Lithium Battery - Materials - Powder Technology

The positive and negative electrode materials of lithium-ion batteries are typical powder materials. 

The particle size, specific surface area, and packing density of electrode material powder are related to the reaction rate and energy density of the battery. 

Therefore, factors such as particle shape, internal structure, and surface properties have a significant impact on the energy density, 

output characteristics, and cycling characteristics of batteries.

The characteristics of powder are directly related to battery performance, so the design and processing of electrode materials are very important. 

This article will introduce the application of powder technology in lithium battery electrode materials.

Electrode materials and powder technology

Control the particle size of electrode materials

The particle size of electrode materials plays a decisive role in the performance of lithium-ion batteries. 

Generally speaking, the particle size of electrode materials directly affects the preparation of battery slurry and electrode sheets. 

Large particle size slurries have low viscosity, good flowability, can use fewer solvents, and high solid content. 

When the particle size of the powder decreases, it can improve the compaction density and capacity to a certain extent.

The particle size of electrode materials is usually tested using a laser particle size analyzer, 

and the equivalent diameter D50 of the largest particle in the particle size distribution curve 

when the cumulative distribution is 50% is considered as the average particle size of the electrode material. 

Taking positive electrode materials as an example, 

the particle size and distribution of positive electrode materials are closely related to the preparation, sintering, and crushing processes of precursors.

For example, lithium cobalt oxide is generally prepared from cobalt trioxide and lithium carbonate as raw materials, 

and its sintering characteristics are very good, 

so the requirements for raw materials are relatively low. Lithium manganese oxide mostly uses 

the same raw material as alkaline manganese batteries - electrolytic manganese dioxide (EMD). 

The production process involves depositing a single piece of MnO2 plate through electrolysis, followed by peeling and crushing to obtain it.

Usually, the raw materials themselves have large irregular particles, so spherical manganese source precursors are used to control the particle size distribution. 

When industrializing materials such as lithium nickel cobalt oxide, lithium nickel cobalt manganese oxide, 

and lithium nickel cobalt aluminum oxide, chemical co precipitation is usually used to achieve atomic level mixing of elements such as Ni, Co, Mn, and Al. 

And achieving high density through controlled crystallization is within the technical scope of powder particle size process control.

Control the specific surface area of electrode materials

In general, the larger the specific surface area of the electrode material, the better the rate characteristics of the battery. 

But it is usually more prone to react with electrolyte materials, 

leading to poor cycling and storage, and its specific surface area is closely related to particle size and distribution,

 surface porosity, surface coating, etc. In the lithium cobalt oxide system, 

the small particle rate electrode material product corresponds to the largest specific surface area.

Due to the poor conductivity of lithium iron phosphate, 

the particles are designed in the form of nano aggregates with amorphous carbon coating on the surface, 

resulting in the electrode material having the highest specific surface area among all positive electrode materials. 

Compared with cobalt based materials, manganese based materials themselves are difficult to sinter, and their specific surface area is generally larger.

How to control the specific surface area that meets the needs of batteries based on the performance characteristics of materials is also 

an application of powder technology research in electrode material preparation.

Control the particle morphology of electrode materials

A typical application of improving electrode material performance through particle morphology is the spheroidization of natural graphite. 

At present, the application of lithium-ion battery negative electrode material manufacturers is gradually developing towards low cost, 

so global research on natural graphite is very important. 

Although natural graphite has the advantages of high specific capacity 

and stable discharge voltage as a negative electrode, it also has obvious disadvantages:

During the charging process, solvent molecules will co embed with lithium ions in the graphite sheet, causing the graphite layer to "peel off", 

resulting in structural damage and rapid deterioration of electrode cycling performance;

Meanwhile, ordinary natural graphite, due to its well-developed layered structure, 

is in the form of flakes and easily arranged parallel to the electrode sheets during filling, 

resulting in a longer diffusion distance for lithium ions, increased diffusion resistance, and reduced charge and discharge performance.

After spheroidization of natural graphite particles, the graphite particles are arranged in layers and distributed in various directions,

 with preferred orientations being smaller and more evenly distributed. 

The diffusion path of lithium ions is relatively short, thereby improving the discharge efficiency.

Similarly, other types of materials can also be modified and modified through appropriate spheroidization treatment. 

Meanwhile, spheroidization treatment can enhance the filling and uniform distribution of powder materials, further improving 

the volumetric energy density and cycling performance of lithium-ion batteries.

Surface modification by coating other powder materials

Nickel cobalt manganese ternary material is currently the most widely used positive electrode material for power batteries. 

With the increasing demand for high energy density, problems such as poor structural stability 

and humidity sensitivity after high nickelation pose challenges for practical applications. 

The top 100 lithium battery industries often use surface coatings to adjust the performance of materials.

Surface coating can effectively stabilize the structure of high nickel materials. 

The surface coating technology reduces the contact area between the electrode material and the electrolyte, 

thereby reducing the side reactions between surface impurities of the material and the electrolyte, 

improving the electronic conductivity of the ternary positive electrode material surface, 

and increasing the stability of the material after cycling. 

Common surface coating materials include metal oxides, phosphates, and other stable electrode materials, which are currently used as coating materials.

Mixing and dispersion of various powder materials

In the production of lithium-ion battery electrodes, various components such as active materials, binders, solvents, 

and additives need to be added and stirred to form a slurry. 

Therefore, the dispersion of particles and the uniformity of composition become very important. 

The electrode material undergoes very complex changes during the actual stirring process, 

in addition to strong physical effects, there are also certain chemical effects.

Even though uniformity has been achieved macroscopically, there are still some material particle aggregates under the microscope. 

Therefore, the stirring of electrode materials is not only macroscopically uniform, but more importantly, relatively uniform microscopically. 

The more uniform the mixing, the more beneficial it is to improve the performance of the battery.

In addition, the uniform mixing of two or more electrode materials can also improve the performance of the battery or achieve certain cost optimization. 

With the continuous updating and upgrading of battery technology,

 production equipment such as lithium battery homogenization systems and powder conveying are also constantly innovating and transforming.

Many lithium battery equipment suppliers conduct in-depth research on hybrid dispersion mechanisms to achieve higher production line integration, 

higher efficiency, lower energy consumption, and more intelligent production line construction. 

These are the foundation for improving processes and achieving higher quality products, as well as a manifestation of the industrialization of powder technology.

conclusion

Powder technology has many applications in the processing of lithium battery electrode materials and even in the battery manufacturing process. 

Powder processing technology has become a key technology in the preparation, post-treatment, 

and electrode production process of lithium-ion battery products such as motorcycle batteries and fish finder batteries. 

It plays an important role in improving the performance of lithium-ion batteries and is worth exploring from the perspective of powder technology.

The powder industry covers multiple industries, and its equipment and process principles often intersect. 

A new understanding of lithium battery electrode materials from the perspective of powder 

can help integrate key points in material preparation and application technology, 

thereby finding new innovative points and further promoting the development of the lithium battery industry.