Application of laser welding machine in new energy lithium battery field
Lithium ion batteries are widely used in various electronic devices due to their advantages of high specific energy, long cycle life, small self-discharge, no memory effect and no pollution (
Such as mobile phones, notebook computers, PDA, digital cameras and digital cameras, etc)And transportation (Patrol cars, electric bicycles, electric vehicles, etc)
In fact, it has become a high-tech industry supported by China's energy sector.
Power Battery refers to the battery applied to electric vehicles, which is relative to small-capacity batteries (Such as mobile phones, notebook computer batteries, etc)
In other words, it has a large capacity and output power, and can be used for secondary batteries in the application fields of electric vehicle driving power supply and large mobile power supply.
There are many manufacturing processes for lithium ion batteries or battery packs, among which there are many processes, such as explosion-proof valve sealing welding, pole ear welding, soft connection welding, safety helmet spot welding, Battery shell sealing welding, module and PACK welding all take laser welding machine as the best process.
The materials used for welding of power batteries mainly include pure copper, aluminum, aluminum alloy, stainless steel, etc.
1. Battery explosion-proof valve welding the explosion-proof valve of the battery is the 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 breaks to prevent the battery from bursting.
The safety valve has a clever structure, and this process requires extremely strict laser welding process.
Before continuous laser welding is not adopted, the welding of battery explosion-proof valve adopts pulse laser welding, which realizes continuous sealing welding through overlapping and covering of welding spots and welding spots, but the welding efficiency is low, and the sealing is relatively poor.
Continuous laser welding can realize high-speed and high-quality welding, and welding stability, welding efficiency and yield can be guaranteed.
2, battery ear welding ear is usually divided into three kinds of materials, the positive electrode of the battery using aluminum (Al)Material, negative electrode uses nickel (Ni)Material or copper nickel plating (Ni-Cu)Material.
In the manufacturing process of power battery, one of the links is to weld the battery lug and pole together.
In the manufacture of the secondary battery, it needs to be welded with another aluminum safety valve.
Welding should not only ensure the reliable connection between the pole lug and the pole column, but also require smooth and beautiful welds.
3. Spot welding of battery pole strip the materials used for battery Pole Strip include pure aluminum strip, nickel strip, aluminum-nickel composite strip and a small amount of copper strip.
Pulse Welding machine is generally used for welding battery strip. With the appearance of QCW quasi-continuous laser of IPG company, it has also been widely used in battery strip welding, at the same time, due to its good beam quality and small welding spot, it can cope with high reflectivity aluminum strip, copper strip and narrow band battery pole strip (The width of the pole band is 1. Below 5mm)The welding of has unique advantages.
4. Welding of power battery shell and cover plate seal the shell materials of power battery include aluminum alloy and stainless steel, among which aluminum alloy is the most, generally 3003 aluminum alloy, and a few use pure aluminum.
Stainless steel is the best material for laser weldability, especially 304 stainless steel. Both pulsed and continuous laser can obtain welds with good appearance and performance.
The laser welding performance of aluminum and aluminum alloy is slightly different according to the different welding methods.
In addition to pure aluminum and 3 Series aluminum alloy using pulse welding and continuous welding are no problem, other series of aluminum alloy optimal selection of continuous laser welding to reduce crack sensitivity.
At the same time, the laser with appropriate power is selected according to the thickness of the power battery shell. Generally, when the thickness of the shell is less than 1mm, the single mode laser within 1000W can be considered, thickness in 1mm or more than 'with 1000W more than single-mode or multi-mode laser. Small-capacity lithium batteries often use relatively thin aluminum shells (The thickness is 0. About 25mm), There are also steel shells such as 18650.
Due to the thickness of the shell, the welding of such batteries generally adopts a lower power laser.
Using Continuous laser to weld thin-shell lithium batteries, the efficiency can be improved by 5 ~ 10 times, and the appearance effect and sealing is better.
Therefore, there is a trend to gradually replace pulsed lasers in this application field.
5. The series-parallel connection between the power battery module and the pack welding power battery is generally completed through the welding of the connecting piece and the single battery. The positive and negative electrodes are made of different materials, generally copper and aluminum, due to the brittle compound formed after laser welding between copper and aluminum, it cannot meet the use requirements. In addition to ultrasonic welding, copper and copper, aluminum and aluminum are generally welded by laser.
At the same time, because the heat transfer of copper and aluminum is very fast, and the laser reflectivity is very high, the thickness of the connecting piece is relatively large, so it is necessary to use a higher power laser to realize welding.