Advanced graphite for your lithium-ion battery production

The anode of a battery consists of an approx. 8 - 18 µm thick copper foil, which is coated with active material (graphite) and various additives.
Graphite is therefore the most important battery anode material in the production of lithium-ion batteries. The black, platelet-shaped mineral is widely sourced and brings a number of numerous advantages for the manufacturer. After coating, the tap density of graphite is relatively high and the electro-chemical performance is relatively stable. Additionally, the actual specific capacity density can be close to the theoretical specific capacity. However, graphite also carries several disadvantages as a battery anode material. Most of all, its capacity to meet the actual demand is insufficient - a demand that is expected to increase rapidly in the next years, mainly driven by the growing number of electric vehicles. 

To meet the demand for graphite in the long term, the graphite in battery production must be processed with as little loss as possible. In this way, the graphite can be used as effectively as possible. In addition, the characteristics of the graphite must be advanced in order to increase the performance of the battery. The particle size plays a role here because it determines how quickly the battery can be charged and discharged. At the same time, the tap density determines the energy density, i.e. the distribution of the graphite on the surface of the anode copper foil. The specific surface area also influences the capacity of the battery after the first charge. 


To achieve the optimum battery performance results, On has developed technologies for advancing both natural and synthetic graphite.

Natural and synthetic graphite

There are two kinds of graphite used in the production of lithium-ion batteries: natural and synthetic or artificial graphite. Natural graphite is sourced directly from graphite mines. As it is a natural raw material, there are always impurities, and the relatively soft graphite can be compromised by the surrounding hard mountain material. As these impurities make natural graphite more abrasive than its synthetic counterpart, the machines used in processing are subject to wear. 

For the end product, in addition to a high yield, customers wish for a steep particle size distribution and a high tap density. At the same time, the top cut must also be adjusted, and the specific surface area should be very low (low BET values). A high product quality later increases the capacity of the batteries. 

Synthetic graphite on the other hand is made by graphitising petroleum coke or needle coke. It is relatively pure, and its mechanical characteristics can be specifically influenced and optimised by the production process. Artificial graphite is usually not explosive and abrasive. However, it can contain metal impurities that are magnetic and should be separated after the pre-grinding process. Apart from product quality, high yields and low specific energy consumption are particularly important for customers. 

In most cases¸ a mix of natural and synthetic graphite is used in the production of battery anode material. 

Feed material and rounded graphite: SEM images (synthetic graphite)

Feed material synthetic graphite:
Tap density 600 g/L

Rounded synthetic graphite:
Tap density 1000 g/L

Feed material natural graphite:
Tap density 426 g/L

Rounded natural graphite:
Tap density 920 g/L

Graphite optimization technology for high-performance anode material

To obtain high performance battery anode material and to make optimal use of the raw material it is necessary to adapt the graphite to the requirements of the application and to process it accordingly. The main focus here is on high product quality, which in turn provides the best possible battery performance. Furthermore, the appropriate graphite technology should also achieve the highest possible yield. At the same time, the specific energy consumption should remain as low as possible. Flexible product parameters and individual settings on the graphite processing plants from On also guarantee that customers receive a product that meets their specific requirements.

Individually configured graphite processing plants

Every customer is different. That's why we develop our machines and systems specifically for each customer. The combined expertise of the entire Hosokawa Micron Group, which stands behind On, helps us to achieve this. Our graphite technologies are perfectly coordinated and interlock smoothly. In addition, trials with customer products can be carried out in our test centres in Augsburg and Doetinchem in order to develop the appropriate process. For our customers, this means that they obtain a product that exactly meets their requirements and a graphite processing system that was developed specifically for them.

Graphite processing and graphite spheroidization

The processing of graphite consists of four steps
Pre-grinding, fine grinding, spheroidization and dedusting and mixing/coating coated with binders and carbon black. 


Pre-milling can be carried out with different types of mills. Which mill is suitable depends on the feed material and the feed size. Possible solutions include a fine impact mill (e.g. Ultraplex UPZ) or a classifier mill (e.g. Zirkoplex ZPS). Natural graphite can usually be processed without pre-grinding. 

Fine milling

This process is the same for both synthetic and natural graphite. It is a continuous process and determines the top cut of the graphite. 

Graphite spheroidization and dedusting

Different graphite machines and processes are required here for natural and synthetic graphite. The particle size distribution is adjustable. Both spheroidization and dedusting are batch operations. 


When a mix of natural and synthetic graphite is used, the specific characteristics of both raw materials need to be combined. This can be achieved by homogenizing these compounds in a mixer. High shear mixers also form a strong coating of other materials, such as carbon black and binders around the rounded graphite particles. 

Why do the platelet-shaped graphite particles have to be rounded or spheroidized?

The roundness of graphite brings numerous advantages. On the one hand, it increases the tap density, and thus ensures a better volumetric storage capacity of the battery anode. On the other hand, the graphite rounding improves the intercalation kinetics so that the battery anode can be charged more quickly. In addition, the battery becomes more durable, and the cycle stability is increased. 


Apart from these advantages for the performance of lithium-ion batteries, On's process has other plus points: Since fewer machines are needed here than for conventional processes, customers save space. Furthermore, the effort for maintenance and service as well as the energy costs are reduced.

Machines for enhancing graphite

On offers various machines for enhancing graphite. Which graphite machine is suitable depends on whether natural graphite or synthetic graphite is processed.  

For pre-milling natural graphite, a fine impact mill like UPZ or a classifier mill like ZPS is recommended. Fine grinding is usually carried out with a classifier mill like ZPS or ACM.   
The graphite spheroidization is carried out by means of the Alpine Particle Rounder APR with downstream classifying. As an alternative the classifier mill ZPS can also be used for rounding. However, this solution requires much more energy and space. 

With synthetic graphite, the UPZ fine impact mill is generally used for pre-milling. For grinding, the ZPS or ACM classifier mills are recommended. As artificial graphite is usually already much more spherical after grinding, it requires less energy for spheroidization. Here, the classifier mill ZPS can also be used to round the graphite in batches with integrated classifying. As alternatives, the TTD or ATP air classifiers can be used for dedusting. Depending on the requirement, the shaping step can be left out. Both kinds of graphite can be mixed and coated with the Nauta and Cyclomix mixers, for coating the Nobilta is recommended.

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