The cutting process requirements for lithium battery packs are analyzed as follows:

Requirements for cutting accuracy

Position accuracy control: During the cutting process, the cutting position accuracy of the electrode sheet is required to be extremely high. For instance, in actual production, the cutting position accuracy of the electrode sheet is generally controlled within ±0.15mm (excluding incoming material errors). To achieve this precision, the cutting mechanism needs to be equipped with high-precision tools and an accurate positioning system. The cutting edge of the tool should be sharp and wear-resistant to ensure that the edge of the electrode sheet is neat and free of burrs during cutting. The positioning system should be capable of accurately determining the position of the electrode sheet to ensure that the deviation of each cutting position is within the allowable range. For instance, advanced visual positioning technology can be adopted to take photos and identify the electrode sheets before cutting. Based on the image analysis results, the tool position can be precisely adjusted to achieve high-precision cutting.

Dimensional consistency requirements: The cutting process must ensure that the electrode sheets have consistent dimensions, which is crucial for battery assembly. High-precision slitting can ensure a tight fit during battery assembly, avoiding a decline in battery performance due to size mismatch. For instance, during the battery assembly process, if the electrode sheet sizes are inconsistent, it may lead to instability in the internal structure of the battery, affecting its performance indicators such as capacity and cycle life.

Cutting quality requirements

Edge quality: The quality of the cutting edge of the electrode sheet has a significant impact on the performance and quality of the battery. Specifically, burrs and impurities should be avoided as they can cause short circuits within the battery, leading to self-discharge and even thermal runaway. It is necessary to ensure dimensional accuracy; otherwise, it cannot be guaranteed that the negative electrode completely wraps the positive electrode, or that the separator completely isolates the positive and negative electrode sheets, thereby causing battery safety issues. It is necessary to prevent situations such as thermal damage to the material and coating peeling, otherwise it will cause the material to lose its activity and fail to function. To reduce the unevenness of the cut edge, otherwise it will cause unevenness during the charging and discharging process of the electrode sheet.

Cross-sectional quality: In the die-cutting process, taking the blanking of metal molds as an example, the cross-sectional area of metal material blanking parts is divided into four parts: collapsed corners, shear zones, fracture zones and burrs. The wider the shear zone of the cross-section is, the smaller the height of the corner collapse and burrs will be, and the higher the quality of the cross-section of the blanking part will be. To improve the quality of the cross-section, it is necessary to reasonably control the punching clearance. In the punching process, there is a corresponding calculation formula for the punching clearance between the upper punch and the lower die. Meanwhile, considering the wear of the die, the effective punching clearance is also defined. As the die wears out, the blanking gap increases, the fillet of the die cutting edge enlarges, and the cross-sectional quality of the blanking part will also change. Therefore, it is necessary to maintain and service the die regularly.

Process stability requirements

Equipment stability: Regular calibration and maintenance of cutting equipment are the foundation for ensuring cutting quality. The stability of the equipment is directly related to the consistency of the products. For instance, in the laser cutting process, laser energy and the cutting movement speed are two key process parameters that have a significant impact on the cutting quality. If the equipment is unstable, it may cause fluctuations in laser power or cutting speed, thereby affecting the cutting quality of the electrode sheet.

Process parameter optimization: For different cutting processes, it is necessary to optimize the corresponding process parameters. Take laser cutting as an example. Due to the structure of lithium-ion battery electrode sheets, which consists of a double-sided coating and an intermediate current collector metal layer, and the significant differences in properties between the coating and the metal foil, their responses to laser action are also different. When the laser acts on the negative electrode graphite layer or the positive electrode active material layer, the coating requires relatively low laser energy for melting and vaporization. However, the metal current collector has a reflective effect on the laser and conducts heat quickly, thus increasing the laser energy for melting and vaporization of the metal layer. When the process parameters are not appropriate, problems such as the peeling off of the edge coating, the exposure of the metal foil, and the appearance of a large amount of foreign objects around the edge may occur. All these can lead to a decline in battery performance and safety quality issues. Therefore, it is necessary to optimize the appropriate process parameters based on the characteristics of the living material and the metal foil, so as to completely cut the electrode sheet and form a good edge quality without leaving any residual metal chips or impurities.

Safety and protection requirements

Operational safety: Adhere to safety operation procedures, take necessary safety measures, and protect the safety of operators and equipment. For instance, during the operation of the cutting equipment, operators should wear protective glasses, gloves and other protective gear to prevent personal injury caused by the splashing of electrode sheet fragments and the like.

Equipment protection: The cutting equipment should be equipped with corresponding protective devices to prevent unexpected accidents. For instance, the equipment should be equipped with safety doors, emergency stop buttons and other devices. When abnormal situations occur, operators can promptly halt the operation of the equipment to prevent the accident from escalating.