KR20180072964A - Process for Preparing Battery Cell Comprising Ablation Step of Burr Using Fiber Pulse Type Laser - Google Patents

Abstract

The present invention provides a battery cell manufacturing method including a process of removing burr and contamination generated in a welding part in laser welding for combining a top cap to an upper end of an open side of a can body made of metal, wherein the removing process is performed by a fiber pulse type laser, and a battery cell manufactured thereby. Accordingly, the present invention can improve process efficiency.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a battery cell including a step of removing a burr by using a fiber pulsed laser,

The present invention relates to a method of manufacturing a battery cell including a process of removing a burr using a fiber pulsed laser.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing. Many researches have been conducted on lithium secondary batteries with high energy density and discharge voltage among such secondary batteries. .

The secondary battery is also attracting attention as an energy source for electric vehicles and hybrid electric vehicles, which are proposed to solve air pollution of existing gasoline vehicles and diesel vehicles using fossil fuels. Accordingly, the types of applications using secondary batteries are diversifying due to the advantages of secondary batteries, and it is expected that secondary batteries will be applied to more fields and products in the future.

The secondary battery is classified into a cylindrical battery and a prismatic battery in which the electrode assembly is housed in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch-shaped battery in which the electrode assembly is housed in a pouch-shaped case of an aluminum laminate sheet . Among them, a prismatic battery and a pouch-shaped battery which can be stacked with a high degree of integration and have a width smaller than a length have attracted particular attention.

Here, FIG. 1 is a schematic view for explaining a general structure of the prismatic battery cell and a brief manufacturing method thereof.

Referring to FIG. 1, the prismatic battery cell 10 generally comprises an electrode assembly 11, a cathode body 12 inserted therein, an insulating plate 14 disposed on the electrode assembly 11, Thereby preventing a short circuit between the electrode assembly 11 and the top cap 13 and bonding the top cap 13 to the top opening of the can main body 12 by welding (indicated by red). Although not shown in the drawing, when the welding is completed as described above, the electrolyte is injected through the electrolyte injection port formed in the top cap, and then the injection port is sealed.

However, in the case of sealing the can body and the top cap by welding in this manner, a burr is generated at the interface during welding of the laser or the like, and the thickness thereof is increased, so that contamination such as generation of foreign matter may occur, Because of such a phenomenon, appearance and dimension are poor, which is inadequate to the needs of the audience.

In order to solve the above problem, the defective battery cell is polished by manual operation. However, the defective battery cell has a problem such as a secondary appearance unevenness due to manual variation among the workers, There is a problem that the efficiency is very low because it must be performed manually.

Therefore, there is a high need for development of a technique capable of solving the problem of appearance caused by laser welding that can solve such a problem.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments, and have found that, in a method of manufacturing a battery cell, burrs generated at a welding portion during laser welding for joining a top cap to an open upper end of a can body made of metal ) And the contamination are finely removed by a fiber pulse type laser, the appearance of the welding surface becomes uniform, and the removal process can be performed by automation. It is confirmed that not only the deviation between the operations is small, but also the process efficiency is increased And completed the present invention.

Accordingly, the method of manufacturing a battery cell according to the present invention includes a step of removing burrs and contamination generated at a welded portion by etching during laser welding for joining a top cap to an open upper end of a can body made of metal And the removal process is performed by a fiber pulse type laser.

2. Description of the Related Art Generally, when a battery cell is manufactured using a metal can case, a can body for housing the electrode assembly and a top cap for sealing the can body by being electrically connected to the electrode terminals of the electrode assembly are welded, Cell.

At this time, for example, an Nd: YAG laser or a carbon dioxide (CO ₂ ) laser is used for the welding. However, such a welding portion after laser welding causes contamination such as a burr, which is a metal protruding foreign matter, caused by melting and solidification at welding, or soot generated by a high temperature, , There is a high level of dissatisfaction from users, and research has been continued to solve this problem.

Therefore, the inventors of the present application have conducted intensive researches on a large number of lasers under various conditions. As a result, when a fiber pulsed laser satisfying a specific condition for removing the burr and the like is used, The burrs and the like can be removed with a simpler method while minimizing the variation occurring in each battery cell.

Generally, the fiber laser is suitable for the present invention because it can perform a precise machining operation with a smaller output than a CO ₂ laser or the like. Here, the fiber laser is classified according to the oscillation method. Here, the oscillation method refers to a method of converting direct-current energy into alternating-current energy by amplifying an optical resonator and includes a continuous (CW) pulse type operation method. In the continuous operation mode, the laser light is continuously operated at a constant intensity, and the pulse operation mode generates laser light only instantaneously and periodically operates by the pulse width and repetition rate.

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

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

This is because the laser within the wavelength range minimizes the thermal damage of the work base material and facilitates the removal of burrs and the like. If the wavelength range is out of the above range but the wavelength range is too short, a more precise operation is possible. However, since the cost is high, the cost ratio is low and the caustic ratio is not good. If the wavelength range is out of the above range, It is not preferable because burrs and the like can remain without being removed.

At this time, the thickness of the bur that is generated during the welding to be removed by the fiber pulsed laser may be 5 to 40 탆, specifically 10 to 30 탆.

If the thickness is too thin, the surface can be irregular and the burr can not be completely removed due to the etching of the burr to be smaller than the burr size. If the thickness to be removed is too thick, Which is undesirable.

The condition of the fiber pulsed laser used for removing the burr in the above range can be set according to the detailed thickness of the burr to be removed.

Concretely, precise control of the laser spot size, spot overlap rate, pulse repetition rate, spot hatching gap, velocity, energy, output, pulse width, etc. is required for etching the burr to a desired extent.

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

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

If the spot size of the laser is too small beyond the above range, the energy density is excessively increased to cause an undesired etching, thereby damaging the battery cell base material. If the size is too large, It is not etched and rather melts are generated, irregular melts are fused to make the appearance worse, and it is very important to adjust to the spot size.

Even in the case of having the spot size within the above range, when the spot overlap ratio is within a certain range, preferable etching is possible, and the etching degree is influenced by the spot overlap ratio.

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

The spot overlap ratio means a degree of overlap between adjacent spots in the traveling direction of the laser.

If the spot overlap ratio is less than 15%, the surface etching hardly occurs. If the spot overlap ratio exceeds 85%, the degree of etching is too large and the base material may be damaged. It is not preferable.

On the other hand, the spot overlap rate is influenced by the speed during processing, the pulse repetition rate, and the like. By adjusting these factors, the spot overlap rate can be satisfactorily adjusted to the desired range to achieve the desired degree of etching.

Specifically, when the speed is increased, when the spot overlap rate is decreased and the pulse repetition rate is increased, the spot overlap rate is also increased. The spot overlap rate is also adjusted, that is, increased or decreased together to adjust the spot overlap rate .

Accordingly, the numerical ranges to which the above elements should be satisfied are not limited. However, a preferable range can be determined in consideration of the output of the actually used laser, the aspect ratio of the laser, 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. However, when the laser speed is too slow, the productivity is lowered compared with the case where the speed is increased on the basis of the same overlapping rate, If the pulse repetition rate is increased, the output is lowered. Therefore, the price of the laser for increasing the output is increased, which is not good in terms of the caustic ratio, and the pulse repetition rate is too high. It is difficult to precisely control the machining head of the laser, which is not preferable.

Further, 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 velocity satisfies a constant velocity, 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 degree of etching of the bur 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%, more specifically 30 to 70% based on one spot size, the same as the spot overlap rate.

The spot hatching gap means the distance between the center of the spot in the first direction and the center of the spot in the second direction at the point where the advancing direction of the laser changes.

If the spot hatching gap is less than 15%, the overlapped portion increases. Therefore, there is a problem that the etching thickness is increased and the metal can is affected, and the etching surface is also roughened. When the spot hatching gap is more than 85% , The etching is hardly caused due to no superposition, and a hatching gap appears on the surface due to irregular etching, which is not preferable.

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

If the value is less than 0.2 mJ, the removal of burrs or the like is not performed well, and if it exceeds 0.9 mJ, the etching thickness is increased to 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. The irradiation energy increases with the increase of the pulse width and with the increase of the output.

Therefore, the numerical ranges to which the above elements should be satisfied are not limited either. However, a preferable range can be determined in consideration of the output of the actually used laser, the caustic ratio, the etching degree, and the like.

Since the etching is not performed when the pulse width is not equal to or larger than the predetermined value at the same overlapping rate even if the output is increased at the output depending on the kind of the laser, Control is important.

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

If the pulse width is too small, the processing is performed only on a fine surface and laser irradiation must be performed a plurality of times. Therefore, the process efficiency is poor. When the pulse width is too large beyond the above range, And the thermal damage of the peripheral parts is high.

As described above, when the fiber pulsed laser satisfies the above conditions, burrs and fumes generated during laser welding for joining the top cap to the open upper end of the can body made of metal It is possible to uniformly make the appearance without damaging the base material while effectively removing it, and by performing the removal process with the laser by adjusting the conditions other than the individual operators, deviation in each battery cell can be reduced, Cell can be manufactured.

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

The specific configuration of the battery cell, for example, the configuration of the electrode assembly of the anode / separator / cathode structure and the electrolyte solution impregnated therein includes all the contents disclosed heretofore, and the description thereof will be omitted herein.

As described above, in the method of manufacturing a battery cell according to the present invention, a burr formed at a welded portion during laser welding for joining a top cap to an open upper end portion of a can body made of metal using a fiber pulsed laser, By removing the contamination, the outer appearance of the welding surface becomes uniform, and the removal process can be performed by automation. Since deviation between operations is small, the defect rate can be reduced and the process efficiency can be increased.

1 is a schematic view showing a conventional method of manufacturing a prismatic battery cell;

Hereinafter, the present invention will be described in further detail with reference to the following experimental examples. However, the following experimental examples are provided for illustrating the present invention, and the scope of the present invention is not limited thereto.

<Experimental Example 1>

In order to confirm the desirable spot overlap rate and energy condition, the etching level was measured by varying the spot overlap rate and the energy condition of the IPG 200W 2 mJ fiber pulse laser (beam diameter 30 μm) on the Al plate. Respectively.

Fixed condition Frequency 200 kHz, pulse width 120 ns, 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 the overlapping ratio are within the above range, the degree of etching can be performed to 40 탆 or less.

Specifically, when the energy value is less than 0.5 mJ and the overlap ratio falls to 30% or less, it is understood that the etching degree is lower. When the energy value is 0.9 mJ and the overlap ratio is 70% or more, , It is confirmed that the etching thickness is 45 탆, and it is not preferable that the energy and the superposition ratio simultaneously have the above range.

<Experimental Example 2>

In order to confirm the etching level according to the overlap ratio, the degree of etching was checked by changing the superposition ratio by controlling the processing speed and the pulse repetition rate of the IPG 200W 2 mJ fiber pulse laser (beam diameter 30 μm) Respectively.

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 Etch thickness - About 10 ㎛ About 15 ㎛ About 18 ㎛ About 20 ㎛ About 25 탆 About 30 탆 About 35 탆

Referring to Table 2, we can see the result of changing the overlap rate by adjusting laser speed and pulse repetition rate while fixing other conditions.

Specifically, as the overlap rate increases, the etch thickness also increases. Therefore, when the overlap ratio is further decreased to 10% or less, it is confirmed that the etching degree is also decreased and the etching is hardly occurred. As the overlap ratio is increased, the etching thickness is also increased. , It can be expected that the etching is performed to 40 탆 or more.

<Experimental Example 3>

To confirm the etching level according to the hatching gap, an IPG 20W fiber pulse laser (beam diameter 30 mu m) was fixed under the conditions of output 80%, pulse repetition rate 20 kHz, speed 500 mm / s and pulse width 200 ns, The degree of etching was confirmed, and it is shown in Table 3 below.

Hatching gap (%) 7 17 27 34 50 67 87 Etch thickness 50 탆
More than About 40 ㎛ About 30 탆 About 20 ㎛ About 15 ㎛ About 10 ㎛ -

Referring to Table 4, it can be seen that as the hatching gap increases, the etching degree decreases as the hatching gap increases. Therefore, if the hatching gap is too small, too much etching occurs. If the gap is too large,

Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims (12)

A method of manufacturing a battery cell, the method comprising: etching and removing burrs and contaminants generated at a welding site during laser welding for joining a top cap to an open upper end of a can body made of metal, Wherein the process is performed by a fiber pulse type laser. The method according to claim 1, wherein the welding portion is a width of 0.2 mm to 1.0 mm in a vertical direction with respect to a contact surface between the can body and the top cap. The method of claim 1, wherein the wavelength of the laser is 700 to 1200 nm. The method of claim 1, wherein the energy of the laser is 0.5 to 0.9 mJ. The method of claim 1, wherein the pulse width of the laser is 0.15 to 200 ns. The method of claim 1, wherein the pulse repetition rate of the laser is 20 to 400 kHz. The method of claim 1, wherein the speed of the laser is 500 to 10000 mm / sec. The method according to claim 1, wherein the laser has a spot size of 5 to 30 탆. The method according to claim 8, wherein the laser spot overlap ratio (%) is 15 to 85% based on one spot size. 9. The method of claim 8, wherein the spot hatching gap of the laser is 15 to 85% based on one spot size. The method for manufacturing a battery cell according to claim 1, wherein the thickness of the burr removed by the laser is 0.1 to 40 탆. 12. A battery cell characterized by removing burrs and contamination on a welding site by the method according to any one of claims 1 to 11.

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