Requirements for double planetary mixer in the production of battery slurry

1. The capacity is large enough

The manufacture of batteries requires more pole pieces and requires better consistency of batteries. This requires that the slurry needs a certain consistency. In the actual mixing process, the slurry in each pot will not be exactly the same due to reasons such as stirring operation, time, and feeding sequence. The viscosity is not necessarily the same. Therefore, the mixer needs to have a certain capacity. At present, the large mixer can reach 2000L. When the capacity is large enough, the mixing ability and the mixing effect of materials must be considered.

2. Good vacuum sealing system

The mixer needs a good vacuum sealing system for three main reasons:

① During the whole stirring process, due to the frequent collision and friction between the materials, as well as the friction between the agitator and the materials, more heat will be generated and the temperature will rise. An increase in temperature will cause some solvents to emit and produce a strong pungent odor, such as NMP, PVDF, etc. Organic gases are very harmful to the human body.

② When the powder is in the dry powder premixing stage, if the closed system is not good enough, the dust will be scattered, which will damage the working environment, affect the product quality and cause harm to employees.

③ There are large voids inside the powder, and after mixing with the solvent, there must be many bubbles inside the slurry. It is necessary to degas the slurry before coating the pole piece. Otherwise, the bubbles will burst during the coating process, the surface density will be different, and even the foil will be exposed, which is extremely detrimental to the performance of the battery.

3. The material of the mixer 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 corrosion of NMP, etc., the mixer needs to have excellent corrosion resistance. During the stirring process, the continuous stirring of the powder by the agitator requires it to be wear-resistant and have a long enough service life.

4. The blade structure of the agitator is reasonable, and the agitation speed design meets the requirements

In addition to sufficient stirring power and stirring range in the mixer, the shape and mechanical design of the mixer blades have a great influence on the slurry preparation.

First of all, it must be ensured that the stirring range of the agitator is large enough, and there is no dead angle in the stirring container. Two-shaft or even three-shaft planetary agitators are currently used in larger mixers to ensure that no fines or lumps of active material are mixed uniformly into the slurry.

Secondly, the shape design of the agitator has an absolute influence on the dispersion, mixing, particle size distribution, fluidity, etc. of the material. At present, the common shapes on the market include paddle type, butterfly type, anchor type, twist type, claw type, frame type, etc. Among the equipment, it is best to be equipped with high-speed dispersion equipment, because some materials require high-speed shear force to disperse them , so it is necessary.

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 design of the main stirring shaft and blades, some equipment has designs such as scraper design and container rotation to improve the efficiency of stirring and the degree of mixing of materials.

5. Mixer safety

The safety design of the mixer must be reasonable, including equipment explosion-proof design, equipment safety emergency stop design and equipment stability, etc., so as not to cause harm to the operator.