The key points analysis of the die-cutting process for lithium battery packs mainly focuses on aspects such as process types, equipment requirements, operation norms, quality inspection, and safety and environmental protection. The following are the specific contents:

Selection of process type

Die-cutting processes mainly include two types: metal die-cutting and laser die-cutting. The metal die cutting is divided into the front and rear knives, which simultaneously punch and cut the foil materials on both sides of the electrode sheet. The structure of the front and rear knives is the same, each with two knives. The movement of the electrode sheet is pulled by the main drive roller of the equipment. When the main drive stops, the die is pressed down to punch and cut. Knife 1 and knife 2 cut simultaneously. The uncut area in the middle is the electrode TAB. The length of the blank cutting area determines the distance between the electrode tabs. Laser die-cutting uses a laser beam to perform non-contact cutting on the electrode sheet. It has the advantages of high precision, no burrs, and no stress. However, the equipment cost is relatively high, and it generates a large amount of cutting dust. Its dust removal structure is much more complex than that of metal die-cutting.

Equipment requirements and inspection

Comprehensive inspection: Before using the die-cutting machine, a comprehensive inspection of the equipment should be carried out. This includes checking whether all the components of the machine are firmly connected, such as whether the belts and chains of the transmission components are loose, because loose transmission components can lead to a decrease in die-cutting accuracy and may even cause machine failure.

Tool inspection: Check the installation of the tools to ensure they are installed correctly and are sharp. The sharpness of the cutting tool directly affects the quality of the cut on the electrode sheet. Blunt cutting tools may cause problems such as edge tearing and burrs on the electrode sheet.

Electrical system inspection: Check whether the electrical system is normal, such as whether the wiring of the motor is correct, and whether each control button and sensor can work properly. Electrical system failures may cause the machine to fail to start, stop or operate abnormally.

Material inspection and parameter setting

Material specification inspection: For lithium battery electrode sheet materials, it is necessary to check whether their specifications meet the requirements, including dimensional parameters such as the thickness, width and length of the electrode sheets. For instance, if the thickness of the electrode sheet exceeds the specified range, it may lead to inappropriate die-cutting pressure, affecting the die-cutting quality.

Material uniformity inspection: Check the material uniformity of the electrode sheet to ensure that there are no obvious wrinkles, holes or other defects on the material surface. The unevenness or defects of the electrode sheet material may cause inconsistent performance of the electrode sheet after die-cutting, affecting the overall quality of the battery.

Die-cutting speed setting: Set the die-cutting speed reasonably. A speed that is too fast may cause the machine to vibrate, thereby reducing the die-cutting accuracy. For instance, during high-speed die-cutting, the tool may fail to cut the electrode sheet precisely along the set path due to vibration, resulting in dimensional deviations. At the same time, an overly rapid speed may also cause the edges of the electrode sheets to heat up, affecting their performance. Especially for some temperature-sensitive lithium battery materials, overheating may alter their chemical properties. However, the die-cutting speed should not be too slow either, otherwise it will affect the production efficiency.

Die-cutting pressure setting: Accurately adjust the die-cutting pressure according to the material and thickness of the electrode sheet. Excessive pressure may cause the electrode sheet to be overly compressed, resulting in deformation, indentation and other problems. For example, for thinner electrode sheets, excessive pressure may directly crush the electrode sheets. If the pressure is too low, the electrode sheet may not be completely cut off, resulting in a continuous cutting phenomenon. Continuous cutting will make the electrode sheet unusable and require manual secondary processing, reducing production efficiency and product quality.

Precision control

Positioning system calibration: To ensure the accuracy of die-cutting, it is necessary to precisely calibrate the positioning system of the machine. For instance, by adjusting the position and parameters of the sensor, the machine can accurately identify the position of the electrode sheet and deliver it to the correct die-cutting position.

Precision component maintenance: Regularly inspect and maintain the precision components of the die-cutting machine, such as lead screws and guide rails. The wear of these components will affect the positioning accuracy of the die-cutting machine, resulting in deviations in the size of the electrode sheets. Electrode plates with excessive deviation may not match well with other components of the battery, affecting the assembly and performance of the battery.

Operational safety and protection

Protective equipment wearing: Operators must wear the corresponding protective equipment, such as protective gloves, goggles, etc.

Dust treatment: During the die-cutting process of lithium battery electrode sheets, a certain amount of dust and waste will be produced. It is necessary to install effective dust collection devices to collect the dust in time and avoid safety accidents such as explosions caused by dust accumulation. For waste materials, there should be a dedicated collection and treatment system. Waste materials may contain harmful substances and need to be properly handled in accordance with environmental protection requirements to prevent pollution to the environment.

Handling of abnormal situations

Abnormal situations such as electrode plate misalignment may occur during the die-cutting process. The misalignment of electrode sheets is one of the more common abnormal phenomena in the lamination process. From a safety perspective, the misalignment of electrode posts can easily cause a short circuit and fire between the positive and negative electrodes, which undoubtedly poses a huge safety hazard and may lead to danger during battery use, endangering the lives and property of users.