Application of Laser Technology in Power Battery Manufacturing

Laser welding

Laser welding has many advantages such as deep melting, fast speed, small deformation, etc., which can greatly improve the safety of power batteries. Laser welding is not demanding on the welding environment, has high power density, is not affected by the magnetic field, is not limited to conductive materials, does not require vacuum working conditions and the welding process does not produce X-rays other advantages, are widely used in new energy vehicles and power battery manufacturing field. Laser welding technology can greatly improve the processing efficiency of power batteries, and welding precision, to ensure safety, reliability, and consistency, reduce costs, and extend service life.

 


In the production of power batteries using laser welding in the cell assembly and battery PACK link.

 

1. Cell assembly section-middle section: the laser welding process is used in the shell, top cover, sealing nails, lugs, and other welding links

2. The core assembly section specifically includes core winding, stacking, lug welding, core into the shell, shell top cover welding, liquid injection, and liquid injection port packaging. The electric core is the smallest unit of the power battery, and the quality of the electric core determines the performance of the battery module, which in turn affects the reliability of the entire power battery system.

 

Compared with traditional argon arc welding and resistance welding, laser welding has significant advantages:

lNarrow heat-affected zone, welding deformation is small, especially suitable for welding of micro-pieces

lThrough the optical fiber guidance or prismatic deflection, can be long-distance welding

lVery high energy density

lDoes not need vacuum protection and X-ray protection, and is not affected by magnetic field.

 

Post-processing section - back section: laser automation system to replace the traditional manual assembly methods used in module PACK

 

The specific links of the post-processing section include chemical composition, testing and classification, and PACK module, and the main equipment includes a chemical composition machine, capacity separation and testing device, process storage and logistics automation, and PACK automation equipment. Among them, the laser automation system is commonly used in the module PACK assembly line to weld the connecting pieces in the battery PACK module.

 

In addition, the laser can also be used for welding explosion-proof valves on the cover plate after the module. The explosion-proof valve is usually two aluminum metal pieces laser welded into a certain shape with grooves designed to rupture and relieve pressure when the battery pressure is too high. Due to the explosion-proof valve and the cover with a small gap, it is difficult to accurately put into position, and thus the laser welding process requirements are extremely strict, requiring weld sealing, and strict control of heat input, to ensure that the weld destructive pressure value stabilized within a certain range, otherwise it will have a greater impact on the safety of the battery. Explosion-proof valves usually use splicing welding and composite welding. As the laser welding process continues to go up, laser welding penetration is expected to go up.

Laser cutting

Laser-cutting technology can be applied to the process of lithium battery manufacturing process such as lug cutting and molding, pole slitting diaphragm slitting, etc. Compared with die-cutting, laser cutting has the advantages of higher accuracy and lower operating costs, which helps to improve efficiency and reduce costs in battery production. Compared with traditional mechanical cutting, laser cutting has the advantages of no physical wear and tear, flexible cutting shape, edge quality control, higher accuracy, and lower operating costs, which is conducive to reducing manufacturing costs, improving production efficiency, and significantly shorten the cycle of die-cutting new products.



 

1. Polar ear cutting

The laser lug forming is currently the mainstream technology, process parameters, control systems, and cutting station design determine the cutting speed and quality. Traditionally, the mechanical die-cutting process is mainly used for lug forming. The mechanical die-cutting process has the limitations of fast mold loss, long time to change the mold, poor flexibility, and low production efficiency, and has been increasingly unable to meet the development requirements of lithium battery manufacturing. Due to the many advantages of laser cutting technology, with the high-power, high-beam quality nanosecond lasers, and single-mode continuous fiber technology maturity, the current laser auricle cutting has gradually become the mainstream of auricle forming technology. Laser lug molding is generally used for roll-to-roll continuous cutting, and its main process flow is as follows: unwinding, tension control, deskew control, laser cutting, secondary de-dusting, and winding.

 

2. Pole piece cutting

Pole piece cutting disc slitting and die-cutting, laser cutting three ways, disc slitting and die-cutting there are tool wear problems, which are likely to cause process instability, resulting in poor quality of the pole piece cutting, resulting in battery performance degradation; laser energy and cutting speed are the two main parameters of the process, the cutting quality of the impact is huge. When the laser power is too low or moving too fast, the pole piece can not be completely cut, and when the power is too high or moving too low, the laser on the material role of the area becomes larger, the size of the slit is bigger.

 

3. Diaphragm cutting

The laser cutting module cuts the diaphragm wound by the turning roller alternately switching two diaphragm winding components, realizing the function of automated uniform cutting of diaphragm, avoiding the phenomena of powder removal, picking silk, broken film, and non-stop cutting during the cutting process, which is convenient for the practical use in the batch production line.

Laser cleaning

Laser cleaning before electrode coating can effectively avoid the damage caused by the original wet ethanol cleaning; laser cleaning before battery welding using a pulsed laser to make the substrate heat vibration expansion of pollutants to overcome the surface of the adsorption force away from the substrate to achieve the decontamination of the role of the battery assembly process of laser cleaning can be insulating plate, end plate laser cleaning, cleaning the surface of the battery cell dirt, roughening the surface of the battery cell, and improve the adhesion of the adhesive or adhesive coating.

 

1. Before coating the pole piece

The positive and negative electrode sheet of the lithium battery is coated with lithium battery positive and negative materials on the metal thin strip, The metal thin strip in the coating of electrode materials needs metal strip cleaning, the metal thin strip is generally aluminum thin or copper thin, the original wet ethanol cleaning, easy to damage other parts of the lithium battery, the laser dry cleaning machine can effectively solve the above problem.

 

2. Battery welding before

The use of pulsed laser direct radiation decontamination, so that the surface temperature rises and thermal expansion occurs, thermal expansion makes the pollutants or substrate vibration, so that the pollutants overcome the surface adsorption from the substrate surface so as to achieve the purpose of removing the object surface stains. This way can effectively remove the dirt, dust, etc. on the end surface of the pole of the electric core, and prepare for the battery welding in advance, in order to reduce the defective products of welding.

 

3. Battery assembly process

In order to prevent lithium battery safety accidents, generally need to lithium battery cell external adhesive treatment, order to play the role of insulation, to prevent the occurrence of short-circuit, as well as to protect the line, to prevent scratching. Laser cleaning of the insulating plate, and end plate, cleaning the surface of the battery cell dirt, roughening the surface of the battery cell, to improve the adhesion of the adhesive or glue, and cleaning will not produce harmful pollutants, belonging to the green cleaning method.

Laser marking

In order to better control the product quality and trace the whole production information of lithium battery, including raw material information, production process, and technology, product batch, manufacturer and date, etc., it is necessary to store the key information within the two-dimensional code and mark it on the battery. Laser marking has the characteristics of strong permanence, high anti-counterfeiting, high precision, strong wear resistance, safety and reliability, etc., which can provide the best solution for product quality tracking.

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