Secondary battery

Abstract

This secondary battery comprises: a laminate in which a plurality of positive electrode layers and negative electrode layers are alternately laminated with solid electrolyte layers interposed therebetween; positive electrode tab leads extending from each positive electrode current collector foil; negative electrode tab leads extending from each negative electrode current collector foil; tab lead assemblies for positive electrodes and negative electrodes, in which predetermined tip-side ranges of each tab lead belonging to the same electrode overlap each other; and a positive electrode tab and a negative electrode tab, the tab lead assemblies and the electrode tabs being joined by means of a joining member, wherein first through-holes into which the joining member is inserted are provided in the tab lead assemblies, second through-holes into which the joining member is inserted are provided in the electrode tabs, the joining member is provided with a body part that is inserted into the first through-holes and the second through-holes, and head parts that are provided at both ends in the axial direction of the body part and sandwich the overlapping portion of the tab lead assemblies and the electrode tabs from both sides in the overlapping direction, and at least one among the first through-holes or the second through-holes have a size that allows a movement of the joining member inside the hole.

Description

secondary battery

[0001] The present invention relates to a secondary battery, and more particularly to a secondary battery having a solid electrolyte layer.

[0002] Laminated batteries are known in which multiple flat positive and negative electrodes are stacked in sequence with separators between them. These batteries often have protruding sheet-like positive and negative electrodes, which are formed by stacking multiple thin metal foils as electrode plate components. When forming a sheet-like electrode made of multiple stacked thin metal foils as an electrode terminal, it is necessary to interconnect the ends of the multiple thin metal foils to improve electrical conduction efficiency. For this purpose, JP 2013-84448 A discloses a method for joining metal foil sheets, in which through-holes are formed in a metal foil laminate made of multiple stacked metal foils and the exposed metal surfaces in the through-holes are welded with high-energy beams.

[0003] In secondary batteries with solid electrolyte layers, cells expand and contract during charging and discharging, causing the volume of the cell stack to vary by several tens of percent between maximum and minimum. In other words, the distance from the metal foil joints to each electrode changes during charging and discharging. If the metal foil is not long enough to accommodate this change in distance, it may be pulled and break. One method to prevent this foil breakage is to lengthen the metal foil so that it is not subjected to excessive pulling force even during maximum expansion. However, the longer the metal foil, the larger the space that must be secured within the exterior housing that houses the battery to accommodate the metal foil that sags as the cell shrinks, resulting in a decrease in volumetric energy density.

[0004] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a secondary battery that can prevent breakage of the metal foil constituting the electrodes due to expansion and contraction while suppressing a decrease in volumetric energy density.

[0005] According to one aspect of the present invention, there is provided a secondary battery comprising: a laminate in which positive electrode layers formed on positive electrode current collector foils and negative electrode layers formed on negative electrode current collector foils are alternately stacked with solid electrolyte layers interposed therebetween; positive electrode tab leads extending from each positive electrode current collector foil; negative electrode tab leads extending from each negative electrode current collector foil; positive and negative electrode tab lead assemblies formed by overlapping predetermined regions on the tip sides of the tab leads belonging to the same electrode with each other; and positive and negative electrode tabs, wherein the tab lead assemblies and the electrode tabs are joined together in an overlapped state with a joining member. In this secondary battery, the tab lead assembly is provided with a first through hole through which the joining member is inserted, and the electrode tabs are provided with a second through hole through which the joining member is inserted, and the joining member has a body portion inserted into the first through hole and the second through hole, and head portions provided at both axial ends of the body portion to sandwich the overlapping portion of the tab lead assembly and the electrode tab from both sides in the overlapping direction. At least one of the first through hole and the second through hole has a size that allows movement of the joining member within the hole.

[0006] Fig. 1 is a cross-sectional view of the positive electrode side of a secondary battery according to an embodiment of the present invention. Fig. 2 is a plan view of a joint. Fig. 3 is an enlarged view of the vicinity of the joint in Fig. 1. Fig. 4 is a cross-sectional view of the positive electrode side of a secondary battery according to Modification 1. Fig. 5 is a cross-sectional view of the positive electrode side of a secondary battery according to Modification 2. Fig. 6 is a plan view of a joint according to Modification 3. Fig. 7 is a plan view of a joint according to Modification 4. Fig. 8 is a plan view of a joint according to Modification 5.

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0008] 1 is a cross-sectional view of the positive electrode side of a secondary battery 10 according to an embodiment of the present invention. The omitted portion on the left side of the drawing is the negative electrode side, which has the same structure as the positive electrode side shown in the drawing. The secondary battery 10 according to this embodiment is an all-solid-state battery, and the electrode structure may be either hyperbolic or non-hyperbolic.

[0009] The secondary battery 10 includes a laminate 1, a positive electrode tab lead 3, a negative electrode tab lead (not shown), a positive electrode tab lead assembly 4, a negative electrode tab lead assembly (not shown), a positive electrode electrode tab 6, a negative electrode electrode tab (not shown), and an exterior body 2 that houses these.

[0010] The laminate 1 is formed by alternately laminating multiple positive electrode layers formed on positive current collector foils and negative electrode layers formed on negative current collector foils with solid electrolyte layers interposed therebetween.

[0011] The positive electrode tab lead 3 extends from one side of a rectangular plate-shaped positive electrode current collector foil. The positive electrode tab lead 3 may be made of the same material as the current collector foil, or may be made of a separate material.

[0012] The positive electrode tab lead assembly 4 is formed by overlapping predetermined areas of the tip ends of the plurality of positive electrode tab leads 3 drawn out from the laminate 1. In this embodiment, the positive electrode tab leads 3 in the upper half of the laminate 1 and the positive electrode tab leads 3 in the lower half of the laminate 1 each constitute a positive electrode tab lead assembly 4.

[0013] The electrode tab 6 for the positive electrode is joined to the tab lead assembly 4 for the positive electrode by a joining member 5 in a state where they are overlapped with each other.

[0014] The negative electrode tab lead (not shown), negative electrode tab lead assembly (not shown), and negative electrode electrode tab (not shown) have the same configuration as the positive electrode tab lead 3, positive electrode tab lead assembly 4, and positive electrode tab 6, respectively. As the positive electrode side and negative electrode side have the same structure as described above, only the positive electrode side will be described below, and the negative electrode side will be omitted. Furthermore, except when it is necessary to distinguish between the positive electrode and the negative electrode, the positive electrode tab lead 3 will be referred to as tab lead 3, the positive electrode tab lead assembly 4 will be referred to as tab lead assembly 4, and the positive electrode electrode tab 6 will be referred to as electrode tab 6.

[0015] The joining member 5 includes a body 5B inserted through the first through hole 4A and the second through hole 6A (described later) and a pair of heads 5A provided at both longitudinal ends of the body 5B and sandwiching the overlapping portion of the tab lead assembly 4 and the electrode tab 6 from both sides in the axial direction (Z-axis direction in FIG. 1 ) of the body 5B. The shapes of the heads 5A and the body 5B are not particularly limited. In this embodiment, the heads 5A are disk-shaped, the body 5B is cylindrical, and the central axis of the body 5B coincides with the center of the pair of heads 5A. Specifically, for example, rivets or bolts and nuts may be used. Using these general-purpose products can reduce costs. Other materials that perform similar functions to rivets, bolts, and nuts may also be used. In the following description, the portion where the tab lead assembly 4 and the electrode tab 6 are joined, including the first through hole 4A, the second through hole 6A, and the joining member 5, is referred to as a joining portion 7.

[0016] Next, the configuration of the joint 7 will be described with reference to FIGS.

[0017] Fig. 2 is a view (also referred to as a plan view) of the joint 7 as viewed from the direction of arrow A in Fig. 1. In Fig. 2, the direction in which the tab leads 4 are pulled out (X-axis direction in the figure) is also referred to as the longitudinal direction, and the direction perpendicular thereto (Y-axis direction in the figure) is also referred to as the lateral direction. Fig. 3 is an enlarged view of the vicinity of the joint 7 in Fig. 1. In Fig. 3, the direction in which the tab lead assembly 4 and the electrode tabs 6 are stacked (Z-axis direction in the figure) is also referred to as the stacking direction.

[0018] The joint 7 has first through holes 4A provided in the upper and lower tab lead assemblies 4 and second through holes 6A provided in the electrode tab 6. At the joint 7, the upper and lower tab lead assemblies 4 are arranged to sandwich the electrode tab 6 from both sides in the Z-axis direction. Note that there are two types of tab lead assemblies 4: one that assembles the upper half of the tab leads and one that assembles the lower half of the tab leads; however, in the following description, they will be simply referred to as tab lead assemblies 4 unless it is necessary to distinguish between upper and lower.

[0019] At least one of the first through holes 4A and the second through holes 6A may be sized to allow movement of the joining members 5 within the hole. However, as shown in FIGS. 1 to 3 , it is desirable that both be sized to allow movement of the joining members 5 within the hole. When the laminate 1 expands, the end of the tab lead 3 facing the laminate 1 moves in the stacking direction, and the tab lead 3 is stretched as shown by the dashed line B in FIG. 1 . In this state, a tensile force is applied to the tab lead 3. However, if the joining members 5 are movable within the hole, the joining members 5 move toward the laminate 1, thereby alleviating the tensile force applied to the tab lead 3. This prevents the tab lead 3 from being cut by the tensile force. The length of each tab lead 3 and the positions of the end of the first through holes 4A and the second through holes 6A facing the laminate 1 are set according to the dimensions and expansion / contraction rate of the laminate 1 so that excessive tensile force is not applied to each tab lead 3 when the volume of the laminate 1 is maximized.

[0020] When the laminate 1 contracts, the tab leads 3 change in the bending direction, opposite to when the laminate 1 expands. If both ends of the tab leads 3 were fixed, the bending deformation would be hindered by adjacent tab leads 3 in the stacking direction, causing stress to concentrate in one area, which could result in plastic deformation. In this regard, in the configuration of this embodiment, the elastic force generated by the bending of the tab leads 3 moves the joining members 5 in a direction away from the laminate 1, thereby reducing the amount of deformation of the tab leads 3 accordingly. This alleviates the stress concentration, making it less likely for plastic deformation to occur.

[0021] Furthermore, it is more desirable that the first through hole 4A and the second through hole 6A have a guide shape that allows movement of the joining member 5 in the longitudinal direction but restricts movement in the lateral direction. As described above, to prevent the tab lead 3 from being cut, it is sufficient that movement of the joining member 5 in the longitudinal direction is permitted. However, movement in the lateral direction may cause twisting of the tab lead 3, and twisting may result in excessive tensile force or plastic deformation in a part of the tab lead 3. Therefore, it is desirable to restrict movement in the unwanted direction by using the above-described guide shape.

[0022] Furthermore, movement of the joining member 5 in the longitudinal direction is stopped by collision of the body portion 5B with the wall surface of the first through hole 4A or the second through hole 6A, but considering the wear and deformation that occurs due to repeated collisions, collision with the electrode tab 6, which has higher mechanical strength, is more suppressed than collision with the tab lead assembly 4, which is an assembly of foil materials, resulting in improved durability. Therefore, when both the first through hole 4A and the second through hole 6A are large enough to allow movement of the joining member 5, it is desirable that the longitudinal dimension of the second through hole 6A be shorter than that of the first through hole 4A.

[0023] From the perspective of durability, it is also desirable to reduce friction between the body portion 5B and the side walls of the first through hole 4A and the second through hole 6A when the joining member 5 moves. The side walls here refer to wall surfaces extending in the longitudinal direction. The lateral dimensions of the first through hole 4A and the second through hole 6A are slightly larger than the diameter of the body portion 5B to allow the joining member 5 to move in the longitudinal direction while limiting its movement in the lateral direction. However, if the pulling direction of the tab lead 3 deviates from the longitudinal direction, the body portion 5B may come into contact with the side walls of the first through hole 4A and the second through hole 6A. Therefore, it is desirable for the joining member 5 to have a configuration in which the body portion 5B is rotatable relative to the head portion 5A. This configuration reduces friction by rotating the body portion 5B in the event of a collision, thereby improving durability. An example of a rotatable configuration is, but is not limited to, a configuration in which the body portion 5B has a double-tube structure, with the inner portion fixed relative to the head portion 5A and the outer portion rotatable relative to the inner portion and the head portion 5A.

[0024] Since the joining of the tab lead assembly 4 and the electrode tab 6 is intended for electrical connection, ensuring a sufficient contact area is important. That is, it is necessary to ensure a sufficient contact area between the head 5A of the joining member 5 and the tab lead assembly 4. In the joining portion 7 of this embodiment, the joining member 5, the lead tab 3, and the electrode tab 6 can move relative to each other. Therefore, it is desirable that the head 5A of the joining member 5 and the tab lead assembly 4 remain in contact even when the joining member 5 moves relative to each other. Therefore, when the longitudinal dimension of the larger hole (first through hole 4A in FIG. 3 ) is A, the longitudinal dimension (i.e., diameter) of the head 5A is B, and the longitudinal dimension (i.e., diameter) of the body 5B is C, the dimensions are set so that the relationship B > 2A - C holds.

[0025] Modifications of the above embodiment will be described below, all of which fall within the scope of the present invention, just like the above embodiment.

[0026] [Modification 1] Modification 1 will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view of the positive electrode side of a secondary battery 10 according to Modification 1. The difference from the above embodiment is that the tab lead assembly 4 and the current collecting tab 8 are connected by welding or the like at a fixing portion 9, and the current collecting tab 8 and the electrode tab 6 are connected to each other at a joint portion 7 via a joint member 5 so as to be movable in the longitudinal direction. In other words, with respect to the joint portion 7, the tab lead assembly 4 in the above embodiment has been replaced with the current collecting tab 8.

[0027] Even with this configuration, it is possible to prevent excessive tensile force from being applied to the tab leads 3 when the laminate 1 expands, as in the above embodiment.

[0028] Modification 2 will be described with reference to Fig. 5. Fig. 5 is a cross-sectional view of the positive electrode side of a secondary battery 10 according to Modification 2. The difference from the above embodiment is that the tab lead assembly 4 combines the upper half tab leads 3 and the lower half tab leads 3 of the laminate 1 into one.

[0029] Even with this configuration, it is possible to prevent excessive tensile force from being applied to the tab leads 3 when the laminate 1 expands, as in the above embodiment.

[0030] Modification 3 will be described with reference to Fig. 6. Fig. 6 is a plan view of the joints 7 according to Modification 3. The difference from the above embodiment is that the joints 7 are provided at multiple locations (three locations in Fig. 6).

[0031] Increasing the number of joints 7 increases the contact area between the head 5A and the tab lead assembly 4. The laminate 1 generates heat during charging and discharging, and this heat is transferred to the joint members 5 via the tab lead assembly 4 and dissipated from the head 5A. Therefore, providing joints 7 in multiple locations increases the amount of heat dissipation. In other words, the heat dissipation performance of the secondary battery 10 is improved.

[0032] However, increasing the number of joints 7 also increases the number of first through holes 4A and second through holes 6A. Furthermore, if multiple joints 7 are provided close to one another, the strength of the tab lead assembly 4 and the electrode tabs 6, particularly in the portions sandwiched between adjacent joints 7, may decrease, and the tab lead assembly 4 and the electrode tabs 6 may be deformed when the joining member 5 moves. Therefore, when providing three or more joints 7, it is desirable to arrange them so that they are not aligned in a straight line in the longitudinal or lateral direction in plan view. By arranging them in this way, the strength of the tab lead assembly 4 and the electrode tabs 6 in the portions sandwiched between adjacent joints 7 can be ensured.

[0033] Modification 4 will be described with reference to Fig. 7. Fig. 7 is a plan view of a joint 7 according to Modification 4. The differences from the above embodiment are that the joints 7 are provided in multiple locations (two locations in Fig. 7) and the configuration of the joint members 5. The effect of providing multiple joints 7 is the same as in Modification 3, so a description thereof will be omitted and the configuration of the joint members 5 will be mainly described.

[0034] Similar to the third modification, each joint portion 7 includes a body portion 5B, but in this modification, the heads 5A of the multiple joint members 5 are integrated together. This allows for a larger contact area between the heads 5A and the tab lead assembly 4 compared to a configuration in which the multiple joint members 5 each have their own individual heads 5A. Increasing this contact area also improves heat dissipation from the heads 5A.

[0035] [Modification 5] Modification 5 will be described with reference to Fig. 8. Fig. 8 is a plan view of a joint 7 according to Modification 5. The difference from the above embodiment is the shape of the second through holes 6A.

[0036] Specifically, the longitudinal end of the second through hole 6A is arc-shaped. The first through hole 4A may have a similar shape. The radius of curvature of the arc is preferably the same as the radius of curvature of the side surface of the body portion 5B.

[0037] With the above configuration, when the joining member 5 moves and collides with the longitudinal end of the second through hole 6A, the colliding portion makes surface contact rather than line contact, thereby suppressing wear of the body portion 5B and the electrode tab 6 and improving durability.

[0038] As described above, this embodiment provides a secondary battery 10 including: a laminate 1 in which positive electrode layers formed on positive electrode current collector foils and negative electrode layers formed on negative electrode current collector foils are alternately stacked with solid electrolyte layers interposed therebetween; a positive electrode tab lead 3 extending from each positive electrode current collector foil; a negative electrode tab lead (not shown) extending from each negative electrode current collector foil; a positive electrode and negative electrode tab lead assembly 4 formed by overlapping predetermined areas of the tip ends of the tab leads 3 belonging to the same electrode; and positive and negative electrode electrode tabs 6, wherein the tab lead assembly 4 and the electrode tabs 6 are joined together by a joining member 5 in an overlapped state. In this secondary battery 10, the tab lead assembly 4 is provided with a first through hole 4A through which the joining member 5 is inserted, and the electrode tab 6 is provided with a second through hole 6A through which the joining member 5 is inserted. The joining member 5 includes a body portion 5B inserted through the first through hole 4A and the second through hole 6A, and head portions 5A provided at both axial ends of the body portion 5B and sandwiching the overlapping portion of the tab lead assembly 4 and the electrode tab 6 from both sides in the overlapping direction. At least one of the first through hole 4A or the second through hole 6A has a size that allows movement of the joining member 5 within the hole. This reduces the tensile force applied to the tab lead 3 when the laminate 1 expands, preventing the tab lead 3 from being cut by the tensile force. Furthermore, when the laminate 1 contracts, the elastic force of the tab lead 3 moves the joining member 5 in the direction opposite to that during expansion, thereby suppressing plastic deformation of the tab lead 3.

[0039] In the first modification, a secondary battery is provided, which includes: a laminate 1 in which positive electrode layers formed on positive current collector foils and negative electrode layers formed on negative current collector foils are alternately stacked with solid electrolyte layers interposed therebetween; a positive electrode tab lead 3 extending from each positive current collector foil; a negative electrode tab lead (not shown) extending from each negative current collector foil; a positive and negative electrode tab lead assembly 4 formed by overlapping predetermined regions on the tip sides of the tab leads 3 belonging to the same electrode; positive and negative electrode current collector tabs 8 joined to the tab lead assembly 4; and positive and negative electrode electrode tabs 6, the current collector tabs 8 and the electrode tabs 6 being joined together in an overlapping state by a joining member 5. In this secondary battery 10, the current collector tabs 8 are provided with a first through-hole 4A through which the joining member 5 is inserted, and the electrode tabs 6 are provided with a second through-hole 6A through which the joining member 5 is inserted. The joining member 5 includes a body 5B that is inserted through the first through hole 4A and the second through hole 6A, and heads 5A that are provided at both axial ends of the body 5B and that sandwich the overlapping portion of the current collecting tab 8 and the electrode tab 6 from both sides in the overlapping direction. At least one of the first through hole 4A and the second through hole 6A has a size that allows movement of the joining member 5 within the hole. With this configuration, the same effects as those of the above embodiment can be obtained.

[0040] In this embodiment, the joining members 5 are rivets or bolts and nuts. This allows general-purpose products to be used as the joining members 5.

[0041] In this embodiment, both the first through hole 4A and the second through hole 6A are sized to allow movement of the joining member 5 within the holes, and the second through hole 6A has a shorter longitudinal dimension, i.e., the direction in which the tab lead 3 is pulled out, than the first through hole 4A. If either hole were sized to not allow movement of the joining member 5, the hole that does not allow movement would be in constant contact with the body portion 5B, which could lead to wear at the contact area. In this embodiment, both holes are sized to allow movement of the joining member 5 within the holes, thereby suppressing such wear. Furthermore, by making the longitudinal dimension of the second through hole 6A shorter than the longitudinal dimension of the first through hole 4A, the movement of the joining member 5 is restricted by the second through hole 6A. In other words, the movement of the joining member 5 is restricted by collision with the electrode tab 6, which has greater strength than the tab lead assembly 4. This suppresses wear of the tab lead assembly 4, thereby improving durability.

[0042] In this embodiment, the first through hole 4A and the second through hole 6A are both sized to allow movement of the joining member 5 within the holes, and when the longitudinal dimension of the larger hole is A, the longitudinal dimension of the head portion 5A is B, and the longitudinal dimension of the body portion 5B is C, the relationship B > 2A - C holds. This ensures a sufficient contact area between the head portion 5A and the tab lead assembly 4 even if the joining member 5 moves.

[0043] In this embodiment, the first through hole 4A or the second through hole 6A, which has a size that allows movement of the joining member 5 within the hole, has a guide shape that allows movement of the joining member 5 in the longitudinal direction but restricts movement in the lateral direction, so that the joining member 5 moves only in the direction corresponding to bending and straightening of the tab lead 3.

[0044] In this embodiment, the joining member 5 is configured such that the body 5B is rotatable relative to the head 5A. As a result, when the body 5B collides with the wall surface of the hole, the body 5B rotates, thereby absorbing the impact of the collision, thereby improving the durability of the secondary battery 10.

[0045] In the third and fourth modifications, a plurality of joints 7 are provided, each of which includes a first through hole 4A, a second through hole 6A, and a joint member 5. This increases the amount of heat dissipation from the head portion 5A.

[0046] In the third modification, three or more joints 7 are arranged so as not to be aligned in a straight line in the longitudinal or lateral direction in plan view, thereby ensuring a sufficient contact area between the joint member 5 and the tab lead assembly 4 while suppressing a decrease in the strength of the tab lead 3 and the electrode tab 6.

[0047] In the fourth modification, the heads 5A of the plurality of joining members 5 are integrated together, which allows the contact area between the joining members 5 and the tab lead assembly 4 to be increased.

[0048] In the fifth modification, the body 5B is cylindrical, and at least one of the first through hole 4A and the second through hole 6A has an arc-shaped longitudinal end, which reduces friction between the body 5B and the side wall of the hole, thereby reducing wear and deformation of both.

[0049] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

Claims

a laminate in which a positive electrode layer formed on a positive electrode current collector foil and a negative electrode layer formed on a negative electrode current collector foil are alternately stacked with a solid electrolyte layer interposed therebetween; a positive electrode tab lead extended from each positive electrode current collector foil; a negative electrode tab lead extended from each negative electrode current collector foil; a positive electrode and a negative electrode tab lead assembly formed by overlapping predetermined areas on the tip side of the tab leads belonging to the same electrode; Positive and negative electrode tabs; Equipped with In a secondary battery in which the tab lead assembly and the electrode tab are joined by a joining member in an overlapping state, the tab lead assembly is provided with a first through hole through which the joining member is inserted, the electrode tab is provided with a second through-hole through which the joining member is inserted, the joining member includes a body portion inserted into the first through hole and the second through hole, and head portions provided at both axial ends of the body portion and sandwiching an overlapping portion between the tab lead assembly and the electrode tab from both sides in the overlapping direction, At least one of the first through hole and the second through hole has a size that allows the joining member to move within the hole. 　 a laminate in which a positive electrode layer formed on a positive electrode current collector foil and a negative electrode layer formed on a negative electrode current collector foil are alternately stacked with a solid electrolyte layer interposed therebetween; a positive electrode tab lead extended from each positive electrode current collector foil; a negative electrode tab lead extended from each negative electrode current collector foil; a positive electrode and a negative electrode tab lead assembly formed by overlapping predetermined areas on the tip side of the tab leads belonging to the same electrode; current collecting tabs for the positive electrode and the negative electrode joined to the tab lead assembly; Positive and negative electrode tabs; Equipped with In a secondary battery in which the current collecting tab and the electrode tab are joined by a joining member in an overlapping state, the current collecting tab is provided with a first through hole through which the joining member is inserted, the electrode tab is provided with a second through-hole through which the joining member is inserted, the joining member includes a body portion inserted into the first through hole and the second through hole, and head portions provided at both axial ends of the body portion and configured to sandwich an overlapping portion between the current collecting tab and the electrode tab from both sides in the overlapping direction, At least one of the first through hole and the second through hole has a size that allows the joining member to move within the hole.

3. The secondary battery according to claim 1, The secondary battery, wherein the joining members are rivets or bolts and nuts.

2. The secondary battery according to claim 1, A secondary battery, wherein the first through hole and the second through hole are both sized to allow movement of the joining member within the holes, and the second through hole has a shorter longitudinal dimension, which is the direction in which the tab lead is pulled out, than the first through hole.

2. The secondary battery according to claim 1, the first through hole and the second through hole each have a size that allows movement of the joining member within the hole; A secondary battery in which the relationship B>2A-C holds when the longitudinal dimension of the larger hole, which is the direction in which the tab lead is pulled out, is A, the longitudinal dimension of the head is B, and the longitudinal dimension of the body is C.

3. The secondary battery according to claim 1, A secondary battery, wherein the first through hole or the second through hole, which is sized to allow movement of the joining member within the hole, has a guide shape that allows movement of the joining member in the longitudinal direction, which is the direction in which the tab lead is pulled out, and restricts movement in the lateral direction perpendicular to the longitudinal direction.

3. The secondary battery according to claim 1, The joining member is configured so that the body portion can rotate relative to the head portion.

3. The secondary battery according to claim 1, A secondary battery having a plurality of joints each including the first through hole, the second through hole, and the joint member.

9. The secondary battery according to claim 8, A secondary battery in which three or more of the joints are arranged so as not to be aligned in a straight line in the longitudinal or lateral direction in a plan view.

9. The secondary battery according to claim 8, The heads of the plurality of joining members are integrated together.

3. The secondary battery according to claim 1, The body portion has a cylindrical shape, At least one of the first through hole and the second through hole has an end in a longitudinal direction, that is, a direction in which the tab lead is pulled out, that is, has an arc shape.

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