JP6780372B2 - Electrode welding equipment - Google Patents

Description

The present invention relates to an electrode welding apparatus.

As a conventional electrode welding apparatus, for example, the technique described in Patent Document 1 is known. The electrode welding apparatus described in Patent Document 1 is a battery case for accommodating a lead led out from one of the electrode groups of an electrode group in which a positive electrode plate and a negative electrode plate are wound via a separator. The lead is laser welded to the sealing plate by irradiating the lead side with a laser in a state where the opening is brought into contact with the sealing plate to be sealed.

Special re-publication 2010-16182

By the way, when welding is performed by irradiating a laser, the temperature distribution of the work (working target) is the highest at the laser-irradiated portion, and the temperature decreases as the distance from the irradiated portion increases. On the other hand, when continuously irradiating while scanning the laser, especially when the work is small or the welded part has a shape in which heat does not easily escape, the temperature tends to rise, and the laser irradiation accompanies it. As a result, the temperature of the entire workpiece or the entire weld along the welding line gradually rises. That is, when the laser is scanned from the start end of the welding to the end of the welding, the temperature of not only the portion adjacent to the irradiation position of the energy beam but also the portion away from the irradiation position gradually rises. Therefore, even if the laser output is constant, the temperature rises in the latter half of welding, particularly near the end of welding, as compared with the beginning of welding, and spatter is likely to occur.

An object of the present invention is to provide an electrode welding apparatus capable of suppressing the occurrence of sputtering.

One aspect of the present invention is an electrode welding apparatus that welds tabs of a plurality of electrodes in a laminated state, wherein a laser irradiation unit that irradiates a tab laminate in which the tabs of a plurality of electrodes are laminated with a laser for laser welding. It is characterized by including a cooling gas injection unit that injects cooling gas toward the laser irradiation end position of the laser irradiation unit.

In such an electrode welding apparatus, a welded portion is formed on the tab laminate by irradiating the tab laminate in which the tabs of a plurality of electrodes are laminated with a laser for laser welding. At this time, in the vicinity of the laser irradiation end of the tab laminate, the temperature of the tab laminate rises before the laser reaches the irradiation end, so that the temperature tends to rise more than necessary due to the laser irradiation, and spatter occurs. It will be easier to do. Therefore, by injecting the cooling gas toward the irradiation end position before the laser reaches the irradiation end position, it is possible to suppress the temperature rise in the vicinity of the laser irradiation end in the tab laminate. As a result, the occurrence of spatter can be suppressed.

The cooling gas injection unit may inject cooling gas toward the irradiation end position so as to avoid the laser irradiation start end position by the laser irradiation unit. Since the temperature does not easily rise near the start of laser irradiation in the tab laminate, the amount of laser penetration is small. Therefore, by injecting the cooling gas toward the laser irradiation end position so as to avoid the laser irradiation start position, the cooling gas is not given to the laser irradiation start position. Therefore, since the temperature drop in the vicinity of the laser irradiation start end in the tab laminate is suppressed, it is possible to prevent the amount of laser penetration in the tab laminate in the vicinity of the laser irradiation start end from being reduced more than necessary.

The electrode welding apparatus may further include an assist gas injection unit that injects the assist gas to the laser irradiation portion by the laser irradiation unit. In this case, since the assist gas prevents oxidation of the laser irradiation portion in the tab laminate, it is possible to prevent a decrease in the welding strength between the tabs of each electrode.

The cooling gas and the assist gas may be the same gas. In this case, it is not necessary to prepare a plurality of types of gas, which is advantageous in terms of cost.

The electrode welding device further includes a control unit that controls the cooling gas injection unit and the assist gas injection unit so that the injection amount of the cooling gas by the cooling gas injection unit is larger than the injection amount of the assist gas by the assist gas injection unit. You may. In this case, since the temperature rise near the end of laser irradiation in the tab laminate is sufficiently suppressed, the occurrence of sputtering can be further suppressed.

According to the present invention, the occurrence of sputtering can be suppressed.

It is sectional drawing which shows the internal structure of the power storage device manufactured by using the electrode welding apparatus which concerns on one Embodiment of this invention. FIG. 2 is a sectional view taken along line II-II of FIG. It is a perspective view of the electrode assembly shown in FIG. It is a schematic plan view which shows the electrode welding apparatus which concerns on one Embodiment of this invention. It is a front view which shows the state of irradiating the tab laminate with a laser by a laser irradiator. It is a side view which shows the mode that the assist gas is injected to the laser irradiation portion by the assist gas injection nozzle, and the cooling gas is injected toward the laser irradiation end position by the cooling gas injection nozzle.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing an internal configuration of a power storage device manufactured by using the electrode welding device according to the embodiment of the present invention. FIG. 2 is a sectional view taken along line II-II of FIG. In FIGS. 1 and 2, the power storage device 1 is a lithium ion secondary battery having a laminated electrode assembly.

The power storage device 1 includes, for example, a case 2 having a substantially rectangular parallelepiped shape, and an electrode assembly 3 housed in the case 2. The case 2 is made of a metal such as aluminum. Although not shown, a non-aqueous (organic solvent-based) electrolytic solution is injected into the case 2. The positive electrode terminal 4 and the negative electrode terminal 5 are arranged on the case 2 so as to be separated from each other. The positive electrode terminal 4 is fixed to the case 2 via the insulating ring 6, and the negative electrode terminal 5 is fixed to the case 2 via the insulating ring 7. Although not shown, the side surfaces and the bottom surface of the electrode assembly 3 are covered with an insulating film, and the case 2 and the electrode assembly 3 are insulated by the insulating film. In FIG. 1, for convenience, a slight gap is provided between the bottom surface of the electrode assembly 3 and the inner bottom surface of the case 2, but in reality, the bottom surface of the electrode assembly 3 is formed through the insulating film of the case 2. It is in contact with the inner bottom surface. By arranging the spacer between the electrode assembly 3 and the case 2, a gap may be formed between the electrode assembly 3 and the case 2.

The electrode assembly 3 has a structure in which a plurality of positive electrodes 8 and a plurality of negative electrodes 9 are alternately laminated via a bag-shaped separator 10. The positive electrode 8 and the negative electrode 9 are electrodes. The positive electrode 8 is wrapped in a bag-shaped separator 10. The positive electrode 8 in a state of being wrapped in the bag-shaped separator 10 is configured as a positive electrode 11 with a separator. Therefore, the electrode assembly 3 has a structure in which a plurality of positive electrodes 11 with separators and a plurality of negative electrodes 9 are alternately laminated. The electrodes located at both ends of the electrode assembly 3 are negative electrodes 9.

The positive electrode 8 has, for example, a metal foil 14 made of an aluminum foil and a positive electrode active material layer 15 formed on both sides of the metal foil 14. The metal foil 14 has a foil main body portion 14a having a rectangular shape in a plan view and a tab 14b integrated with the foil main body portion 14a. The tab 14b projects from the edge of the foil body 14a near one end in the longitudinal direction. The tab 14b penetrates the separator 10. The tab 14b is connected to the positive electrode terminal 4 via the conductive member 12. In FIG. 2, tab 14b is omitted for convenience.

The positive electrode active material layer 15 is formed on the foil main body portion 14a. The positive electrode active material layer 15 is a porous layer formed by containing the positive electrode active material and the binder. Examples of the positive electrode active material include composite oxides, metallic lithium, sulfur and the like. Composite oxides include, for example, at least one of manganese, nickel, cobalt and aluminum and lithium.

The negative electrode 9 has, for example, a metal foil 16 made of copper foil and negative electrode active material layers 17 formed on both sides of the metal foil 16. The metal foil 16 has a foil main body portion 16a having a rectangular shape in a plan view and a tab 16b integrated with the foil main body portion 16a. The tab 16b projects from the edge of the foil body 16a near one end in the longitudinal direction. The tab 16b is connected to the negative electrode terminal 5 via the conductive member 13. Note that in FIG. 2, tab 16b is omitted for convenience.

The negative electrode active material layer 17 is formed on the foil body 16a. The negative electrode active material layer 17 is a porous layer formed by containing the negative electrode active material and the binder. Examples of the negative electrode active material include graphite, highly oriented graphite, mesocarbon microbeads, carbon such as hard carbon and soft carbon, alkali metals such as lithium and sodium, metal compounds, and SiOx (0.5 ≦ x ≦ 1.5). ) And other metal oxides or boron-added carbon and the like.

The separator 10 has a rectangular shape in a plan view. Examples of the material for forming the separator 10 include a porous film made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP), and a woven cloth or non-woven fabric made of polypropylene, polyethylene terephthalate (PET), methyl cellulose and the like. ..

FIG. 3 is a perspective view of the electrode assembly 3. In FIG. 3, the electrode assembly 3 is a tab stacking in which a plurality of positive electrodes 8 and a plurality of negative electrodes 9 are alternately laminated via a separator 10 and a tab 14b of the plurality of positive electrodes 8 is laminated. It has a body 21 and a tab laminated body 22 in which tabs 16b of a plurality of negative electrodes 9 are laminated.

The tab laminates 21 and 22 project from one side surface of the assembly main body 20 in the X-axis direction. The X-axis direction is a direction perpendicular to the longitudinal direction (Y-axis direction) of the assembly main body 20 and the stacking direction (Z-axis direction) of the positive electrode 8 and the negative electrode 9. The tab laminates 21 and 22 are arranged apart from each other in the Y-axis direction. The tab laminates 21 and 22 are pressurized by a pressurizing unit (not shown). As a result, the tabs 14b of the tab laminate 21 are in contact with each other, and the tabs 16b of the tab laminate 22 are in contact with each other.

The tab laminate 21 has two side surfaces 21a, a tip surface 21b and an upper surface 21c. The front end surface 21b and the upper surface 21c connect the side surfaces 21a. The tab 14b is not provided with the positive electrode active material layer 15. Further, the number of tabs 14b constituting the tab laminate 21 is about half the number of electrodes constituting the electrode assembly 3. Therefore, the tip surface 21b of the tab laminate 21 formed by laminating the tabs 14b according to the height of one side surface of the assembly main body 20 becomes thinner toward the tip of the tab laminate 21. It is an inclined surface like this. The tab laminate 21 is placed on the conductive member 12. A protective plate 23 is placed on the upper surface 21c of the tab laminate 21. Therefore, the tab laminate 21 is sandwiched by the conductive member 12 and the protective plate 23 in the Z-axis direction.

The thickness of the conductive member 12 is larger than the thickness of the tab 14b. The thickness of the protective plate 23 is larger than the thickness of the tab 14b, but smaller than the thickness of the conductive member 12. The length of the conductive member 12 in the Y-axis direction is larger than the length of the tab laminate 21 in the Y-axis direction. The tip position of the tab laminate 21 coincides with the edge of the conductive member 12. The length of the protective plate 23 in the Y-axis direction is equal to the length of the tab laminate 21 in the Y-axis direction. The materials of the conductive member 12 and the protective plate 23 are the same as those of the metal foil 14.

On both side surfaces 21a of the tab laminate 21, a welded portion 24 in which each tab 14b of the tab laminate 21 is welded is provided. The welded portion 24 extends from the protective plate 23 to the conductive member 12. The welded portion 24 is formed by laser welding.

The tab laminate 22 has two side surfaces 22a, a tip surface 22b and an upper surface 22c. The front end surface 22b and the upper surface 22c connect the side surfaces 22a. The tab 16b is not provided with the negative electrode active material layer 17. Further, the number of tabs 16b constituting the tab laminate 22 is about half the number of electrodes constituting the electrode assembly 3. Therefore, the tip surface 22b of the tab laminate 22 formed by laminating the tabs 16b according to the height of one side surface of the assembly main body 20 becomes thinner toward the tip of the tab laminate 22. It is an inclined surface like this. The tab laminate 22 is placed on the conductive member 13. A protective plate 25 is placed on the upper surface 22c of the tab laminate 22. Therefore, the tab laminate 22 is sandwiched in the Z-axis direction by the conductive member 13 and the protective plate 25.

The thickness of the conductive member 13 is larger than the thickness of the tab 16b. The thickness of the protective plate 25 is larger than the thickness of the tab 16b, but smaller than the thickness of the conductive member 13. The length of the conductive member 13 in the Y-axis direction is larger than the length of the tab laminate 22 in the Y-axis direction. The tip position of the tab laminate 22 coincides with the edge of the conductive member 13. The length of the protective plate 25 in the Y-axis direction is equal to the length of the tab laminate 22 in the Y-axis direction. The materials of the conductive member 13 and the protective plate 25 are the same as those of the metal foil 16.

On both side surfaces 22a of the tab laminate 22, a welded portion 26 in which the tabs 16b of the tab laminate 22 are welded to each other is provided. The welded portion 26 extends from the protective plate 25 to the conductive member 13. The welded portion 26 is formed by laser welding.

FIG. 4 is a schematic plan view showing an electrode welding apparatus according to an embodiment of the present invention. In FIG. 4, the electrode welding apparatus 30 of the present embodiment welds the tabs 14b of the plurality of positive electrodes 8 in the laminated state to each other and the tabs 16b of the plurality of negative electrodes 9 in the laminated state. Although FIGS. 4 to 6 show only the configuration in which the tabs 14b of the plurality of positive electrodes 8 are welded to each other, the same applies to the configuration in which the tabs 17b of the plurality of negative electrodes 9 are welded to each other.

The electrode welding device 30 includes four laser irradiators 31 (laser irradiating unit), four assist gas injection nozzles 32 (assist gas injection unit), four cooling gas injection nozzles 33 (cooling gas injection unit), and a controller. It is equipped with 34 (control unit). In FIG. 4, the laser irradiator 31, the assist gas injection nozzle 32, and the cooling gas injection nozzle 33 are shown two by two. The laser irradiator 31, the assist gas injection nozzle 32, and the cooling gas injection nozzle 33 may be movable, for example, movable in the three-axis direction (XYZ-axis direction), or may be a fixed type attached to some component. You may.

The laser irradiator 31 irradiates the side surfaces 21a and 22a of the tab laminates 21 and 22 with the laser L for laser welding, respectively. As a result, welded portions 24 and 26 are formed on the side surfaces 21a and 22a of the tab laminates 21 and 22, respectively. As shown in FIG. 5, the laser irradiator 31 irradiates the laser L from above the tab laminates 21 and 22 toward the side surfaces 21a and 22a of the tab laminates 21 and 22, respectively. The irradiation direction of the laser L from the laser irradiator 31 is inclined at a predetermined angle with respect to the side surfaces 21a and 22a of the tab laminates 21 and 22.

As shown in FIG. 6, the laser irradiator 31 scans the laser L on the side surfaces 21a and 22a of the tab stacks 21 and 22 from the irradiation start position P1 to the irradiation end position P2 along the X-axis direction, respectively. And irradiate. Specifically, the laser irradiator 31 scans the laser L along the X-axis direction while reciprocating the laser L with respect to the side surfaces 21a and 22a of the tab laminates 21 and 22, respectively. At this time, the amount of displacement of the laser L in the Z-axis direction is larger than the thickness of the tab laminates 21 and 22.

The irradiation start end position P1 is a position at which the laser irradiator 31 starts irradiating the laser L. The irradiation start end position P1 is a position corresponding to one end of the protective plates 23 and 25 in the X-axis direction. The irradiation end position P2 is a position at which the laser irradiator 31 ends the irradiation of the laser L. The irradiation end position P2 is a position corresponding to the other end of the protective plates 23 and 25 in the X-axis direction. The irradiation start end position P1 and the irradiation end position P2 are located at the center in the Z-axis direction on the side surfaces 21a and 22a of the tab laminates 21 and 22. The line H passing through the irradiation start position P1 and the irradiation end position P2 extends in the X-axis direction.

The assist gas injection nozzle 32 injects the assist gas Ga to the irradiation point of the laser L by the laser irradiator 31. As shown in FIG. 6, the assist gas injection nozzle 32 is arranged at a height position corresponding to the tab laminates 21 and 22. The assist gas injection nozzle 32 injects the assist gas Ga from the irradiation start position P1 side toward the irradiation end position P2 side along the X-axis direction. At this time, the assist gas injection nozzle 32 injects the assist gas Ga so as to pass through the center positions of the side surfaces 21a and 22a of the tab laminates 21 and 22. N ₂ gas is used as the assist gas Ga. The reason for injecting the assist gas Ga is to prevent oxidation of the molten portion due to the heat of the laser L.

The cooling gas injection nozzle 33 injects the cooling gas Gc toward the irradiation end position P2 of the laser L by the laser irradiator 31. As shown in FIG. 6, the cooling gas injection nozzle 33 is arranged above the tab laminates 21 and 22. Therefore, the cooling gas injection nozzle 33 is arranged at a higher position than the assist gas injection nozzle 32.

Specifically, the cooling gas injection nozzle 33 injects the cooling gas Gc toward the irradiation end position P2 of the laser L so as to avoid the irradiation start position P1 of the laser L by the laser irradiator 31. The injection direction of the cooling gas Gc from the cooling gas injection nozzle 33 is inclined with respect to the line H passing through the irradiation start position P1 and the irradiation end position P2. That is, the injection direction of the cooling gas Gc from the cooling gas injection nozzle 33 is inclined with respect to the injection direction of the assist gas Ga from the assist gas injection nozzle 32. In the present embodiment, as the cooling gas Gc, N ₂ gas having the same supply source as the assist gas Ga is used.

The controller 34 is composed of a CPU, RAM, ROM, an input / output interface, and the like. The controller 34 controls the laser irradiator 31, the assist gas injection nozzle 32, and the cooling gas injection nozzle 33 so that the assist gas injection nozzle 32 and the cooling gas injection nozzle 33 are operated at the same time when the laser irradiator 31 is operated. To do. At this time, the controller 34 has the assist gas injection nozzle 32 and the cooling gas injection nozzle 33 so that the injection amount of the cooling gas Gc by the cooling gas injection nozzle 33 is larger than the injection amount of the assist gas Ga by the assist gas injection nozzle 32. To control.

As described above, in the present embodiment, the welded portion 24 is formed on the tab laminate 21 by irradiating the tab laminate 21 on which the tabs 14b of the plurality of positive electrodes 8 are laminated with the laser L for laser welding. At the same time, the welded portion 26 is formed on the tab laminate 22 by irradiating the tab laminate 22 on which the tabs 16b of the plurality of negative electrodes 9 are laminated with the laser L for laser welding. At this time, in the vicinity of the irradiation end of the laser L in the tab laminates 21 and 22, the temperature of the tab laminates 21 and 22 rises before the laser L reaches the irradiation end, so that the irradiation of the laser L makes it more than necessary. The temperature is likely to rise and spatter is likely to occur. Therefore, by injecting the cooling gas Gc toward the irradiation end position P2 before the laser L reaches the irradiation end position P2, the laser in the tab laminates 21 and 22 is reached before the laser L reaches the irradiation end position P2. It suppresses the temperature rise near the end of irradiation of L. As a result, the occurrence of spatter can be suppressed. As a result, it is possible to improve the welding quality by the laser L.

On the other hand, in the vicinity of the irradiation start end of the laser L in the tab laminates 21 and 22, the temperature does not easily rise, so that the amount of the laser L dissolved is small. Therefore, by injecting the cooling gas Gc toward the irradiation end position P2 of the laser L so as to avoid the irradiation start position P1 of the laser L, the cooling gas Gc is not given to the irradiation start position P1 of the laser L. Therefore, since the temperature drop in the vicinity of the irradiation start end of the laser L in the tab laminates 21 and 22 is suppressed, the amount of the laser L dissolved in the vicinity of the irradiation start end of the laser L in the tab laminates 21 and 22 may be reduced more than necessary. Be prevented. This makes it possible to further improve the welding quality of the laser L.

Further, in the present embodiment, since the assist gas Ga is injected to the irradiation portion of the laser L by the laser irradiator 31, the assist gas Ga prevents the oxidation of the irradiation portion of the laser L in the tab laminates 21 and 22. Therefore, it is possible to prevent a decrease in welding strength between the tabs 14b of each positive electrode 8 and between the tabs 16b of each negative electrode 9. This makes it possible to further improve the welding quality of the laser L.

Further, in the present embodiment, since the same gas is used as the cooling gas Gc and the assist gas Ga, it is not necessary to prepare a plurality of types of gases. Therefore, it is advantageous in terms of cost.

Further, in the present embodiment, since the injection amount of the cooling gas Gc by the cooling gas injection nozzle 33 is larger than the injection amount of the assist gas Ga by the assist gas injection nozzle 32, the irradiation end of the laser L in the tab laminates 21 and 22 The temperature rise in the vicinity is sufficiently suppressed. Therefore, the occurrence of spatter can be further suppressed.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the assist gas injection nozzle 32 injects the assist gas Ga from the irradiation start position P1 side toward the irradiation end position P2 side along the X-axis direction, but the present invention is not particularly limited to that form. For example, the injection position of the assist gas Ga by the assist gas injection nozzle 32 may be shifted according to the irradiation location of the laser L on the tab laminates 21 and 22.

Further, in the above embodiment, the same N ₂ gas is used as the assist gas Ga and the cooling gas Gc, but the present invention is not particularly limited to this, and different gases are used for the assist gas Ga and the cooling gas Gc. May be good. For example, one of the assist gas Ga and the cooling gas Gc may be N ₂ gas, and the other of the assist gas Ga and the cooling gas Gc may be Ar gas.

Further, in the above embodiment, the injection amount of the cooling gas Gc by the cooling gas injection nozzle 33 is larger than the injection amount of the assist gas Ga by the assist gas injection nozzle 32, but the cooling gas Gc causes the vicinity of the irradiation end of the laser L. As long as the temperature rise of the cooling gas Gc is suppressed, the injection amount of the cooling gas Gc may be the same as the injection amount of the assist gas Ga, or the injection amount of the cooling gas Gc may be smaller than the injection amount of the assist gas Ga.

Further, in the above embodiment, the assist gas Ga is injected to the irradiation portion of the laser L by the assist gas injection nozzle 32, but the present invention is not particularly limited to that embodiment, and the irradiation portion of the laser L in the tab laminate 21 and 22 When the influence of oxidation is small, the assist gas injection nozzle 32 may not be particularly provided.

Further, in the above embodiment, the power storage device 1 is a lithium ion secondary battery, but the present invention is not particularly limited to the lithium ion secondary battery, and other secondary batteries such as a nickel hydrogen battery and an electric double layer. It can also be applied to electrode welding in power storage devices such as capacitors or lithium ion capacitors.

8 ... Positive electrode (electrode), 9 ... Negative electrode (electrode), 14b ... Tab, 16b ... Tab, 21 ... Tab laminate, 22 ... Tab laminate, 30 ... Electrode welding device, 31 ... Laser irradiator (laser irradiation unit) , 32 ... Assist gas injection nozzle (assist gas injection unit), 33 ... Cooling gas injection nozzle (cooling gas injection unit), 34 ... Controller (control unit), P1 ... Irradiation start position, P2 ... Irradiation end position, L ... Laser , Ga ... Assist gas, Gc ... Cooling gas.

Claims (4)

In an electrode welding device that welds tabs of a plurality of electrodes in a laminated state,
A laser irradiation unit that irradiates a tab laminate in which the tabs of the plurality of electrodes are laminated with a laser for laser welding.
A cooling gas injection unit that injects cooling gas toward the irradiation end position of the laser by the laser irradiation unit is provided .
The electrode welding device is characterized in that the cooling gas injection unit injects the cooling gas toward the irradiation end position so as to avoid the irradiation start end position of the laser by the laser irradiation unit . Electrode welding apparatus according to claim 1, further comprising an assist gas injection unit for injecting an assist gas to the irradiation position of the laser by the laser irradiation unit. The electrode welding apparatus according to claim 2, wherein the cooling gas and the assist gas are the same gas. Further, a control unit that controls the cooling gas injection unit and the assist gas injection unit is further provided so that the injection amount of the cooling gas by the cooling gas injection unit is larger than the injection amount of the assist gas by the assist gas injection unit. The electrode welding apparatus according to claim 2 or 3 , wherein the electrode welding apparatus is provided.

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