The explosive growth of new energy vehicles in the past two years has attracted more and more attention from the outside world, not only from the consumer side, but also from the industrial sector, new energy vehicles leading the technological trend has also grown into a powerful force that can not be ignored.battery pilot line We are going to discuss today, is the core of the power of laser welding new energy vehicles, batteries.

With the increase in sales of new energy vehicles, the installed capacity of power batteries is also growing rapidly. In the power battery manufacturing process, low cost, high quality and high efficiency are the three major goals of manufacturing companies, can achieve these three goals of technology and intelligent equipment favored by battery manufacturers.

Power battery is also a complex system, from the battery, battery module, battery components, through a manufacturing process, and finally assembled into a power battery system. Among them, material-to-material connection, module-to-module connection, and the structure of battery components all involve the highly demanding welding process - laser welding.

The reasonable choice of welding methods and processes in the power battery manufacturing process will directly affect the cost, quality, safety and consistency of the battery.laser welding machine for lithium ion batteries Next I organize the content of power battery welding.

Power battery system common welding technology applications

Batteries are divided into square batteries, cylindrical batteries and flexible batteries. At present, in battery production, the use of laser welding link mainly includes

Midway process: pole lug welding (including pre-welding), pole piece spot welding, electric core pre-welding into the shell, shell top cover sealing, liquid injection port sealing and welding.

Post process: Including the battery pack PACK module connectors when welding,ESS lithium battery machine as well as the cover plate after the explosion-proof valve welding.

Welding of battery shell and cover plate

The shell and cover of the power battery play a role in encapsulating the electrolyte and supporting the electrode material, providing a stable and airtight environment for the storage and release of electrical energy, and its welding quality directly determines the sealing and compressive strength of the battery, which in turn affects its life and safety performance. The battery shell is mainly made of Al3003 aluminum alloy, which is generally welded by low-power pulse laser.

Battery positive and negative pole pole welding

Battery pole is a battery positive and negative contact piece, the general business of the positive material using aluminum, negative can use copper, its role is mainly to let the battery pole through the connection piece welding, the formation of series, parallel control circuit, components of the battery module.

Battery explosion-proof valve seal welding

Explosion-proof valve 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 first rupture deflation, release the pressure to prevent the battery from bursting. Explosion-proof valve structure is ingenious, mostly using laser welding solid shape of two thin aluminum alloy plate. When the internal pressure of the battery rises to a certain value, the aluminum sheet is detached from the design slot position to prevent further expansion of the battery, causing an explosion. Therefore, this process requires very strict requirements for the laser welding process, strict requirements for the weld sealing, the heat input should be strictly controlled to ensure that the weld pressure damage within a certain range of stability, too large or too small will have a great impact on the safety of the battery.

Battery adapter welding

The adapter and flexible connection is the key component to connect the battery cover and battery cell. It must consider the requirements of overcurrent, strength and low spattering of the battery at the same time, so it is important to have enough weld width during the welding process with the cover to make sure that no particles fall on the cell to avoid short-circuiting of the battery. Copper, as the negative electrode material, is a high reflectivity material with low absorption rate, and welding requires higher energy density. The latest blue composite laser of Lianweng Laser can solve the traditional process problems such as high reflectivity and spattering.

Battery pole welding

The poles on the battery cover are divided into the internal and external parts of the battery. The internal connection of the battery is the welding of the electrode lugs of the battery with the electrode posts of the cover plate, while the external connection of the battery is the welding of the electrode posts of the battery through the connectors to form a series circuit and a parallel circuit to form a battery module.

The main problem with laser welding of battery electrode posts is also the burst hole defect, similar to a blowout valve. In essence, the weld of the electrode post is the mating surface between the aluminum rotor block and the electrode post, where impurities such as stamping oils and cleaning agents are easily left behind. The high energy density of the laser makes the temperature of the weldment surge, resulting in rapid vaporization of the impurities remaining in the pole, bubbles escape, overcome the surface tension of the molten pool and leave the molten pool caused by the burst hole defect. In this process, the rapid change in pulsed laser power further increases the tendency to form burst holes. Therefore, in addition to strengthening pre-weld cleaning, burst hole defects can be reduced by optimizing the laser power variation.

Power automobile battery module and PACK welding

Battery module can be understood as a lithium-ion battery cell by the series-parallel mode of different combinations, and the addition of a single battery system monitoring and management work devices. Battery module structure optimization and design companies can often decide their own a battery pack performance and safety. Its structure must play an important role in supporting, fixing and protecting the environment for the electric cells. At the same time, how we can meet the overcurrent requirements, current uniformity, how to effectively meet the control of the temperature of the battery cell, as well as whether there is a serious impact on the abnormality of the power can be cut off, to avoid the chain reaction time, etc., will be the standard for judging the merits of the battery module.

At the same time, due to the fast heat transfer of copper and aluminum, high reflectivity of the laser, the thickness of the connecting parts is relatively large, and it is necessary to use a higher power laser to achieve welding.

At present, the main problems in laser welding of power batteries are porosity, cracks, poor molding, and air holes. These defects lead to reduced strength, sealing and conductivity of the battery pack, causing a series of safety problems such as battery explosion, leakage and heat generation. In order to solve these problems, a large number of studies have focused on the optimization of the laser welding process, which can effectively reduce welding defects by adjusting the laser welding power, pulse width, welding speed, defocusing and other parameters.

It is not difficult to see that the welding process of power battery is a delicate work, and any small problem will affect the performance and safety of the subsequent finished power battery. Therefore, high-quality materials and high-quality laser welding instruments are the basis for ensuring the success of the welding process. Intelligent technologies such as laser welding path planning, weld identification, defect recognition, quality monitoring and so on are also one of the hot spots for future research.