Small Knowledge of Lithium Battery Mixing Process

I. What is mixing

Definition of mixing

Generally speaking, the production process of lithium batteries is generally divided into three stages: front, middle and back.

Front stage: pole piece production includes mixing, coating, pressing, baking, striping, sheeting, and pole ear forming processes.

Middle stage: battery cell assembly includes winding or lamination, battery cell pre-packaging into shells, electrolyte injection, and sealing.

Back stage: Back stage processing includes battery cell capacity division, standing, testing, and sorting.

And mixing, as the first process of lithium battery production, plays a vital role. mixing refers to the process of mixing active material powder, binder, conductive agent, etc. and solvent in a certain order and conditions to make a stable suspension.

Overview of lithium battery mixing

Pulping is the first process and core link in lithium battery production, and is also a necessary condition for the high-quality completion of subsequent coating, rolling and other processes. The process flow is to mix, dissolve and disperse various powders such as battery active materials, conductive agents and polymer binders in a solvent to form a uniform and stable suspension system. The prepared finished slurry is used in the electrode coating process. The quality of the slurry (uniformity, stability, consistency, etc.) plays a decisive role in the internal resistance, capacity, cycle life, rate, consistency, safety and yield of lithium battery products.

2. The importance of lithium battery mixing process

It has an important impact on the internal resistance, capacity, cycle life and rate performance of the battery.

The electrodes of lithium batteries need to have good mechanical properties, good electron transmission and ion transmission capabilities to achieve optimal performance. When the slurry is not mixed and dispersed sufficiently, the active material and conductive agent particles agglomerate, the binder is unevenly distributed, and a stable connection cannot be achieved. There is no good ion channel and electron channel, which will lead to a large internal resistance of the battery and the inability to fully utilize the battery capacity. Especially under high current, the battery capacity decays seriously, the heat generation is serious, and the cycle life becomes worse.

It has an important impact on the consistency and safety of the battery.

During the pulping process, it is necessary to ensure that the active material, the conductive agent and the binder are fully mixed and dispersed evenly, otherwise the performance of the single cells such as the internal resistance, capacity and cycle life of the same batch of batteries will be quite different. At the same time, the pulping process needs to avoid metal particles, debris, dust and the like from being mixed into the slurry as much as possible. If the debris is mixed, it may cause a micro short circuit inside the battery, and in severe cases, the battery will catch fire and explode. These put forward high requirements on the material selection and process control capabilities of the pulping equipment.

It has an important impact on the subsequent battery pole processing procedures such as coating and rolling.

For example, the fineness and viscosity of the slurry determine whether the slurry is suitable for coating. If the fineness is not up to standard, scratches will be generated during the coating process. If the viscosity is not appropriate, the slurry cannot be evenly coated on the current collector. The solid content of the slurry will affect the drying efficiency of the coating and the quality of the pole piece. The stability of the slurry will affect the stable storage time of the slurry. The uniformity of the slurry determines whether the pole piece pressed out by the coating roller is uniform. In the case that there is no difference in raw materials, the quality of the slurry is determined by the pulping process and pulping equipment.

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