Application of Laser Welding in Energy Storage Battery Assembly Lines
From the manufacturing of energy storage battery cells to the assembly of battery packs, welding is a crucial manufacturing process. The conductivity, strength, airtightness, metal fatigue, and corrosion resistance of lithium batteries are typical evaluation standards for battery welding quality. The selection of welding methods and processes directly affects the cost, quality, safety, and consistency of the battery.
Among various welding methods, laser welding stands out with the following advantages: First, laser welding has high energy density, small welding deformation, and a small heat-affected zone, which can effectively improve the precision of parts, resulting in smooth, impurity-free, uniform, and dense welds without the need for additional grinding.
Second, laser welding can be precisely controlled, with a small focused spot and high-precision positioning. Combined with robotic arms, it is easy to automate, improving welding efficiency, reducing labor time, and lowering costs. Furthermore, when laser welding thin plates or fine-diameter wires, it is not prone to the problem of remelting as easily as arc welding.
The main welding methods for energy storage batteries include wave soldering, ultrasonic welding, laser welding, and dissimilar metal laser welding, with laser welding currently being the most mainstream method.
Energy Storage Battery Welding Methods:
① Wave Soldering: Essentially a combination of ultrasonic welding and laser welding;
② Ultrasonic Welding: This method is simple to use, but requires more space, resulting in lower module assembly efficiency;
③ Laser Welding: Currently the most widely used method, but with slight structural differences;
④ Dissimilar Metal Laser Welding: This welding method also has high assembly efficiency and fast production speed.
What is Laser Welding?
Laser welding uses an optical system to focus a high-energy-density laser beam as a heat source into a very small area, creating a highly concentrated heat source zone at the weld site in a very short time. This melts the materials being welded, forming a strong weld point or weld seam.
Laser welding is a new welding method currently in a stage of rapid development. Laser welding offers several advantages: a smaller heat-affected zone, smaller weld points, higher dimensional accuracy, and non-contact welding requiring no external force, resulting in minimal product deformation, high weld quality, high efficiency, and ease of automation.
Batteries typically incorporate various materials such as steel, aluminum, copper, and nickel. These metals can be used to form electrodes, wires, or casings. Therefore, welding between single or multiple materials places high demands on the welding process.
The advantage of laser welding lies in its ability to weld a wide range of materials, enabling welding between different materials.
Types of Laser Welding
Laser welding includes laser heat conduction welding and laser deep penetration welding. The main difference between heat conduction welding and deep penetration welding lies in the power density applied to the metal surface per unit time; different metals have different critical values.
Three Commonly Used Lasers for Laser Welding of Energy Storage Batteries
Energy storage batteries are an integrated system consisting of battery energy storage devices (from individual components → battery pack modules → battery cabinets → battery energy storage units → battery energy storage equipment), PCS (Power Control System), and filtering components.
In the field of laser welding for energy storage batteries, the most commonly used lasers are pulsed lasers, continuous lasers, and quasi-continuous lasers.
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Pulsed lasers: YAG lasers, MOPA lasers;
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Continuous lasers: Continuous semiconductor lasers, continuous fiber lasers;
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Quasi-continuous lasers: QCW laser series.
These lasers can be understood as follows: hammering a thumbtack in one stroke at a time is pulsed; pressing the thumbtack in directly by hand is continuous; drilling continuously for 10 seconds, resting for one second, then drilling continuously for another 10 seconds, then resting for one second, is quasi-continuous.
Pulsed lasers refer to lasers with a single laser pulse width of less than 0.25 seconds, operating only once at regular intervals. They have high output power and are suitable for laser marking, cutting, and ranging.
Common pulsed lasers include solid-state lasers such as yttrium aluminum garnet (YAG) lasers, ruby lasers, and neodymium glass lasers, as well as nitrogen molecular lasers and excimer lasers. Pulsed lasers are based on the YAG laser principle, with high single-pulse energy and high power consumption, requiring regular replacement of consumables such as xenon lamps and necessitating a chiller.
These lasers are very mature, with relatively low unit costs, and are currently the most widely used laser for metal welding. However, due to technological limitations based on the YAG laser principle, the industry as a whole cannot currently achieve very high laser power; The electro-optical conversion efficiency is not high (around 13%).
Continuous-wave lasers are lasers that emit light continuously, meaning they have a stable operating state, i.e., a steady state. In a continuous-wave laser, the number of particles at each energy level and the radiation field within the cavity have a stable distribution.
The operating characteristic of continuous-wave lasers is that the excitation of the working medium and the corresponding laser output can continue continuously over a relatively long period of time. Solid-state lasers excited by continuous light sources, as well as gas lasers and semiconductor lasers operating by continuous electrical excitation, all belong to this category.
Because overheating is often unavoidable during continuous operation, most require appropriate cooling measures.
Continuous-wave lasers are based on the principle of YLP fiber lasers. Because they can continuously emit light at a constant power (when the laser emission points are fast enough and numerous, they are connected into a line), the output laser energy is constant, the laser stability is very good, the beam pattern is excellent, and the electro-optical conversion efficiency is very high (around 30%).
ACEY gantry-type continuous galvanometer laser welding machine uses the internationally advanced fiber laser as its laser source. Combined with the gantry machine tool independently developed, designed, and manufactured by our company, it has excellent rigidity and stability. It runs with precision guide rail transmission and is equipped with a high-response servo motor, which is highly accurate and fast. It is suitable for welding copper, aluminum, iron, nickel, or their alloy metals, and is especially suitable for welding aluminum busbars or nickel-to-square battery connections.
Quasi-continuous-wave lasers (QCW), also called long-pulse lasers, produce pulses on the order of milliseconds with a duty cycle of 10%. This allows the pulsed light to have a peak power more than ten times higher than continuous light, which is very advantageous for applications such as drilling. The repetition frequency can be modulated up to 500Hz depending on the pulse width. QCW lasers can operate simultaneously in continuous and high-peak-power pulse modes. Unlike traditional continuous-wave (CW) lasers, quasi-continuous-wave (QCW) lasers always maintain the same peak and average power in both CW and CW/modulation modes. In contrast, the peak power of a QCW laser in pulsed mode is 10 times higher than its average power.
Therefore, this allows for the generation of high-energy microsecond and millisecond pulses at repetition frequencies ranging from tens of hertz to kilohertz, achieving average and peak power of kilowatts.
Advantages of laser welding equipment in energy storage batteries:
1. The welding process is non-contact, minimizing internal stress on the weld ribs.
2. The welding process does not produce any overflow or release of substances, preventing secondary pollution.
3. The weld has high strength and airtightness, meeting functional requirements.
4. Laser welding can weld different materials, including membrane materials and dissimilar materials.
5. Laser welding is easily integrated into automated systems and can be implemented synchronously according to production capacity needs, resulting in high efficiency and low internal stress.
6. Laser welding involves simple and convenient structures, reducing the complexity of mold structures.
7. The welding process can be digitally and intelligently monitored, meeting the need for data visualization.
8. This type of welding process can be effectively integrated with automated production lines, meeting the needs of mass production and achieving high-efficiency production with low consumption.
Acey New Energy specializes in providing complete production equipment and one-stop solutions for lithium ion battery pack assembly line—from cell to pack—tailored to newcomers in the lithium battery energy storage field. Whether it's production line planning, equipment integration, or key stages such as module stacking, laser welding, BMS integration, and final pack testing, we deliver reliable technical support and efficient, stable production systems. We sincerely welcome customers from all over the world and hope to be your professional and reliable partner to create a better future together.
