished LFP powder moves from a mixer or a temporary storage container to the final packaging area. Before the batch can be released or moved on, quality control samples need to be taken to make sure the material meets the set standards. These tests might check for things like particle size, moisture level, chemical makeup and any impurities, how much space the powder takes up, and how evenly mixed it is.
Just taking a sample from the top of a container or after the powder has settled won’t give a true picture of the whole batch. Differences in particle size, weight, or how the powder flows can cause it to separate as it’s being loaded, moved, or emptied.
That’s why the suggested sampling point is placed right on the processing equipment, ideally where the powder is actively moving in a predictable way. This could be:
- under a mixer
- on a storage bin
- in a gravity-fed transfer line
- just before the final packaging
The goal is to grab a specific amount of LFP powder without opening up the equipment and with as little disruption to the powder flow as possible. The sampling spot also needs to be safe for taking samples, easy to clean, and accessible for checks or repairs.
We can’t decide on the exact best spot based on the powder alone. It requires looking at the shape of the equipment, how the powder moves, how big the batches are, the order of operations, and what the lab tests are for.
So, getting a truly representative sample needs to be part of the production and quality control plan. Factors like where the sample is taken, how the powder flows, how much powder is sampled, the equipment design, and the conditions during sampling can all impact the sample’s accuracy. This study looks at how to set up a sampling system for LFP cathode powder within a closed process, while also dealing with powder separation, contamination, and keeping workers safe.
The Sampling Challenge
Taking a sample of LFP cathode powder isn’t just about grabbing a little bit from the process. The sample needs to accurately represent the whole batch and be good enough for lab tests. A few things can mess up the results:
Particle Segregation
Powder particles can vary in size, shape, or how heavy they are. When the powder is moved, dumped from a hopper, or put into a container, these differences can make certain particles gather in specific spots. So, if you take a sample from the wrong place, it might only represent one type of particle from the powder. This is especially important if the size of the particles is part of what makes the product meet its requirements.
How the Powder Flows
The sampling chamber needs to fill up and empty properly. If the powder sticks together, forms bridges, gets too compacted, or just piles up, you might not get a full or consistent sample. You have to test how the LFP powder actually flows in the sampling device. Just knowing the particle size isn’t enough to guess how it will behave.
Moisture Exposure
LFP cathode materials can be damaged by moisture. So, when you take a sample, you should try to limit its contact with the air, especially if the moisture level or surface condition is important. Using a sealed sampling system can reduce how much the sample gets exposed to the air between the process and the container. But, how much protection you need depends on the manufacturer’s specs for the material and the process conditions.
Contamination Risk
The sample could pick up dirt from a previous batch, from materials that shouldn’t touch it, from outside particles, or from being handled. So, you need to think about the equipment design, the surface condition, how it’s cleaned, and how the sample container connects, all together. If metal bits getting into the sample are a big concern, the producer needs to say what materials are okay and how much of certain impurities are allowed.
Operator Exposure
Opening a port or scooping powder by hand can release fine particles into the air where people are working. A closed sampling system can cut down on direct handling and help keep the powder contained while you collect it. Still, you have to figure out how much containment is needed based on a formal risk assessment and the rules for workplace exposure limits. You can’t just decide based on the fact that it’s “LFP powder.“
Sampling Repeatability
Samples taken by different people or at different points in the transfer process might not be comparable. Setting a specific sampling spot, sample size, collection order, and clear operating steps can make the samples more alike.
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Discover how FAMAT helps manufacturers minimize contamination risks while improving sample integrity and operator safety.
Why Representative Sampling Matters
Lab equipment only looks at the material it receives. Even the best analysis can’t fix a sample that doesn’t accurately represent the whole batch. When it comes to LFP cathode powder, mistakes in sampling can mess up how we understand several quality factors.
Particle Size
Distribution How big the powder particles are affects how the powder is handled and how electrodes are made. If big and small particles separate while the powder is being moved, a sample taken from just one spot might not show the size distribution of the entire batch.
Chemical Composition and Impurities
Chemical tests usually use only a small amount of material. If there are local differences or if contamination happens during sampling, the reported composition can be wrong. This is especially a problem when manufacturers have strict rules for tiny amounts of certain elements or metal impurities.
Moisture Content
The moisture a lab measures might not be the actual moisture in the material if the sample picks up water while it’s being collected, moved, or stored. So, the system used for sampling, the container, and how it’s handled must keep the powder in its original condition until it’s tested.
Bulk and Tapped Density
The results for bulk and tapped density can be influenced by particle spread, how settled the powder is, and how the sample is handled. Too much shaking, squeezing, or unevenly filling the sample container can change the condition of the material collected.
Batch Homogeneity
One sample only tells you about one spot at one time. Depending on what you need to know, you might need to take several samples from different parts of the process or discharge, and then test them separately or mix them into one composite sample.
How many samples you need and how often you take them should be decided by the producer’s sampling plan.
You can’t just figure this out based on the batch size alone. ISO 14488 explains how to get representative test samples from powdered materials. It also points out how sampling, dividing samples, and the properties being measured are all connected. ISO 14488:2007 was reviewed and confirmed in 2023.
💡 Engineering Insight
Sampling should be designed backwards from the laboratory objective. The property being measured determines how the sample must be collected, protected, divided and transported.
Proposed Sampling Approach
For this application, the sampling system is built directly into the process equipment. The idea is to collect a set amount of LFP powder under controlled conditions while keeping the product path fully closed.
Sampling from Moving Powder
Whenever possible, take the sample while the powder is in motion. Sampling from a moving stream gives you access to different parts of the batch and reduces the risk of grabbing material that’s only near the wall or sitting on top of a static bed.
That said, representativeness still depends on how the powder flows and where the sampler is placed. Hopper discharge can create preferential flow channels, stagnant areas, or particle segregation—so it’s not a guarantee on its own.
Defined Sample Volume
A sampling chamber with a fixed internal volume gives you a repeatable nominal sample size. The chamber needs to be sized based on:
- How much powder the lab actually needs
- The bulk density of the powder
- How readily it fills the chamber
- The number of increments required
- The process connection available
The rated chamber volume doesn’t automatically mean it’ll fill up every time. That’s something you have to verify with the real powder under representative operating conditions.
Closed Sample Recovery
Once the chamber is full, the sample goes into a suitable container. A closed or sealed connection helps limit dust release, external contamination, and exposure to the atmosphere.
The container has to be compatible with the analysis you’re running. For example, moisture testing might require a different closure and handling approach than particle-size analysis.
Multiple Increments
If a single sample won’t adequately represent the batch, you can collect several increments at specified intervals during discharge or transfer.
The increments can be:
- Analysed separately to identify variations during the process
- Combined to form a composite sample representing the batch
- Retained for traceability or investigation
The quality-control plan should define how often to sample and how to combine the increments.
Cleaning Between Samples or Batches
Residual powder inside the valve or chamber can influence the next sample. leaning requirements depend on the acceptable carryover, the frequency of product changes and the characteristics of the powder.
The system can be cleaned manually or tied into an appropriate cleaning procedure. Either way, its cleanability should be evaluated as part of the complete setup.
💡 Engineering Insight
A defined chamber volume improves repeatability only if the chamber fills and empties consistently. Testing with the actual powder remains essential.
Selecting the Sampling Location
The sampling location has a direct influence on the quality of the collected sample. It must be selected according to the purpose of the analysis and the behaviour of the powder throughout the process. For LFP cathode powder, several locations may be considered.
Below a Blender
Installing the sampling valve below a blender allows material to be collected after the blending operation.
This position may be suitable for evaluating final blend homogeneity before the powder is transferred to the next production stage. The sampler should be located where the discharged material represents the blender contents and not only a stagnant area near the outlet.
On a Storage Hopper
A sampler installed on a hopper can provide direct access to the stored powder. However, the material close to the hopper wall may not have the same composition or particle-size distribution as the powder moving through the central flow channel.
The internal hopper geometry and discharge pattern must therefore be assessed before choosing this position.
On a Gravity Transfer Line
A gravity transfer line can provide a suitable location when the objective is to collect increments during product transfer.
The installation angle, pipe diameter, powder velocity and available space must allow the sampling chamber to fill without creating excessive product retention or obstructing the main flow.
Before Final Packaging
Sampling immediately before packaging can help evaluate the material at the final stage of production. It may also allow several increments to be collected during the filling sequence.
However, a sample collected at this point represents the material entering the packaging system. It does not necessarily identify where an earlier process variation or contamination occurred.
Recommended Approach for This Application
For the application considered here, the preferred starting point would be either:
- below the final blender, if the objective is to verify blend homogeneity
- on the gravity transfer line before packaging, if the objective is to represent the discharged batch
The final selection requires a review of the actual process drawings, powder flow direction, sampling frequency and required laboratory quantity.
💡 Engineering Insight
There is no universally representative sampling point. The correct location depends on which stage of the process the laboratory result is intended to represent.
The proposed configuration is intended to improve the control and consistency of the sampling operation. The benefits listed below are functional expectations and must be confirmed during commissioning and process validation.
More Consistent Sampling
A fixed sampling location and defined chamber volume can reduce variations caused by operators using different tools, quantities or collection methods.
Consistency still depends on complete chamber filling, reliable discharge and a clearly defined operating procedure.
Reduced Open Handling
Collecting the sample directly from closed process equipment can reduce the need to open a hatch, access the powder surface or transfer material manually.
This can help limit powder release into the working environment and reduce opportunities for external contamination.
Improved Sample Protection
A closed connection between the sampling valve and the receiving container can limit exposure to ambient air and moisture.
The degree of protection depends on the complete sampling arrangement, including the container, seals, connection method and handling after collection.
Lower Cross-Contamination Risk
A sampling system designed for inspection and cleaning can help control residues between batches or sampling sequences.
The acceptable carryover limit and cleaning verification method must be defined by the battery-material producer.
Integration into the Process Sequence
An actuated valve can be incorporated into the production control system and operated at predefined stages of the batch transfer.
This may support:
- Collection at defined time intervals
- Multiple increments across a batch
- Consistent valve operating sequences
- Traceability of sampling events
Automation does not by itself guarantee representative sampling. The timing must correspond to actual product flow and the sampler must operate reliably under process conditions.
Better Operator Protection
A closed sampling procedure can reduce direct contact with fine powder. The actual level of containment must be assessed through the complete installation and confirmed against the site’s occupational health requirements.
It would be incorrect to assign a containment performance level without appropriate testing.
💡Engineering Insight
The main benefit of an integrated sampling valve is greater control over how, where and when the sample is collected. Its performance must still be demonstrated with the actual powder and process.
Engineering Considerations
Before selecting the final sampling configuration, the powder characteristics, process conditions and analytical requirements must be reviewed together.
| Parameter | Why it matters | Information required |
| Particle size distribution | Influences segregation and chamber filling | Typical range and proportion of fine particles |
| Particle morphology | Affects friction, cohesion and flow behaviour | Shape and surface characteristics |
| Bulk density | Determines the approximate sample mass obtained from a defined volume | Loose and, if relevant, tapped density |
| Flowability | Influences chamber filling and sample discharge | Evidence of bridging, sticking or compaction |
| Moisture sensitivity | Determines the required protection from ambient air | Maximum exposure and permitted moisture level |
| Process temperature | Affects seals, handling and powder behaviour | Normal and maximum temperatures |
| Process pressure | Determines valve and actuator requirements | Normal, maximum and differential pressure |
| Required sample quantity | Defines chamber volume or number of increments | Minimum mass needed for each analysis |
| Sampling frequency | Influences manual or automated operation | Samples per batch or time interval |
| Contact-material requirements | Helps control chemical or metallic contamination | Approved materials, seals and surface finish |
| Cleaning method | Influences valve design and accessibility | Dry, wet, manual or integrated cleaning |
| Containment requirement | Determines the sample-container interface | Risk assessment and exposure limits |
Powder Testing
When flow behaviour is uncertain, testing should be performed with a representative quantity of the actual LFP powder. A substitute powder with a similar nominal particle size may behave differently because of variations in morphology, moisture, surface condition or electrostatic properties.
Testing should verify:
- entry of the powder into the sampling chamber
- consistency of the collected mass
- complete sample discharge
- product retention after operation
- operation across the expected process conditions
- cleaning between samples or batches
Sampling Plan
The mechanical design must be supported by a documented sampling plan defining:
- the purpose of each sample
- the selected sampling point
- when the sample is collected
- the number of increments
- whether increments are analysed separately or combined
- the container and identification method
- storage and transport conditions
- the laboratory sample-division procedure
💡Engineering Insight
A sampling valve provides the mechanical means of collecting material. Representative results require the valve, sampling plan and laboratory procedure to function as one complete system.
Conclusion
Representative sampling of LFP cathode powder requires more than selecting a valve with an appropriate connection size. The complete sampling system must reflect the characteristics of the powder, the process flow, the purpose of the analysis and the required level of containment.
A sampling valve installed directly on a blender, hopper or transfer line can provide a controlled method for collecting a defined quantity of powder. However, the selected location must correspond to the part of the process that the laboratory result is intended to represent.
For a successful installation, the following elements should be assessed together:
- Particle size distribution and powder flowability
- Bulk density and required sample mass
- Risk of segregation during transfer
- Moisture and contamination limits
- Sampling point and operating sequence
- Chamber filling and discharge behaviour
- Product-contact materials
- Sample-container connection
- Cleaning and inspection requirements
- Manual or automated operation
Testing with the actual LFP powder is recommended whenever filling, discharge, retention or flow behaviour cannot be predicted reliably.
By integrating the sampling device into the process and defining a consistent sampling procedure, manufacturers can improve control over how samples are collected and protected before laboratory analysis.
Discuss Your LFP Powder Sampling Application
Every battery-material process has different powder characteristics, equipment geometry and analytical requirements.
FAMAT Sampling can review your application according to:
- Powder properties
- Process conditions
- Required sample quantity
- Preferred sampling location
- Containment requirements
- Cleaning procedure
- Manual or automated operation
