The production and manufacture of lithium-ion batteries is a process closely linked by process steps. On the whole, the production of lithium batteries includes pole piece manufacturing process, battery assembly process and the final injection, pre-charging, formation and aging process. In these three stages of the process, each process can be divided into several key processes, and each step will have a great impact on the final performance of the battery.

In the pole piece manufacturing process stage, can be subdivided into slurry preparation, slurry coating, pole piece rolling, pole piece cutting, pole piece drying five processes. In the battery assembly process, according to the different battery specifications and models, it is roughly divided into winding, into the shell, welding and other processes. In the final liquid injection stage, it includes liquid injection, exhaust, sealing, pre-filling, formation, aging and other processes. Every process in the battery manufacturing process will cause a certain amount of waste. The reasons for the waste are employee errors, equipment errors, environmental reasons, etc. In order to ensure that the cost rate of the product is good enough, try to ensure that every step of the product is qualified.

The preparation of electrode slurry is the most critical part of the whole process, and the quality of electrode slurry directly affects whether the next step can be carried out. Slurry preparation is a non-Newtonian high viscosity fluid formed by mixing active substances, adhesives, solvents, thickeners and other powders evenly. The fluid needs to have a certain viscosity, good fluidity and a sufficiently small particle size. There is a little difference between factory operation and laboratory battery trial:

• Laboratory battery testing requires aSimple process, simple operation, time-saving and labor-saving, high degree of mechanizationand other characteristics;

• In actual production, the lithium battery slurry preparation system mainlyByMaterial conveying, slurry preparation, slurry conveyingSuch as process composition.
   
  

1. material conveying process
 

The material transportation of positive and negative electrode slurry is similar. The difference is that the characteristics of raw materials need to be considered. The following figure is a schematic diagram of the positive electrode material transportation process.

Lithium-ion battery automatic batching systemis designedFully automatic batching and feeding of slurry raw materialsDesign of intelligent production system; the system consists:

1. Metering system;

2. Powder feeding and conveying system;

3. Computer central control system;

4. Stored materials;

5. Transit buffer tank system.

The whole system implements automatic transportation and measurement, and requires high-precision weighing modules and instruments;

• Ensure dosing efficiency and accuracy;

• Can more effectively isolate the air, prevent material deterioration, improve the production workshop environment.

The first is the preparation of living substances, which is carried out by the ton bag feeding station, and then the feeding can be carried out according to the required proportion through vacuum feeding or load feeding and weighing system. After the preliminary powder feeding is completed, the dry powder is premixed in a premixing tank. Lithium battery positive and negative active material and conductive agent, adhesive powder particle size, bulk density, porosity, etc. are different, the purpose of dry powder premixing is to fully mix the components. In this process, it is mainly stirred at medium and low speed. With the stirring, the particles collide together more evenly, and the bulk density of the powder increases gradually and eventually tends to be consistent.

2. slurry stirring system

3. slurry conveying process

The equipment and devices designed for the slurry conveying process include conveying pumps (screw pumps, gear pumps, diaphragm pumps and other types), filtering devices, dispersing devices, storage tanks, etc.       

Taking into account the stability of the slurry output will have an important impact on the current collector coating, so the choice of the transfer pump to choose a stable power of the transport equipment. Since a small amount of large particles may exist after the stirring is completed, in order to prevent the large particles from negatively affecting the coating head and the coating effect, the slurry needs to be filtered with large particles. The size of the filter screen needs to be selected according to the coating equipment and the nature of the slurry. Too small screen affects the work efficiency, and too large screen can not play an effective filtering role.

After filtration, the slurry enters the slurry storage tank and needs to go through a homogenization process. After the slurry is stirred, there may be some agglomeration of particles and instability of the slurry through the pipeline, which is not conducive to the coating of the slurry. The homogenizer is mainly composed of a high-pressure homogenizing chamber and a booster. The inside of the high-pressure homogenizing chamber has a specially designed geometric shape. Under the action of the pressurizing mechanism, the homogenizing machine and the high-pressure solution quickly pass through the homogenizing chamber. The materials will be subjected to mechanical forces such as high-speed shearing, high-frequency oscillation, cavitation and convection impact and corresponding thermal effects at the same time. The mechanical forces and chemical effects caused by this can induce changes in the physical, chemical and structural properties of macromolecules, finally achieve the effect of homogenization. After the process of homogenizer dispersion, the slurry is carried out in the intermediate tank, and the electrode coating can be carried out.