Secondary battery

Abstract

To provide a secondary battery which is capable of suppressing damage of a tab group of an electrode body and also improves processing easiness.SOLUTION: Disclosed is a secondary battery comprising an electrode body 40, a battery terminal, etc. The battery terminal includes a guide part 28b which is disposed along an end face of the electrode body 40 in an X-axis direction, an electrode joint part 28c which extends from the guide part 28b, and a bent part 28d between the guide part 28b and the electrode joint part 28c. The electrode joint part 28c has a joint surface Mb at a position corresponding to a tab group 56 on at least one surface. A position of the bent part 28d in a Z-axis direction is different from the tab group 56 of the electrode body 40. In a state where the tab group 56 is joined to the joint surface Mb of the electrode joint part 28c, a joint location of the electrode joint part 28c and the tab group 56 is bent in the bent part 28d so as to be opposed with the end face of the electrode body 40 in the X-axis direction.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] Conventionally, secondary batteries used in electric vehicles such as electric automobiles that use a motor as a drive source include an electrode assembly, a case that houses the electrode assembly, battery terminals that are attached to the case and electrically connected to the electrode assembly, etc. An example of such a secondary battery is the battery disclosed in Patent Document 1.

[0003] The battery described in Patent Document 1 has a single electrode body housed in a battery case, and a positive terminal and a negative terminal connected to this electrode body as battery terminals. The positive terminal and the negative terminal have guide portions that abut against the end faces of the electrode body, and connection joint portions that are bendably extended from the guide portions via bending portions and can be connected to a group of tabs extending from the electrode body. Specifically, the positive terminal and the negative terminal have recesses in the bending portions to improve bending workability and bending accuracy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 140779 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the battery described in Patent Document 1, the tab group of the electrode body is bent while overlapping the connection joint and bent portion of the battery terminal, which raises concerns about damage to the tab group. Also, because the tab group of the electrode body and the bent portion of the battery terminal must be bent while overlapping, there is room for improvement in terms of ease of processing.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide a secondary battery that can suppress damage to the tab group of the electrode body and also has improved ease of processing. [Means for solving the problem]

[0007] The secondary battery according to the present invention, which achieves the above object, has the following characteristic configuration: A secondary battery comprising: a housing having an opening; a lid attached to the opening of the housing; a flat electrode body formed by laminating a positive electrode material and a negative electrode material with a separator interposed therebetween; and a battery terminal attached to the lid, The electrode body is a tab group formed by stacking tabs of the positive electrode material and the negative electrode material, and housed in the housing; The tab group extends from an end surface in a second direction perpendicular to a first direction that is a thickness direction of the electrode body, The battery terminals are a guide portion disposed along an end surface of the electrode body in the second direction, a plate-shaped electrode joint portion extending from the guide portion, and a bent portion between the guide portion and the electrode joint portion, the electrode joint portion has a joint surface at a position corresponding to the tab group on at least one surface, the bent portion is positioned differently from the tab group of the electrode body in a third direction perpendicular to the first direction when viewed in the second direction, The point is that when the tab group is joined to the joining surface of the electrode joining portion, the joining point between the electrode joining portion and the tab group is bent at the bending portion so as to face the end surface of the electrode body in the second direction.

[0008] According to the above-described characteristic configuration, since the bent portion of the battery terminal and the tab group do not overlap, the bending load acting on the tab group when bending the electrode joint is reduced, thereby suppressing damage to the tab group. Furthermore, since the bent portion of the battery terminal and the tab group do not overlap, the electrode joint is easily bent at the bent portion during secondary battery manufacturing, improving ease of processing.

[0009] Further characteristic configurations of the secondary battery according to the present invention are as follows: An accommodation space is provided between the end surface of the electrode body in the second direction and the joint surface of the electrode joint portion, and the tab group is accommodated in the accommodation space.

[0010] According to the above characteristic configuration, the dimension of the electrode body in the second direction can be increased to increase the battery capacity without changing the size of the casing, compared to when there is no storage space.

[0011] Further characteristic configurations of the secondary battery according to the present invention are as follows: A plurality of the electrode bodies is provided, The tab group of each of the plurality of electrode assemblies is joined to the joining surface of the electrode joining portion.

[0012] According to the above characteristic configuration, since a plurality of electrode bodies are electrically connected to the electrode junction, the capacity of the secondary battery is increased.

[0013] Further characteristic configurations of the secondary battery according to the present invention are as follows: an overlapping portion in which the tab group of all the electrode bodies overlaps in a direction perpendicular to the joining surface of the electrode joining portion; The overlapping portion is joined to the joining surface of the electrode joining portion.

[0014] According to the above-described characteristic configuration, the joining of the tab group of each electrode body to the electrode joint portion can be performed, for example, by a single ultrasonic joining operation with the overlapping portion facing the joining surface of the electrode joint portion. Therefore, even if the number of electrode bodies increases, the increase in the time required to join the tab group of each electrode body to the electrode joint portion can be suppressed. Therefore, the capacity of the secondary battery can be increased while suppressing the increase in the time required to assemble the secondary battery. [Effects of the Invention]

[0015] As described above, the secondary battery according to the present invention can suppress damage to the tab group of the electrode body and also improves ease of processing. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is an exploded perspective view of a secondary battery according to a first embodiment; [Figure 2] FIG. 1 is a cross-sectional view showing a schematic configuration of a secondary battery. [Figure 3] FIG. 2 is a perspective view showing a partially developed electrode assembly. [Figure 4] FIG. 10 is a perspective view illustrating the positional relationship between the electrode body and the negative electrode current collector terminal before ultrasonic bonding. [Figure 5] FIG. 3 is a cross-sectional view taken along the arrows VV in FIG. 2. [Figure 6] FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 2. [Figure 7] FIG. 10 is a partial cross-sectional plan view of a secondary battery of a comparative example. [Figure 8] FIG. 10 is a partial perspective view of a secondary battery according to a second embodiment. [Figure 9] FIG. 4 is a cross-sectional view showing a schematic configuration of a secondary battery according to a second embodiment. [Figure 10] FIG. 10 is a partial cross-sectional plan view of an electrode body and a current collector terminal of a secondary battery according to a second embodiment. [Figure 11] FIG. 10 is a partial cross-sectional plan view of an electrode body and a current collector terminal of a secondary battery of another embodiment. [Figure 12] FIG. 10 is a partial cross-sectional plan view of an electrode body and a current collector terminal of a secondary battery of another embodiment. [Figure 13] FIG. 10 is a partial perspective view of a secondary battery according to a first modified example of the second embodiment. [Figure 14] FIG. 10 is a partial cross-sectional plan view of a secondary battery according to a first modified example of the second embodiment. [Figure 15] FIG. 10 is a partial cross-sectional plan view of a secondary battery of another embodiment. [Figure 16] FIG. 10 is a partial cross-sectional plan view of a secondary battery according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] A secondary battery according to one embodiment of the present invention will be described below with reference to the drawings. In the following, an example in which the secondary battery is a lithium-ion secondary battery will be described. In addition, in the following, each description and each drawing will be appropriately simplified for clarity.

[0018] [Overview of Secondary Battery 1] An overview of a secondary battery 1 according to this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is an exploded perspective view of the secondary battery 1. FIG. 2 is a cross-sectional view showing a schematic configuration of the secondary battery 1. In the following description, the direction parallel to the height direction of the secondary battery 1 is referred to as the Z-axis direction, the direction parallel to the winding axis direction of the electrode body 40 is referred to as the X-axis direction, and the direction parallel to the thickness direction of the electrode body 40 is referred to as the Y-axis direction. The Z-axis direction is parallel to the up-down direction, and the X-axis and Y-axis directions are perpendicular to each other and parallel to the horizontal direction. In this embodiment, the Y-axis direction corresponds to the "first direction," the X-axis direction corresponds to the "second direction," and the Z-axis direction corresponds to the "third direction."

[0019] 1 and 2, the secondary battery 1 includes a battery case 10 consisting of a case body 11 and a sealing plate 13, battery terminals PS and NS consisting of external terminals 25, 26 and current collecting terminals 27, 28 attached to the sealing plate 13, and one electrode body 40 electrically connected to the current collecting terminals 27, 28. The secondary battery 1 is a sealed secondary battery in which the one electrode body 40 and the current collecting terminals 27, 28 are housed inside the case body 11, the opening of the case body 11 is sealed with the sealing plate 13, and an electrolyte is poured into the inside of the case body 11.

[0020] [Configuration of battery case 10] As shown in FIGS. 1 and 2, a battery case 10 of this embodiment is composed of a case body 11 that is roughly rectangular and has an open top, and a sealing plate 13 that seals the opening of the case body 11. In the battery case 10 of this embodiment, the case body 11 and the sealing plate 13 are both made of aluminum, but this is not limited to this. Various metals and alloys can be used as materials for the case body 11 and the sealing plate 13. In this embodiment, the case body 11 corresponds to the "casing," and the sealing plate 13 corresponds to the "lid."

[0021] In this embodiment, the sealing plate 13 has a shape corresponding to the shape of the opening of the case body 11 and is configured to be able to seal the opening of the case body 11. Specifically, the sealing plate 13 in this embodiment is made of a flat plate member that is generally rectangular when viewed in the Z-axis direction. The sealing plate 13 has a positive battery terminal PS disposed at one end in the longitudinal direction (X-axis direction) and a negative battery terminal NS disposed at the other end in the longitudinal direction.

[0022] In this embodiment, the outer peripheral edge 13a of the sealing plate 13 and the opening edge 11a of the case body 11 are laser welded together, and the opening of the case body 11 is closed by the sealing plate 13, as will be described in detail later.

[0023] [Configuration of electrode body 40] Fig. 3 is a perspective view showing a partially developed electrode assembly 40. As shown in Fig. 3, the electrode assembly 40 is composed of a wound body obtained by stacking long strip-shaped positive electrode material 41 and negative electrode material 46 with a similarly strip-shaped separator 49 interposed therebetween, winding the stack, and then compressing the stack into a flat shape. In this embodiment, the positive electrode material 41 is aluminum foil, and the negative electrode material 46 is copper foil.

[0024] The cathode material 41 has a cathode coated portion 41a in which a cathode active material is applied to both sides, and a cathode uncoated portion 41b at one end in the X-axis direction where the cathode active material is not applied. The cathode material 41 also has a plurality of cathode tabs 42 extending outward at intervals from the end at one end in the X-axis direction. The intervals between the plurality of cathode tabs 42 are set so that, after winding, a cathode tab group 51 is formed in the center of the electrode assembly 40 in the height direction.

[0025] The negative electrode material 46 has a negative electrode coated portion 46a in which a negative electrode active material is coated on both sides, and a negative electrode uncoated portion 46b in which the negative electrode active material is not coated at the end on the other side in the X axis direction. The negative electrode material 46 also has a plurality of negative electrode tabs 47 extending outward at intervals from the end on the other side in the X axis direction. The intervals between the plurality of negative electrode tabs 47 are set so that, after winding, a negative electrode tab group 56 is formed in the center of the electrode assembly 40 in the height direction.

[0026] The separator 49 is disposed so as to insulate the positive electrode coated portion 41a of the positive electrode material 41 from the negative electrode coated portion 46a of the negative electrode material 46. The separator 49 can be made of an insulating material (such as a porous insulating resin material) that is permeable to ions.

[0027] The electrode body 40 has a positive electrode tab group 51 extending from one end face in the winding axis direction (X-axis direction) and a negative electrode tab group 56 extending from the other end face. The positive electrode tab group 51 and the negative electrode tab group 56 are formed by stacking the positive electrode tabs 42 and the negative electrode tabs 47 in layers when the positive electrode material 41 and the negative electrode material 46, on which the plurality of positive electrode tabs 42 and the negative electrode tabs 47 are formed, are wound.

[0028] In this embodiment, the positive electrode tab group 51 extends along the winding axis direction from one end face of the electrode assembly 40, from a portion on one side in the thickness direction (Y axis) of the electrode assembly 40 and on the central side in the height direction (Z axis) of the electrode assembly 40 when viewed from the winding axis direction (X axis direction). On the other hand, the negative electrode tab group 56 extends along the winding axis direction from a portion on the other end face of the electrode assembly 40, from a portion on one side in the thickness direction of the electrode assembly 40 and on the central side in the height direction of the electrode assembly 40 when viewed from the winding axis direction. Note that the positive electrode tab group 51 and the negative electrode tab group 56 are rectangular in shape with their longitudinal direction parallel to the height direction of the electrode assembly 40 when viewed from the thickness direction of the electrode assembly 40. Thus, the tab groups 51 and 56 extend from both end faces in the X axis direction, which is perpendicular to the Y axis direction, which is the thickness direction of the electrode assembly 40.

[0029] [Configuration of the positive electrode side and negative electrode side] In this embodiment, the secondary battery 1 includes, as its positive electrode side configuration, a positive battery terminal PS consisting of a positive electrode external terminal 25 and a positive electrode current collector terminal 27, a positive electrode insulating member 29, and a positive electrode gasket 31. The secondary battery 1 also includes, as its negative electrode side configuration, a negative electrode battery terminal NS consisting of a negative electrode external terminal 26 and a negative electrode current collector terminal 28, a negative electrode insulating member 30, and a negative electrode gasket 32.

[0030] Although detailed description will be omitted, in the secondary battery 1 of this embodiment, the positive electrode external terminal 25 and the positive electrode current collector terminal 27, and the negative electrode external terminal 26 and the negative electrode current collector terminal 28 are integrated by crimping to form the respective battery terminals PS and NS. In this embodiment, the positive electrode external terminal 25 and the positive electrode current collector terminal 27 that constitute the positive electrode battery terminal PS are both made of aluminum. On the other hand, with regard to the negative electrode battery terminal NS, the negative electrode external terminal 26 is made of aluminum, and the negative electrode current collector terminal 28 is made of copper.

[0031] In this embodiment, the positive electrode external terminal 25 and the negative electrode external terminal 26 are insulated from the sealing plate 13 by a positive electrode gasket 31 and a negative electrode gasket 32. The positive electrode current collector terminal 27 and the negative electrode current collector terminal 28 are insulated from the sealing plate 13 by a positive electrode insulating member 29 and a negative electrode insulating member 30. Airtightness is maintained between each battery terminal PS, NS and the sealing plate 13 by each insulating member 29, 30 and each gasket 31, 32. In this embodiment, the insulating members 29, 30 and the gaskets 31, 32 are made of PFA resin, but the material is not limited to PFA resin. The insulating members 29, 30 and the gaskets 31, 32 may be made of any insulating material.

[0032] In this embodiment, each current collecting terminal 27, 28 is formed by bending a plate-like member and includes a base portion 27a, 28a that is crimped to each external terminal 25, 26, a guide portion 27b, 28b that is continuous with the base portion 27a, 28a, and an electrode joint portion 27c, 28c that is continuous with the guide portion 27b, 28b. The electrode joint portion 27c, 28c includes a first portion 27c1, 28c1 that extends in the X-axis direction and a second portion 27c2, 28c2 that extends from the first portion 27c1, 28c1 in the Z-axis direction. A bent portion 27d, 28d is provided between the guide portion 27b, 28b and the first portion 27c1, 28c1.

[0033] In this embodiment, each current collecting terminal 27, 28 is arranged on the underside of the sealing plate 13 so that its base portion 27a, 28a, which is generally rectangular when viewed in the Z-axis direction, is aligned horizontally. The guide portion 27b, 28b of each current collecting terminal 27, 28 is a generally rectangular portion when viewed in the X-axis direction that extends downward in the Z-axis direction from the end of the base portion 27a, 28a to near the center of the electrode body 40 in the Z-axis direction, and is arranged between the electrode body 40 and the end side wall of the case body 11.

[0034] The electrode joint portions 27c, 28c of each current collecting terminal 27, 28 are formed at positions that allow them to be joined to the tab groups 51, 56 of the electrode assembly 40. Specifically, before the electrode assembly 40 is assembled, each electrode joint portion 27c, 28c (first portions 27c1, 28c1 and second portions 27c2, 28c2) is a generally rectangular portion when viewed in the Y-axis direction that extends along the X-axis direction from one edge of the guide portions 27b, 28b, and the second portions 27c2, 28c2 are located below the lower ends of the guide portions 27b, 28b. Note that the boundary portions between the first portions 27c1, 28c1 and the guide portions 27b, 28b are bent portions 27d, 28d. The second portions 27c2, 28c2 of each electrode joint 27c, 28c have joint surfaces Ma, Mb on their inner sides in the Y-axis direction (surfaces facing the center of the electrode assembly 40 when viewed in the X-axis direction), and the tab groups 51, 56 are joined to these joint surfaces Ma, Mb. As will be described in detail later, the electrode joints 27c, 28c of each current collecting terminal 27, 28 are bent at bent portions 27d, 28d so that joint regions (joint locations) A between each electrode joint 27c, 28c and each tab group 51, 56 face the end faces of the electrode assembly 40 in the X-axis direction, with the corresponding tab groups 51, 56 joined to the joint surfaces Ma, Mb (see FIGS. 2 and 6).

[0035] Here, in the present embodiment, when the electrode joints 27c, 28c are bent at the bending portions 27d, 28d, a storage space S is formed between the joint surfaces Ma, Mb of the electrode joints 27c, 28c (specifically, the second portions 27c2, 28c2) and the end surface of the electrode assembly 40 in the X-axis direction (see FIGS. 2 and 6). In the present embodiment, the tab groups 51, 56 are housed in this storage space S. Therefore, compared to a case where the storage space S is not formed, the dimension of the electrode assembly 40 in the X-axis direction can be made longer, and the volume of the electrode assembly 40 that occupies in the battery case 10 can be increased. Therefore, the battery capacity can be increased without changing the size of the battery case 10 (specifically, the length in the X-axis direction).

[0036] Next, a method for assembling the electrode body 40 to each of the current collector terminals 27, 28 will be described with reference to Figures 4 to 6. Figure 4 is a partial perspective view illustrating the positional relationship between the electrode body 40 and the negative current collector terminal 28 before ultrasonic bonding. Figures 5 and 6 are plan sectional views illustrating the positional relationship between the electrode body 40 and the negative current collector terminal 28 in a state in which the electrode joint portions 27c, 28c are bent after ultrasonic bonding.

[0037] 4, the electrode assembly 40 is placed on the negative electrode current collector terminal 28 attached to the sealing plate 13 so that the electrode joint 28c and the tab group 56 corresponding to the electrode joint 28c face each other in the Y-axis direction. In other words, the negative electrode current collector terminal 28 is placed so that the negative electrode tab group 56 of the electrode assembly 40 and the joint surface Mb of the electrode joint 28c (second portion 28c2) face each other in the Y-axis direction. Furthermore, although not shown in the figure, the positive electrode current collector terminal 27 is placed so that the positive electrode tab group 51 of the electrode assembly 40 and the joint surface Ma of the electrode joint 27c (second portion 27c2) face each other in the Y-axis direction.

[0038] Next, each electrode joint 27c, 28c is bonded to each tab group 51, 56. Specifically, the bonding surfaces Ma, Mb of each electrode joint 27c, 28c (second portions 27c2, 28c2) are brought into contact with the surfaces of each tab group 51, 56 that face the bonding surfaces Ma, Mb. Next, an anvil (not shown) is pressed against the surfaces of each electrode joint 27c, 28c opposite the bonding surfaces Ma, Mb, and a horn is pressed against the surfaces of each tab group 51, 56 opposite the surfaces that face the bonding surfaces Ma, Mb along the Y-axis direction to apply pressure. Thereafter, ultrasonic vibrations are applied in the vertical direction by the horn. This bonds each electrode joint 27c, 28c to each tab group 51, 56.

[0039] Next, with the electrode joint portions 27c, 28c of each current collecting terminal 27, 28 joined to each tab group 51, 56, the electrode joint portions 27c, 28c are bent at the bending portions 27d, 28d to abut the first portions 27c1, 28c1 against the guide portions 27b, 28b, and each joint portion A is opposed to the end face of the electrode body 40 in the X-axis direction (see Figures 5 and 6).

[0040] FIG. 7 is a partial plan cross-sectional view of a secondary battery of a comparative example. In a structure in which an electrode joint 78c and a negative electrode tab group 56 corresponding to the electrode joint 78c face each other in the X-axis direction and the negative electrode tab group 56 is folded to cover the electrode joint 78c from the outside, as in the comparative example shown in FIG. 7 , when the electrode joint 78c is bent, the negative electrode tab group 56 is folded while overlapping the electrode joint 78c. Therefore, the bending area is increased by the thickness of the guide portion 78b and the electrode joint 78c, and the bending load acting on the negative electrode tab group 56 increases, making it more susceptible to damage. Furthermore, because the electrode joint 78c is difficult to bend when the electrode joint 78c and the negative electrode tab group 56 overlap, processing to make it easier to bend (for example, processing to reduce the thickness of the bent portion) may be required.

[0041] In contrast, in the secondary battery 1 of this embodiment, the bent portion 27d and the negative electrode tab group 56 do not overlap, so when the electrode joint portion 28c is bent, there is no increase in the bending area due to the plate thickness of the guide portion 28b or the electrode joint portion 28c as in the comparative example, and the secondary battery 1 is easy to bend. Therefore, the bending load acting on the negative electrode tab group 56 can be reduced, damage to the negative electrode tab group 56 can be suppressed, and bending accuracy can be improved. In other words, in the secondary battery 1 of this embodiment, damage to the tab groups 51, 56 during manufacturing can be suppressed and ease of processing can be improved.

[0042] Second Embodiment Next, a secondary battery according to a second embodiment will be described. The following mainly describes configurations different from the first embodiment, and a description of configurations identical to those of the first embodiment will be omitted. As shown in FIGS. 8 to 10, the secondary battery according to the second embodiment includes two electrode assemblies 40 inside a battery case 10. The negative electrode tab groups 56 of the two electrode assemblies 40 are joined to the electrode joint 28c in a state overlapping the joining surface Mb side of the second portion 28c2 of the electrode joint 28c (FIGS. 8 and 10). Although not shown, the positive electrode tab groups 51 are also joined to the electrode joint 28c in a state overlapping the joining surface Ma side of the second portion 27c2 of the electrode joint 27c, except that their positional relationship with the electrode joint 28c in the Y-axis direction is reversed. That is, in the secondary battery of the second embodiment, there is an overlapping portion D where the positive electrode tab groups 51, 51 of all the electrode bodies 40, 40 overlap in a direction perpendicular to the second parts 27c2, 28c2 of the electrode joints 27c, 28c, and an overlapping portion D where the negative electrode tab groups 56, 56 overlap, and each tab group 51, 56 is joined to the second parts 27c2, 28c2 of the electrode joints 27c, 28c at the overlapping portion D, respectively.

[0043] 10, the electrode joint portion 28c is disposed in a position closer to one of the electrode bodies 40 than the center of the two electrode bodies 40 in the Y-axis direction. After the overlapping portion D of the two negative electrode tab groups 56 is ultrasonically joined to the electrode joint portion 28c at the joint portion A, the two negative electrode tab groups 56 are bent so that the second portion 28c2 of the electrode joint portion 28c faces outward (in other words, so that the joint portion A faces the end face of one of the two electrode bodies 40), and are then accommodated in the accommodation space S. The same applies to the positive electrode side.

[0044] The positional relationship between the electrode joints 27c, 28c and the two electrode assemblies 40, 40 and the position of the tab groups 51, 56 of the electrode assembly 40 in the Y-axis direction are not particularly limited. For example, as shown in Fig. 11 , the electrode joint 28c may be disposed on the center line C of the two electrode assemblies 40, 40 in the Y-axis direction, with the negative electrode tab group 56 of one electrode assembly 40 formed closer to the center line C and the negative electrode tab group 56 of the other electrode assembly 40 formed at a position away from the center line C. In this case, although there is a difference in the protruding lengths of the two negative electrode tab groups 56, 56 in the X-axis direction, this does not pose a problem as long as the two negative electrode tab groups 56, 56 have an overlapping portion D and the overlapping portion D and the second portion 28c2 are joined at a joining portion A that is equal to or larger than a predetermined area. Furthermore, as shown in FIG. 12, it is also conceivable that the negative electrode tab group 56 of one electrode body 40 may protrude from the electrode joint portion 28c in the X-axis direction, in which case the protruding portion 56a of the negative electrode tab group 56 may be appropriately cut off before bending.

[0045] In the secondary battery of the second embodiment, the multiple electrode bodies 40 are electrically connected to the electrode joints 27c and 28c, thereby increasing the capacity of the secondary battery. In addition, by joining the overlapping portions D to the electrode joints 27c and 28c, the tab groups 51 and 56 of each electrode body 40 can be joined and electrically connected to the electrode joints 27c and 28c by a single ultrasonic joining process. Therefore, it is possible to achieve a high capacity secondary battery while suppressing an increase in the time required to assemble the secondary battery.

[0046] [Modification of the second embodiment] Next, a secondary battery according to a modification of the second embodiment will be described. As shown in FIGS. 13 and 14 , in the secondary battery according to the modification of the second embodiment, the electrode joint 28c has joint surfaces Mb1 and Mb2 on both sides thereof, and is disposed between the tab groups 56 of the two electrode assemblies 40 in the Y-axis direction. The electrode joint 28c is disposed on the center line C of the two electrode assemblies 40 in the Y-axis direction. One of the two negative electrode tab groups 56 is ultrasonically bonded to the joint surface Mb1 at the joint region A, and the other is ultrasonically bonded to the joint surface Mb2 at the same joint region A. While bonded to the electrode joint 28c, the two negative electrode tab groups 56 are bent together with the electrode joint 28c so as to fit along the end surface of one of the electrode assemblies 40. The same applies to the positive electrode side.

[0047] In this modification, the positional relationship between the electrode junctions 27c, 28c and the two electrode assemblies 40, 40 and the position of the tab groups 51, 56 of the electrode assembly 40 in the Y-axis direction are not particularly limited. As shown in Fig. 15, the electrode junction 28c may be disposed in a position closer to one of the electrode assemblies 40 and away from the center of the two electrode assemblies 40 in the Y-axis direction. Furthermore, an overlapping portion D where the tab groups 51, 56 of the plurality of electrode assemblies 40 overlap may be joined to the respective joining surfaces Mb1, Mb2 of the electrode junctions 27c, 28c.

[0048] Third Embodiment Next, a secondary battery according to a third embodiment will be described. The following description will focus primarily on configurations different from those of the first and second embodiments, and will omit a description of other configurations. As shown in FIG. 16 , the secondary battery according to the third embodiment includes three electrode assemblies 40, 40, 40 inside a battery case 10. The negative electrode tab groups 56, 56, 56 of each of the three electrode assemblies 40, 40, 40 are joined to the electrode joint 28c in a state where they overlap the joining surface Mb side of the second portion 28c2 of the electrode joint 28c. Although not shown, the same applies to the positive electrode side. That is, in the secondary battery according to the third embodiment, the tab groups 51, 56 are joined to the second portions 27c2, 28c2 of the electrode joints 27c, 28c at the overlapping portions D where the tab groups 51, 56 overlap.

[0049] In the secondary battery of the third embodiment, the negative electrode tab groups 56 are disposed in a position facing the end face of the central electrode assembly 40 in the Y-axis direction and closer to one of the electrode assembly 40 adjacent to the central electrode assembly 40. Although the three negative electrode tab groups 56 have different protruding lengths relative to the electrode joint 28c, the three negative electrode tab groups 56 have overlapping portions D, and the overlapping portions D are joined to the second portion 28c2 at joint portions A that are equal to or larger than a predetermined area. This ensures a bonded state between the electrode joint 28c and the three negative electrode tab groups 56. Furthermore, the protruding portions 56b of the three negative electrode tab groups 56 that protrude from the electrode joint 28c can be appropriately cut off to allow the electrode assembly 40 to be disposed inside the battery case 10. Although not shown, the electrode joint 28c may be disposed in a position sandwiched between two of the three negative electrode tab groups 56.

[0050] [Another embodiment] [1] In the above embodiment, a storage space S is provided between the end surface of the electrode body 40 in the X-axis direction and the bonding surfaces Ma, Mb, Mb1, Mb2 of the electrode bonding portions 27c, 28c, and the tab groups 51, 56 are stored in the storage space S. However, the present invention is not limited to this. An embodiment in which there is no storage space between the end surface of the electrode body in the X-axis direction and the bonding surfaces of the electrode bonding portions is also possible.

[0051] [2] In the above embodiment, the tab groups 51, 56 extend from a portion of each end face of the electrode assembly 40 that is located on one side in the thickness direction (Y-axis direction) of the electrode assembly 40 when viewed from the winding axis direction (X-axis direction). However, the present invention is not limited to this. For example, the tab groups 51, 56 may extend from a central portion of each end face of the electrode assembly 40 in the thickness direction (Y-axis direction) of the electrode assembly 40 when viewed from the winding axis direction (X-axis direction).

[0052] [3] In the above embodiment, the secondary battery includes a maximum of three electrode bodies 40. However, the present invention is not limited to this. The number of electrode bodies may be four or more. In this case, the number of electrode junctions of the current collecting terminals may be increased according to the number of electrode bodies, or multiple tab groups may be stacked according to the number of electrode bodies to form triple or quadruple overlapping portions, and the tab groups and electrode junctions may be joined at the overlapping portions. This allows the number of electrode bodies to be increased while suppressing an increase in the number of parts.

[0053] [4] In the above embodiment, the positive electrode tab group 51 and the negative electrode tab group 56 of each electrode assembly 40 are positioned at the same position in the Z-axis direction, but this is not limited to this. The positive electrode tab group and the negative electrode tab group of each electrode assembly may be positioned above or below the center in the Z-axis direction. The positive electrode tab group and the negative electrode tab group of each electrode assembly may be positioned at different positions in the Z-axis direction.

[0054] [5] In the above embodiment, the electrode assembly 40 is a wound body, but the present invention is not limited to this. The electrode assembly 40 is not particularly limited as long as it has a structure including a positive electrode tab group and a negative electrode tab group, and various structures used in general sealed secondary batteries can be employed.

[0055] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Explanation of symbols]

[0056] 1: Secondary battery 11: Case body (housing) 13: Sealing plate (lid body) 40: Electrode body 42: Positive electrode tab 47: Negative electrode tab 51: Positive electrode tab group 56: Negative electrode tab group PS: Positive battery terminal (battery terminal) NS: Negative battery terminal (battery terminal) 27,28: Current collector terminal 27b, 28b: Guide section 27c, 28c: Electrode joint 27c1, 28c1: 1st part (electrode joint) 27c2, 28c2: 2nd part (electrode joint) 27d, 28d: Bent section Ma,Mb: Joint surface A: Joint area (joint point) D: Overlapped part S: Storage space

Claims

1. A secondary battery comprising: a housing having an opening; a lid attached to the opening of the housing; a flat electrode body formed by laminating a positive electrode material and a negative electrode material with a separator interposed therebetween; and a battery terminal attached to the lid, The electrode body is a tab group formed by stacking tabs of the positive electrode material and the negative electrode material, and housed in the housing; The tab group extends from an end surface in a second direction perpendicular to a first direction that is a thickness direction of the electrode body, The battery terminals are a guide portion disposed along an end surface of the electrode body in the second direction, a plate-shaped electrode joint portion extending from the guide portion, and a bent portion between the guide portion and the electrode joint portion, the electrode joint portion has a joint surface at a position corresponding to the tab group on at least one surface, the bent portion is positioned differently from the tab group of the electrode body in a third direction perpendicular to the first direction when viewed in the second direction, A secondary battery, wherein the tab group is joined to the joining surface of the electrode joining portion, and the joining point between the electrode joining portion and the tab group is bent at the bending portion so as to face the end surface of the electrode body in the second direction.

2. an accommodation space is provided between the end surface of the electrode body in the second direction and the joint surface of the electrode joint portion; The secondary battery according to claim 1 , wherein the tab group is housed in the housing space.

3. A plurality of the electrode bodies is provided, The secondary battery according to claim 1 , wherein the tab group of each of the plurality of electrode assemblies is joined to the joining surface of the electrode joining portion.

4. an overlapping portion in which the tab group of all the electrode bodies overlaps in a direction perpendicular to the joining surface of the electrode joining portion; The secondary battery according to claim 3 , wherein the overlapping portion is joined to the joining surface of the electrode joining portion.

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