JP2012086254A - Welding method, welding apparatus, method of manufacturing battery, and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method and welding apparatus that can suitably carry out welding of an electrode plate and a current collecting plate; to provide a method of manufacturing a battery; and to provide a battery.SOLUTION: When a positive electrode current collecting plate 110 is welded to a positive electrode plate P, a laser is used which has an irradiation center region Z and a high-intensity outer periphery region Y. The high-intensity outer periphery region is higher in laser intensity than the irradiation center region Z. The laser is scanned so that: an irradiation center region X is scanned at the center of a welding width direction; and the high-intensity outer periphery region Y is scanned on both sides of the center thereof. Thus, projecting portions X2 and X3 appear, each of which projects toward a laser irradiation direction in a cross section that is perpendicular to a laser scanning direction at a portion to be welded, in a cross-sectional shape of a portion to be affected by heat. Moreover a recessed portion X1 appears between the projecting portions X2 and X3.

Description

  The present invention relates to a welding method, a welding apparatus, a battery manufacturing method, and a battery. More specifically, the present invention relates to a welding method, a welding apparatus, a battery manufacturing method, and a battery that are characteristic of welding between an electrode plate (a positive electrode plate and a negative electrode plate) and a current collector plate.

  Batteries are used in various fields such as electronic devices such as mobile phones and personal computers, vehicles such as hybrid vehicles and electric vehicles. Such a battery includes a positive electrode plate, a negative electrode plate, and an electrolyte. Further, in order to insulate the positive electrode plate and the negative electrode plate, it is common to provide a separator between them. In many cases, a laminated electrode body in which positive plates and negative plates are alternately arranged and a separator is sandwiched between them is used. This is to improve the volume energy density.

  In such a laminated electrode body, the positive electrode current collector plate is bonded to the positive electrode plate, and the negative electrode current collector plate is bonded to the negative electrode plate. In order to perform a suitable current collection, it is preferable to perform this joining reliably. This is because if the joint at the joint location is insufficient, the electrical resistance at that location is high. If the junction itself is not made, these parts are of course not conducting. Therefore, no current flows at that point.

  Therefore, techniques for suitably joining the electrode plate and the current collector plate have been developed. For example, Patent Document 1 discloses a technique for laser welding an electrode plate and a current collector plate. As a result, it is possible to perform bonding without performing complicated processes such as processing and fixing of leads. Patent Document 2 discloses a technique of beam welding an electrode plate and a current collector plate in a vacuum. Thereby, it can be said that it can join without producing the influence by heat in other parts other than a joining location.

JP 2002-042769 A JP 2004-006407 A

  By the way, in Patent Document 1 and other laser welding, a Gaussian mode laser is usually used. In a Gaussian mode laser, the laser intensity is highest at the center of the laser irradiation area. Therefore, the place where heat is input from the center of the laser irradiation region is melted most (see FIG. 5 of Patent Document 1). For this reason, there is a possibility that the portion of heat input from the center of the laser irradiation region will be melted too much. If the amount of heat input is large, a large amount of heat is transmitted to the separator, and the separator is burnt.

  On the other hand, when beam welding is performed in vacuum as in Patent Document 2, it is necessary to perform welding in vacuum. In order to realize this vacuum state, many processes such as a decompression process and a decompression process are required. And it takes time to perform these steps. That is, the cycle time becomes long. Furthermore, it is necessary to provide equipment for creating a vacuum.

  The present invention has been made to solve the above-described problems of the prior art. That is, the subject is to provide a welding method, a welding apparatus, a battery manufacturing method, and a battery capable of suitably welding the electrode plate and the current collector plate.

  The welding method according to an aspect of the present invention, which has been made for the purpose of solving this problem, is a method of performing welding by irradiating a welding object with a laser. The laser has a high-intensity outer peripheral region having a laser intensity higher than the laser intensity at the center of the laser irradiation region at the outer peripheral portion of the laser irradiation region, and the laser scanning direction as viewed from the center of the laser irradiation region. A laser having a laser intensity lower than the laser intensity at the other outer peripheral part is used. In this welding method, the amount of heat input to the center of the laser irradiation region is suppressed. Therefore, there is no possibility that the welding depth becomes too deep at the center of the laser irradiation region. Further, since the laser of the high-intensity outer peripheral region is irradiated on both sides of the region where the center of the laser irradiation region is scanned, welding can be performed with a sufficient welding width.

  In the welding method described above, the current collector may be welded to the positive electrode plate or the negative electrode plate of the electrode body in which the positive electrode plate and the negative electrode plate are alternately arranged with a separator interposed therebetween. This is because welding of the electrode plate and the current collector can be performed while suppressing the occurrence of separator burn.

  In the welding method described above, it is more preferable to use a laser in which the width of the irradiation center region located between the high-strength outer peripheral region is within a range of 10 to 30% of the entire width of the laser irradiation region. This is because it is suitable for securing a sufficient welding width and performing welding in which the welding depth does not become too deep.

  Further, the battery manufacturing method according to another aspect of the present invention includes an electrode body preparation step in which a positive electrode plate and a negative electrode plate are alternately laminated with a separator interposed therebetween, A current collector welding process in which at least one of the positive electrode plate and the negative electrode plate is welded to the current collector to form a welded body, and the welded body is disposed inside the battery container and an electrolyte is injected into the battery container. A battery assembly process for sealing. In the current collector welding process, the laser has a high-intensity outer peripheral region having a laser intensity higher than the laser intensity at the center of the laser irradiation region at the outer peripheral portion of the laser irradiation region, and the laser irradiation region. A laser is used in which the laser intensity at the outer periphery before and after the laser scanning direction as viewed from the center is lower than the laser intensity at the other outer periphery. In such a battery manufacturing method, the amount of heat input to the center of the laser irradiation region is suppressed in the current collector welding process. Therefore, there is no possibility that the welding depth becomes too deep at the center of the laser irradiation region. Further, since the laser of the high-intensity outer peripheral region is irradiated on both sides of the region where the center of the laser irradiation region is scanned, welding can be performed with a sufficient welding width.

  In the battery manufacturing method described above, in the current collector welding process, it is preferable to use a laser that transmits a prism having a rectangular pyramid shape with a rectangular bottom surface. This is because a high-strength outer peripheral region can be formed in the outer peripheral portion of the laser irradiation region.

  In the battery manufacturing method described above, in the current collector welding step, a laser that transmits a triangular prism may be used. This is because a high-strength outer peripheral region can be formed in the outer peripheral portion of the laser irradiation region.

  In the battery manufacturing method described above, in the current collector welding step, the width of the irradiation center region located between the high-strength outer peripheral region is within a range of 10 to 30% of the entire width of the laser irradiation region. It is even better to use a laser. This is because it is suitable for securing a sufficient welding width and performing welding in which the welding depth does not become too deep.

  A battery according to still another aspect of the present invention includes a positive electrode plate and a negative electrode plate that are alternately disposed with a separator interposed therebetween, and at least one of the positive electrode plate and the negative electrode plate. A battery having a laser-welded current collector. And in the cross section perpendicular | vertical to the scanning direction of the laser in a welding location, the cross-sectional shape of a heat affected zone is the 1st convex part and 2nd convex part which protrude in the direction which irradiates a laser, and 1st convex part And a second concave portion that is recessed in a direction opposite to the direction of laser irradiation. In such a battery, the heat-affected zone at the weld does not reach the separator. Therefore, the occurrence of burnt separator is suppressed. And the welding width is sufficient.

  A welding apparatus according to still another aspect of the present invention includes a laser oscillator that oscillates a laser, an optical fiber that transmits the laser oscillated by the laser oscillator and includes a laser irradiation port, and a laser that is irradiated from the laser irradiation port. It has a collimating lens for collimating light and a prism for diffracting the laser that has been collimated by the collimating lens. The prism has a quadrangular pyramid shape with a rectangular bottom surface, and is arranged so that the laser is incident in a direction from the bottom surface toward the apex of the quadrangular pyramid shape. In such a welding apparatus, it is possible to irradiate a laser having a high-intensity outer peripheral region having a higher energy intensity than the center of the laser irradiation region. By using this laser, it is possible to secure a sufficient welding width and perform welding that is not too deep.

  ADVANTAGE OF THE INVENTION According to this invention, the welding method and welding apparatus which can perform welding with an electrode plate and a current collector plate suitably, the manufacturing method of a battery, and a battery are provided.

It is a partially broken perspective view for demonstrating the battery which concerns on embodiment. It is sectional drawing for demonstrating the structure of the welded body which welded the current collecting plate to the laminated electrode body of the battery which concerns on embodiment. It is a schematic block diagram for demonstrating the laser welding apparatus used for the manufacturing method of the battery which concerns on embodiment. It is a top view for demonstrating the prism of the laser welding apparatus used for the manufacturing method of the battery which concerns on embodiment. It is FIG. (1) which shows intensity distribution of the laser used for the manufacturing method of the battery which concerns on embodiment. It is FIG. (2) which shows intensity distribution of the laser used for the manufacturing method of the battery which concerns on embodiment. It is sectional drawing for demonstrating the scanning method of the laser in the manufacturing method of the battery which concerns on embodiment. It is a top view for demonstrating the scanning method of the laser in the manufacturing method of the battery which concerns on embodiment. It is sectional drawing (the 1) which shows the middle of the laser welding in the manufacturing method of the battery which concerns on embodiment. It is sectional drawing (the 2) which shows the middle of the laser welding in the manufacturing method of the battery which concerns on embodiment. It is sectional drawing which shows the welding location of the positive electrode current collecting plate and positive electrode plate of the battery which concerns on embodiment. It is a schematic diagram which shows a response | compatibility with the intensity distribution of the laser used for the manufacturing method of the battery which concerns on embodiment, and a welding location. It is a schematic diagram which shows a response | compatibility with the intensity distribution of the laser used for the manufacturing method of the conventional battery, and a welding location. It is a top view for demonstrating the prism of the laser welding apparatus used for the manufacturing method of another battery which concerns on embodiment. It is a figure (the 1) which shows the intensity distribution of the laser used for the manufacturing method of another battery which concerns on embodiment. It is FIG. (2) which shows intensity distribution of the laser used for the manufacturing method of another battery which concerns on embodiment. It is FIG. (3) which shows intensity distribution of the laser used for the manufacturing method of another battery which concerns on embodiment. It is a perspective view for demonstrating the prism of the laser welding apparatus used for the manufacturing method of another battery which concerns on embodiment.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. The present embodiment embodies the present invention regarding a nickel metal hydride battery and a method for manufacturing the same.

1. Battery A nickel metal hydride battery according to the present embodiment will be described. FIG. 1 is a partially broken perspective view of a battery cell 10 of the present embodiment. As shown in FIG. 1, the battery cell 10 includes a battery container 11, a sealing plate 12, a safety valve 13, and a laminated electrode body 100. The battery container 11 is a case in which the laminated electrode body 100 is inserted and the electrolytic solution is accommodated therein. The sealing plate 12 is for sealing the battery cell 10. The safety valve 13 is a valve that opens when the internal pressure of the battery cell 10 increases too much. As will be described later, the positive electrode current collector plate and the negative electrode current collector plate are joined to the laminated electrode body 100. These are in a position that cannot be seen from the broken portion in FIG.

  FIG. 2 is a cross-sectional view illustrating the welded body 200 extracted from the battery cell 10. Here, the welded body 200 is obtained by joining the positive electrode current collector plate 110 and the negative electrode current collector plate 120 to the laminated electrode body 100. As shown in FIG. 2, the laminated electrode body 100 includes a positive electrode plate P, a negative electrode plate N, and a separator S. The separator S is always laminated between the positive electrode plate P and the negative electrode plate N so as to be disposed therebetween. This is because the positive electrode plate P and the negative electrode plate N are insulated. In other words, the laminated electrode body 100 is an electrode body in which the positive plates P and the negative plates N are alternately arranged and the separator S is interposed between the positive plates P and the negative plates N. The direction indicated by the arrow F in FIG. 2 is the same as the direction indicated by the arrow A in FIG. 1, and is the stacking direction of these members.

  The positive electrode plate P is obtained by filling a part of the positive electrode substrate with a positive electrode active material. The positive electrode plate P includes a positive electrode filling part P1 and a positive electrode non-filling part P2. The positive electrode filling portion P1 is located between the separators S as shown in FIG. As shown in FIG. 2, the positive electrode unfilled portion P <b> 2 is in a position where it is not sandwiched between the separators S. The positive electrode filling part P1 is a positive electrode plate reaction part in which a positive electrode substrate is filled with a positive electrode active material. On the other hand, the positive electrode unfilled portion P2 is a positive plate non-reacting portion in which the positive electrode substrate is not filled with the positive electrode active material. The positive electrode plate reaction part is a part where an electrode reaction occurs on the surface thereof and a part that actually contributes to power generation. Here, the positive electrode substrate is, for example, foamed nickel. The positive electrode active material is, for example, nickel hydroxide. Note that the positive electrode active material does not appear in FIG. This is because the surface of the nickel foam is only slightly formed.

  The negative electrode plate N is obtained by filling a part of a negative electrode substrate with a negative electrode active material. The negative electrode plate N includes a negative electrode filling part N1 and a negative electrode non-filling part N2. The negative electrode filling portion N1 is located between the separators S as shown in FIG. The negative electrode non-filling portion N2 is in a position not sandwiched between the separators S as shown in FIG. The negative electrode filling part N1 is a negative electrode plate reaction part in which a negative electrode substrate is filled with a negative electrode active material. On the other hand, the negative electrode unfilled portion N2 is a negative electrode plate non-reactive portion where the negative electrode substrate is not filled with the negative electrode active material. The negative electrode plate reaction part is a part where an electrode reaction occurs on the surface and a part that actually contributes to power generation. Here, the negative electrode substrate is, for example, nickel punching metal. The negative electrode active material is, for example, a hydrogen storage alloy. Note that the negative electrode active material does not appear in FIG.

  Further, as shown in FIG. 2, the positive electrode filling portion P1 and the negative electrode filling portion N1 are stacked in contact with the separator S. A part of the positive electrode unfilled portion P <b> 2 protrudes to one side of the laminated electrode body 100. The tip end portion PX of the positive electrode unfilled portion P <b> 2 is joined to the positive electrode current collector plate 110. That is, the positive electrode substrate and the positive electrode current collector plate 110 are electrically connected. A part of the negative electrode non-filling portion N <b> 2 protrudes to the other side of the laminated electrode body 100. The protruding direction is opposite to the protruding direction of the positive electrode unfilled portion P2. The leading end NX of the negative electrode non-filling portion N2 is joined to the negative electrode current collector plate 120. That is, the negative electrode substrate and the negative electrode current collector plate 120 are electrically connected. Here, the thickness of each current collecting plate 110, 120 is about 0.4 to 1 mm. The thickness of the electrode plates P and N is about 50 to 200 μm.

  As shown in FIG. 2, bent portions 111 are formed at both ends of the positive electrode current collector plate 110. An end surface 111 a is formed on the bent portion 111. The end surface 111a is perpendicular to the electrode plates P and N. Similarly, bent portions 121 are formed at both ends of the negative electrode current collector plate 120.

2. The welding method of an electrode plate and a current collector plate The welding method of this form is demonstrated. This embodiment is characterized by the type of laser used for laser welding. Therefore, the laser welding apparatus and laser intensity distribution used in this embodiment will be described.

2-1. Configuration of Laser Welding Apparatus The configuration of the laser welding apparatus 1000 in this embodiment is shown in FIG. In FIG. 3, members to be welded such as the positive electrode current collector 110 are also drawn.

  As shown in FIG. 3, the laser welding apparatus 1000 includes a laser oscillator 1001, an optical fiber 1010, a collimator lens 1020, a prism 1030, and a condenser lens 1040. The laser oscillator 1001 is a device for oscillating a laser. The optical fiber 1010 is for transmitting a laser. The cross section of the inner wall is rectangular. Therefore, the cross-sectional shape of the laser irradiated from the optical fiber 1010 is a rectangular shape. At the tip of the optical fiber 1010 is an irradiation port 1011. The collimating lens 1020 is for making the laser diffused from the irradiation port 1011 of the optical fiber 1010 into parallel light. The prism 1030 is for changing the intensity distribution of the transmitted laser. The condensing lens 1040 is for condensing the laser slightly diffused by the prism 1030.

  FIG. 4 is a plan view for explaining the prism 1030 of the laser welding apparatus 1000. The prism 1030 has a quadrangular pyramid shape with the tip 1039 as a vertex. The prism 1030 is a pentahedron whose surface is covered with surfaces 1033, 1034, 1035, 1036 and a bottom surface. The bottom surface of the prism 1030 is a rectangle surrounded by the long side 1031 and the short side 1032.

  Next, the laser irradiated by the laser welding apparatus 1000 will be described (see FIG. 3). First, the laser oscillator 1001 oscillates a laser. The laser is transmitted by the optical fiber 1010. The laser is diffusely emitted from the irradiation port 1011 of the optical fiber 1010. The laser irradiated diffusely travels in parallel by passing through the collimating lens 1020. At this stage, the cross-sectional shape of the laser is rectangular, and its intensity is highest at the irradiation center. Subsequently, the parallel laser is diffracted by the prism 1030. At that time, the laser is incident in a direction from the bottom surface toward the apex of the square pyramid. At this stage, as will be described later, the laser intensity is maximized at locations other than the irradiation center. Then, the laser is condensed by a condenser lens 1040. The laser intensity distribution thus obtained will be described next.

2-2. Laser Intensity Distribution FIG. 5 shows the intensity distribution of the laser irradiated by the laser welding apparatus 1000. The directions indicated by arrows I and J in FIG. 5 are directions corresponding to the directions indicated by arrows I1 and J1 in FIG. That is, the direction of arrow I in FIG. 5 and the direction of arrow I1 in FIG. 4 are parallel. The direction of arrow J in FIG. 5 and the direction of arrow J1 in FIG. 4 are parallel.

  A line L indicates the laser irradiation center. The intensity distribution of the laser is not axially symmetric (rotationally symmetric) with respect to the line L as shown in FIG. However, the intensity distribution of the laser is symmetric with respect to the plane including the lines V and L. Further, it is symmetric with respect to a plane including the line W and the line L. Here, the line V is a line passing through the center O which is an intersection of the line L and the zero energy surface. The line W is a line that passes through the center O and is perpendicular to the line V.

  As is clear from FIG. 5, the laser used in this embodiment has a region whose intensity is higher than the intensity at the center of the irradiation region. When expressed by the laser intensity in FIG. 5, a dent appears near the center of the irradiation region. This dent is caused by the difference between the angle between the surfaces 1033 and 1035 and the bottom surface and the angle between the surfaces 1034 and 1036 and the bottom surface in the prism 1030 of FIG. The angle formed between the surfaces 1033 and 1035 and the bottom surface is larger than the angle formed between the surfaces 1034 and 1036 and the bottom surface. Because of this deviation, the point where the laser intensity is maximum can be shifted from the center of the laser irradiation area.

  When this laser is used for welding, the laser scanning direction is the direction of arrow J in FIG. Details will be described later.

  The left figure of FIG. 6 is a figure which shows the laser intensity in the plane containing the line L and the line V in FIG. A cross section parallel to the laser scanning direction (arrow J in FIG. 5) is shown. As shown in the left diagram of FIG. 6, in the energy distribution, the vicinity of the center (line L) of the laser irradiation region is flat. Here, R0 is the intensity of the laser on the line L. R1 and R2 are the laser intensities at the outer periphery of the laser. Changes in the laser intensity at the outer periphery of the laser are as shown in FIG. 5 and FIG. 6, but the laser intensities R1 and R2 were selected as representative points for explanation. The laser intensities R1 and R2 are almost the same value as the laser intensity R0. Or slightly weak. R1 and R2 are the laser intensities at locations on the outer periphery of the laser irradiation region and in the regions before and after the scanning direction.

  The right diagram in FIG. 6 is a diagram showing the laser intensity on a plane including the line L and the line W in FIG. A cross section perpendicular to the laser scanning direction (arrow J in FIG. 5) is shown. As shown in the right diagram of FIG. 6, in the energy distribution, the vicinity of the center (line L) of the laser irradiation region is concave, and convex shapes appear on both sides thereof. The laser intensities Q1 and Q2 are the maximum values of the laser intensity in the laser irradiation region. The laser intensities Q1 and Q2 are about 1.2 times the laser intensity R0.

  As shown in the right diagram of FIG. 6, there is a high-strength outer peripheral region Y at the outer peripheral portion of the laser irradiation region. Here, the high-intensity outer peripheral region Y is a region having a laser intensity value significantly higher than the laser intensity R0 at the laser irradiation center. The high-intensity outer peripheral region Y is an outer peripheral portion of the laser irradiation region, except for the front and rear of the irradiation center in the laser scanning direction. The high-intensity outer peripheral region Y is on both sides of the laser irradiation central region Z. The laser irradiation center region Z is about 10 to 30% of the entire width of the laser irradiation region. In this case, as will be described later, it is suitable for securing a sufficient welding width and performing welding in which the welding depth is not too deep.

2-3. Next, the laser welding method of this embodiment will be described. The laser welding method of this embodiment can be used both when the positive electrode current collector plate 110 and the positive electrode plate P are welded and when the negative electrode current collector plate 120 and the negative electrode plate N are welded. Therefore, as a representative of these, the case where the positive electrode current collector plate 110 and the positive electrode plate P are welded will be described.

  FIG. 7 is a diagram for explaining a welding method using the laser of this embodiment. When performing laser welding, the laminated electrode assembly 100 is pressurized in the left-right direction (arrow E) in FIG. The pressurizing jig 2000 is a jig for reducing the thickness of the laminated electrode body 100 in the laminating direction (the direction of arrow F in FIG. 2). This is because welding in such a manner can be accommodated in the battery container 11 and the volume energy density of the battery can be increased. Note that the pressure jig 2000 is only used in the welding process and does not remain in the battery cell 10.

  The bent portion 111 of the positive electrode current collector plate 110 is supported by the upper surface 2001 of the pressure jig 2000. The end surface 111 a faces the upper surface 2001 and is in contact with the pressing jig 2000. At this time, the tip portion PX of the positive electrode plate P is in contact with the positive electrode current collector plate 110.

  Subsequently, the laser is scanned in the direction of arrow B in FIG. 7 while irradiating the positive electrode current collector plate 110 with the laser. Here, the scanning speed of the laser is, for example, 65 mm / sec. Of course, other scanning speeds may be used. The direction of arrow B in FIG. 7 is parallel to the direction of arrow F shown in FIG. Thereby, the laser irradiation spot in the positive electrode current collector plate 110 is heated and melted.

  FIG. 8 is a plan view seen from the direction of arrow C in FIG. An arrow M in FIG. 8 indicates the scanning direction of the laser. A line M0 in FIG. 8 is a line indicating a region in which the portions of the laser intensities R0, R1, and R2 shown in the right diagram of FIG. 6 are scanned. A line M1 in FIG. 8 is a line that indicates a region in which the laser intensity Q1 portion of the laser intensity shown in the right diagram of FIG. 6 is scanned. A line M2 in FIG. 8 is a line indicating a region in which the laser intensity Q2 portion of the laser intensity shown in the right diagram of FIG. 6 is scanned.

  As shown in FIG. 8, the laser is scanned so that the laser intensities Q1 and Q2 having the maximum values pass through both sides of the center (line M0) in the welding width direction. For this reason, the high-strength outer peripheral region Y does not pass through the center (line M0) in the welding width direction. This is to suppress excessive heat input to the center (line M0) in the welding width direction, as will be described later.

  9 is a cross-sectional view showing a part of the GG cross section of FIG. 8 (corresponding to the HH cross section in FIG. 2). 9 is drawn with the negative electrode plate N omitted (the same applies to FIGS. 10 to 13). FIG. 9 shows a state immediately after heat input to the positive electrode current collector plate 110 by the laser is started. As shown in FIG. 9, the positive electrode current collector 110 is melted from a portion where the intensity of the irradiated laser is high. FIG. 9 shows a melted portion 112 where a part of the positive electrode current collector plate 110 is melted. The melted portion 112 is a portion melted by heat input from the high-strength outer peripheral region Y. On the other hand, at the initial stage shown in FIG. 9, the portion where heat is input by the laser irradiation center (line L) is not yet melted.

  Thereafter, heat input by the laser proceeds. FIG. 10 is a cross-sectional view showing a state in which more time has passed for the same cross section as in FIG. 9. The melted portion 113 in FIG. 10 exists over a wider area than the melted portion 112 in FIG. Even in this state, it is the portion where the laser intensity is high that melts to the deepest position in the melted portion 113. Here, a sufficiently wide region is melted in the weld width direction. In the vicinity of the center in the laser irradiation region, the melt is not so deep.

  When the heat input by the laser is finished, the temperature of the region irradiated with the laser begins to drop. The molten portion 113 is solidified again. FIG. 11 is a diagram showing a case where the melted portion 113 shown in FIG. 10 is solidified. As shown in FIG. 11, the heat affected zone X is formed from the positive electrode current collector plate 110 to a part of the front end portion PX of the positive electrode plate P. At this stage, the positive electrode current collector plate 110 and the positive electrode plate P are welded.

  Similarly, by welding the negative electrode current collector plate 120 and the negative electrode plate N, the welded body 200 shown in FIG. 2 is obtained.

3. Here, the cross-sectional shape of the welded part in the battery according to this embodiment will be described with reference to FIG. FIG. 11 is a cross-sectional view showing a part of a cross section perpendicular to the laser scanning direction at a welding location. Convex parts X2 and X3 appear in the cross section of the heat affected zone X shown in FIG. And the recessed part X1 appears between these convex parts X2 and X3. The convex part X2 and the convex part X3 protrude in the direction in which the laser is irradiated. The concave portion X1 is located between the convex portion X2 and the convex portion X3. And it is dented in the opposite direction to the direction of laser irradiation.

  In FIG. 11, the heat affected zone X does not reach the location of the separator S. Therefore, the separator S is not combusted. This is because the welding depth T is a depth that does not reach the location of the separator S. Here, the welding depth T means the distance from the surface 110a on the front side of the positive electrode current collector plate 110 to the top X2A of the convex portion X2 (or the top X3A of the convex portion X3) in the heat affected zone.

  The welding width D at this time is, for example, 0.5 mm. This welding width D is a sufficient width. That is, the welding strength between the positive electrode current collector plate 110 and the positive electrode plate P is sufficient. The welding width D is as shown in FIG. Here, the weld width D refers to the width of the heat affected zone X at the joint between the positive electrode plate P and the positive electrode current collector plate 110.

  FIG. 12 is a diagram showing the relationship between the intensity distribution of the laser and the cross section of the welded portion welded by the laser. As shown in FIG. 12, the places where heat is input by the high-intensity outer peripheral region Y of the laser are the locations of the convex portions X2 and X3 of the heat-affected zone X. And the location where heat is input by the laser irradiation center (line L) becomes the location of the recess X1 of the heat affected zone X. The line U1 in FIG. 12 is drawn virtually.

  The battery cell 10 of this embodiment has a welded body 200 that is suitably welded. In the welded body 200, the separator is hardly burned. Further, almost no through holes are formed in the positive electrode current collector plate 110 and the negative electrode current collector plate 120. Therefore, the battery cell 10 which can collect current suitably from the laminated electrode body 100 is realized. Insulation between the positive electrode plate P and the negative electrode plate N is maintained.

4). Comparison with Prior Art For comparison between the present embodiment and the prior art, a case where welding is performed using a Gaussian laser will be described. The upper diagram of FIG. 13 is a profile showing the intensity distribution of a Gaussian laser. The lower part of FIG. 13 is a cross-sectional view showing a case where laser welding is performed using a Gaussian laser. A Gaussian laser has the strongest energy intensity at the center of the irradiated area.

  When laser welding is performed using a Gaussian laser, the heat from the laser may reach the position of the separator S as shown in the lower diagram of FIG. Thereby, there exists a possibility that the separator S may burn. When the separator S burns, electrolyte permeation may not occur in the burning portion. Furthermore, the positive electrode plate P and the negative electrode plate N may not be insulated at the burning portion.

  Even when a Gaussian laser is used, of course, heat may not be transmitted to the separator S so much. However, since the intensity of the laser takes the maximum value at the center of the irradiation region, heat is more easily transmitted to the separator S than in the case where the laser of this embodiment is used. In order to suppress the combustion of the separator S, it is conceivable to reduce the intensity of the laser as a whole. In that case, however, the weld width may be insufficient. That is, the welding strength is not sufficient.

5. Battery Manufacturing Method The battery manufacturing method according to the present embodiment is characterized in that the above-described welding method is performed for welding the laminated electrode body 100 to the positive electrode current collector plate 110 and the negative electrode current collector plate 120. is there.

5-1. Electrode plate preparation process The positive electrode plate P is prepared by filling a positive electrode substrate with a positive electrode active material. Here, the portion of the positive electrode substrate filled with the positive electrode active material becomes the positive electrode filling portion P1. A portion of the positive electrode substrate that is not filled with the positive electrode active material is a positive electrode unfilled portion P2. The negative electrode plate N is prepared by applying a negative electrode active material to a negative electrode substrate. Here, the portion filled with the negative electrode active material in the negative electrode substrate becomes the negative electrode filling portion N1. A portion of the negative electrode substrate that is not filled with the negative electrode active material is a negative electrode non-filled portion N2.

5-2. Electrode body preparation process Then, the positive electrode plate P, the negative electrode plate N, and the separator S are laminated | stacked. At that time, the positive plates P and the negative plates N are alternately arranged. Then, the separator S is necessarily laminated between the positive electrode plate P and the negative electrode plate N. At that time, the positive electrode plate P is stacked so that the positive electrode unfilled portion P2 protrudes from one side and the negative electrode unfilled portion N2 of the negative electrode plate N protrudes to the opposite side. Thereby, the laminated electrode body 100 is created.

5-3. Current Collector Welding Step Next, the positive electrode current collector plate 110 and the negative electrode current collector plate 120 are welded to the laminated electrode body 100. FIG. 7 shows the laminated electrode body 100 and the positive electrode current collector plate 110 before welding. Here, the positive electrode current collector plate 110 is welded to the front end portion PX of the positive electrode unfilled portion P2 using the laser described above. Similarly, the negative electrode current collector plate 120 is welded to the tip portion NX of the negative electrode unfilled portion N2. The order of these joinings may be either.

5-4. Battery Assembly Step Subsequently, the laminated electrode body 100 is disposed inside the battery container 11. Then, an electrolytic solution is injected into the battery container 11. Thereby, the laminated electrode body 100 is immersed in the electrolytic solution. Subsequently, the sealing plate 12 is joined to the battery container 11. Thereby, the battery cell 10 of this embodiment is assembled. After this, various inspection processes may be performed. Through the above steps, the battery cell 10 of this embodiment is manufactured.

6). Modification 6-1. High-intensity outer peripheral region In this embodiment, as shown in FIG. 6, the laser intensities R1 and R2 at the outer periphery of the laser and before and after the laser scanning direction are set to be equal to or lower than the laser intensity R0 at the laser irradiation center. . However, the laser intensities R1 and R2 before and after the laser scanning direction may be larger than the laser intensity R0 at the laser irradiation center. However, the laser intensities R1 and R2 are smaller than the laser intensities Q1 and Q2. That is, it is only necessary to use a laser in which the laser intensity in the outer peripheral part before and after the laser scanning direction is lower than the laser intensity in the other outer peripheral part when viewed from the center of the laser irradiation region.

6-2. Prism Shape and Laser Intensity Distribution In this embodiment, the prism 1030 having a rectangular bottom surface shown in FIG. 4 is used. However, it is also possible to use a prism 1130 having a square bottom as shown in FIG. In this case, the profile of the energy intensity of the laser is as shown in FIG.

  The cross section of FIG. 15 is shown in FIG. FIG. 16 shows a high-strength outer peripheral region Y1 and a high-strength outer peripheral region Y2. Here, the high-strength outer peripheral region Y1 only needs to be sufficiently narrow. In the battery cell manufactured using this laser, the cross section shown in FIG. 11 has a concave portion that is slightly smaller than the concave portion X1. Even in this case, it is possible to perform welding in which the welding depth T is not excessively deep while ensuring the welding width D.

6-3. Twin Beam In this embodiment, a laser having the laser intensity profile shown in FIGS. 5 and 6 was used. However, the same effect can be obtained by using two lasers. FIG. 17 shows the laser profile in that case. In order to use the laser having the profile shown in FIG. 17, the prism 1230 having the shape shown in FIG. 18 may be used. The prism 1230 has a triangular prism shape. Here, an arrow I3 in FIG. 18 indicates a direction parallel to the arrow I1 in FIG. An arrow J3 in FIG. 18 indicates a direction parallel to the arrow J1 in FIG.

  Alternatively, if a twin beam is generated, two optical fibers may be used for laser irradiation. By adjusting the energy intensity of the laser, the necessary welding width can be obtained and the separator can be made difficult to burn.

7). Summary As described above in detail, the welding method according to the present embodiment, when welding the positive electrode current collector plate 110 to the tip portion PX of the positive electrode plate P, the laser at the irradiation center in the laser irradiation region. In this method, a laser having a high-intensity outer peripheral region Y that takes a laser intensity higher than the intensity R0 is used. And the high intensity | strength outer peripheral part area | region Y is made not to pass the center of a welding width direction. For this reason, there is almost no risk of burning the separator by this laser welding. In addition, unlike beam welding, there is no need to perform welding in a vacuum state. Therefore, there is no need for a vacuuming process. That is, the cycle time is short. The same applies to the case where the negative electrode current collector plate 120 is welded to the tip NX of the negative electrode plate N. This realizes a welding method and a battery manufacturing method that hardly cause the separator S to melt during laser welding.

  Further, in the battery according to this embodiment, the convex portions X2 and X3 appear in the cross section perpendicular to the welding direction in the heat-affected zone of the welded portion. The convex part X2 and the convex part X3 protrude in the direction in which the laser is irradiated. Two convex portions X2 and X3 that are convex toward the opposite side of the laser irradiation surface, and a concave portion X1 are formed between the convex portions X2 and X3. Therefore, the shape of the heat affected zone X is wide in the direction of the welding width D and shallow in the direction of the welding depth T. That is, the welded body 200 has a sufficient welding width D and the separator S is not burned. Therefore, the battery of this embodiment is less likely to cause an internal short circuit.

  Further, the welding apparatus of the present embodiment has a quadrangular pyramid prism 1030 having a rectangular bottom surface. Therefore, it is possible to oscillate a laser having a high-intensity outer peripheral region Y that takes a laser intensity higher than the intensity R0 of the laser at the irradiation center in the laser irradiation area.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, it is not limited to a nickel metal hydride battery. The present invention can also be applied to a lithium ion battery. Even in this case, it has a positive electrode plate having a positive electrode plate reaction part and a positive electrode plate non-reaction part, and a negative electrode plate having a negative electrode plate reaction part and a negative electrode plate non-reaction part. What is necessary is just to weld to an electric plate. In addition, it is applicable to any battery in which the tip PX of the positive electrode unfilled portion P2 is welded to the positive electrode current collector plate 110 or the tip NX of the negative electrode unfilled portion N2 is welded to the negative electrode current collector plate 120. Can do. Further, the electrode body is not limited to the stacked electrode body 100 stacked in a flat manner. For example, a wound wound electrode body may be used.

  Further, in this embodiment, the positive electrode current collector plate 110 and the tip portion PX of the positive electrode plate P are already in contact with each other during welding. However, there may be a slight gap between them. This is because welding can be performed.

DESCRIPTION OF SYMBOLS 10 ... Battery cell 100 ... Laminated electrode body 110 ... Positive electrode current collecting plate 111, 121 ... Bending part 120 ... Negative electrode current collecting plate 200 ... Welding body 1000 ... Laser welding apparatus 1001 ... Laser oscillator 1010 ... Optical fiber 1020 ... Collimating lens 1030, 1130 , 1230 ... prism 1040 ... condensing lens D ... welding width P ... positive electrode plate P1 ... positive electrode filling part P2 ... positive electrode unfilling part PX ... tip part N ... negative electrode plate N1 ... negative electrode filling part N2 ... negative electrode unfilling part NX ... tip Part S ... Separator X ... Heat-affected zone X1 ... Concave part X2, X3 ... Convex part X2A, X3A ... Top part Y, Y1, Y2 ... High-strength outer peripheral area Z ... Irradiation center area

Claims (9)

A welding method for performing welding by irradiating a welding object with a laser,
As a laser,
In the outer periphery of the laser irradiation region, there is a high-intensity outer peripheral region that is higher than the laser intensity at the center of the laser irradiation region,
A welding method characterized by using a laser whose laser intensity at the outer periphery before and after the laser scanning direction as viewed from the center of the laser irradiation region is lower than the laser intensity at the other outer periphery. The welding method according to claim 1,
A welding method comprising welding a current collector to the positive electrode plate or the negative electrode plate of an electrode body in which a positive electrode plate and a negative electrode plate are alternately arranged with a separator interposed therebetween. A welding method according to claim 1 or claim 2, wherein
The width of the irradiation center region located between the high-strength outer peripheral regions is
A welding method using a laser that is within a range of 10 to 30% of the entire width of a laser irradiation region. An electrode body preparation step in which a positive electrode plate and a negative electrode plate are alternately laminated with a separator interposed therebetween,
A current collector welding step of welding at least one of the positive electrode plate and the negative electrode plate of the electrode body to a current collector to form a welded body;
A battery assembling step of disposing the welded body inside a battery container and injecting an electrolyte into the battery container and sealing the battery,
In the current collector welding process,
As a laser,
In the outer periphery of the laser irradiation region, there is a high-intensity outer peripheral region that is higher than the laser intensity at the center of the laser irradiation region,
A method of manufacturing a battery, comprising using a laser whose laser intensity at the outer periphery before and after the laser scanning direction as viewed from the center of the laser irradiation region is lower than the laser intensity at the other outer periphery. A method of manufacturing a battery according to claim 4,
In the current collector welding process,
A method of manufacturing a battery, characterized by using a laser having a bottom surface of a rectangular pyramid prism. A method of manufacturing a battery according to claim 4,
In the current collector welding process,
A method for manufacturing a battery, comprising using a laser beam transmitted through a prism having a triangular prism shape. A method of manufacturing a battery according to any one of claims 4 to 6,
In the current collector welding process,
The width of the irradiation center region located between the high-strength outer peripheral regions is
A method for producing a battery, comprising using a laser that is within a range of 10 to 30% of a total width of a laser irradiation region. An electrode body in which a positive electrode plate and a negative electrode plate are alternately arranged with a separator interposed therebetween,
A battery having a current collector laser welded to at least one of the positive electrode plate and the negative electrode plate at a welding point;
In the cross section perpendicular to the laser scanning direction at the weld location,
The cross-sectional shape of the heat affected zone is
A first protrusion and a second protrusion protruding in the direction of irradiating the laser;
A battery having a shape in which a concave portion is formed between the first convex portion and the second convex portion and is recessed in a direction opposite to the direction of laser irradiation. A laser oscillator that oscillates a laser;
An optical fiber that transmits a laser oscillated by the laser oscillator and includes a laser irradiation port;
A collimating lens that collimates the laser emitted from the laser irradiation port;
A welding device having a prism that diffracts a laser beam made parallel by the collimating lens,
The prism is
A quadrangular pyramid shape with a rectangular bottom,
A welding apparatus, wherein the laser is arranged so as to be incident in a direction from the bottom surface toward the apex of the quadrangular pyramid shape.

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