JP2019061949A - Electrical storage device, and laser welding method for electrical storage device - Google Patents

Abstract

To provide an electrical storage device which can suppress the occurrence of a break of an uncoated part without a protection plate, and a laser welding method for such an electrical storage device.SOLUTION: A secondary battery comprises: an electrode assembly 12 having a tab group 18 having a plurality of tabs 26 laminated therein; an electrode terminal for providing electricity to the electrode assembly 12 and receiving electricity therefrom; and a conductive member 17 for electrically connecting the electrode assembly 12 with the electrode terminal. It is noted that a direction in which the plurality of tabs 26 are laminated is defined as a lamination direction. The conductive member 17 is disposed on one end side of the tab group 18 in the lamination direction. The secondary battery has an outside welding part 31 to which the plurality of tabs 26 including the tab 26 located at the other end in the lamination direction are laser-welded. The outside welding part 31 has two straight line parts 33. In addition, the secondary battery has an inside welding part 32 to which the conductive member 17 and the tab group 18 are laser-welded. When viewing the tab group 18 from the other end in the lamination direction, the two straight line parts 33 are present in the state of being spaced from each other by a distance of 4.0 mm, and the inside welding part 32 is located between the two straight line parts 33.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an electricity storage device including an electrode assembly having an uncoated portion group, an electrode terminal for exchanging electricity with the electrode assembly, and a conductive member for electrically connecting the electrode assembly and the electrode terminal. The present invention relates to a laser welding method of a power storage device.

  BACKGROUND Conventionally, in vehicles such as EVs (Electric Vehicles) and PHVs (Plug in Hybrid Vehicles), lithium ion secondary batteries and the like are mounted as power storage devices for storing power supplied to motors and the like. The secondary battery includes an electrode assembly in which a plurality of sheet-like positive electrodes and negative electrodes are alternately stacked in an insulated state, and a case for housing the electrode assembly.

  The positive electrode and the negative electrode have a metal foil, an active material layer present on both sides or one side of the metal foil, and an uncoated portion where the active material layer is not present and the metal foil is exposed. The uncoated portion is, for example, a tab protruding from one side of the metal foil. The electrode assembly includes tabs as uncoated portions in which tabs of each polarity are stacked. Power extraction from the secondary battery is performed through an electrode terminal electrically connected to the electrode assembly. The electrode assembly and the electrode terminal are electrically connected by laser welding and joining the tab group and a part of the electrode terminal (for example, a conductive member).

  By the way, in welding of the tab group and the conductive member, as the number of tabs constituting the tab group increases, the penetration depth in the stacking direction of the tabs when welding all the tabs at one time becomes deeper, so it is necessary for welding The energy of the laser is increased. In this case, a break may occur in the tabs close to the laser irradiation position in the tab group. On the other hand, in Patent Document 1, for example, the tab group is sandwiched between the protective plate and the conductive member and laser welding is performed to suppress breakage of the tab at the time of welding.

JP, 2016-002566, A

  However, since the protective plate is welded to the tabs when welding the tabs to the conductive member, the protective plate is required each time the tabs and the conductive member are welded. In addition, the protective plate leads to an increase in the number of parts of the secondary battery.

  The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a power storage device and a laser welding method of the power storage device which can suppress the occurrence of breakage of an uncoated portion without a protective plate. It is in.

  The electricity storage device for solving the above problems does not have a rectangular sheet metal foil, an active material layer present on at least one surface of the metal foil, and the metal foil exposed without the active material layer. An electrode assembly comprising an uncoated portion group in which electrodes of a positive electrode and a negative electrode having a coated portion are laminated in an insulated state, and a plurality of the uncoated portions are laminated with the same polarity; A power storage device comprising: an electrode terminal for exchanging electricity with an electrode assembly; and a conductive member for electrically connecting the electrode assembly and the electrode terminal, wherein the direction in which the uncoated portion is laminated And the conductive member is disposed on one end side of the uncoated portion group in the laminating direction, and the plurality of uncoated portions including the uncoated portion positioned at the other end of the laminating direction Are two laser welded first welds, the conductive member and the uncoated portion group And the first two welds are larger than 0.5 mm and not larger than 4.0 mm when the uncoated portion group is viewed from the other end side in the laminating direction. The gutters may be spaced apart, and the second weld may be present between the two first welds.

  According to this, the interval between the two first welds is set to be larger than 0.5 mm and not more than 4.0 mm, so that in the uncoated portion group, the two first welds are adjacent in the stacking direction. Unmatched uncoated parts are in close contact with each other. Therefore, by forming the second welded portion with respect to the uncoated portion group in which the first welded portion is formed, melting easily proceeds in the laminating direction, and the laser is applied to the uncoated portion close to the laser irradiation position. Concentration of energy is suppressed. Therefore, generation | occurrence | production of the tear of an uncoated part can be suppressed by the structure without a protective plate.

In the power storage device, the penetration depth of the first welded portion in the stacking direction is preferably 0.2 to 0.3 mm.
According to this, since a sufficient number of uncoated portions can be brought into close contact with each other, it is possible to further suppress the occurrence of tearing of the uncoated portion when the uncoated portion group and the conductive member are laser welded.

  In the power storage device, the second welded portion is recessed from the surface of the uncoated portion located at the other end in the stacking direction toward the conductive member, and is recessed from the surface of the uncoated portion When the portion is a recess, the dimension of the recess in the short direction of the second welded portion on the surface of the uncoated portion located at the other end of the stacking direction is the uncoated portion of the conductive member It is preferable that it is 2 to 6 times the dimension of the latitudinal direction of the said 2nd welding part in the end surface by the side of a group.

  When laser welding the conductive member and the non-coated portion group under welding conditions such that the dimension of the recess is less than twice the dimension of the second welded portion, the non-coated portion and the conductive member located at one end in the laminating direction There is a possibility that sufficient bonding strength can not be obtained due to lack of bonding area with the above. On the other hand, when the conductive member and the uncoated portion group are laser welded under welding conditions such that the dimension of the recess is larger than six times the dimension of the second welded portion, the other end side in the stacking direction close to the laser irradiation position There is a possibility that a tear may occur in the uncoated portion located in Therefore, by performing laser welding under welding conditions such that the size of the recess is 2 to 6 times as large as the size of the second welded portion, it is possible to suppress the occurrence of breakage of the uncoated portion at the time of welding and Sufficient bonding strength with the uncoated portion group can be obtained.

  In the power storage device, the second welded portion is recessed from the surface of the uncoated portion located at the other end in the stacking direction toward the conductive member, and is recessed from the surface of the uncoated portion When the portion is a recess, the dimension of the recess in the short direction of the second welded portion on the surface of the uncoated portion located at the other end of the stacking direction is the second welded portion in the stacking direction 10 to 50% of the penetration depth of

  When laser welding the conductive member and the uncoated portion group under welding conditions such that the dimension of the recess is less than 10% of the penetration depth of the second welded portion, the uncoated portion located at one end in the laminating direction There is a possibility that sufficient bonding strength can not be obtained because the bonding area with the conductive member is insufficient. On the other hand, when the conductive member and the non-coated portion group are laser welded under welding conditions such that the dimension of the recess is greater than 50% of the penetration depth of the inner weld, the other end in the lamination direction closer to the laser irradiation position There is a possibility that a tear may occur in the uncoated portion located on the side. Therefore, while performing the laser welding under the welding conditions such that the dimension of the recess is 10 to 50% of the penetration depth of the second welded portion, it is possible to suppress the occurrence of breakage of the uncoated portion at the time of welding and Sufficient bonding strength between the member and the uncoated portion group can be obtained.

  In the laser welding method of a storage device for solving the above problems, a metal sheet in the form of a rectangular sheet, an active material layer present on at least one surface of the metal foil, and the active material layer are not present. An electrode assembly comprising an uncoated portion group in which an electrode of a positive electrode and a negative electrode having an uncoated portion exposed is laminated in an insulated state, and the uncoated portion of the electrode is laminated with the same polarity. And a non-coated portion for manufacturing a power storage device including: an electrode terminal for exchanging electricity with the electrode assembly; and a conductive member for electrically connecting the electrode assembly and the electrode terminal. It is a laser welding method of the electrical storage apparatus which carries out the laser welding of the group and the said electroconductive member, Comprising: When the direction in which the said uncoated part is laminated is made into the lamination direction, the said electroconductive member is made into the lamination direction of the said uncoated part group. From the other end side of the stacking direction in the state of being disposed on one end side of the A pressing step of pressing the uncoated portion group, and irradiating a laser from the other end side in the laminating direction to weld a plurality of the uncoated portions to form two first welded portions A welding step, and a second welding step of irradiating a laser from the other end side in the stacking direction to weld the conductive member and the uncoated portion group to form a second welded portion; When the coated portion group is viewed from the other end side in the stacking direction, the two first welded portions are formed at an interval of more than 0.5 mm and 4.0 mm or less, and the second welded portion is formed by It makes it a summary to be formed between two 1st welding parts.

  According to this, by welding a plurality of uncoated portions in a state where the uncoated portion group is pressurized, the first welded portion is adhered in a state where the uncoated portions adjacent in the stacking direction are in close contact with each other. It can be formed. Further, by setting the distance between the two first welds to be larger than 0.5 mm and 4.0 mm or less, unpainted portions adjacent to each other in the stacking direction may be formed between the two first welds in the uncoated portion group. The working parts are in close contact with each other. Therefore, by forming the second welded portion with respect to the uncoated portion group in which the first welded portion is formed, melting easily proceeds in the laminating direction, and the laser is applied to the uncoated portion close to the laser irradiation position. Concentration of energy is suppressed. Therefore, generation | occurrence | production of the tear of an uncoated part can be suppressed, without using a protective plate.

Further, in the laser welding method of the electric storage device, in the first welding step, the penetration depth of the first welded portion in the stacking direction is preferably 0.2 to 0.3 mm.
According to this, since a sufficient number of uncoated portions can be brought into close contact with each other, it is possible to further suppress the occurrence of tearing of the uncoated portion when the uncoated portion group and the conductive member are laser welded.

Further, in the laser welding method of the power storage device, in the first welding step, it is preferable that the laser welding is a heat conduction method.
In laser welding by the heat conduction method, generation of spatter is suppressed as compared with laser welding by the keyhole method. Therefore, in the first welding step, adhesion of spatter to the pressing jig for pressing the uncoated portion group can be suppressed. As a result, the frequency of cleaning and replacement of the pressing jig can be reduced.

Further, in the laser welding method of the power storage device, in the second welding step, the laser welding is preferably a keyhole method.
The laser welding by the keyhole method can make the penetration depth deeper than the laser welding by the heat conduction method. Therefore, it is suitable for the 2nd welding process which carries out laser welding of the electric conduction member and the uncoated part group which consists of a plurality of uncoated parts.

  In the laser welding method of a storage device for solving the above problems, a metal sheet in the form of a rectangular sheet, an active material layer present on at least one surface of the metal foil, and the active material layer are not present. An electrode assembly comprising an uncoated portion group in which an electrode of a positive electrode and a negative electrode having an uncoated portion exposed is laminated in an insulated state, and the uncoated portion of the electrode is laminated with the same polarity. And a non-coated portion for manufacturing a power storage device including: an electrode terminal for exchanging electricity with the electrode assembly; and a conductive member for electrically connecting the electrode assembly and the electrode terminal. It is a laser welding method of the electrical storage apparatus which carries out the laser welding of the group and the said electroconductive member, Comprising: When the direction in which the said uncoated part is laminated is made into the lamination direction, the said electroconductive member is made into the lamination direction of the said uncoated part group. From the other end side of the stacking direction in the state of being disposed on one end side of the In the pressing step of pressing the uncoated portion group, and during the pressing step, a laser is irradiated from the other end side in the laminating direction to weld a plurality of the uncoated portions to form a linear shape. During the first welding step of forming two first welded portions, and during the pressing step and after the first welding step, laser is irradiated from the other end side in the laminating direction, and the conductive member and the uncoated portion And a second welding step of forming a second welded portion by welding with a group, and when the uncoated portion group is viewed from the other end side in the stacking direction, the two first welded portions are A laser welding method of a power storage device, which is formed at an interval of more than 5 mm and 4.0 mm or less, and the second welding portion is formed between the two first welding portions.

  According to this, by welding a plurality of uncoated portions in a state where the uncoated portion group is pressurized, the first welded portion is adhered in a state where the uncoated portions adjacent in the stacking direction are in close contact with each other. It can be formed. Further, by setting the distance between the two first welds to be larger than 0.5 mm and 4.0 mm or less, unpainted portions adjacent to each other in the stacking direction may be formed between the two first welds in the uncoated portion group. The working parts are in close contact with each other. Therefore, by forming the second welded portion with respect to the uncoated portion group in which the first welded portion is formed, melting easily proceeds in the laminating direction, and the laser is applied to the uncoated portion close to the laser irradiation position. Concentration of energy is suppressed. Therefore, generation | occurrence | production of the tear of an uncoated part can be suppressed, without using a protective plate.

  Further, in the laser welding method of the power storage device, the first welding portion is formed to be connected to a connection welding portion extending in a direction different from the first welding portion.

  ADVANTAGE OF THE INVENTION According to this invention, there is no protective plate and it can suppress generation | occurrence | production of the tear of an uncoated part.

The disassembled perspective view of the secondary battery of embodiment. FIG. 2 is a partial cross-sectional view of a secondary battery. (A) is sectional drawing which shows the welding part in the state which extended the tab group, (b) is a top view which shows the welding part in the state which extended the tab group. FIG. (A), (b) is sectional drawing which shows the welding method. (A), (b) is a top view which shows the welding method. The table | surface which shows the presence or absence of generation | occurrence | production of the tab tear in embodiment and experiment 1-3. (A)-(d) is a top view which shows another example of a welding part. Sectional drawing which shows typically another example of an inner side welding part. Sectional drawing which shows typically another example of an inner side welding part.

Hereinafter, an embodiment in which a storage device and a method of welding a storage device are embodied in a secondary battery and a method of welding a secondary battery will be described according to FIGS. 1 to 7.
As shown in FIG. 1, a secondary battery 10 as a power storage device includes a case 11. The secondary battery 10 includes an electrode assembly 12 housed in a case 11 and an electrolyte (not shown). The case 11 has a rectangular parallelepiped case body 13 and a rectangular flat lid 14 closing the opening 13 a of the case body 13. The case main body 13 and the lid 14 constituting the case 11 are both made of metal (for example, stainless steel or aluminum). Moreover, the secondary battery 10 of the present embodiment is a square battery whose appearance is square. In addition, the secondary battery 10 of the present embodiment is a lithium ion battery.

  The secondary battery 10 includes a pair of electrode terminals 15 for extracting electricity from the electrode assembly 12. Of the pair of electrode terminals 15, one electrode terminal 15 is a positive electrode terminal, and the other electrode terminal 15 is a negative electrode terminal. Each electrode terminal 15 penetrates the through hole 14 a of the lid 14 and protrudes out of the case 11. A ring-shaped insulating ring 16 for insulating the lid 14 is attached to each of the electrode terminals 15. Each electrode terminal 15 has a rectangular plate-like conductive member 17 in the case 11. Each electrode terminal 15 is electrically connected to the conductive member 17.

  As shown in FIG. 2, the electrode assembly 12 includes a positive electrode 21 as a plurality of (for example, 60) sheet-like positive electrodes and a plurality of (for example, 61) sheet-like negative electrodes. And a negative electrode 22. The electrode assembly 12 has a layered structure which is alternately stacked in a state in which the separator 23 is interposed between the positive electrode 21 and the negative electrode 22 for insulation. In FIG. 3 and the subsequent figures, the electrode assembly 12 in which the numbers of the positive electrode 21, the negative electrode 22, and the separator 23 are omitted is illustrated.

  The positive electrode 21 and the negative electrode 22 are provided with a metal sheet 24 in the form of a rectangular sheet. The metal foil 24 of the positive electrode 21 is, for example, an aluminum foil, and the metal foil 24 of the negative electrode 22 is, for example, a copper foil. The thickness of the metal foil 24 is about 10 μm. The positive electrode 21 and the negative electrode 22 have active material layers 25 present on both sides of the metal foil 24. The active material layer 25 contains an active material, a conductive material, and a binder according to the polarity. The positive electrode 21 and the negative electrode 22 have rectangular tabs 26 protruding from a part of one of the edges along the pair of long sides. In the present embodiment, the longitudinal direction of the tab 26 coincides with the projecting direction of the tab 26 from the edge. The tab 26 is an uncoated portion where the active material layer 25 does not exist and the metal foil 24 is exposed. Thus, the thickness of the tab 26 is about 10 μm, the same as the thickness of the metal foil 24.

  The electrode assembly 12 is a tab group 18 as an uncoated portion group in which the tab 26 of each positive electrode 21 is collected at one end in the direction in which the positive electrode 21, the negative electrode 22, and the separator 23 are stacked. Equipped with Similarly, in the electrode assembly 12, the tab 26 of each negative electrode 22 is collected at one end in the direction in which the positive electrode 21, the negative electrode 22, and the separator 23 are stacked, and then stacked. A tab group 18 is provided. The direction in which the tabs 26 are stacked is referred to as the stacking direction. Each tab group 18 is present on the end face 12 a facing the lid 14 in the electrode assembly 12. As shown in FIGS. 1 and 2, the electrode assembly 12 is accommodated in the case 11 in a state where the proximal end and the distal end of the tab group 18 in the projecting direction of the tab 26 are bent. The conductive member 17 is located between one end face of the tab group 18 in the stacking direction and the inner surface of the lid 14. In FIG. 3 and later, for convenience of explanation, the tab group 18 is illustrated in a state of being extended without being bent.

  As shown in FIGS. 3A and 3B, the secondary battery 10 includes an outer welding portion 31 and an inner welding portion 32. As shown in FIG. 3A, the outer welding portion 31 is formed by laser welding a plurality of tabs 26 including the tabs 26 located at the other end in the stacking direction. The inner welding portion 32 is formed by laser welding all the tabs 26 constituting the tab group 18 and the conductive member 17.

  As shown in FIG. 3B, when the tab group 18 is viewed from the other end side in the stacking direction, the outer welding portion 31 has a track shape. The outer welding portion 31 is composed of two linear portions 33 as first welding portions and two arc portions 34 as connection welding portions connected to the linear portions 33. One end of one linear portion 33 is connected to one end of one arc 34, and the other end of one linear portion 33 is connected to one end of the other arc 34. Further, one end of the other linear portion 33 is connected to the other end of one arc 34 and the other end of the other linear portion 33 is connected to the other end of the other arc 34 . The longitudinal direction of the straight portion 33 extends in the lateral direction of the tab 26. The arc 34 extends in a direction different from that of the straight portion 33.

  In the present embodiment, the dimensions of the straight portion 33 and the arc portion 34 in the lateral direction are each about 1.0 mm. The short side direction of the arc portion 34 is a direction connecting the inner periphery and the outer periphery of the arc portion 34. The dimension A in the longitudinal direction of the outer welding portion 31 is 18.0 mm. Here, the dimension A in the longitudinal direction of the outer welding portion 31 refers to the end A1 of the ends in the short direction of one arc 34 and the other end A1 closer to the other arc 34 and the short side of the other arc 34 It refers to the longest distance to the end A2 closer to one of the arcs 34 of the direction ends. The two straight portions 33 are present at an interval B of 4.0 mm. Here, the distance B between the two straight portions 33 refers to the distance between the inner edge B1 of one straight portion 33 and the inner edge B2 of the other straight portion 33. The penetration depths of the straight portion 33 and the arc portion 34 in the stacking direction are each about 0.2 mm. That is, in the outer welding portion 31, about 20 tabs 26 on the other end side in the stacking direction are welded.

  When the tab group 18 is viewed from the other end side in the stacking direction, the inner welding portion 32 as the second welding portion is linear and exists inside the outer welding portion 31. The longitudinal direction of the inner weld 32 extends in the lateral direction of the tab 26, and the lateral direction of the inner weld 32 extends in the longitudinal direction of the tab 26. In the longitudinal direction of the tab 26, the inner welding portion 32 exists between one straight portion 33 of the outer welding portion 31 and the other straight portion 33. In the present embodiment, the longitudinal dimension of the inner weld 32 is 14.0 mm, and the lateral dimension of the inner weld 32 is 1.0 mm. In the longitudinal direction of the tab 26, the inner welding portion 32 is separated from each of the two straight portions 33 of the outer welding portion 31. That is, in the longitudinal direction of the tab 26, a gap is present between the inner welding portion 32 and the straight portions 33 of the outer welding portion 31.

Next, a welding method for forming the outer welding portion 31 and the inner welding portion 32 will be described.
The welding method includes a foil collecting step, a pressing step, a first welding step, and a second welding step.

  The foil collecting step is a step of collecting the plurality of tabs 26 provided in the electrode assembly 12 to form the tab group 18. First, all the tabs 26 of the electrode assembly 12 are disposed on the conductive member 17 placed on a work table (not shown). Next, all the tabs 26 are pressed from the opposite side of the conductive member 17 sandwiching the tabs 26 with a foil collector (not shown) to form the tab group 18. Thus, the conductive member 17 is disposed at one end side of the tab group 18 in the stacking direction.

The pressing step is a step of pressing the tab group 18 from the other end side in the stacking direction. A pressing jig 50 is used in the pressing step.
As shown in FIG. 4, the pressing jig 50 includes a cylindrical first pressing jig 51 and a columnar second pressing jig 52. The first pressing jig 51 has a through hole 51 a formed by the inner circumferential surface. The shape of the first pressure jig 51 is a track shape in a plan view as viewed from the direction in which the through hole 51 a penetrates, and the shape of the second pressure jig 52 is the axial line of the second pressure jig 52. It has an elliptical shape in plan view seen from the extending direction. The second pressing jig 52 can be inserted into the through hole 51 a of the first pressing jig 51.

  The first pressing jig 51 is configured of two linear first base portions 53 in a plan view, and two circular second base portions 54 in a plan view connected to the first base 53. One end of one first base 53 is connected to one end of one second base 54, and the other end of one first base 53 is connected to one end of the other second base 54. . Further, one end of the other first base 53 is connected to the other end of one second base 54, and the other end of the other first base 53 is the other end of the other second base 54. Connected to The first pressing jig 51 includes a first pressing unit 55 that protrudes from the bottom surface of the first base 53 and the second base 54. The first pressurizing unit 55 includes a linear pressurizing unit 55a existing along the first base 53 in a linear shape in plan view, and an arc-shaped pressurizing unit 55b existing along a second base 54 in an arc shape in plan view. Prepare. That is, the plan view shape of the first pressing portion 55 is a track shape.

  In the present embodiment, the dimension C in the longitudinal direction of the first pressing jig 51 is slightly larger than 20.0 mm. Here, the direction in which the inner periphery and the outer periphery of the second base 54 are connected is taken as the short direction of the second base 54. The dimension C in the longitudinal direction of the first pressing jig 51 is an end C 1 of the ends in the short side direction of one second base 54 and the end C 1 closer to the other second base 54 and the other second base 54 Point at the longest distance to the end C2 closer to the second base 54 in one of the latitudinal ends of the Also, the distance D between the two first bases 53 is slightly larger than 6.0 mm. Here, the distance D between the two first bases 53 refers to the distance between the inner edge D1 of one first base 53 and the inner edge D2 of the other first base 53.

  The second pressing jig 52 includes a base 56 and a second pressing unit 57 projecting from the bottom of the base 56. The plan view shape of the second pressing portion 57 is an elliptical shape. The longitudinal dimension E of the second pressing jig 52 is slightly smaller than 18.0 mm, and the transverse dimension F of the second pressing jig 52 is slightly smaller than 4.0 mm.

  In the pressing step, the first pressing jig 51 and the second pressing jig 52 are disposed on the tab 26 positioned at the other end of the tab group 18 in the stacking direction. Then, by pressing the first pressing jig 51 and the second pressing jig 52 with a pressing device (not shown), the first pressing unit 55 and the second pressing unit 57 stack the tab group 18 in the stacking direction. Apply pressure from the other end of the As a result, the tabs 26 adjacent in the stacking direction are in close contact with each other.

  As shown in FIGS. 5 (a) and 6 (a), the first welding step is a step of forming the outer welding portion 31. As shown in FIG. The first welding process of the present embodiment is performed by heat conduction laser welding. The laser irradiation device (not shown) irradiates the laser from between the first pressing jig 51 and the second pressing jig 52 which pressurize the tab group 18. That is, the laser is irradiated from the other end side of the tab group 18 in the stacking direction. As a result, the plurality of tabs 26 including the tabs 26 located at the other end in the stacking direction are welded, and the outer welding portion 31 is formed. The energy of the laser in the first welding step is set to a size (for example, 900 W) in which the penetration depth of the outer welding portion 31 in the stacking direction is 0.2 mm. Further, in the present embodiment, the irradiation direction of the laser is inclined by 15 degrees with respect to the stacking direction. After the first welding process, the second pressing jig 52 is removed. When the second pressing jig 52 is removed, a part of the tab 26 in a non-welded state is present inside the outer welding portion 31. The first pressing jig 51 keeps pressing the tab group 18 from the other end side in the stacking direction.

  As shown in FIG. 5 (b) and FIG. 6 (b), the second welding step is a step of forming the inner welding portion 32. The second welding process of the present embodiment is performed by keyhole laser welding. The inside of the first pressure jig 51 is irradiated with a laser by a laser irradiation device (not shown). That is, the laser is irradiated from the other end side of the tab group 18 in the stacking direction. Thereby, the conductive member 17 and the tab group 18 are welded to form the inner welding portion 32. The energy of the laser in the second welding step is set to a size (for example, 1200 W) at which the conductive member 17 and all the tabs 26 constituting the tab group 18 are welded. Further, in the present embodiment, the irradiation direction of the laser is inclined by 15 degrees with respect to the stacking direction. After the second welding process, the first pressing jig 51 is removed.

Next, the operation of the present embodiment will be described.
When the inner welding portion 32 is formed in a state where the outer welding portion 31 is not formed, there is a high possibility that the tabs 26 adjacent to each other in the stacking direction are not in close contact with each other. The energy of the laser tends to be concentrated on the tab 26 located on the near side. Therefore, melting may easily proceed along the surface direction of the tab 26 located on the other end side in the stacking direction, and the tab 26 may be broken. On the other hand, by joining the plurality of tabs 26 by the outer welding portion 31 so that the distance B between the two straight portions 33 is 4.0 mm, the two outer welding portions 31 in the tab group 18 are formed. Between the straight portions 33, the tabs 26 adjacent in the stacking direction are in close contact with each other. For this reason, at the time of formation of the inner side welding part 32, melting advances easily in the lamination direction, and generation | occurrence | production of the tear of the tab 26 is suppressed.

  By the way, although the dimension A of the longitudinal direction of the outer side welding part 31 was 18.0 mm and the space | interval B of the two linear parts 33 was 4.0 mm in said Example, even if it changes the dimension A or the space | interval B Experiments 1 to 3 were conducted to confirm whether or not the occurrence of breakage of the tab 26 could be suppressed. In Experiments 1 to 3, conditions other than the dimension A in the longitudinal direction of the outer welding portion 31 and the distance B between the two straight portions 33 are the same as those in the above-described embodiment.

  As shown in the table of FIG. 7, in Experiment 1, the dimension A in the longitudinal direction of the outer welding portion 31 was 3.0 mm, and the distance B between the two straight portions 33 was 2.0 mm. In Experiment 2, the dimension A in the longitudinal direction of the outer welding portion 31 was 5.0 mm, and the distance B between the two straight portions 33 was 4.0 mm as in the example. In Experiment 3, the dimension A in the longitudinal direction of the outer welding portion 31 was 7.0 mm, and the distance B between the two straight portions 33 was 6.0 mm. As a result, in Experiment 1 and Experiment 2, breakage of the tab 26 in the second welding process did not occur, and in Experiment 3, breakage of the tab 26 occurred in the second welding process.

  From the embodiment and the experiment 2, if the distance B between the two straight portions 33 is 4.0 mm, the dimension A in the longitudinal direction of the outer welding portion 31 is for the breakage of the tab 26 which may occur in the second welding step. It turns out that it does not affect. Also, from Experiment 1 to Experiment 3, if the distance B between the two straight portions 33 exceeds 6.0 mm, the tab 26 is broken in the second welding step, and if the distance B is 4.0 mm or less, 2. It can be seen that the tab 26 does not break in the welding process. As the distance B between the two straight portions 33 is larger, the length of a part of the tab 26 existing between the straight portions 33 is longer. For this reason, with respect to a part of the tab 26 existing between the two straight portions 33, the degree of adhesion between adjacent ones in the stacking direction decreases. On the other hand, as the distance B between the two straight portions 33 is smaller, the length of a part of the tab 26 existing between the two straight portions 33 is shorter. For this reason, the tabs 26 existing between the two straight portions 33 are easily in close contact with each other in the stacking direction. Thus, the occurrence of breakage of the tab 26 in the second welding step is suppressed.

Next, the effects of the present embodiment will be described.
(1) The plurality of tabs 26 are welded in a state where the tab group 18 is pressurized by the first pressing jig 51 and the second pressing jig 52, so that the adjacent tabs 26 in the stacking direction are in close contact with each other. The outer welding portion 31 can be formed in a state where it is allowed to move. Further, by setting the distance B between the two linear portions 33 to be larger than 0.5 mm and 4.0 mm or less, the tabs 26 adjacent to each other in the stacking direction in the tab group 18 are closely attached to each other. It will be in a state of Therefore, by forming the inner welding portion 32 with respect to the tab group 18 in which the linear portion 33 is formed, melting easily proceeds in the stacking direction, and the energy of the laser is concentrated on the tab 26 close to the laser irradiation position. Is suppressed. Therefore, generation | occurrence | production of the tear of the tab 26 as an uncoated part can be suppressed, without using a protective plate.

  (2) The penetration depth of the outer welding portion 31 in the stacking direction is about 0.2 mm. That is, among the approximately 60 tabs 26 constituting the tab group 18, approximately 20 tabs 26 on the other end side in the stacking direction can be brought into close contact with each other. Therefore, it is possible to further suppress the occurrence of breakage of the tab 26 when the tab group 18 and the conductive member 17 are laser-welded.

  (3) The first welding step is performed by heat conduction laser welding. In laser welding by the heat conduction method, generation of spatter is suppressed as compared with laser welding by the keyhole method. Therefore, in the first welding step, adhesion of spatter to the pressing jig 50 for pressing the tab group 18 can be suppressed. As a result, the frequency of cleaning and replacement of the pressing jig 50 can be reduced.

  (4) The second welding process is performed by keyhole laser welding. The laser welding by the keyhole method can make the penetration depth deeper than the laser welding by the heat conduction method. Therefore, it is suitable for the 2nd welding process which carries out laser welding of the conductive member 17 and the tab group 18 which consists of a plurality of tabs 26.

The above embodiment may be modified as follows.
The electrode assembly 12 may be a wound electrode assembly. Although not shown, the wound electrode assembly has a layered structure in which a long strip-like positive electrode and a long strip-like negative electrode are insulated and wound. The positive electrode and the negative electrode each have a strip-like uncoated portion in which the metal foil is exposed without an active material layer present at one of the edges along the pair of long sides. The electrode assembly includes an uncoated portion group in which strip-shaped uncoated portions are stacked with the same polarity. The uncoated portion group of the positive electrode is present at one end of the winding axis, and the uncoated portion group of the negative electrode is present at the other end of the winding axis. In the winding type electrode assembly, the number of layers on which the band-shaped uncoated portion is stacked is taken as the number of uncoated portions.

In the positive electrode 21 and the negative electrode 22, the active material layer 25 may be present on one side of the metal foil 24.
The uncoated portions of the positive electrode 21 and the negative electrode 22 are not limited to the tab 26. For example, the uncoated portion may be present along the projecting edge of the tab 26 in addition to the tab 26. In addition, the uncoated portion may be configured not to include the tab 26 and to be present along the edge of the metal foil 24.

  The penetration depth of the straight portion 33 of the outer welding portion 31 in the stacking direction may be appropriately changed in accordance with the number of tabs 26 constituting the tab group 18 and the thickness of the tabs 26. For example, in the case where the number of tabs 26 constituting the tab group 18 is about 60 to 90 and the thickness of each tab 26 is about 10 μm, the penetration depth is preferably about 0.2 to 0.3 mm .

  ○ The longitudinal direction of the straight portion 33 and the inner welding portion 32 of the outer welding portion 31 extends in the longitudinal direction of the tab 26, and the short direction of the straight portion 33 of the outer welding portion 31 and the inner welding portion 32 is the short of the tab 26 It may extend in the hand direction.

The dimension A in the longitudinal direction of the outer welding portion 31 may be changed as appropriate.
The dimension in the longitudinal direction of the inner welding portion 32 may be changed as appropriate as long as the inner welding portion 32 can exist between the two straight portions 33 of the outer welding portion 31.

The dimension in the lateral direction of the straight portion 33 of the outer welding portion 31 and the dimension in the lateral direction of the inner welding portion 32 may be appropriately changed in the range of 0.5 to 1.0 mm.
The distance B between the straight portions 33 as the two first welded portions of the outer welding portion 31 may be changed in the range of more than 0.5 mm and 4.0 mm or less.

The shape of the outer welding portion 31 may be changed as appropriate.
For example, as shown to Fig.8 (a), you may change the arc part 34 as a connection welding part connected with the linear part 33 into linear form. As shown in FIG. 8 (b), the outer welding portion 31 may be configured from straight portions 33 as two first welding portions. That is, the arc 34 may be omitted. As shown in FIG. 8C, the straight portions 33 as the two first welding portions of the outer welding portion 31 may have a dotted line shape. As shown in FIG. 8 (d), the longitudinal direction of the straight portions 33 as the two first welds of the outer weld 31 extends in the longitudinal direction of the tab 26, and the longitudinal direction of the inner weld 32 is the tab 26. It may extend in the short direction of However, in each example, the distance B between the two straight portions 33 is 4.0 mm or less.

  As shown in FIGS. 9 and 10, the inner welding portion 32 may be recessed toward the conductive member 17 from the surface of the tab 26 located at the other end in the stacking direction. A portion in which the inner welding portion 32 is recessed from the surface of the tab 26 located at the other end in the stacking direction is referred to as a recess 32 a.

  As shown in FIG. 9, the dimension W of the recess 32 a in the short direction of the inner welded portion 32 on the surface of the tab 26 located at the other end in the stacking direction is the end face 17 a on the tab group 18 side of the conductive member 17. It is preferable that it is 2 to 6 times the dimension X of the width direction of the inner side welding part 32. As shown in FIG.

  When laser welding the conductive member 17 and the tab group 18 under welding conditions such that the dimension W of the recess 32a is less than twice the dimension X of the inner welding portion 32, the tab 26 and the conductive member located at one end in the stacking direction There is a possibility that a sufficient bonding strength can not be obtained because the bonding area with 17 is insufficient. On the other hand, when the conductive member 17 and the tab group 18 are laser welded under the welding condition that the dimension W of the recess 32 a is larger than six times the dimension X of the inner welding portion 32, the plurality of tabs 26 constituting the tab group 18 Among them, there is a possibility that the tab 26 located on the other end side in the stacking direction near the irradiation position of the laser may be broken. Therefore, the dimension W of the recess 32 a in the short direction of the inner welding portion 32 on the surface of the tab 26 located at the other end of the stacking direction is 2 to 6 times the dimension X of the short direction of the inner welding portion 32 By performing laser welding under such welding conditions, generation of breakage of the tab 26 at the time of welding can be suppressed, and sufficient bonding strength between the conductive member 17 and the tab group 18 can be obtained.

  As shown in FIG. 10, the dimension W of the recess 32a in the short direction of the inner welding portion 32 on the surface of the tab 26 located at the other end of the stacking direction is the penetration depth in the lamination direction in the cross section of the inner welding portion 32. It is preferable that it is 10 to 50% of Y.

  When laser welding the conductive member 17 and the tab group 18 under welding conditions such that the dimension W of the recess 32a is less than 10% of the penetration depth Y of the inner welding portion 32, the tab 26 located at one end in the stacking direction The bonding area with the conductive member 17 is insufficient, and there is a possibility that sufficient bonding strength can not be obtained. On the other hand, when the conductive member 17 and the tab group 18 are laser welded under the welding condition such that the dimension W of the recess 32 a is larger than 50% of the penetration depth Y of the inner welding portion 32, a plurality of tabs constituting the tab group 18 Among the tabs 26, the tab 26 located on the other end side in the stacking direction near the irradiation position of the laser may be broken. Therefore, the dimension W of the recess 32 a in the short direction of the inner welding portion 32 on the surface of the tab 26 positioned at the other end of the stacking direction is 10 to 50% of the penetration depth Y of the inner welding portion 32 By performing the laser welding under the welding conditions, it is possible to suppress the occurrence of breakage of the tab 26 at the time of welding and to obtain sufficient bonding strength between the conductive member 17 and the tab group 18.

The laser welding in the first welding process is not limited to the heat conduction method. For example, a keyhole system may be used.
The laser welding in the second welding process is not limited to the keyhole system. For example, a heat conduction system may be used.

The power storage device is also applicable to power storage devices other than secondary batteries, such as capacitors.
The secondary battery 10 may be another secondary battery other than a lithium ion secondary battery. The point is that the ions move between the active material for the positive electrode and the active material for the negative electrode and the charge is taught.

DESCRIPTION OF SYMBOLS 10 ... Secondary battery as an electrical storage apparatus, 12 ... Electrode assembly, 15 ... Electrode terminal, 17 ... Conducting member, 17a ... End surface, 18 ... Tab group as an uncoated part group, 21 ... Positive electrode as an electrode, 22: negative electrode as electrode, 24: metal foil, 25: active material layer, 26: tab as uncoated part, 32: inner welding part as second welded part, 32a: concave part, 33: first welding Straight part as a part, 34 ... arc part as a connection weld part, W ... dimension, X ... dimension, Y ... penetration depth.

Claims (10)

An electrode of a positive electrode and a negative electrode having a rectangular sheet metal foil, an active material layer present on at least one surface of the metal foil, and an uncoated portion where the active material layer does not exist and the metal foil is exposed An electrode assembly comprising an uncoated portion group in which the plurality of uncoated portions are stacked in the same polarity and stacked in an insulated state;
An electrode terminal for exchanging electricity with the electrode assembly;
A conductive member for electrically connecting the electrode assembly and the electrode terminal;
A storage device comprising
The conductive member is disposed at one end side in the stacking direction of the group of uncoated portions, where the direction in which the uncoated portion is stacked is the stacking direction.
Two first welds where a plurality of uncoated parts including the uncoated part located at the other end of the laminating direction are laser-welded;
And a second welding portion in which the conductive member and the uncoated portion group are laser-welded.
When the uncoated portion group is viewed from the other end side in the stacking direction, the two first welded portions are present at an interval of more than 0.5 mm and 4.0 mm or less, and the second welded portion is A storage device characterized by existing between the two first welds.   The power storage device according to claim 1, wherein a penetration depth of the first welding portion in the stacking direction is 0.2 to 0.3 mm. The second welded portion has a shape which is recessed from the surface of the uncoated portion located at the other end in the laminating direction toward the conductive member, and when the portion recessed from the surface of the uncoated portion is a recessed portion,
The dimension of the recess in the short direction of the second welded portion on the surface of the uncoated portion located at the other end of the stacking direction is the dimension at the end face of the conductive member on the uncoated portion group side The power storage device according to claim 1, wherein the size is 2 to 6 times the dimension of the second welding portion in the short direction. The second welded portion has a shape which is recessed from the surface of the uncoated portion located at the other end in the laminating direction toward the conductive member, and when the portion recessed from the surface of the uncoated portion is a recessed portion,
The dimension of the recess in the lateral direction of the second welded portion on the surface of the uncoated portion located at the other end of the laminating direction is 10 to 10 times the penetration depth of the second welded portion in the laminating direction. The power storage device according to claim 1, which is 50%. An electrode of a positive electrode and a negative electrode having a rectangular sheet metal foil, an active material layer present on at least one surface of the metal foil, and an uncoated portion where the active material layer does not exist and the metal foil is exposed An electrode assembly comprising an uncoated portion group in which the uncoated portions of the electrode are stacked in the same polarity and stacked in an insulated state, an electrode terminal for exchanging electricity with the electrode assembly, A laser welding method of an electric storage device for laser welding the uncoated portion group and the conductive member for manufacturing an electric storage device comprising an electrode assembly and a conductive member electrically connecting the electrode terminal. And
When the direction in which the uncoated portion is stacked is the stacking direction,
A pressing step of pressing the non-coated portion group from the other end side in the stacking direction while the conductive member is disposed at one end side in the stacking direction of the non-coated portion group;
A first welding step of irradiating a laser from the other end side in the stacking direction and welding a plurality of uncoated portions to form two first welded portions;
A second welding step of irradiating a laser from the other end side in the stacking direction to weld the conductive member and the uncoated portion group to form a second welded portion;
Equipped with
When the non-coated portion group is viewed from the other end side in the stacking direction, the two first welded portions are formed at an interval of more than 0.5 mm and 4.0 mm or less, and the second welded portion is A laser welding method of a power storage device, characterized in that it is formed between the two first welds.   The laser welding method for a power storage device according to claim 5, wherein a penetration depth of the first welding portion in the stacking direction is 0.2 to 0.3 mm in the first welding step.   The laser welding method according to claim 5 or 6, wherein the laser welding is a heat conduction system in the first welding step.   The laser welding method according to any one of claims 5 to 7, wherein the laser welding is a keyhole system in the second welding step. An electrode of a positive electrode and a negative electrode having a rectangular sheet metal foil, an active material layer present on at least one surface of the metal foil, and an uncoated portion where the active material layer does not exist and the metal foil is exposed An electrode assembly comprising an uncoated portion group in which the uncoated portions of the electrode are stacked in the same polarity and stacked in an insulated state, an electrode terminal for exchanging electricity with the electrode assembly, A laser welding method of an electric storage device for laser welding the uncoated portion group and the conductive member for manufacturing an electric storage device comprising an electrode assembly and a conductive member electrically connecting the electrode terminal. And
When the direction in which the uncoated portion is stacked is the stacking direction,
A pressing step of pressing the non-coated portion group from the other end side in the stacking direction while the conductive member is disposed at one end side in the stacking direction of the non-coated portion group;
A first welding step of irradiating a laser from the other end side in the laminating direction during the pressing step to weld a plurality of uncoated portions to form two first welded portions in a linear shape; ,
During the pressurizing step and after the first welding step, a laser is irradiated from the other end side in the laminating direction to weld the conductive member and the uncoated portion group to form a second welded portion Welding process,
Equipped with
When the uncoated portion group is viewed from the other end side in the stacking direction, the two first welded portions are formed at an interval of more than 0.5 mm and 4.0 mm or less, and the second welded portion A laser welding method of a power storage device, characterized in that it is formed between the two first welds. The method according to claim 9, wherein the first welding portion is formed to be connected to a connection welding portion extending in a direction different from the first welding portion.