KR102301294B1 - Process for Preparing Battery Cell Comprising Ablation Step of Burr Using Fiber Pulse Type Laser - Google Patents

Abstract

In a method for manufacturing a battery cell, the present invention includes a step of removing burrs and contamination generated in a welding area during laser welding for bonding a top cap to an open upper end of a can body made of metal by etching, , The removal process provides a battery cell manufacturing method, characterized in that performed by a fiber pulse laser, and a battery cell manufactured by the manufacturing method.

Description

{Process for Preparing Battery Cell Comprising Ablation Step of Burr Using Fiber Pulse Type Laser}

The present invention relates to a method for manufacturing a battery cell comprising a process of removing burrs using a fiber pulse laser.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. is being used

In addition, secondary batteries are attracting attention as an energy source for electric vehicles, hybrid electric vehicles, etc., which are proposed as a way to solve air pollution such as gasoline and diesel vehicles using fossil fuels. Accordingly, the types of applications using the secondary battery are being diversified due to the advantages of the secondary battery, and it is expected that the secondary battery will be applied to more fields and products in the future than now.

According to the shape of the battery case, the secondary battery is classified into a cylindrical battery and a prismatic battery in which the electrode assembly is embedded in a cylindrical or prismatic metal can, and a pouch-type battery in which the electrode assembly is embedded in a pouch-type case of an aluminum laminate sheet. . Among them, prismatic batteries and pouch-type batteries that can be stacked with high integration and have a small width compared to their length are receiving particular attention.

Here, a schematic diagram for explaining the general structure of the prismatic battery cell and a simple manufacturing method thereof is shown in FIG. 1 .

Referring to FIG. 1 , the prismatic battery cell 10 is generally manufactured by manufacturing an electrode assembly 11 and inserting it into the can body 12 , and then an insulating plate 14 is interposed on the top of the electrode assembly 11 . Thus, short circuit between the electrode assembly 11 and the top cap 13 is prevented, and the top cap 13 is connected to the upper opening of the can body 12 by welding (indicated in red). Although not shown in the drawings, after the welding is completed as described above, the electrolyte is injected through the electrolyte injection hole formed in the top cap, and then the injection hole is sealed.

However, in the case of sealing the can body and the top cap by welding in this way, burrs are generated at the interface during welding such as laser, the thickness increases, and contamination such as foreign matter may occur. Due to this phenomenon, there was a problem in that the appearance and the dimension (dimension) were poor, so that the bar did not respond to the demands of the consumer, and the production efficiency was very low because it was caught as defective.

Accordingly, in order to solve the above problem, a quality improvement process of manually polishing battery cells with poor appearance was performed, but there was a problem such as secondary appearance non-uniformity due to manual deviation between workers, and all processes were Since it has to be done manually, there is a problem in that efficiency is greatly reduced.

Therefore, there is a high need for development of a technology that can solve the appearance defect that occurs during laser welding that can solve this problem.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

The inventors of the present application, after repeated in-depth research and various experiments, in a method for manufacturing a battery cell, a burr generated at the welding site during laser welding for bonding the top cap to the open upper end of the can body made of metal ) and contamination are finely removed by a fiber pulse laser, the appearance of the welding surface becomes uniform and the removal process is possible by automation, so it is confirmed that the process efficiency is increased as well as the deviation between operations is small and came to complete the present invention.

Accordingly, the method for manufacturing a battery cell according to the present invention includes a process of removing burrs and contamination generated in the welding area during laser welding for bonding the top cap to the open upper end of the can body made of metal by etching. And, the removal process is characterized in that it is performed by a fiber pulse (fiber pulse) laser.

In general, when a battery cell is manufactured using a can case made of a metal material, a can body for accommodating an electrode assembly and a top cap for sealing the can body while being electrically connected to the electrode terminals of the electrode assembly are welded to the battery. manufacture the cell.

At this time, in the welding, for example, an Nd:YAG laser or a carbon dioxide (CO ₂ ) laser is used. However, after such laser welding, contamination such as burrs, which are metal protruding foreign substances caused by melting and hardening during welding, or soot caused by high temperatures, occur in the welding area after such laser welding, which can lead to poor appearance, etc. , the complaints from users are high, and research to solve this problem has been continued.

Accordingly, the inventors of the present application repeated in-depth studies under various conditions for numerous lasers, and as a result, when a fiber pulse laser satisfying specific conditions is used to remove the burr, damage to the battery cell It was found that burrs and the like can be removed in a simpler way while minimizing

In general, a fiber laser has a _{smaller output than a CO 2} laser, but it is suitable for the present invention because it can perform a precise processing operation. At this time, the fiber laser is classified according to its oscillation method. Here, the oscillation method refers to a method of converting DC energy into AC energy by amplifying an optical resonator, and largely includes a continuous (CW) type operation method and a pulse (CW) type operation method. pulse) type operation method. In the continuous operation method, the laser light continuously operates with a constant intensity, and in the pulse operation method, the laser light is generated only momentarily and operates periodically according to the width and repetition rate of the pulse.

In the present invention, compared to a continuous wave (CW) oscillation type laser, the fiber pulse oscillation type laser can easily control the energy output from the laser, so that the removal of burrs and the like can be performed more closely. , it can be confirmed that the battery cell is less damaged, so it is most preferable for the removal process.

In addition, the wavelength range output from the fiber pulse laser may be, in detail, 700 to 1200 nm.

This is because the laser within the wavelength range minimizes thermal damage to the processing base material and facilitates the removal of burrs and the like. If the wavelength range is too short out of the above range, more precise work is possible, but since it is expensive, there is a loss in terms of cost, so the cost-effectiveness is not good. It is not preferable because it cannot be removed, and burrs and the like may remain without being removed.

In this case, the thickness of the burr generated during welding removed by the fiber pulse laser may be 5 to 40 μm, specifically, 10 to 30 μm.

If it is removed too thinly outside the above range, it is etched smaller than the size of the burr and cannot completely remove the burr, so the surface may be irregular. can be, which is not desirable.

For the fiber pulse laser used to remove the burrs in the above range, the conditions may be set according to the detailed thickness of the burrs to be removed.

Specifically, precise control of laser spot size, spot overlap rate, pulse repetition rate, spot hatching gap, speed, energy, power, pulse width, etc. is required for desired degree of burr etching.

First, the spot size of the laser used in the removal process may be 5 to 30 μm, specifically, 10 to 30 μm, and more specifically 10 to 25 μm.

Since the spot size is 50% or more smaller than the optimal spot size of the conventional Nd:YAG laser device described above, the precision of the removal operation of burrs and the like can be increased, and the amount of device power required for the same operation can be greatly reduced. .

Out of the above range, if the laser spot size is too small, the energy density increases too much to cause an undesirable degree of etching to damage the battery cell base material, and if the size is too large, the power density is Since the etching is not made low, rather, the melting occurs, and the irregular melt is fused to further deteriorate the appearance, so it is very important to adjust the spot size.

Even when the spot size is in the above range, when the spot overlap ratio is in a certain range, a preferable etching is possible, and the etching degree is affected by the spot overlap ratio.

Specifically, when the spot overlap rate increases, the degree of etching also increases. Accordingly, the spot overlap ratio for removing the thickness in the above range may be 15 to 85%, specifically 30 to 70%, based on one spot size.

The spot overlap ratio refers to the degree of overlap between adjacent spots in the laser travel direction.

Out of the above range, when the spot overlap rate is less than 15%, surface etching hardly occurs, and when the spot overlap rate exceeds 85%, the etching degree is too large to cause damage to the base material. Bar, Not desirable.

On the other hand, the spot overlap rate is affected by the processing speed, pulse repetition rate, etc., and if the spot overlap rate is satisfied within the above range by adjusting these factors, a desired degree of etching is possible.

Specifically, when the speed is increased, the spot overlap rate falls, and when the pulse repetition rate is increased, the spot overlap rate also increases. can

Accordingly, the numerical range that the above elements must satisfy is not limited. However, a preferable range may be determined in consideration of the output of the laser actually used, the aspect of cost-effectiveness, and the like.

Specifically, the speed of the laser may be 500 to 10000 mm/sec, specifically, 1000 to 10000 mm/sec.

The laser speed may vary depending on the frequency of the laser, but if the speed is too slow outside the above range, the productivity is lowered compared to the case of increasing the speed based on the same overlap ratio, and there is a risk of thermal damage to the processing base material, If it is too fast, the pulse repetition rate must also be increased to have the spot overlap rate. When the pulse repetition rate is increased, the output is lowered, so the price of the laser to increase the output is increased, which is not good in terms of cost-effectiveness, Since it is difficult to precisely control the processing head of the laser, it is not preferable.

In addition, as described above, the spot overlap rate is also affected by the pulse repetition rate, and increases as the pulse repetition rate increases. When the speed satisfies the constant speed, the pulse repetition rate for satisfying the spot overlap rate may be 20 to 400 KHz, specifically 30 to 300 KHz.

Similar to the spot overlap rate, the etching degree of the burr using the laser of the present invention is also affected by the spot hatching gap.

Specifically, the spot hatching gap may be 15 to 85%, specifically 30 to 70%, based on one spot size, identical to the spot overlap ratio.

The spot hatching gap refers to a distance between the center of the spot in the first direction and the center of the spot in the second direction at a point where the traveling direction of the laser is changed.

Out of the above range, if the spot hatching gap is less than 15%, the overlapping portion increases, so the etching thickness may increase to affect the metal can, and there is a problem in that the etching surface is also rough, and if it exceeds 85% , it is not preferable because etching hardly occurs because the overlap is not made, and a hatching gap appears on the surface due to irregular etching.

On the other hand, the larger the irradiation energy of the laser, the easier it is to remove, but considering the thermal damage and the thickness of the burr to be removed, it may be 0.2 to 1.0 mJ, specifically 0.5 to 0.9 mJ.

If it is less than 0.2 mJ out of the above range, the removal of burrs and the like is not performed well, and if it exceeds 0.9 mJ, the etched thickness increases, which may affect the metal can, which is not preferable.

The irradiation energy of the laser is determined by the output of the laser and the pulse width, and the irradiation energy increases as the output increases and the pulse width increases.

Accordingly, again, the numerical range that the above elements must satisfy is not limited. However, a preferable range may be determined in consideration of the actually used laser power, cost ratio, etching degree, and the like.

There is a limit to increasing the output depending on the type of laser, and even if the output is increased, etching is not performed when the pulse width does not represent a predetermined value or more at the same overlap rate. Control is important.

Here, the pulse width of the laser in the preferred range may be 0.15 ns to 200 ns, specifically, 10 to 200 ns.

Out of the above range, if the pulse width is too small, only a fine surface is processed and laser irradiation has to be performed multiple times, so the process efficiency is lowered, the cost-effectiveness is not good, and if the pulse width is too large outside the above range, the processing base material It is undesirable because there is a high probability of thermal damage to and surrounding components.

As described above, when the fiber pulse laser satisfies the above conditions, burrs and fume generated during laser welding for bonding the top cap to the open upper end of the can body made of metal are eliminated. It can be effectively removed without damaging the base material, and the appearance can be made uniform, and by performing the removal process with a laser by controlling the conditions rather than individual workers, the deviation for each battery cell can also be reduced, so that the battery of good quality is more reliable. cells can be made.

The present invention also provides a battery cell in which foreign substances such as burrs and contamination generated at the welding site during welding are removed and the surface of the welding site is made uniform.

The specific configuration of the battery cell, for example, an electrode assembly having a positive electrode/separator/negative electrode structure, and an electrolyte impregnated therein include all previously disclosed contents, and description thereof will be omitted herein.

As described above, the method for manufacturing a battery cell according to the present invention uses a fiber pulse laser to combine a top cap with an open upper end of a metal can body. By removing the contamination, the appearance of the welded surface becomes uniform, and the removal process is possible by automation, so that the deviation between operations is small, so that the defect rate can be reduced and the process efficiency is increased.

1 is a schematic diagram showing a conventional method for manufacturing a prismatic battery cell;

Hereinafter, the present invention will be described in more detail through experimental examples, but the following experimental examples are intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

<Experimental Example 1>

In order to confirm the desired spot overlap rate and energy conditions, the etching level was measured by varying the spot overlap rate and energy conditions of an IPG 200W 2mJ fiber pulse laser (beam diameter 30㎛) on the Al plate, and the results are shown in Table 1 below. indicated.

fixed condition Frequency 200kHz, pulse width 120ns, hatching gap 33.3% Energy (mJ) 0.5 0.7 0.9 Overlap rate (%)

30 8.7 9.8 20.8 50 8.8 19.7 30.8 70 14 24.2 45.3

Referring to Table 1, when the energy and overlap ratio within the above range are obtained, the etch rate may be 40 μm or less.

Specifically, when the energy value is 0.5 mJ or less and the overlap rate drops to 30% or less, it can be seen that the etching degree is further reduced, the energy value is 0.9 mJ, and the overlap ratio is 70% or more When it exceeds, it can be confirmed that the etched thickness has a 45 μm, and it is not preferable that the energy and the overlap ratio have more than the above range at the same time.

<Experimental Example 2>

In order to confirm the etching level according to the overlap rate, the etching level was confirmed by changing the overlap rate by adjusting the processing speed and pulse repetition rate of a fiber pulse laser (beam diameter of 30 μm) of IPG 200W 2mJ, which is shown in Table 2 below. did.

Frequency (kHz) 200 200 200 200 200 200 200 200 speed (m/s) 9 8 7 6 5 4 3 2 Overlap rate (%) 10 20 30 40 50 60 70 80 Etched thickness - about 10 μm about 15 μm about 18 μm about 20 μm about 25 μm about 30 μm about 35 μm

Referring to Table 2, results of changing the overlap rate by adjusting the laser speed and pulse repetition rate while other conditions are fixed can be seen.

Specifically, as the overlap rate increases, the etch thickness also increases. Therefore, when the overlap ratio further falls to 10% or less, it can be seen that the etching degree also decreases and etching hardly occurs. If it exceeds, it can be expected to be etched to 40 μm or more.

<Experimental Example 3>

In order to check the etching level according to the hatching gap, IPG 20W fiber pulse laser (beam diameter 30㎛) was fixed to 80% output, pulse repetition rate 20kHz, speed 500mm/s, pulse width 200ns, and only the hatching gap was adjusted. The etching degree was confirmed, and it is shown in Table 3 below.

Hatching Gap (%) 7 17 27 34 50 67 87 Etched thickness 50 μm
more about 40 μm about 30 μm about 20 μm about 15 μm about 10 μm -

Referring to Table 4, it can be seen that the etching degree decreases as the hatching gap increases while other conditions are fixed. Therefore, if the hatching gap is too small, too much etching occurs, and if the gap is too large, it hardly occurs.

Although described above with reference to the experimental examples of the present invention, those of ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Claims (12)

A method for manufacturing a battery cell, comprising: removing burrs and contamination generated in a welding area during laser welding for bonding a top cap to an open upper end of a can body made of metal by etching; The process is performed by a fiber pulse laser,
The pulse width of the laser is 0.15 to 200 ns,
The pulse repetition rate of the laser is 20 to 400 kHz,
The energy of the laser is 0.5 to 0.9 mJ,
The speed of the laser is 500 to 10000 mm / sec,
The spot size of the laser is 5 to 30 μm,
The spot overlap rate (%) of the laser is 15 to 85% based on one spot size,
The laser spot hatching gap (hatching gap) is a battery cell manufacturing method, characterized in that 15 to 85% based on one spot size. delete The method according to claim 1, wherein the laser has a wavelength range of 700 to 1200 nm. delete delete delete delete delete delete delete According to claim 1, wherein the thickness of the burr removed by the laser is a battery cell manufacturing method, characterized in that 0.1 to 40㎛. delete

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