There are many factors that affect the welding quality of 18650 lithium batteries, mainly focusing on welding temperature and welding techniques. From the manufacturing of lithium battery cells to the assembly of battery packs, battery welding is a very important 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 welding processes will directly affect the cost, quality, safety, and consistency of batteries. Among various welding methods, laser welding stands out with the following advantages: firstly, laser welding has high energy density, small welding deformation, and small heat affected zone, which can effectively improve the accuracy of the workpiece. The weld seam is smooth and free of impurities, uniform and dense, and does not require additional polishing work; Secondly, laser welding can be precisely controlled, with small focusing points and high-precision positioning. It is easy to achieve automation with a robotic arm, improving welding efficiency, reducing working hours, and lowering costs; In addition, when laser welding thin plates or fine diameter wires, it is not as susceptible to the problem of remelting as arc welding.
1. The pole ear is made of nickel sheet and can be welded with WEELDING88C welding wire and WEELDING88C-F welding flux
Welding method: First preheat the fixed pole ears with a soldering iron, then apply the soldering wire dipped in flux to the welding area, and then use the soldering iron to assist in melting the soldering wire dipped in flux into shape.
2. If the pole ear is made of aluminum, it can be welded with WEWELDING M51 welding wire at a low temperature of 179 degrees and M51-F welding flux
Welding method: First preheat the fixed pole ears with a soldering iron, then apply the soldering wire dipped in flux to the welding area, and then use the soldering iron to assist in melting the soldering wire dipped in flux into shape.
The aluminum shell thickness of general power batteries is required to be below 1.0 millimeters. Currently, mainstream manufacturers mainly use two shell material thicknesses, 0.6mm and 0.8mm, based on different battery capacities. The welding methods are mainly divided into side welding and top welding, among which the main advantage of side welding is that it has less impact on the interior of the battery cell, and splashes will not easily enter the inner side of the shell cover.
Due to the possibility of protrusions after welding, it may have a slight impact on the subsequent assembly process. Therefore, the side welding process has high requirements for the stability of the laser, the cleanliness of the material, and the clearance between the top cover and the aluminum shell of the power battery. The top welding process, due to being welded on one surface, can use a more efficient scanning welding method with a vibrating mirror, but it requires high requirements for the previous process of shell insertion and positioning, and high automation requirements for the equipment.
Attention:
1. Welding strength: ≥ 15, increased internal resistance of the battery, decreased battery performance, and short service time
2. Spot welding appearance: There is no explosion, virtual welding, or peeling phenomenon on the pole ear, and there are no welding penetration, protrusions, deformations, explosions or other adverse phenomena at the bottom of the shell; Poor appearance and easy rusting; If it is welded through, liquid will leak and the battery will be scrapped.
3. Parameters of spot welding: welding current, pre pressing time, pressure; Poor spot welding
4. Central hole damage: battery cell short circuit
5. Insulation leakage: It is impossible to ensure complete isolation between the positive and negative electrodes, which poses a safety hazard
6. Short circuit test: DC150V, 500uA leakage detection; There may be safety hazards such as heating and explosion.