Introduction and Characteristics to Lithium Battery Electrode Slitting

During the cutting process of lithium-ion battery, the quality of the cutting edge of the electrode plate has an important impact on the performance and quality of the battery, including:

(1) burr and impurities will cause short circuit in the battery, causing self-discharge and even thermal runaway;

(2) The dimension accuracy is poor, which can not guarantee that the negative pole completely wraps the positive pole, or the diaphragm completely isolates the positive and negative pole pieces, causing the battery safety problem;

(3) Material thermal damage, coating peeling, etc., resulting in material deactivation and inability to use;

(4) The unevenness of the trimming leads to the non-uniformity of the electrode charge and discharge process. Therefore, the cutting process of lithium-ion battery electrode should prevent these problems and improve the process quality.

1. Disc shearing

The disc slitting is mainly composed of upper and lower disc cutters, which are installed on the cutter shaft of the slitter. The rolling shear principle is used to cut the positive and negative pole plates with a thickness of 0.01~0.1mm.

2. Die punching/slitting

The die-cutting process of lithium ion battery electrode is divided into two types:

(1) Die-cutting of wood plate, the sharp blade is installed on the wood plate, and the blade is used to cut the electrode under certain pressure. This process mold is simple and low cost, but the punching quality is not easy to control, and it is now being phased out.

(2) The metal die is used for punching, and the pole piece is cut by using the very small gap between the punch and the lower die. There’s also battery slitting machine can slit electrode piece into certain width strips. The coating particles are connected together by adhesive. During the punching process, the coating particles are peeled off under stress, and the metal foil undergoes plastic strain. After reaching the breaking strength, cracks appear, and the cracks grow and separate. The section of metal material punching parts is divided into four parts: angle collapse, shear zone, fracture zone and burr. The wider the shear band of the section, the smaller the height of the collapse angle and burr, and the higher the section quality of the punched part.

3. Laser cutting of lithium ion battery electrode

There is a problem of tool wear in disc cutting and die cutting, which is easy to cause process instability, resulting in poor cutting quality of electrode pieces, and the battery performance degradation. Laser cutting has the characteristics of high production efficiency and good process stability, and has been applied to the cutting of lithium-ion battery electrode plates in industry. Its basic principle is to use a high power density laser beam to irradiate the cut battery electrode plates, so that the electrode plates are quickly heated to a high temperature, and rapidly melt, vaporize, ablate or reach the ignition point to form holes. As the beam moves on the electrode plates, the holes continue to form narrow slits, Complete the cutting of the electrode plate.

Among them, laser energy and cutting speed are two important process parameters, which have a great impact on cutting quality. When the laser power is too low or the moving speed is too fast, the electrode cannot be cut completely. When the laser power is too high or the moving speed is too low, the area of the laser for material use becomes larger and the size of the slit becomes larger.

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