SHINHOP laser

Lithium-ion batteries are widely used in various electronic devices (such as mobile phones, laptops, PDAs, digital cameras, and camcorders) as well as transportation tools (patrol cars, electric bicycles, electric vehicles, etc.) due to their advantages of high energy density, long cycle life, low self-discharge, no memory effect, and no pollution, making them a key high-tech industry supported in the energy sector of our country.
Power batteries refer to batteries used in electric vehicles, which have larger capacity and output power compared to small capacity batteries (such as those in mobile phones and laptops). They can be used as power sources for electric vehicles and large mobile power applications. The manufacturing process of lithium-ion batteries or battery packs involves many steps, among which several processes, such as explosion-proof valve sealing welding, tab welding, soft connection welding, safety cap spot welding, battery shell sealing welding, module and PACK welding, are best performed using laser welding. The materials used for welding power batteries mainly include pure copper, aluminum, aluminum alloys, and stainless steel.
1. Battery explosion-proof valve welding
The explosion-proof valve of the battery is a thin-walled valve body on the battery sealing plate. When the internal pressure of the battery exceeds the specified value, the explosion-proof valve body ruptures to prevent the battery from exploding. The structure of the safety valve is ingenious, and this process has very strict requirements for laser welding technology. Before the use of continuous laser welding, the welding of the battery explosion-proof valve was done using pulsed lasers, achieving continuous sealed welding through the overlap and coverage of welding points, but the welding efficiency was relatively low, and the sealing was relatively poor. Continuous laser welding can achieve high-speed, high-quality welding, ensuring stability, efficiency, and yield.
2. Battery tab welding
Tabs are usually made of three types of materials: aluminum (Al) for the positive electrode and nickel (Ni) or nickel-plated copper (Ni-Cu) for the negative electrode. One step in the manufacturing process of power batteries is to weld the battery tabs to the pole. In the production of secondary batteries, it is necessary to weld them to another aluminum safety valve. The welding must ensure a reliable connection between the tabs and the poles, and the welds must be smooth and aesthetically pleasing.
3. Battery strip spot welding
The materials used for battery strips include pure aluminum strips, nickel strips, aluminum-nickel composite strips, and a small amount of copper strips. The welding of battery strips generally uses a pulsed welding machine. With the emergence of IPG's QCW quasi-continuous laser, it has been widely applied in the welding of battery strips. Due to its good beam quality and the ability to achieve very small weld spots, it has unique advantages in welding high-reflectivity aluminum strips, copper strips, and narrow battery strips (with a width of less than 1.5mm).
4. Power battery shell and cover sealing welding
The shell materials of power batteries include aluminum alloys and stainless steel, with aluminum alloys being the most commonly used, generally 3003 aluminum alloy, and a few using pure aluminum. Stainless steel has the best laser welding properties, especially 304 stainless steel, which can achieve good appearance and performance welds with both pulsed and continuous lasers.
The laser welding performance of aluminum and aluminum alloys varies slightly depending on the welding method used. Except for pure aluminum and 3 series aluminum alloys, which can be welded using both pulsed and continuous welding without issues, other series of aluminum alloys are best welded using continuous laser welding to reduce crack sensitivity. Additionally, the appropriate power of the laser should be selected based on the thickness of the power battery shell. Generally, for shell thicknesses below 1mm, a single-mode laser within 1000W can be considered, while for thicknesses above 1mm, a single-mode or multi-mode laser above 1000W is required.
Small capacity lithium batteries often use relatively thin aluminum shells (about 0.25mm thick), and some like 18650 use steel shells. Due to the thickness of the shell, welding of these batteries generally uses lower power lasers. Using continuous lasers to weld thin-shelled lithium batteries can increase efficiency by 5 to 10 times, and the appearance and sealing are better. Therefore, there is a trend to gradually replace pulsed lasers in this application area.
5. Power battery module and pack welding
The series and parallel connections between power batteries are generally completed by welding connecting pieces to individual batteries. The positive and negative electrode materials are different, generally copper and aluminum. Due to the formation of brittle compounds after laser welding between copper and aluminum, which cannot meet usage requirements, ultrasonic welding is usually used. Copper to copper and aluminum to aluminum are generally welded using laser welding. Additionally, since both copper and aluminum have high thermal conductivity and high reflectivity to lasers, and the thickness of the connecting pieces is relatively large, higher power lasers are required for welding.
Characteristics of laser welding lithium batteries:
From the manufacturing of lithium battery cells to the assembly of battery PACKs, welding is a very important manufacturing process. The conductivity, strength, airtightness, metal fatigue, and corrosion resistance of lithium batteries are typical quality evaluation standards for battery welding. The choice of welding methods and processes will directly affect the cost, quality, safety, and consistency of the batteries. Laser welding, with its advantages of safety, reliability, precision, and environmental friendliness, has become the preferred solution for many welding tasks.
Analysis of the development status of the lithium battery industry
1. Development status of the lithium battery industry
After more than ten years of development, China's lithium battery industry has established a complete industrial chain that includes lithium ore mining, material supply, cell and PACK, and battery recycling. Driven by downstream market demand, the lithium battery industry has maintained rapid growth in production scale, increasing from 17.2 GWh in 2012 to 88.7 GWh in 2017, a fourfold increase in five years.
Electric transportation tools (mainly new energy vehicles), 3C digital, and energy storage industries are the three major driving forces for the development of the lithium battery industry. In 2016, the demand for new energy vehicles exceeded 30.8 GWh, surpassing 3C digital, becoming the largest consumer market for lithium batteries. By 2017, the production of power batteries increased to 44.5 GWh. The development potential of energy storage batteries is huge, but due to technical and policy reasons, it is still in the market introduction stage, lagging behind power batteries. In the future, as technology matures, the energy storage market will also become another driving force for lithium battery consumption.
2. Development status of new energy vehicles and power battery industries
With the global energy crisis and environmental pollution issues becoming increasingly prominent, the energy-saving and environmentally friendly development of industries has been highly valued, leading to explosive growth in new energy vehicles. Production increased from 12,600 units in 2012 to 794,000 units in 2017, with a compound annual growth rate of 99.4%. In 2017, production and sales were 794,000 and 777,000 units respectively, representing year-on-year growth of 53.6% and 53.3%, with the growth rates of production and sales increasing by 2.1 and 0.3 percentage points respectively. The market share of new energy vehicles in 2017 was 2.7%, an increase of 0.9 percentage points from the previous year. China has surpassed the United States to become the world's largest market for new energy vehicles, maintaining the highest production and sales for three consecutive years.
As the core component of new energy vehicles, power batteries have developed in line with the overall market trend of new energy vehicles, and the power battery market has also shown an explosive growth trend, with a significant increase in production driven by a large influx of capital.
Laser welding application market analysis -- lithium battery
In 2017, the production of power batteries for automobiles in China reached 44.5 GWh, a year-on-year increase of 45%. OFweek predicts that in the next four years, the demand for power batteries will maintain a compound annual growth rate of over 40%, and by 2020, the demand for power batteries for new energy vehicles in China will exceed 120 GWh.