Laser welding has many advantages such as deep penetration, fast speed, and small deformation, which can greatly improve the safety of power batteries. Laser welding does not have high requirements on the welding environment, has high power density, is not affected by magnetic fields, is not limited to conductive materials, does not require vacuum working conditions, and does not produce X-rays during the welding process. It is widely used in new energy vehicles and Power battery manufacturing field. Laser welding technology can greatly improve the processing efficiency and welding accuracy of power batteries, ensure safety, reliability, and consistency, reduce costs, and extend service life.
In the production of power batteries, laser welding is used in the battery cell assembly process and battery PACK process.
Battery core assembly section - middle section: The laser welding process is applied to welding links such as casings, top covers, sealing nails, and pole tabs. The battery cell assembly section specifically includes the winding, lamination, tab welding, and cell insertion. Shell, shell top cover welding, liquid injection, liquid injection port packaging, etc. The battery cell is the smallest unit of the power battery. The quality of the battery cell determines the performance of the battery module and affects the reliability of the entire power battery system. Compared with traditional argon arc welding and resistance welding methods, laser welding has significant advantages:
- ☆ The heat-affected zone is narrow and the welding deformation is small, which is especially suitable for the welding of micro parts;
- ☆ Through optical fiber guidance or prism deflection, long-distance welding can be performed ;
- ☆ Extremely high energy density;
- ☆ Does not require vacuum protection and X-ray protection, and is not affected by magnetic fields.
Post-processing Section - Back Section: The laser automation system replaces the traditional manual assembly method and is used in the module PACK post-processing section. The specific links include chemical composition, testing and binning, and PACK modules. The main equipment includes the chemical composition machine and the volume classification detection device. , process warehousing and logistics automation, PACK automation equipment. Among them, laser automation systems are commonly used in module PACK assembly lines to weld connecting pieces when packaging battery modules.
In addition, laser can also be used for welding explosion-proof valves on the cover plate behind the module. The explosion-proof valve is usually two aluminum metal sheets welded by laser into a certain shape. It is designed with grooves to rupture and release the pressure when the battery pressure is too high. Since the fit gap between the explosion-proof valve and the cover plate is small, it is difficult to place it accurately. Therefore, the requirements for the laser welding process are extremely strict.
The weld seam is required to be sealed and the heat input is strictly controlled to ensure that the damage pressure value of the weld seam is stable within a certain range. Otherwise, the safety of the battery will be greatly affected. Explosion-proof valves usually use splicing welding or composite welding. As laser welding technology continues to develop, laser welding penetration is expected to rise.
Laser cutting technology can be used in processes such as tab cutting and shaping, pole piece slitting, and separator slitting in the lithium battery manufacturing process. Compared with die cutting, laser cutting has the advantages of higher precision and lower operating costs, which helps Improve efficiency and reduce costs in battery production. Compared with traditional mechanical cutting, laser cutting has the advantages of no physical wear, flexible cutting shape, edge quality control, higher accuracy and lower operating costs. It is conducive to reducing manufacturing costs, improving production efficiency and significantly shortening the mold of new products. cut cycle.
Tab cutting and laser tab forming is currently the mainstream technology. Process parameters, control system, and cutting station design determine the cutting speed and quality. Traditionally, tab forming mainly uses mechanical die-cutting process. The mechanical die-cutting process has limitations such as fast mold loss, long mold change time, poor flexibility, and low production efficiency. It is increasingly unable to meet the development requirements of lithium battery manufacturing.
Due to the many advantages of laser cutting technology, and with the maturity of high-power, high-beam-quality nanosecond lasers and single-mode continuous fiber technology, laser tab cutting has gradually become the mainstream of tab forming technology. Laser tab forming generally adopts roll-to-roll continuous cutting. Its main process flow is: unwinding, tension control, correction control, laser cutting, secondary dust removal, and rewinding.
Pole piece cutting There are three ways to cut pole pieces: disc slitting, die cutting, and laser cutting. Both disc slitting and die cutting have tool wear problems, which can easily cause process instability and lead to poor pole piece cutting quality. , causing battery performance to decrease; laser energy and cutting movement speed are two main process parameters, which have a huge impact on cutting quality. When the laser power is too low or the moving speed is too fast, the pole piece cannot completely cut. When the power is too high or the moving speed is too low, the laser's action area on the material becomes larger and the slit size becomes larger.
Diaphragm cutting uses a laser cutting component to cut the diaphragm rolled by two diaphragm curling components alternately switched by a flip roller, realizing the function of automatically cutting the diaphragm evenly and avoiding powder removal, wire picking, broken film and continuous cutting during the cutting process. phenomenon, which is convenient for practical use in mass production lines.
Laser cleaning before pole piece coating can effectively avoid the damage caused by the original wet ethanol cleaning; before battery welding, laser cleaning uses pulsed laser to heat and vibrate the substrate to expand, so that the pollutants overcome the surface adsorption force and break away from the substrate to achieve decontamination; during the battery assembly process Laser cleaning can clean the insulation board and end plate, clean the dirt on the surface of the battery core, roughen the surface of the battery core, and improve the adhesion of glue or glue.
Before the electrode plates are coated, the positive and negative electrode plates of the lithium battery are made by coating the positive and negative electrode materials of the lithium battery on the metal thin strips. When the metal thin strips are coated with electrode materials, the metal thin strips need to be cleaned. Thin strips are generally made of aluminum or copper. The original wet ethanol cleaning can easily cause damage to other parts of the lithium battery. The laser dry cleaning machine can effectively solve the above problems.
Before battery welding, pulse laser is used to directly radiate decontamination, which causes the surface temperature to rise and cause thermal expansion. The thermal expansion causes the contaminants or the substrate to vibrate, so that the contaminants overcome the surface adsorption force and break away from the substrate surface to achieve the purpose of removing stains on the surface of the object. . This method can effectively remove dirt, dust, etc. from the end surface of the battery pole, and prepare for battery welding in advance to reduce welding defective products.
In order to prevent safety accidents in lithium batteries during the battery assembly process, it is generally necessary to apply glue to the lithium battery cells to provide insulation, prevent short circuits, protect circuits, and prevent scratches. Laser cleaning of insulating plates and end plates can clean the dirt on the surface of the battery core, roughen the surface of the battery core, and improve the adhesion of glue or glue. It will not produce harmful pollutants after cleaning. It is a green and environmentally friendly cleaning method.
In order to better control product quality and trace the entire production information of lithium batteries, including raw material information, production process and technology, product batch, manufacturer and date, etc., it is necessary to store key information in the QR code and on the battery. Make identification. Laser marking has the characteristics of strong permanence, high anti-counterfeiting, high precision, strong wear resistance, safety and reliability, etc., and can provide the best solution for product quality tracking.