What problems does lithium iron phosphate material bring in the processing of lithium battery packs?

by:CTECHi     2021-07-27

What problems does the lithium iron phosphate material bring in the processing of lithium battery packs? Lithium iron phosphate is now widely selected as the positive electrode material of the power lithium-ion battery in China, from the market analysis of the government, scientific research institutions, enterprises and even securities companies Members are optimistic about this material and regard it as the development direction of power-type lithium battery packs. However, lithium iron phosphate battery packs will also encounter some defects. What series of problems will the lithium iron phosphate material bring about during the processing of lithium battery packs?

Lithium iron phosphate Batteries refer to lithium-ion batteries that use lithium iron phosphate as the positive electrode material. The cathode materials of lithium battery packs mainly include lithium cobalt oxide, lithium manganate, lithium nickelate, ternary materials, and lithium iron phosphate. Because lithium iron phosphate has some performance defects, such as low tap density and compact density, the energy density of lithium-ion batteries is low, and the cost of material preparation and battery manufacturing costs are high. Lithium battery packs will encounter some of the following problems:

1. Coating uniformity problems for lithium iron phosphate batteries

Uneven distribution not only causes poor consistency of lithium battery packs, but also concerns issues such as design and use safety. Therefore, the uniformity of coating is strictly controlled during the production of lithium battery packs. Knowing the formula and coating process, the smaller the material particles, the more difficult it is to make uniform coating. The fundamental thing is to improve the material, such as increasing the conductivity of the particles, making the particles spherical, etc., which may have limited effects in a short period of time. Based on the existing materials, from the perspective of lithium battery processing, the ways to improve can be tried from the following:

Use 'linear' conductive agent: use ' 'Linear' conductive agents are currently mainly VGCF (carbon fiber) and CNTs (carbon nanotubes), metal nanowires, etc.

Improve the dispersion effect: a slurry with a good dispersion effect will greatly reduce the probability of particle contact and agglomeration, and the stability of the slurry will be greatly improved.

Improve the slurry transfer process: When storing the slurry, consider increasing the stirring speed to avoid the slurry from sticking; for the use of turnover buckets to transfer the slurry, shorten the discharge to the greatest possible extent. During the coating time, use pipeline transportation if possible to improve the viscosity of the slurry.

Using extrusion coating (spraying): Extrusion coating can improve the surface texture and thickness unevenness of the blade coating, but the equipment price is relatively high, and the Stability requirements are high.

2. The lithium iron phosphate battery is difficult to dry

Because the lithium iron phosphate battery pack has a larger surface area and the amount of binder When the slurry is large, the amount of solvent required for preparing the slurry is large, and it is more difficult to dry after coating. How to control the volatilization rate of solvents is a problem worthy of attention.

3. The flexibility of the lithium iron phosphate battery is poor

Currently, when the lithium iron phosphate pole piece is processed, it is generally felt that it is extremely The sheet is hard and brittle, which may not have a small impact on the laminated sheet, but it is very disadvantageous when it is wound. The flexibility of the pole piece is not good, and it is easy to drop powder and break when winding and bending, resulting in short circuit and other defects.

4. The binding performance of lithium iron phosphate battery is poor

The particles of lithium iron phosphate material are small, and the surface ratio is more The proportion of lithium cobaltate and lithium manganate has increased a lot, and more binders are needed. However, if the binder is used too much, the energy density will decrease if the content of the active material is reduced. Therefore, when possible, the amount of binder will be reduced as much as possible during the production process of the lithium battery pack.

5. Finally, the problem of material dispersion

Pulping is one of the most critical processes in the production of lithium battery packs , Its core task is to evenly mix active materials, conductive agents, binders and other materials so that the performance of the materials can be better played. To mix well, it must first be able to disperse. As the particles decrease, the corresponding specific surface area increases, and the surface energy increases. The tendency of particles to polymerize increases, and the corresponding effective dispersion space increases.

A more effective method is to use ultrasonic dispersion technology. Ultrasonic dispersion process time is short, the overall energy consumption is reduced, the slurry dispersion effect is good, the polymerization of the material particles is effectively delayed, and the stability is greatly improved.

The above is a series of problems that lithium iron phosphate materials may encounter during the production and processing of lithium battery packs, but these problems have targeted solutions, so you Don't worry too much, lithium iron phosphate battery packs are still very popular in the market at present, and will lead the trend of lithium battery packs in the future. There are many advantages of lithium iron phosphate batteries that we need to know.

The advantages of lithium battery packs:

Small size, lighter weight, high energy density;

Long service life;

Excellent high temperature performance;

High rate discharge;

Quick charge and discharge;

Safety, environmental protection and no pollution;

No memory effect and so on.

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