In the pole piece manufacturing process, it can be subdivided into five processes: slurry preparation, slurry coating, pole piece rolling, pole piece cutting, and pole piece drying. In the battery assembly process, according to the different specifications of the battery, it is roughly divided into winding, shelling, welding and other processes.
The manufacture of lithium-ion batteries is a process in which the process steps are closely linked. On the whole, the production of lithium batteries includes the pole piece manufacturing process, the battery assembly process, and the final liquid injection, pre-filling, chemical formation, and aging processes. In these three stages of the process, each process can be divided into several key processes, each step will have a great impact on the final performance of the battery.
In the pole piece manufacturing process, it can be subdivided into five processes: slurry preparation, slurry coating, pole piece rolling, pole piece cutting, and pole piece drying. In the battery assembly process, according to the different specifications of the battery, it is roughly divided into winding, shelling, welding and other processes.
In the final liquid injection stage, it also includes various processes such as liquid injection, exhaust, sealing, pre-charging, chemical formation and aging. Every process in the battery manufacturing process will cause a certain waste. The reasons for waste are employee error, equipment error, environmental reasons, etc. In order to ensure that the cost rate of the product is good enough, we try to ensure that each step is qualified.
The preparation of the electrode slurry is the most critical part of the whole process, and the quality of the electrode slurry directly affects whether the next step can be carried out. Slurry preparation is a non-Newtonian high viscosity fluid formed by mixing a powder, such as a living substance, a binder, a solvent, a thickener, etc., and the fluid needs to have a certain viscosity, good fluidity, and a sufficiently small particle size. . Workers must first sharpen their tools, and what kind of equipment is needed to prepare the electrode paste to meet the requirements?
First, the capacity is large enough
The manufacture of batteries requires more pole pieces and requires better consistency of the batteries. This requires that the slurry needs a certain consistency. In the actual mixing process, the slurry of each pot is not completely the same due to the stirring operation, time, feeding sequence, etc., even under the same process conditions. The viscosities are not necessarily the same. Therefore, the mixer needs a certain capacity. At present, the large mixer can achieve 2000L. When the capacity is large enough, the mixing ability and the mixing effect of the materials must be considered.
Second, have a good vacuum closed system
The mixer requires a good vacuum containment system. The main reasons are three:
1 During the whole mixing process, due to frequent collisions between materials, friction, and friction between the agitator and the material, more heat is generated, resulting in an increase in temperature. Increased temperature will cause some solvents to occur, resulting in a very irritating odor, such as NMP, PVDF, etc., organic gases have great harm to the human body.
2 In the premixing stage of dry powder, if the closed system is not good enough, it will make the dust rise, destroying the working environment and affecting the quality of the product and causing harm to employees.
3 There is a large gap inside the powder. After mixing with the solvent, there will be many bubbles inside the slurry. It is necessary to defoam the slurry to carry out the pole piece coating. Otherwise, bubble cracking, uneven surface density or even foil phenomenon may occur during the coating process, which is extremely unfavorable for the performance of the battery.
Third, the mixer material has strong corrosion resistance, wear resistance and stable physical and chemical properties.
Obviously, regardless of the strong alkalinity of the positive electrode material, the strong corrosiveness of NMP, etc., the mixer is required to have excellent corrosion resistance. During the agitation process, the agitator requires continuous agitation of the powder to provide wear resistance and a long enough service life.
Fourth, the mixer blade structure is reasonable, the mixing speed design meets the requirements
In addition to sufficient agitation power and agitation range in the mixer, the shape of the agitator blades, mechanical design, etc. have a great influence on the preparation of the slurry. First of all, it must be ensured that the agitator has a sufficient agitation range and no dead angle in the agitated vessel. Biaxial or even triaxial planetary agitators are currently used in larger mixers to ensure that no powder or agglomerated material is not uniformly mixed into the slurry.
Secondly, the shape design of the agitator has an absolute influence on the dispersion, mixing, particle size distribution and fluidity of the materials. Common shapes currently on the market include paddle, butterfly, anchor, twist, claw, frame, etc. The equipment is preferably equipped with high-speed dispersing equipment, because some materials require high-speed shear force to disperse them. Therefore, it has certain necessity. The third requirement is that the equipment has a stirring speed that meets the requirements to meet the requirements of high molecular weight and ultrafine powder dispersion.
In addition to the main mixing shaft, blade and other designs, some equipment has scraper design, container rotation and other design to improve the mixing efficiency and material mixing.
Five, mixer safety
The safety design of the mixer must be reasonable, including the explosion-proof design of the equipment, the safety and emergency stop design of the equipment, and the stability of the equipment to avoid injury to the operator.
The above is the basic requirement for the lithium battery slurry preparation equipment, and corresponding changes are required as the material properties are different. At present, some domestic equipment manufacturers will not repeat them one by one.
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