JP2008084803A - Manufacturing method of gastight battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a gastight battery, in which an outer can made of an aluminum group metal can be sealed with a cover at a speed of 100 mm/s or higher by using a CW (continuous wave) type laser welding machine. <P>SOLUTION: In the manufacturing method of the sealed battery, in which an outer can made of an aluminum group metal is welded and sealed with a cover arranged at the opening of the outer can by irradiating a laser beam, the laser beam is of a CW type and the theoretical spot diameter of the beam is 0.1 mm or larger and 0.6 mm or smaller, and an output density is set to 5 kW/mm<SP>2</SP>or higher and 33 kW/mm<SP>2</SP>or lower. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a sealed battery welded using a continuous wave (CW) laser welding apparatus, and more particularly, an aluminum-based metal made at a high speed of 100 mm / s or more using a CW laser welding apparatus. The present invention relates to a method for manufacturing a sealed battery capable of sealing an outer can and a cover plate.

  With the rapid spread of portable electronic devices, the required specifications for the batteries used for them are becoming stricter year by year, and in particular, small and thin, high capacity, excellent cycle characteristics, and stable performance are required. Yes. In the field of secondary batteries, lithium non-aqueous electrolyte secondary batteries, which have a higher energy density than other batteries, are attracting attention, and the proportion of lithium non-aqueous electrolyte secondary batteries shows a significant increase in the secondary battery market. ing.

This lithium non-aqueous electrolyte secondary battery mainly uses a carbonaceous material such as graphite capable of occluding and releasing lithium ions as a negative electrode active material, and includes lithium-containing cobalt oxide (LiCoO ₂ ), lithium-containing manganese oxide (LiMnO _2, LiMn). Those using lithium-containing transition metal oxides such as ₂ O ₄ ) as the positive electrode active material are widely used as small, light and high capacity batteries.

  By the way, in a device in which this type of non-aqueous electrolyte secondary battery is used, the space for storing the battery is often a rectangular shape (flat box shape). Non-aqueous electrolyte secondary batteries are often used. An example of such a square sealed nonaqueous electrolyte secondary battery will be described with reference to the drawings.

  FIG. 5 is a perspective view showing a conventional rectangular non-aqueous electrolyte secondary battery produced by cutting in the vertical direction. This nonaqueous electrolyte secondary battery 10 accommodates a flat spiral electrode body 14 in which a positive electrode plate 11 and a negative electrode plate 12 are wound via a separator 13 inside a rectangular battery outer can 15, A rectangular battery outer can 15 is sealed with a cover plate 16.

  The flat spiral electrode body 14 is wound so that the positive electrode plate 11 is exposed at the outermost periphery, and the exposed outermost positive electrode plate 11 is a rectangular battery outer can 15 that also serves as a positive electrode terminal. It is in direct contact with and electrically connected to the inner surface. The negative electrode plate 12 is electrically connected via a current collector 19 to a negative electrode terminal 18 formed at the center of the lid plate 16 and attached via an insulator 17.

  Since the rectangular battery outer can 15 is electrically connected to the positive electrode plate 11, in order to prevent a short circuit between the negative electrode plate 12 and the rectangular battery outer can 15, the flat spiral electrode body 14. By inserting the insulating spacer 20 between the upper end of the battery and the lid plate 16, the negative electrode plate 12 and the rectangular battery outer can 15 are electrically insulated.

  In this rectangular nonaqueous electrolyte secondary battery, after the flat spiral electrode body 14 is inserted into the rectangular battery outer can 15, the cover plate 16 is laser welded to the opening of the rectangular battery outer can 15. Thereafter, a non-aqueous electrolyte is injected from the electrolyte injection hole 21 to seal the electrolyte injection hole 21. Such a rectangular sealed non-aqueous electrolyte secondary battery has an excellent effect that there is little wasted space during use, and battery performance and battery reliability are high.

  Here, the process of laser welding the lid plate of the sealed nonaqueous electrolyte secondary battery disclosed in Patent Document 1 to the opening of the rectangular battery outer can will be described with reference to FIG. In FIG. 6, the same components as those of the nonaqueous electrolyte secondary battery shown in FIG. The cover plate 16 of the sealed nonaqueous electrolyte secondary battery disclosed in the following Patent Document 1 has a substantially rectangular shape, and a negative electrode terminal 18 attached via an insulator 17 is provided at the center. In addition, an electrolyte injection hole 21 is provided at the peripheral edge. After this cover plate 16 is attached to the inner edge of the opening of the outer can 15, the laser beam oscillated in a pulsed manner is radiated intermittently while being sent in order in the circumferential direction to the joint between the cover plate 16 and the battery outer can 15. A weld bead array 22 is formed, and a weld bead array 23 on the laser beam irradiation start side and a weld bead array 24 on the irradiation end side are overlapped to form a lap 25, whereby irradiation of these wraps 25 for discrimination is performed. It can be used as a mark.

Japanese Patent Laying-Open No. 2003-31186 (Claims, paragraphs [0013] to [0018], FIGS. 1 to 3) JP-A-10-156565 (claims, paragraphs [0016] to [0017], [0038], FIG. 7) JP-A-10-230379 (claims, paragraphs [0016], [0026] to [0035])

  The laser welding employed in the invention disclosed in Patent Document 1 employs a method of welding with a pulsed laser that oscillates in a pulsed manner. At this time, a laser that oscillates in a pulse form sporadically forms a melted portion. Therefore, about 1/3 of the melt spot diameter obtained when one pulse of laser is irradiated to seal the welded portion is used as a pitch. Seam welding is performed by scanning. Therefore, a portion of about 2/3 of the melting spot diameter is melted and once solidified and then heated again to be melted, so that it is difficult to increase the welding speed.

  That is, the pulse repetition number of the welding pulsed laser is about 200 to 500 times per second at the maximum. In this case, even if the number of repetitions of the pulse is 500 times per second, if the melting spot diameter is 0.7 mm and the overlap is 70%, the welding speed is limited to 105 mm per second. Moreover, under the conditions used for laser welding of sealed batteries, the number of pulse repetitions is often limited to about 100 to 200 times per second due to the capability of the laser oscillator. Therefore, when welding is performed using a pulsed laser welding apparatus that oscillates in a pulsed manner, it is practically difficult to perform welding at a high speed of 100 mm or more per second.

  For example, when a cover plate having a thickness of 2 mm is fitted to an outer can made of aluminum alloy and having a thickness of 2 mm, and welding is performed by irradiating the fitting portion with a high energy laser pulse, the energy amount per pulse is about 20 J. is necessary. Since the output of the welded portion of a pulse laser device capable of fine welding to a small device such as a sealed battery is about 500 W, 500 (W = J / s) / 20 (J) = 25 (1 / S), laser irradiation can be performed about 25 times per second. In this case, if the pulse pitch is 0.28 mm, the welding speed is 25 (1 / s) × 0.28 (mm) = 7 (mm / s), and only a welding speed of about 7 mm per second can be obtained. .

  In order to increase the welding speed, it is conceivable to apply a welding method using a CW laser instead of a welding method using a pulsed laser. Recently, since a high-power CW type laser oscillator with an output of about 3 kW to about 5 kW has been put into practical use, a method of irradiating an iron-based plate material by scanning a beam with a CW laser at high speed and starting welding is being used. However, for aluminum-based metals, which have a higher thermal conductivity than iron-based metals, the heat applied to the welds spreads over a wide range, so that only the parts to be joined cannot be melted stably and welding with a CW laser is possible. Was difficult.

  In welding to seal the battery cover plate, the laser must be operated with a small radius of curvature along the corner of the battery, but the laser beam is scanned by moving the laser processing head or battery on the XY table. Then, it is difficult to scan the corner portion at a high speed, and the welding speed is lowered at a portion where the radius of curvature of the corner portion is small. As a result, the corner is heated by the laser for a longer time than the straight part, and excessive heat input causes excessive melting and defects.

On the other hand, in Patent Document 2, as shown in FIGS. 7A and 7B, even in the case of shallow penetration welding where the melting depth of the laser welding portion is relatively shallow, For the purpose of suppressing the occurrence of solidification cracking, the laser beam applied to the joint 58 between the box-shaped container body 52 having one end face opened and the lid 54 closing the opening of the container body 52 is used. In the method for manufacturing the battery container 51 including the step of welding the container body 52 and the lid body 54, the battery body 51 is bent in a substantially vertical direction with respect to the flat plate portion of the lid body 54, and at the peripheral portion of the opening of the container body 52. The plate thickness of the standing portion 56 to be abutted is t ₁ , the plate thickness of the peripheral portion of the opening of the container main body 52 is t ₂ , and the bent portion of the standing portion 56 with respect to the flat plate portion to the end surface of the standing portion 56. of length when the _{t 3,} 1.0mm> _t 1 + _2, t ₃ and ≧ t _{1 +} t standing portion 56 formed so as to satisfy the relation of _2, the laser beam irradiated to the joining portion 58 of the peripheral portion of the opening portion of the standing portion 56 and the container body 52 Battery container having a step of irradiating a laser beam so as to satisfy the relationship of t ₁ + t ₂ ≧ d ≧ (t ₁ + t ₂ ) / 2 where d is the length in the plate thickness direction of A manufacturing method is disclosed. 7A is a schematic configuration diagram showing a laser welding apparatus, and FIG. 7B is a longitudinal sectional view of a main part for explaining a laser welding portion of the battery container.

In Patent Document 2, a controller 62 is connected to the laser oscillator 60 of the pulse laser device 59, and the controller 62 adjusts the beam spot diameter d from the pulse laser device 59 to an arbitrary value. It is also shown that the method can be applied to the case of an aluminum alloy material and can be welded using not only the pulse laser device 59 but also a CW laser. However, in the method for manufacturing the battery container disclosed in the above cited document 2, the plate thickness t ₂ of the peripheral portion of the opening of the container body 52 and the lid, as is apparent from the relational expression of t _{1 to} t _3. standing total thickness of the thickness t ₁ of the portion 56 of 54 is required to be less than 1.0 mm, in such a thin container body and lid battery container made of high-strength aluminum-based metal In addition, the above-mentioned patent document 2 has no description that suggests how much the scanning speed of the laser beam should be.

  In Patent Document 3, the time when the laser output becomes 0 is 1.0 ms when laser welding is performed on the butt portion between the container body made of an aluminum alloy material containing 2.2 wt% or more of Mg and the lid. A method for manufacturing a container made of aluminum alloy to be laser welded is shown below, and it is also shown that a CW laser is used as the laser beam, but a description suggesting how much the scanning speed of the laser beam will be Absent.

  As described above, it has been known that welding is performed between an outer can made of an aluminum-based metal and a lid plate using a CW laser. However, it is possible to perform welding at a high speed using the CW laser. Nothing was known about the conditions for obtaining a good weld.

  The present invention has been made to solve the above-mentioned problems of the conventional example. The purpose of the present invention is to provide a straight line when welding between an aluminum-based outer can and a cover plate using a CW laser. It is an object of the present invention to provide a method for manufacturing a sealed battery in which not only a portion but also a curved portion can be welded at a high speed to improve a processing speed and to prevent welding failure.

In order to achieve the above object, a method for producing a sealed battery according to the present invention includes irradiating a laser beam to an aluminum metal outer can and an aluminum metal cover plate disposed in an opening of the outer can. In the method for manufacturing a sealed battery sealed by welding, the laser beam is CW type, the beam has a theoretical spot diameter of 0.1 mm to 0.6 mm, and an output density of 5 kW / mm ^{2 to} 33 kW / mm. It is characterized by being ² or less. The aluminum metal in the present invention includes not only a pure aluminum metal but also an aluminum alloy that is usually employed in a sealed battery.

  Further, the present invention is characterized in that, in the above sealed battery manufacturing method, the laser beam has a scanning speed of 100 mm / second or more, and is scanned using a scanning device.

  Further, the present invention is characterized in that, in the above-described sealed battery manufacturing method, a groove is provided at a position along the welded portion of the lid plate, and the lid plate is melted more than the outer can.

  Further, the present invention is characterized in that, in the above sealed battery manufacturing method, a CW type laser generator having an output of 1.2 kW or more is used as the laser beam generator.

  The present invention has the following excellent effects by adopting the above manufacturing method. That is, according to the present invention, a CW type laser beam can be used to weld an aluminum-based metal outer can and a lid plate disposed in the opening of the outer can at a high speed. Efficiency is improved.

  In addition, if the theoretical condensing diameter (spot diameter) of the laser beam is 0.6 mm or less, a smaller one is preferable because the necessary welding depth can be obtained within a short time in which heat does not spread to the surroundings. However, when the welding point shift occurs, the production ratio of defective welds increases, so it is preferably up to about ½ of the thickness of the outer can. Since the thickness of the outer can is generally in the range of 0.2 mm to 1 mm, the theoretical focused diameter of the laser beam is preferably 0.1 mm or more.

Furthermore, if the output density of the laser beam is 5 kW / mm ² or more, the aluminum-based metal outer can and the lid plate arranged at the opening of the outer can can be welded, but the output density is too high. Too much is not preferable because it is too soluble. When a cover plate with a thickness of 2 mm is fitted to an outer can made of aluminum alloy with a thickness of 0.4 mm and the fitting part is irradiated with a high energy laser pulse and welded, the output density is 5 kW / mm ^{2 to} 33 kW / mm. Although it was confirmed to be able to weld in a ^second range, in order to be welded to better vary the state of the welding surface is preferably 6.5 kW / mm ² or more 11kW / mm ² or less. The power density can be lowered by adjusting the irradiation optical system and shifting the focus.

  In addition, according to the present invention, laser beam scanning is used for welding between an aluminum-based metal outer can and a lid plate disposed at the opening of the outer can, which has conventionally been difficult to weld at high speed. By scanning using the apparatus, laser welding can be performed at a high scanning speed of 100 mm / s not only on the straight line portion but also on the curved portion or even the corner portion of the sealed battery.

  Further, according to the present invention, since the groove portion is provided at a position along the welded portion of the lid plate, the heat applied to the welded portion does not spread over a wide range, and the lid plate is melted more than the outer can. Therefore, the melted portion of the outer can does not sag outside, and a sealed battery with good dimensional accuracy can be manufactured.

Further, according to the present invention, if the CW laser has an output of about 1 kW, it can be welded at a scanning speed of 100 mm / s or more. However, in order to increase the output density of the CW laser to 5 kW / mm ² or more, output 1. 2 kW or more is desirable. The output of the laser device should be large, but if it is too large, it will be too expensive, so it may be selected as appropriate in consideration of economy.

  Hereinafter, the best mode for carrying out the present invention will be described in detail by various experimental examples, taking as an example the case of welding a square sealed battery using a CW type laser beam. However, the following experimental examples are given for the purpose of understanding the technical idea of the present invention, and are not intended to specify the present invention as the experimental examples. The present invention can equally be applied to those in which various modifications are made without departing from the technical idea shown in.

[Preliminary experiment 1]
As a preliminary experiment 1, a cover plate having a thickness of 2 mm was fitted into an outer can made of aluminum alloy and having a thickness of 0.4 mm, and a CW type laser welding apparatus having an output of 1.6 kW was used. A sample for measurement was prepared by condensing to 4 mm and performing a simulation analysis when the condensing point was scanned with a scanner at a speed of 120 mm per second and actually welding under the same conditions. The result is shown in FIG. 1A shows a simulation result showing the melting range of the longitudinal section in the vicinity of the welding point in the preliminary experiment 1, and FIG. 1B is a longitudinal sectional view of the sample after welding. The CW laser scan uses a combination of a commercially available CW laser oscillator and a laser scan head, and scans the CW laser at a predetermined speed by controlling the rotation of the mirror of the scan head by PC control. is there).

  The following can be understood from the result shown in FIG. That is, the outer direction of the outer can is not connected to metal but is air. However, since the thermal conductivity of air is low, the amount of heat on the outer can generated by the irradiated laser is less likely to escape to the outside due to thermal conduction, so the melted portion spreads outward to some extent. On the other hand, metal is connected to the lid plate side, and the heat conductivity of this metal is very good, so the heat generated on the lid plate side by the irradiated laser is rapidly conducted inside the lid plate. As a result, the temperature tends to decrease and the melted portion in the lateral direction of the cover plate does not spread. In addition, the welding depth at this time is 0.24 mm, and the cross-sectional shape of the welded portion has a large amount of melting on the outer can side, as shown in FIG. It was lower than.

[Preliminary experiment 2]
The welded part shown in FIG. 1 (b) had a good result, but even if the laser was irradiated between the outer can and the lid plate, it melted on the outer can side and the lid plate side. Since there is a difference, even if the laser irradiation position is slightly shifted outward, the lid plate is not easily joined to the outer can, or the outer can can be melted too much and the welded portion is likely to be bent outward. In addition, since heat is rapidly transmitted to the inside of the lid plate, the resin component provided on the terminal portion of the lid plate is easily exposed to high temperatures, so that the resin component is liable to be defective due to thermal effects.

  Therefore, as preliminary experiment 2, as shown in FIG. 2, a groove is provided in the vicinity of the welded portion of the cover plate, and the simulation analysis and actual welding are performed under the same conditions when the heat conduction in the lateral direction of the cover plate is reduced. Thus, a measurement sample was prepared. The groove is provided in a size of 0.25 mm deep and 0.5 mm wide inside 0.4 mm from the end of the cover plate. FIG. 2 shows a plan view of the sealed battery in the case where a groove is provided in the lid, and FIG. 3A shows a simulation result showing a melting range of a longitudinal section in the vicinity of the welding point. A surface view is shown in FIG.

  According to the simulation result shown in FIG. 3A, it can be seen that the amount of heat on the inside of the lid body is reduced by providing the groove portion, so that the melting amount on the lid side is increased. Thus, by providing the groove portion, the lid can be more easily melted than the outer can. The actual shape of the welded portion was substantially the same on both the outer can side and the lid side as shown in FIG.

[Experimental Examples 1 to 22]
Next, using the same outer can and lid as in the preliminary experiment 1, the theoretical condensing diameter of the CW laser is changed in the range of 0.28 mm to 0.6 mm, and the output density is 3.53 kW / mm ^2. Welding was performed by changing the speed in the range of ˜32.48 kW / mm ² and further changing the scanning speed of the CW laser in the range of 133 mm / s to 250 mm / s. The measurement conditions and measurement results of Experimental Examples 1 to 22 are collectively shown in Table 1, and the relationship between the output density and the scanning speed is shown in FIG. 4 together with the measurement results.

The measurement result is
○: Welded well even if the welding surface was not good ●: Somewhere the power density was too strong and partly melted (○): Good welding when defocused on ● △: Good welding if the welding surface is good ▲: If the power density is weak and the welding surface is good, welding was possible. ×: We could not weld. evaluated. The “weld surface state” means the state of the joint surface between the outer can and the lid, and since the precision processing is not performed on the joint surface in the actual manufacturing process, there is a slight gap. May be possible. A material having a small gap was expressed as a good welded surface.

From the results shown in Table 1 and FIG. 4, at least when the theoretical condensing diameter of the CW laser is 0.6 mm or less, if the output density is 5 kW / mm ² or more and 33 kW / mm ² or less, the scanning is 133 mm / s or more. It was confirmed that welding was possible at a speed. However, the range of the power density that can be favorably welded even if the state of the welding surface varies is considered to be 6.5 kW / mm ^{2 to} 11 kW / mm ² . In view of the results of Preliminary Experiment 2 and Experimental Example, by providing a groove in the lid, the range of power density that can be favorably welded is widened, and in accordance with the range that can be favorably welded without a groove, It is clear that the welding state is further stabilized.

In addition, if the theoretical condensing diameter is reduced, the CW laser can be welded at a scanning speed of 100 mm / s or more if the output is about 1 kW. However, as is clear from the results of Experimental Example 15, when the theoretical light collection diameter is about 0.6 mm, the output density is small, resulting in poor welding. Even when the theoretical focused diameter is about 0.6 mm, an output of 1.2 kW or more is desirable in order to make the output density of the CW laser 5 kW / mm ² or more.

  Here, an aluminum can made of aluminum alloy having a thickness of 0.4 mm and a lid plate having the same thickness made of aluminum alloy having a thickness of 2 mm are used, and the groove portion has a depth of 0 mm inside 0.4 mm from the end of the lid plate. Although the measurement results for those provided with a size of .25 mm and a width of 0.5 mm are shown, the thickness of the outer can is 0.2 mm to 1 mm, the thickness of the cover plate is 0.8 mm to 2 mm, and the depth of the groove portion. The length may be 0.2 mm to 0.5 mm, the width of the groove is 0.3 to 1 mm, and the distance from the end of the cover plate to the groove may be 0.3 to 0.6 mm. CW welding can be performed at a scanning speed of / s or more.

FIG. 1A shows a simulation result showing a melting range of a longitudinal section in the vicinity of a welding point in the preliminary experiment 1, and FIG. 1B is a longitudinal sectional view of a sample after welding. It is a top view of a closed type battery at the time of providing a slot in a lid. FIG. 3A shows a simulation result showing the melting range of the longitudinal section in the vicinity of the welding point in the preliminary experiment 2, and FIG. 3B is a longitudinal sectional view of the sample after welding. It is the graph which showed the relationship between a power density and a scanning speed with the measurement result. It is a perspective view which cut | disconnects the square sealed nonaqueous electrolyte secondary battery of a prior art example in the vertical direction. It is a figure which shows the process of laser welding the lid plate of a prior art example to the opening part of a square battery exterior can. FIG. 7A is a schematic configuration diagram showing a conventional laser welding apparatus, and FIG. 7B is a longitudinal sectional view of a main part for explaining a laser welding portion of the battery container.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery 11 Positive electrode plate 12 Negative electrode plate 13 Separator 14 Spiral electrode body 15 Outer can 16 Cover plate 18 Negative electrode terminal 21 Electrolyte injection hole 22 Weld bead row

Claims (4)

In the manufacturing method of a sealed battery in which an aluminum-based metal outer can and an aluminum-based metal lid plate disposed in an opening of the outer can are sealed by irradiation with a laser beam, the laser beam Is a continuous oscillation type beam beam having a theoretical spot diameter of 0.1 mm to 0.6 mm and an output density of 5 kW / mm ^{2 to} 33 kW / mm ² .   The method for manufacturing a sealed battery according to claim 1, wherein the laser beam has a scanning speed of 100 mm / second or more and is scanned using a scanning device.   The method for manufacturing a sealed battery according to claim 1, wherein a groove is provided at a position along the welded portion of the lid plate, and the lid plate is melted more than the outer can.   The method for manufacturing a sealed battery according to any one of claims 1 to 3, wherein a continuous wave laser generator with an output of 1.2 kW or more is used as the laser beam generator.

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