How Can Laser Welding Boost Lithium Battery Production?

CIOE Laser Technology & Intelligent Manufacturing Expo focuses on innovative applications of lasers in downstream areas, concentrating on popular products such as laser materials and components, lasers, laser components and auxiliary systems, laser equipment, mechanical system and numerical control system, 3D printing/additive manufacturing, 3C electronic intelligent equipment, robot, and industrial automation.

In this article, CIOE will start with laser welding to give you a comprehensive understanding of laser applications in the manufacture of lithium batteries.

Laser Welding: High technology for process, new battery technologies such as large cylinders increase the amount of welding

Principle: Ensuring battery safety, and welding quality depends on laser energy control and process parameters

Laser welding has many advantages, such as depth of fusion, high speed, and small deformation, which can significantly improve the safety of power batteries. According to the prospectus of UW Laser Welding, as a modern welding technology, laser welding has the pros of low requirements for the welding environment, high power density, not being affected by a magnetic field, not being limited to conductive materials, does not require vacuum working conditions, and does not produce X-rays during the welding process, etc. It is widely used in high-end precision manufacturing, especially in the new energy vehicle and power battery industries. Power battery welding parts, difficult, high precision requirements, power battery manufacturers on the battery production equipment automation, safety, precision, and processing efficiency requirements are high. The unique benefits of laser welding technology can significantly improve battery safety, reliability, and consistency, reduce costs, and extend service life, making it the optimal choice for power cell manufacturers. More importantly, in the power battery industry, laser welding has non-standard customization, strong customer stickiness, and other characteristics, so the barriers have higher requirements.

The main elements that determine the quality of laser welding are laser energy control and the welding process technique.


(1) Laser Energy Control

According to the prospectus of UW Laser Welding, as the material to be welded has different absorption rates for different wavelengths of laser (which can range from 5% to 50%), the welding effect is completely different with different laser choices. To output a uniform and stable welding laser beam to the welded, consistency of the laser output power is necessary, or the laser output power can be precisely controlled. Too low a power can lead to insufficient welding fusion and affect the quality of the weld, and too high a power or up and down fluctuations can lead to undesirable effects such as spatter and porosity. Therefore, laser energy control has become one of the most critical technologies for laser welding.


(2) Welding Process Technology

According to the laser prospectus, the process of laser and material action is more complex, the laser welding effect with the laser wavelength, power density size, welding time, welding head angle, focal distance, the weldments on the laser absorption rate and cleanliness, the thickness of the weldments and thermal conductivity, shielding gas type and flow, and dozens of other factors. Therefore, laser welding process technology is also one of the key factors affecting the quality of welding, which requires laser welding process technicians to continuously explore and summarize longtime experimental accumulation to obtain good welding results.

According to UW Laser Welding's prospectus, laser welding can be classified into five categories: heat conduction welding, deep fusion welding, composite welding, laser brazing, and laser conduction welding, based on different operating principles and adapted to different processing scenarios. According to different customers and different processing application scenarios, appropriate welding methods are selected to achieve the best welding results.


Application status: The value of cell manufacturing and PACK welding is about 10-30 million RMB/GWh.

In the production of power batteries, laser welding is used in the cell assembly process and battery PACK process. According to information from the UW Laser, the main laser welding processes used in the production of power batteries include:

(1) Cell Assembly Section - Middle Section

Laser welding technology is applied to the welding of the shell, top cover, sealing nail, tab, and other parts in the cell assembly section, including winding, stacking, tab welding, cell insertion into the shell, top cover welding, injection, and sealing of the injection port. The cell is the smallest unit of a power battery, and the quality of the cell determines the performance of the battery module, which in turn affects the reliability of the entire power battery system. Laser welding technology is applied to the welding of the shell, top cover, sealing nail, tab, and other parts, as well as the welding of the explosion-proof valve before the cell.


Compared with traditional argon arc welding and resistance welding, laser welding has significant advantages: Firstly, the heat-affected zone is narrow, and the welding deformation is small, making it particularly suitable for the welding of micro-components. Secondly, it can be welded at a long distance through optical fiber guidance or prism deflection. Thirdly, it has extremely high energy density. Fourth, it does not require vacuum protection and X-ray protection and is not affected by magnetic fields.


(2) Post-processing Section - Rear Section

Laser automation systems replace traditional manual assembly methods and are applied to module PACKs. The specific processes in the post-processing section include formation capacity, testing and grading, and PACK module, and the main equipment includes formation machines, capacity detection devices, process storage and logistics automation, and PACK automation equipment. Among them, laser automation systems are widely used in module PACK assembly lines for welding connection pieces during battery PACK module production.

In addition, lasers can also be used for welding explosion-proof valves on module covers. The explosion-proof valve is a thin-walled valve body on the battery sealing plate. When the internal pressure of the battery is too high, the explosion-proof valve ruptures and releases gas to relieve the pressure, avoiding battery explosion. The explosion-proof valve is usually made up of two aluminum metal sheets welded by laser into a certain shape, with grooves designed on them. When the battery pressure is too high, it ruptures and vents. Due to the small clearance between the explosion-proof valve and the cover plate, it is difficult to accurately position it, so the requirements for laser welding technology are extremely strict, requiring the welding be sealed, strictly controlling the heat input, and ensuring that the destruction pressure value of the welding seam is stable within a certain range, or it will affect the safety of the battery. The explosion-proof valve usually uses splicing welding, and composite welding lasers have advantages.

The value of laser welding is about 10-30 million RMB/GWh. According to the UW Laser's prospectus, laser welding equipment accounts for about 5-15% of the investment of power battery manufacturers. According to information on the website of GGII, the investment in equipment for a single GWh of power battery is about 200 million RMB. Combining the above data, we can calculate that the unit investment of power battery laser welding equipment is 10-30 million RMB/GWh.


Incremental market: new technologies such as large cylindrical shapes are Increasing laser welding volume. It is predicted that the penetration rate of laser welding will increase.

(1) The 4680 battery requires higher demands on the laser welding process, and the uncontrolled shape of the tab is a process difficulty. According to information on the website of the HUAON Industry Research Institute, the 4680 battery uses a full tab process, breaking the traditional mode of one positive and one negative tab. The processing difficulty lies in the uncontrolled shape of the tab, which is prone to short circuits. During production, the two ends are sealed, hindering the penetration of the electrolyte. Moreover, it is difficult to fold multiple tabs neatly, requiring higher demands on the laser welding process.

(2) Compared with square batteries and small cylindrical batteries, the laser welding process and required equipment for 4680 large cylindrical batteries have increased. According to information on the website of the HUAON Industry Research Institute.

Compared with square batteries, the full tab of the large cylindrical battery requires a surface welding process, increasing the laser welding process from 5 steps to 7 steps.

• Compared with small cylindrical batteries, a single GWh production line for 4680 batteries requires an additional 5 pieces of welding equipment compared to 18650 and 21700 batteries. Considering the above situation, we believe that the demand for laser welding of 4680 large cylindrical batteries is expected to increase compared to square batteries and small cylindrical batteries.

Other welding link technology: to solve the problem of dissimilar metal welding, such as battery PACK in the busbar welding is expected to be replaced by laser welding, we judge that, as the laser welding process continues to move upward, laser welding penetration is expected to move upward.

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