Application of laser welding in the field of lithium batteries
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Lithium-ion batteries are widely used in various electronic devices (such as mobile phones, laptops, PDAs, digital cameras and digital video cameras, etc.) and transportation vehicles (patrol cars, electric bicycles, electric cars, etc.) due to the advantages of high specific energy, long cycle life, small self-discharge, no memory effect and no pollution, and have become a high-tech industry supported by China's energy sector.
Power batteries refer to batteries used in electric vehicles, which are secondary batteries with larger capacity and output power relative to small capacity batteries (e.g. mobile , laptop batteries, etc.) that can be used in electric vehicle drive power and large mobile power applications. Lithium-ion batteries or battery packs are made in a very large number of processes, and several of these processes, such as explosion-proof valve seal welding, lug welding, flexible connection welding, battery case seal welding, module and PACK welding all use laser welding as the best process. The main materials used for welding power batteries are pure copper, aluminium and aluminium alloy, stainless steel, etc.
batter pack
1'Battery explosion-proof valve welding
The explosion-proof valve of the battery is a thin-walled valve body on the sealing plate of the battery, when the internal pressure of the battery exceeds the specified value, the explosion-proof valve body ruptures to prevent the battery from bursting. The safety valve structure is ingenious and this process is extremely demanding on the laser welding process. Prior to continuous laser welding, battery explosion-proof valves were welded using pulsed lasers, which overlapped and covered joints to achieve continuous seal welding, but the welding efficiency was low and the seal was relatively poor. The use of continuous laser welding can achieve high speed and high quality welding, welding stability, welding efficiency and yield can be guaranteed.
2'Battery lug welding
The positive electrode of the battery is made of aluminium (Al) and the negative electrode is made of nickel (Ni) or nickel-plated copper (Ni-Cu). One part of the manufacturing process for power cells is the welding of the lugs to the poles. In the manufacture of secondary cells it is necessary to weld them together with an additional aluminium safety valve. The welding should not only ensure a reliable connection between the pole lug and the pole post, but also require a smooth and beautiful weld.
3'Battery pole strip spot welding
The materials used for the battery pole strip include pure aluminium strip, nickel strip, aluminium-nickel composite strip and a small amount of copper strip. With the emergence of the QCW quasi-continuous laser from IPG, it has been widely used in the welding of battery strips. At the same time, due to its good beam quality and small welding spot, it has unique advantages in dealing with the welding of highly reflective aluminium strips, copper strips and narrow strip battery strips (strip width below 1.5 mm).
4, power battery shell and cover plate sealing welding
Power battery shell materials are aluminum alloy and stainless steel, of which the use of aluminum alloy is the most, generally aluminum alloy, there are also a few pure aluminum. Stainless steel is the best material for laser welding, especially 304 stainless steel, either pulse or continuous laser are able to obtain the appearance and performance of good weld.
The laser welding performance of aluminium and aluminium alloys varies slightly depending on the welding method used. With the exception of pure aluminium and 3-series aluminium alloys, for which both pulsed and continuous welding is not a problem, continuous laser welding is the preferred method to reduce crack sensitivity. At the same time, according to the thickness of the power battery shell to choose the appropriate power of the laser, the general shell thickness of 1mm or less, can be considered to use a single-mode laser within W, the thickness of more than 1mm need to use more than W single-mode or multi-mode lasers.
Small capacity lithium batteries often use a relatively thin aluminum case (thickness of 0.25mm or so), there are also and so on using the steel case. Due to the thickness of the case, the welding of such batteries is generally done with a lower power laser. The use of continuous lasers for welding thin-case lithium batteries can increase efficiency by a factor of 5 to 10, and the appearance and sealing is better. Therefore there is a trend to gradually replace pulsed lasers in this application area.
5, power battery module and pack welding
Series and parallel connection between the power battery is generally completed by connecting the piece with the single battery welding, positive and negative pole materials are different, there are generally copper and aluminum 2 materials, due to the formation of brittle compounds between copper and aluminum after laser welding, can not meet the use of requirements, usually using ultrasonic welding outside, copper and copper, aluminum and aluminum are generally used laser welding. At the same time, as both copper and aluminium transfer heat very quickly and have a very high reflectivity to the laser, the thickness of the connection piece is relatively large, so a higher power laser is required to achieve welding.
Features of laser welded lithium batteries
From the manufacture of lithium battery cells to the formation of battery packs, welding is a very important manufacturing process. The conductivity, strength, gas tightness, metal fatigue and corrosion resistance of lithium batteries are typical criteria for evaluating the quality of battery welding. The choice of welding method and welding process will directly affect the cost, quality, safety and consistency of the battery. Laser welding has become the preferred solution for many welding tasks due to the advantages of safe and reliable welding, process precision and environmental protection.
Lithium battery laser welding machine
Laser welding process is an important process in lithium battery manufacturing. It has the advantages of high precision, fast speed and high level of automation. It directly affects the cost, quality, safety and consistency of the battery. Before the emergence of laser technology, the lithium battery industry usually used traditional machinery for processing and cutting. During use, the die-cutting knife will inevitably wear and tear, causing dust to fall off and burrs to occur, which may cause the battery to overheat, short-circuit, and explode. and other dangerous problems; and the hardware die-cutting process has limitations such as fast mold loss, long mold change time, poor flexibility, and low production efficiency, and it is increasingly unable to meet the development requirements of lithium battery manufacturing.
Laser welding machine VS ordinary welding machine
Compared with traditional welding processes, laser welding has high energy density, small welding deformation and small heat-affected zone, which can effectively improve the accuracy of parts. The welds are smooth, impurity-free, uniform and dense, and do not require additional grinding work. Secondly, laser welding can achieve precise Control, small focused light spot, high-precision positioning, easy to realize automation with robotic arms, improve welding efficiency, reduce working hours, and reduce costs; in addition, when laser welding thin plates or thin-diameter wires, they are not as susceptible to meltback as arc welding trouble.
Laser welding machine workflow
Application of sensors in laser welding machines
Laser welding equipment is widely used in lithium battery manufacturing. It runs through almost every link of production. It can weld and seal battery structural parts economically and quickly. It is used in battery explosion-proof valves, pole welding, adapter plate welding, and shell welding. Body sealing, battery tabs, power battery modules and PACK welding, etc.
industrial camera
Using cameras to position and track lithium batteries and detect product defects has the following advantages:
1. With the IA box (small size), it can replace the original industrial computer and reduce the space used by the equipment; 2. Instead of the traditional PC for calculation and image processing, the smart camera (box) serves as the hardware platform for the AI algorithm; 3. Use deep learning Automatically extract image features instead of artificially designed features, and have stronger generalization capabilities.
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slot sensor
The positioning limit applied to the motion mechanism module has the following advantages:
1. There are 12 shapes available, including outlet type and plug-in F.T.R.L.K.T., which can be used in a variety of scenarios;
2. Normally open and normally closed output can be switched;
3. The groove depth is 8.5mm, which can prevent the measured object from hitting the bottom of the groove to the greatest extent.
Magnetic sensor
Applied to the upper limit of the cylinder module, the magnetic sensor detects the position of the cylinder to control the lifting and falling of the cylinder. It has the following two advantages:
1. Positioning accuracy and reliable performance;
2. The maximum switching frequency can reach Hz.
Through-beam photoelectric sensor
It is used to detect the presence of loaded lithium batteries. Since the customer's conveyor belt and mobile platform will jitter, the use of through-beam photoelectricity can ensure the stability of the detection and has the following advantages:
1. Through-beam photoelectricity is not affected by the color of the object being measured;
2. There are few restrictions on detection objects. Since the photoelectric sensor is based on the detection principle of light shading and reflection caused by the detection object, it can detect almost all objects such as glass, plastic, wood, liquid, etc.;
3. Short response time and high resolution.
safety light curtain
Implementing safety protection during equipment operation to prevent dangers caused by personnel accidentally entering during equipment operation has the following advantages:
1. It can provide detection of various sizes of fingers, palms, arms, etc., and can detect opaque objects with a minimum size of 3.75mm or more;
2. Various appearance sizes, protection heights, and detection methods are optional;
3. Can be quickly customized according to various non-standard needs of customers.
Temperature Sensor
Detecting the temperature of the cooling water chiller has the following advantages:
1. Suitable for small pipe diameters and confined spaces;
2. Fast response time;
3. Different probe lengths and diameters are available.
Laser processing technology is one of the innovations in traditional processing technology in the lithium battery industry, and plays a prominent role in power battery production. Meiji Sensors is manufactured with ingenuity and high-quality sensors to provide support for lithium battery intelligent manufacturing equipment companies to become industry leaders.
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