Secondary battery

Abstract

To provide a secondary battery capable of increasing a battery capacity by increasing the number of electrode bodies of the secondary battery while suppressing an increase in the number of components.SOLUTION: In a secondary battery 1 including a plurality of electrode bodies 40 and two battery terminals PS and NS, tab groups 51 and 56 extend from both end parts of the plurality of electrode bodies 40, and the tab group 51 on one end side in a first direction in each electrode body 40 is different in a position in a second direction orthogonal to a thickness direction when viewed in the first direction. The tab group 56 on the other end side in the first direction in the respective electrode bodies 40 is different in a position in a second direction, and the battery terminals PS and NS have a plurality of electrode bonding parts 27d, 28c, and 28d formed in a single member, and the respective electrode bonding parts 27d, 28c, and 28d are bonded to the respective tab groups 51 and 56 formed at positions that can be bonded to the electrode bonding parts 27d, 28c, and 28d.SELECTED DRAWING: Figure 1

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, and battery terminals that are attached to the case and electrically connected to the electrode assembly. In this type of secondary battery, for example, to achieve high capacity, multiple electrode assemblies may be housed within the case. For example, a battery manufactured by the method disclosed in Patent Document 1 has been proposed as an example of such a secondary battery that includes multiple electrode assemblies.

[0003] The battery described in Patent Document 1 has an electrode assembly consisting of three electrode bodies housed in a battery case, and positive and negative terminals are connected to these three electrode bodies. Specifically, in the battery described in Patent Document 1, the current collecting portion of the positive terminal is electrically connected to the positive electrode of each electrode body inside the battery case, and the current collecting portion of the negative terminal is electrically connected to the negative electrode of each electrode body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-97821 Summary of the Invention [Problem to be solved by the invention]

[0005] In the battery disclosed in Patent Document 1, each current collecting portion of the positive and negative terminals (battery terminals) is composed of a member constituting a first current collecting portion and three members constituting a second current collecting portion joined to the first current collecting portion and the electrode body, respectively. In other words, in this battery, one member constituting a second current collecting portion is required for each electrode body connected to the terminal. Therefore, in the battery described in Patent Document 1, the number of members constituting the second current collecting portion increases or decreases depending on the number of electrode bodies housed in the battery, and increasing the number of electrode bodies inevitably increases the number of parts constituting the battery terminals.

[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 increase the number of electrode bodies in the secondary battery and increase the battery capacity while suppressing an increase in the number of parts. [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 plurality of flat electrode assemblies formed by stacking positive and negative electrode materials with separators interposed therebetween; and two battery terminals attached to the lid, The plurality of electrode bodies a tab group formed by stacking tabs of the positive electrode material and the negative electrode material, the tabs being arranged in a thickness direction of the electrode body and accommodated in the housing; The tab group extends from both end portions in a first direction perpendicular to the thickness direction, When viewed in the first direction, the tab group at one end side in the first direction of each electrode body is different in position in a second direction perpendicular to the thickness direction, and the tab group at the other end side in the first direction of each electrode body is different in position in the second direction, The two battery terminals are Each electrode joint has a plurality of plate-shaped electrode joints formed on a single member, the electrode joint portion of each of the one battery terminals is formed at a position where it can be joined to the tab group on one end side of the electrode body in the first direction, and the electrode joint portion of each of the other battery terminals is formed at a position where it can be joined to the tab group on the other end side of the electrode body in the first direction, When each of the electrode junctions is joined to each of the tab groups formed at a position that allows joining to the electrode junction, the joining points between each of the electrode junctions and each of the tab groups are bent so as to overlap with the end face of the electrode body in the first direction when viewed in the first direction.

[0008] According to the above-described characteristic configuration, since the tabs of each electrode body can be joined to multiple electrode junctions formed on a single member, an increase in the number of parts can be suppressed even when the number of electrode bodies is increased. In other words, with the secondary battery of the present invention, the battery capacity can be increased by increasing the number of electrode bodies while suppressing an increase in the number of parts. Furthermore, the tab group at one end of each electrode body in the first direction and the electrode joint portion formed at the corresponding position are positioned differently in the second direction, and the tab group at the other end of each electrode body in the first direction and the electrode joint portion formed at the corresponding position are positioned differently in the second direction, which allows the joining of each tab group to each electrode joint body to be performed by ultrasonic joining using a horn and anvil.

[0009] Further characteristic configurations of the secondary battery according to the present invention are as follows: In each of the electrode bodies, the tab group at one end in the first direction and the tab group at the other end in the first direction are positioned at different positions in the second direction.

[0010] According to the above characteristic configuration, when viewed in the thickness direction of the electrode body, the fixing axis of each electrode body does not coincide with the fixing axis of the other electrode bodies, and rotation of the electrode body around the fixing axis is suppressed by the other electrode bodies. Therefore, in the secondary battery of the present invention, wobbling of the electrode bodies is suppressed.

[0011] Further characteristic configurations of the secondary battery according to the present invention are as follows: The battery terminal has thin-walled portions formed therein so as to separate the battery terminals into regions in which the electrode junctions are formed, as viewed in the first direction.

[0012] According to the above characteristic configuration, the battery terminal can be easily divided into a plurality of parts along the thin-walled portion, improving work efficiency when disassembling the secondary battery.

[0013] Further characteristic configurations of the secondary battery according to the present invention are as follows: The tab group is formed at the center in the thickness direction of each of the electrode bodies when viewed in the first direction.

[0014] According to the above characteristic configuration, it is easy to increase the number of tabs of the positive electrode material and the negative electrode material that make up the tab group. Therefore, by increasing the number of tabs, the conductive paths can be increased, and the conductive paths of the electrode materials as a whole can be shortened, thereby realizing a secondary battery with little current loss. [Effects of the Invention]

[0015] As described above, the secondary battery according to the present invention can increase the number of electrode assemblies and increase the battery capacity while suppressing an increase in the number of parts. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is an exploded perspective view of a secondary battery according to an 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. [Figure 5] FIG. 10 is a front view illustrating the positional relationship between two electrode bodies and a current collecting terminal before ultrasonic bonding. [Figure 6] FIG. 10 is a side view illustrating the positional relationship between two electrode bodies and a current collecting terminal during ultrasonic bonding. [Figure 7] FIG. 2 is a perspective view showing a state in which two electrode bodies are assembled to a current collecting terminal. [Figure 8] FIG. 10 is a perspective view showing a current collecting terminal according to another embodiment. [Figure 9] FIG. 10 is a side view showing the internal structure of the negative electrode side of a secondary battery according to another 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 20 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 X-axis direction corresponds to the "first direction" and the Z-axis direction corresponds to the "second 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 and 26 and current collecting terminals 27 and 28 attached to the sealing plate 13, and two electrode bodies 40, 40 electrically connected to the current collecting terminals 27, 28. The secondary battery 1 is a sealed secondary battery in which the two electrode bodies 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. Fig. 4 is a front view showing the electrode assembly 40. As shown in Figs. 3 and 4, 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 on both sides of which a cathode active material is applied, and an end portion on one side in the X-axis direction has a cathode uncoated portion 41b on which the cathode active material is not applied. The cathode material 41 also has a plurality of cathode tabs 42 extending outward from the end on one side in the X-axis direction at intervals. The intervals between the plurality of cathode tabs 42 are set so that, after winding, a cathode tab group 51 is formed below 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 above the center in the height direction of the electrode body 40.

[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 in the winding axis direction (X-axis direction) and a negative electrode tab group 56 extending from the other end. 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] The positive electrode tab group 51 of this embodiment extends along the winding axis direction from one end of the electrode assembly 40, from a portion that is on one side in the thickness direction (Y axis direction) of the electrode assembly 40 and lower than the center in the height direction (Z axis direction) 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 that is on one side in the thickness direction of the electrode assembly 40 and higher than the center in the height direction of the electrode assembly 40 when viewed from the winding axis direction of the electrode assembly 40 when viewed from the winding axis direction. The positive electrode tab group 51 and the negative electrode tab group 56 are rectangular in shape with their longitudinal directions parallel to the height direction of the electrode assembly 40 when viewed from the thickness direction of the electrode assembly 40.

[0029] In this way, in the electrode body 40 of this embodiment, the positive electrode tab group 51 extending from one end in the X-axis direction and the negative electrode tab group 56 extending from the other end are located at different positions in the height direction of the electrode body 40.

[0030] The secondary battery 1 of this embodiment includes two electrode bodies 40, and these two electrode bodies 40 are housed in the case body 11 lined up in the thickness direction (Y-axis direction) with one electrode body 40 turned upside down. That is, in this embodiment, the positive electrode tab groups 51 of the two electrode bodies 40 lined up in the thickness direction are vertically shifted in the Z-axis direction, and similarly, the negative electrode tab groups 56 are vertically shifted in the Z-axis direction (see FIG. 1).

[0031] [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.

[0032] 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.

[0033] 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.

[0034] In this embodiment, each current collecting terminal 27, 28 is formed by bending a plate-like member, and has base portions 27a, 28a that are crimped to the respective external terminals 25, 26, main portions 27b, 28b that are continuous with the base portions 27a, 28a, and first electrode joint portions 27c, 28c and second electrode joint portions 27d, 28d that are continuous with the main portions 27b, 28b. In other words, the two electrode joint portions 27c, 27d, 28c, 28d in each current collecting terminal 27, 28 are formed from a single member.

[0035] In this embodiment, each of the current collecting terminals 27, 28 has a generally rectangular shape when viewed in the Z-axis direction, and is disposed on the lower surface side of the sealing plate 13 so that its base portions 27a, 28a are aligned horizontally. The main portions 27b, 28b of each of the current collecting terminals 27, 28 are generally rectangular when viewed in the X-axis direction and extend downward in the Z-axis direction from the ends of the base portions 27a, 28a, and are disposed between the electrode body 40 and the end side wall of the case body 11.

[0036] The two electrode joints 27c, 27d, 28c, 28d of each current collecting terminal 27, 28 are formed at positions where they can be joined to the tab groups 51, 56 of the electrode assembly 40. Specifically, before the electrode assembly 40 is assembled, each electrode joint 27c, 27d, 28c, 28d is a generally rectangular portion when viewed in the Y-axis direction that extends along the X-axis direction from both edge portions of the main portions 27b, 28b, with the first electrode joint 27c, 28c formed above the center in the Z-axis direction and the second electrode joint 27d, 28d formed below the center in the Z-axis direction. The tab groups 51, 56 are joined to the outer surfaces (joining surfaces) of each electrode joint 27c, 27d, 28c, 28d in the Y-axis direction. Details will be described later, but the two electrode junctions 27c, 27d, 28c, 28d of each collector terminal 27, 28 are bent so that, with the corresponding tab groups 51, 56 joined, the junction points between each electrode junction 27c, 27d, 28c, 28d and each tab group 51, 56 overlap the end face of the electrode body 40 in the X-axis direction (see Figures 2 and 7).

[0037] Next, a method for assembling two electrode bodies 40 to each of the current collecting terminals 27, 28 will be described with reference to Figures 5 to 7. Figure 5 is a front view illustrating the positional relationship between the two electrode bodies 40 and each of the current collecting terminals 27, 28 before ultrasonic bonding. Figure 6 is a side view showing the negative electrode side for illustrating the positional relationship between the two electrode bodies 40 and each of the current collecting terminals 27, 28 after ultrasonic bonding. Figure 7 is a perspective view showing the state in which the two electrode bodies 40 have been assembled to the current collecting terminals 27, 28. Note that components such as the sealing plate 13 and the external terminals 25, 26 are not shown in Figure 7.

[0038] 5, two electrode bodies 40 are placed on the current collecting terminals 27, 28 attached to the sealing plate 13 so that the electrode joints 27c, 27d, 28c, 28d and the tab groups 51, 56 corresponding to the electrode joints 27c, 27d, 28c, 28d face each other in the Y-axis direction. That is, the positive electrode current collecting terminal 27 is placed so that the positive electrode tab group 51 of one electrode body 40 faces the second electrode joint 27d, and the positive electrode tab group 51 of the other electrode body 40 faces the first electrode joint 27c. In addition, the negative electrode current collecting terminal 28 is placed so that the negative electrode tab group 56 of one electrode body 40 faces the first electrode joint 28c, and the negative electrode tab group 56 of the other electrode body 40 faces the second electrode joint 28d.

[0039] Next, the electrode joints 27c, 27d, 28c, 28d are joined to the tab groups 51, 56. Specifically, the opposing surfaces of the electrode joints 27c, 27d, 28c, 28d and the tab groups 51, 56 are brought into contact with each other, and the electrode joints 27c, 27d, 28c, 28d and the tab groups 51, 56 are ultrasonically joined using a horn H and an anvil A.

[0040] Here, in the secondary battery 1 of this embodiment, on both the positive and negative electrode sides, the tab groups 51, 56 of one electrode body 40 and the electrode joints 27d, 28c facing them and the tab groups 51, 56 of the other electrode body 40 and the electrode joints 27c, 28d facing them are vertically shifted in position in the Z-axis direction.

[0041] 6, for example, on the negative electrode side, a space exists on the side of the first electrode joint 28c and the second electrode joint 28d that does not face the negative electrode tab group 56. Therefore, an anvil A is pressed against the first electrode joint 28c of the negative electrode current collector terminal 28, and a horn H is pressed against the negative electrode tab group 56 of one electrode assembly 40 (the negative electrode tab group 56 located at the upper right in FIG. 6) to apply pressure, and horizontal ultrasonic vibrations are applied by the horn to join the first electrode joint 28c and the negative electrode tab group 56 of one electrode assembly 40. Similarly, the second electrode joint 28d and the negative electrode tab group 56 of the other electrode assembly 40 can be joined by ultrasonic joining using the horn H and the anvil A. Note that, although not shown, a space also exists on the positive electrode side on the side of the first electrode joint 27c and the second electrode joint 27d that does not face the positive electrode tab group 51. Therefore, it is possible to join the electrode joint portions 27c, 27d of the positive electrode current collector terminal 27 and the positive electrode tab group 51 by ultrasonic joining using the horn H and the anvil A.

[0042] Thereafter, with the electrode joints 27c, 27d, 28c, and 28d and the tab groups 51 and 56 joined together, the joints are bent so that they overlap the end faces of the electrode assembly 40 in the X-axis direction. Specifically, the electrode joints 27c and 27d of the positive current collector terminal 27 are bent so that the surface opposite to the side facing the positive electrode tab group 51 abuts against the side of the main portion 27b. Similarly, the electrode joints 28c and 28d of the negative current collector terminal 28 are bent so that the surface opposite to the side facing the negative electrode tab group 56 abuts against the side of the main portion 28b. As a result, two electrode bodies 40 are assembled to each current collector terminal 27 and 28, as shown in FIG. 7.

[0043] In this way, in the secondary battery 1 of this embodiment, the tab groups 51, 56 of the two electrode bodies 40 can be joined to the electrode joint portions 27c, 27d, 28c, 28d of the current collecting terminals 27, 28 made of a single member, respectively. Therefore, the number of electrode bodies 40 can be increased to increase the battery capacity while suppressing an increase in the number of parts.

[0044] Furthermore, in the secondary battery 1 of this embodiment, the positive electrode tab group 51 and the negative electrode tab group 56 of each electrode assembly 40 are located at different positions in the Z-axis direction. Each electrode assembly 40 is fixed by joining the electrode joint portions 27c, 27d, 28c, and 28d to the positive electrode tab group 51 and the negative electrode tab group 56, which are located at different positions in the Z-axis direction. That is, as shown in FIG. 2 , the fixed axis P1 of one electrode assembly 40 extends obliquely upward from the positive electrode tab group 51 toward the negative electrode tab group 56 when viewed in the Y-axis direction, and the fixed axis P2 of the other electrode assembly 40 extends obliquely downward from the positive electrode tab group 51 toward the negative electrode tab group 56 when viewed in the Y-axis direction. In other words, each fixed axis P1 and P2 extends obliquely with respect to the X-axis direction between the positive electrode tab group 51 and the negative electrode tab group 56 of each electrode assembly 40, and the fixed axis P1 and the fixed axis P2 intersect. Therefore, the rotation of each electrode body 40 around the fixed axis is suppressed by the other electrode body 40. Therefore, in the secondary battery 1 of this embodiment, wobbling of each electrode body 40 is suppressed. Note that in this embodiment, the positive electrode tab group 51 of each electrode body 40 corresponds to the "tab group on one end side in the first direction," and the negative electrode tab group 56 corresponds to the "tab group on the other end side in the second direction."

[0045] [Another embodiment] [1] In the above embodiment, the electrode joints 27c, 27d, 28c, and 28d of the current collecting terminals 27 and 28 extend from both edge portions of the main portions 27b and 28b along the X-axis direction. However, the present invention is not limited to this. The shape of each current collecting terminal is not particularly limited as long as it has a plurality of electrode joints. Fig. 8 is a perspective view showing a current collecting terminal 60 according to another embodiment. The current collecting terminal 60 may have a shape as shown in Fig. 8, for example. The current collecting terminal 60 has a base 60a, a main portion 60b continuous with the base 60a, a first electrode joint 60c formed by bending and rising between a pair of slits S1 formed with one edge of the main portion 60b as a starting point, and a second electrode joint 60d formed by bending and rising between a pair of slits S2 formed with the other edge of the main portion 60b as a starting point. Furthermore, thin-walled portions 61, 62 are formed in the current collecting terminal 60 so as to separate a region R1 where the first electrode joint portion 60c is formed from a region R2 where the second electrode joint portion 60d is formed when viewed in the X-axis direction. Specifically, the current collecting terminal 60 has groove-shaped thin-walled portions 61, 62 formed to extend from the ends of the slits S1, S2 to the edges of the main portion 60b. Use of this current collecting terminal 60 also makes it possible to increase the number of electrode bodies and thereby increase battery capacity while minimizing an increase in the number of parts, and to ultrasonically bond each electrode joint portion 60c, 60d to each tab group 51, 56 using a horn H and anvil A. Furthermore, because the current collecting terminal 60 has thin-walled portions 61, 62, it is easy to divide the current collecting terminal 60 along the thin-walled portions 61, 62 and separate the current collecting terminal 60 from the two electrode bodies 40. Therefore, use of the current collecting terminal 60 improves work efficiency when disassembling a secondary battery.

[0046] [2] In the above embodiment, the tab groups 51, 56 extend from a portion of each end of the electrode assembly 40 that is located on one side in the thickness direction (Y-axis direction) of the electrode assembly 40 as viewed from the winding axis direction (X-axis direction). However, this is not limited to this configuration. FIG. 9 is a side view showing the internal structure of the negative electrode side of a secondary battery according to another embodiment. For example, as shown in FIG. 9, the negative electrode tab group 56 may extend from a central portion of each end of the electrode assembly 40 in the thickness direction (Y-axis direction) of the electrode assembly 40 as viewed from the winding axis direction (X-axis direction). This makes it easy to increase the number of negative electrode tabs 47 of the negative electrode material 46 that constitute the negative electrode tab group 56. Therefore, by increasing the number of tabs, the conductive paths can be increased, shortening the conductive paths of the electrode material as a whole, thereby realizing a secondary battery with low current loss. Note that the positive electrode tab group 51 may also extend from a central portion in the thickness direction (Y-axis direction) of the electrode assembly 40 as viewed from the winding axis direction (X-axis direction). In addition, in an embodiment in which each tab group extends from the center in the thickness direction (Y-axis direction) of the electrode body when viewed from the winding axis direction (X-axis direction), it is preferable to use the current collecting terminal 60 rather than the current collecting terminals 27, 28. In the current collecting terminals 27, 28, the electrode joints 27c, 27d, 28c, 28d extend along the X-axis direction from both edge portions of the main portions 27b, 28b. Therefore, when the current collecting terminals 27, 28 are used, the size of the main portions 27b, 28b must be reduced, narrowing the conduction path. In contrast, when the current collecting terminal 60 is used, the reduction in size of the main portions 60b can be suppressed compared to when the current collecting terminals 27, 28 are used, and the conduction path can be widened.

[0047] [3] In the above embodiment, an embodiment including two electrode bodies 40 has been described, but the present invention is not limited to this embodiment. The number of electrode bodies may be three or more. In this case, by increasing the number of electrode junctions of the current collecting terminals according to the number of electrode bodies, the number of electrode bodies can be increased while suppressing an increase in the number of parts.

[0048] [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 different positions in the Z axis direction. However, this is not limited to this. The positive electrode tab group and the negative electrode tab group of each electrode assembly may be positioned at the same position in the Z axis direction. For example, in a secondary battery having two electrode assemblies as in the above embodiment, the positive electrode tab group and the negative electrode tab group of one electrode assembly may be positioned above the center in the Z axis direction, and the positive electrode tab group and the negative electrode tab group of the other electrode assembly may be positioned below the center in the Z axis direction. Even in this case, the positive electrode tab groups of the two electrode assemblies aligned in the thickness direction are vertically shifted in the Z axis direction, and the negative electrode tab groups are also vertically shifted in the Z axis direction.

[0049] [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 20 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.

[0050] 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]

[0051] 1: Secondary battery 11: Case body (housing) 13: Sealing plate (lid body) 40: Electrode body 41: Cathode material 42: Positive electrode tab 46: Anode material 47: Negative electrode tab 49: Separator 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 27c, 28c: First electrode junction (one of multiple electrode junctions) 27d, 28d: Second electrode junction (one of multiple electrode junctions)

Claims

1. A secondary battery comprising: a housing having an opening; a lid attached to the opening of the housing; a plurality of flat electrode assemblies formed by stacking positive and negative electrode materials with separators interposed therebetween; and two battery terminals attached to the lid, The plurality of electrode bodies a tab group formed by stacking tabs of the positive electrode material and the negative electrode material, the tabs being arranged in a thickness direction of the electrode body and accommodated in the housing; The tab group extends from both end portions in a first direction perpendicular to the thickness direction, When viewed in the first direction, the tab group at one end side in the first direction of each electrode body is different in position in a second direction perpendicular to the thickness direction, and the tab group at the other end side in the first direction of each electrode body is different in position in the second direction, The two battery terminals are: Each electrode joint has a plurality of plate-shaped electrode joints formed on a single member, the electrode joint portion of each of the one battery terminals is formed at a position where it can be joined to the tab group on one end side of the electrode body in the first direction, and the electrode joint portion of each of the other battery terminals is formed at a position where it can be joined to the tab group on the other end side of the electrode body in the first direction, A secondary battery in which each of the electrode junctions is joined to each of the tab groups formed in a position that can be joined to the electrode junctions, and the joining points between each of the electrode junctions and each of the tab groups are bent so as to overlap with the end face of the electrode body in the first direction when viewed in the first direction.

2. The secondary battery according to claim 1 , wherein in each of the electrode bodies, the tab group at one end in the first direction and the tab group at the other end in the first direction are positioned differently in the second direction.

3. The secondary battery according to claim 1 , wherein the battery terminals are formed with thin-walled portions so as to separate the battery terminals into regions in which the electrode junctions are formed, as viewed in the first direction.

4. 4. The secondary battery according to claim 1, wherein the tab group is formed at a center portion in a thickness direction of each of the electrode bodies when viewed in the first direction.

Images