New energy: also known as unconventional energy.
It refers to all forms of energy other than traditional energy.
Refers to the energy that has just started to be developed and utilized or is being actively studied and popularized, such as solar energy, geothermal energy, wind energy, ocean energy, biomass energy and nuclear fusion energy.
Since its introduction in 1990, lithium battery has been favored by 3C digital and power tool industries for its advantages of high energy density, high voltage, environmental protection, long life and fast charging, and its contribution to the new energy vehicle industry is particularly outstanding.
As the power source of new energy vehicles, the lithium battery industry has huge market potential and is an important part of the national strategic development. It is expected that in the next 5-10 years, the industrial scale is expected to exceed 160 billion yuan.
As the core component of new energy vehicle, the quality of power battery directly determines the performance of the vehicle.
Lithium battery manufacturing equipment generally consists of front-end equipment, mid-end equipment and back-end equipment. The precision and automation level of the equipment will directly affect the production efficiency and consistency of the product.
As an alternative to traditional welding technology, laser machining technology has been widely used in lithium battery manufacturing equipment.
Based on the application of laser in power battery industry, this paper expounds the technological characteristics of laser welding in the field of lithium battery, and lists the technological characteristics of multiple processes and the development trend of equipment.
Welding is a very important manufacturing process from lithium battery cell manufacturing to automatic production line group of lithium battery PACK line. The conductivity, strength, air tightness, metal fatigue and corrosion resistance of lithium battery are typical evaluation criteria of battery welding quality.
The selection of welding method and welding process will directly affect the cost, quality, safety and consistency of the battery.
Next, the author will take you to understand the laser welding in the field of lithium battery applications.
1. Battery explosion-proof valve welding
Battery explosion-proof valve 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 is broken to avoid the battery bursting.
The structure of the safety valve is ingenious, which is very strict to the process of laser welding machine.
Before the use of continuous laser welding, the battery explosion-proof valve is welded by pulse laser welding, through the overlap and cover of solder joint and solder joint to achieve continuous sealing welding, but the welding efficiency is low, and the sealing is relatively poor.
Using continuous laser welding can achieve high speed and high quality welding, welding stability, welding efficiency and yield can be guaranteed.
2, battery ear welding
The electrode ear is usually divided into three materials. The positive electrode of the battery is made of aluminum (Al) and the negative electrode is made of nickel (Ni) or copper plated nickel (Ni-Cu).
In the manufacturing process of power battery, one of the steps is to weld the battery pole ear and pole column together.
The secondary battery is fabricated by welding it to another aluminium safety valve.
Welding should not only ensure the reliable connection between the pole ear and pole column, but also require a smooth and beautiful weld.
3, battery pole spot welding
The materials used for battery electrode strip include pure aluminum strip, nickel strip, aluminum - nickel composite strip and a small amount of copper strip, etc.
Commonly used for the welding of battery pole with pulse welding machine, with the emergence of interpublic QCW quasi continuous laser company, its on the battery pole with welding has been widely used, at the same time, due to its good beam quality, welding spot can do is very small, in response to the high reflectivity of aluminum, copper and narrowband battery polar zone (polar zone width below 1.5 mm) welding has a unique advantage.
4, power battery shell and cover sealing welding
The shell materials of power battery are aluminum alloy and stainless steel, among which the most aluminum alloy is used, generally 3003 aluminum alloy, but also a few pure aluminum.
Stainless steel is the best material for laser weldability, both pulse and continuous laser can obtain good appearance and performance of the weld.
Using continuous laser to weld thin-shell lithium batteries, the efficiency can be increased by 5~10 times, and the appearance and tightness are better.
So there is a tendency to replace pulsed laser in this application field.
5. Power battery module and PACK welding
Power battery series parallel between general by connecting piece and welding to complete, of monomer battery anode materials are different, generally with copper and aluminum material, formed after the adoption of laser welding between copper and aluminum brittle compounds, cannot meet the use requirements, usually by ultrasonic welding, copper and copper, aluminum and aluminum generally adopt laser welding.
At the same time, because the heat transfer of copper and aluminum are very fast, and the laser reflectivity is very high, the thickness of the connecting piece is relatively large, so it needs to use a high power laser to be able to achieve welding.