Secondary battery, battery pack, and method for bonding collector plate of secondary battery

Abstract

The invention provides a secondary battery and a battery pack, which can suppress the mechanical vibration of a collector plate from acting on a battery cover when the collector plate and a metal foil exposed part are subjected to ultrasonic welding, thereby reducing the reject ratio. The secondary battery comprises: an electrode body (13) comprising a positive electrode material and a negative electrode material; a battery container (11) for accommodating the electrode body (13); and a battery lid (6) for sealing the battery container. A collector plate (14) disposed inside the battery container (11) and joined to the electrode body (13) by ultrasonic welding; and an external electrode terminal (8) provided on the outer surface of the battery cover (6) and connected to the collector plate (14), and a gas discharge valve (9) provided on the battery cover (6), the secondary battery being characterized in that: one side of the collector plate (14) is electrically connected to the external electrode terminal (8) and fixed to the battery cover (6), and the other side of the collector plate (14) is joined to the electrode body (13); a joining region (42) where the collector plate (14) and the electrode body (13) are joined is formed so as to be close to a tip (47) on the other side of the collector plate (14).

Description

Technical Field

[0001] This invention relates to a secondary battery, a battery pack obtained by combining the secondary batteries, and a method for joining the current collector plate of the secondary battery. Background Technology

[0002] The development of high-energy-density lithium-ion secondary batteries, such as those used as power sources in vehicles like electric vehicles, has been ongoing. In particular, prismatic secondary batteries with high volumetric density are known for use in vehicles and similar applications.

[0003] The secondary battery is obtained by rolling a positive electrode (obtained by coating positive active material on both sides of a positive electrode foil) and a negative electrode (obtained by coating negative active material on both sides of a negative electrode foil) together in a flat shape with a separator, and then storing the rolled body (electrode body) and electrolyte solution in a square battery container.

[0004] In such a secondary battery, metal foil exposure portions are formed at both ends of the winding body in the direction of the winding axis, exposing metal foils for the positive and negative electrodes respectively. A current collector, which is connected to external electrode terminals, is then connected to the metal foil exposure portions using welding or the like, shortening the current path and reducing the connection resistance. Furthermore, secondary batteries using solid electrolytes are also being developed, and this invention also targets such secondary batteries.

[0005] Furthermore, various methods can be considered for welding the exposed metal foil to the current collector as described above, but ultrasonic welding is commonly used to join the exposed metal foil to the current collector. For example, International Patent Publication No. 2018 / 159197 (Patent Document 1) discloses a solid-state bonding method that uses an ultrasonic amplitude transformer and an anvil to clamp the exposed metal foil and the current collector.

[0006] In Patent Document 1, a current collector is pre-installed and fixed on a battery cap that seals the battery canister, with the current collector overlapping the exposed metal foil portion of the wound body and placed on a bonding fixture. Then, the anvil of an ultrasonic welding device is brought into contact with the current collector in a clamping manner, and after the ultrasonic amplitude transformer is brought into contact with the exposed metal foil to press the current collector and the exposed metal foil into a pressed state using the anvil and the ultrasonic amplitude transformer, the ultrasonic amplitude transformer is vibrated to solidify the current collector and the exposed metal foil together.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent document 1: International Publication No. 2018 / 159197. Summary of the Invention

[0010] The technical problem that the invention aims to solve

[0011] However, a gas vent valve is integrally provided on the battery cover. When the pressure inside the battery container rises, the gas vent valve opens (or cracks) to release gas from inside the battery container, thereby reducing the pressure inside the battery container and ensuring the safety of the secondary battery. The gas vent valve can be formed, for example, by making the wall of the battery cover thin-walled, or by pressing a separately manufactured sealing plug into a through hole formed in the battery cover.

[0012] As described above, the current collector is ultrasonically welded to the exposed metal foil portion while being mounted and fixed to the battery cover. Therefore, the mechanical vibration generated by the ultrasonic amplitude transformer used for ultrasonic bonding propagates through the current collector to the battery cover, and thus the mechanical vibration acting on the battery cover acts as an external force on the gas exhaust valve (hereinafter, the external force generated from the ultrasonic amplitude transformer to the battery cover will be referred to as mechanical force). Therefore, a structure capable of suppressing the mechanical vibration applied to the battery cover during ultrasonic welding is required.

[0013] The purpose of this invention is to provide a current collector joining method for secondary batteries, battery packs, and secondary batteries that can suppress the mechanical vibration of the current collector on the battery cover and reduce the defect rate when ultrasonically welding the current collector and the exposed metal foil portion.

[0014] Means for solving technical problems

[0015] The present invention is a secondary battery, characterized in that it comprises: an electrode body including a positive electrode material and a negative electrode material; a battery container for housing the electrode body and a battery cover for sealing the battery container; a current collector disposed inside the battery container; and external electrode terminals disposed on the outer surface of the battery cover and a gas vent valve disposed on the battery cover, one side of the current collector being electrically connected to the external electrode terminals and fixed to the battery cover, the other side of the current collector being engaged with the electrode body, and the engagement area where the current collector is engaged with the electrode body being formed in an end region on the other side of the current collector in a direction away from one side.

[0016] The present invention is a battery pack, characterized in that it is constructed by stacking multiple secondary batteries, each secondary battery having: an electrode body including a positive electrode material and a negative electrode material; a battery container housing the electrode body and a battery cover sealing the battery container; a current collector plate disposed inside the battery container and joined to the electrode body by ultrasonic welding; and external electrode terminals disposed on the outer surface of the battery cover and connected to the current collector plate, and a gas vent valve disposed on the battery cover. The above-described secondary battery is used as a secondary battery.

[0017] This invention relates to a method for joining current collector plates in a secondary battery. The secondary battery comprises: an electrode body including a positive electrode material and a negative electrode material; a battery container housing the electrode body and a battery cover sealing the battery container; a current collector plate disposed inside the battery container and joined to the electrode body by ultrasonic welding; external electrode terminals disposed on the outer surface of the battery cover and connected to the current collector plate; and a gas vent valve disposed on the battery cover. Ultrasonic welding is performed by an anvil pressing the current collector plate and an ultrasonic amplitude transformer pressing the electrode body. The anvil is positioned close to the front end of the current collector plate on the opposite side from the side fixed to the battery cover. The ultrasonic amplitude transformer is positioned corresponding to the anvil's position. In this state, the ultrasonic amplitude transformer is mechanically vibrated, forming a joining area between the current collector plate and the electrode body at the position where the anvil is located.

[0018] Invention Effects

[0019] By employing this invention, the propagation distance from the joint area of ​​the current collector to the fixed position of the current collector on the battery cover can be increased. The longer propagation distance of the current collector can be used to reduce or absorb the mechanical force generated by the mechanical vibration of the ultrasonic welding acting on the battery cover. Therefore, damage to the gas discharge valve can be suppressed, thereby reducing the defect rate. Attached Figure Description

[0020] Figure 1 This is a perspective view of the battery pack obtained by combining the secondary batteries of the present invention.

[0021] Figure 2 This is a perspective view of the secondary battery according to an embodiment of the present invention.

[0022] Figure 3 It is Figure 2 The diagram shows a three-dimensional image obtained from the disassembly of a secondary battery.

[0023] Figure 4 It means Figure 3 The diagram shows a three-dimensional view of the structure of the electrode.

[0024] Figure 5 This is a perspective view of the current collector and battery cover of an embodiment of the present invention before assembly.

[0025] Figure 6 This is a perspective view of the assembled current collector and battery cover according to an embodiment of the present invention.

[0026] Figure 7 This is an explanatory diagram illustrating the state of ultrasonic welding of the current collector and electrode body according to an embodiment of the present invention.

[0027] Figure 8This is a perspective view of the current collector plate in an embodiment of the present invention, viewed from the side that contacts the anvil.

[0028] Figure 9 The modified example of the current collector plate according to an embodiment of the present invention is shown in a perspective view from the side in contact with the anvil. Detailed Implementation

[0029] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below, and various modifications and applications are also included within the scope of the technical concept of the present invention.

[0030] Figure 1 This refers to a battery pack obtained by stacking multiple secondary batteries according to embodiments of the present invention. The battery pack 100 of this embodiment is a battery pack obtained by alternately arranging flat, square secondary batteries 20 with spacer members 2 in the thickness direction. In the following description, an XYZ orthogonal coordinate system is sometimes used, where the thickness direction of the secondary battery 20 is set as the X-axis direction, the width direction of the secondary battery 20 is set as the Y-axis direction, and the height direction of the secondary battery 1 is set as the Z-axis direction.

[0031] The battery pack 100 of this embodiment includes: a plurality of secondary batteries 20; a plurality of spacer members 2 disposed between each secondary battery 20; a pair of end spacer members 3 disposed opposite to each other at their ends in the stacking direction; a pair of end plates 4 disposed opposite to each other on the outside of the end spacer members 3; and a pair of side plates 5 disposed opposite to each other on both sides of the end plates 4.

[0032] Alternatively, a structure in which the end plate is omitted can be used. In this case, the secondary battery 20 is held in place by the side plate 5.

[0033] A battery cover 6 is mounted on the upper side of the secondary battery 20. Positive-side external electrode terminal 8P and negative-side external electrode terminal 8N are provided on both sides in the width direction. A gas vent valve 7 and a sealing plug 9 are provided between the positive-side external electrode terminal 8P and the negative-side external electrode terminal 8N. The gas vent valve 7 functions to open and reduce the gas pressure when the internal gas pressure of the secondary battery 20 reaches a predetermined value, ensuring safety. Furthermore, the sealing plug 9 seals the battery after liquid electrolyte is injected into it.

[0034] Figure 2 This diagram shows the appearance of a square-shaped secondary battery 20. The secondary battery 20 shown includes a battery casing 11 and a battery cover 6. Inside the battery casing 11 are electrode bodies 13, which serve as power generators (see reference). Figure 4The upper opening of the battery casing 11 is sealed by the battery cover 6. The battery cover 6 is welded to the battery casing 11 by laser welding, and the battery casing 11 and the battery cover 6 constitute the battery container.

[0035] The battery cover 6 is provided with a positive electrode terminal 8P and a negative electrode terminal 8N. Through these positive electrode terminals 8P and negative electrode terminals 8N, the electrode body 3 (refer to...) can be... Figure 4 It can charge and supply power to external loads.

[0036] Furthermore, a thin-walled gas vent valve 7 is integrally formed on the wall of the battery cover 6. When the pressure inside the battery container rises, the gas vent valve 7 opens, releasing gas from inside the battery container and thus reducing the pressure inside the battery container. This ensures the safety of the secondary battery 20. Additionally, a sealing bolt 9 is welded to the battery cover 6, and an injection port 10 for injecting electrolyte into the battery housing 11 (see reference) is also provided. Figure 3 )seal.

[0037] Figure 3 It is Figure 2 The diagram shows an exploded view of the secondary battery 20. Inside the battery casing 11 of the secondary battery 20 shown, the electrode body 13 is housed through an insulating sheet 12.

[0038] Here, electrode body 13 is Figure 4 The structure shown. The positive electrode (positive electrode) 301 and the negative electrode (negative electrode) 302 are wound in a flat shape around the winding axis L, separated by a diaphragm 303. Thus, a pair of opposing curved portions 13a and 13b, with approximately semi-circular cross-sections, are formed in the electrode body 13 (see reference). Figure 3 ); and the flat portion 13c continuously formed between the pair of curved portions 13a, 13b (see reference 13c). Figure 3 ).

[0039] At least a portion of the planar portion 13c of the electrode body 13, and at least a portion of the positive electrode foil exposed portion 301c and the negative electrode foil exposed portion 302c (described later), are gathered together to form a flat plate shape, thereby forming a positive electrode-side gathered flat plate-shaped portion 301d (see reference). Figure 3 ) and the negative electrode side converged plate-shaped portion 302d (refer to) Figure 3 Additionally, the positive electrode side converged plate-shaped portion 301d and the negative electrode side converged plate-shaped portion 302d are sometimes also referred to as the positive electrode foil exposed portion 301c and the negative electrode foil exposed portion 302c.

[0040] Furthermore, the positive electrode side converged plate-shaped portion 301d and the negative electrode side converged plate-shaped portion 302d overlap with a portion of the joint area portion 42P on one end side of the positive electrode side current collector plate 14P and a portion of the joint area portion 42N on one end side of the negative electrode side current collector plate 14N, respectively, and are connected by ultrasonic welding.

[0041] The joining regions 42P and 42N are joined with the positive electrode side convergent plate-shaped portion 301d and the negative electrode side convergent plate-shaped portion 302d, therefore, in Figure 3 In the diagram, there are joint areas 42P and 42N on opposite sides of the positive electrode current collector 14P and the negative electrode current collector 14N, which are indicated by dashed boxes.

[0042] Furthermore, the joining regions 42P and 42N are formed solely by ultrasonic welding, and therefore are depicted virtually. The locations where these joining regions 42P and 42N are formed are the subject of this embodiment, and this will be explained later using the accompanying drawings.

[0043] The electrode body 13 is inserted into the battery housing 11 from one bend 13b side with its winding axis L along the transverse width direction of the battery housing 1, and is configured such that the other bend 13a side becomes the upper opening side of the battery housing 11.

[0044] The other end of the positive-side current collector 14P and the other end of the negative-side current collector 14N are connected to the positive-side external electrode terminal 8P and the negative-side external electrode terminal 8N, respectively, via the battery cover 6. Furthermore, the positive-side external electrode terminal 8P and the negative-side external electrode terminal 8N have welded joints that are welded to a bus bar (not shown). These welded joints are rectangular blocks protruding upwards from the battery cover 6, with their lower surface facing the surface of the battery cover 6 and their upper surface parallel to the battery cover 6 at a predetermined height.

[0045] On the lower surface of the welding joint of the positive electrode terminal 8P, a positive electrode connection portion 12P for connecting the positive electrode terminal 8P to the positive electrode current collector 14P is integrally formed. On the lower surface of the welding joint of the negative electrode terminal 8N, a negative electrode connection portion 12N for connecting the negative electrode terminal 8N to the negative electrode current collector 14N is integrally formed.

[0046] Furthermore, the positive electrode side current collector 14P and the negative electrode side current collector 14N have rectangular plate-shaped fixing bases 41P and 41N arranged opposite to the lower surface of the battery cover 6. Opening holes 43P and 43N are formed on these fixing bases 41P and 41N respectively, for insertion into the positive electrode connection portion 12P and the negative electrode connection portion 12N formed on the positive electrode side external electrode terminal 8P and the negative electrode side external electrode terminal 8N.

[0047] In addition, the positive electrode side current collector 14P and the negative electrode side current collector 14N are bent at the side ends of the fixing base 41P and 41N and extend along the width of the battery casing 11 to the bottom surface. They have joint areas 42P and 42N that are joined to the positive electrode side flat plate 301d and the negative electrode side flat plate 302d in a state that are opposite to and overlap with the positive electrode side flat plate 301d and the negative electrode side flat plate 302d of the electrode body 13.

[0048] The positive electrode connection portion 12P of the positive electrode side external electrode terminal 8P and the negative electrode connection portion 12N of the negative electrode side external electrode terminal 8N have cylindrical shapes with their respective front ends protruding from the lower surfaces of the positive electrode side external electrode terminal 8P and the negative electrode side external electrode terminal 8N, which can be inserted into the through holes 6P and 6N formed on the battery cover 6.

[0049] The positive electrode connection portion 12P and the negative electrode connection portion 12N pass through the through holes 6P and 6N into the battery cover 6, and protrude through the openings 43P and 43N of the fixing bases 41P and 41N towards the inner side of the battery casing 11, respectively, and their front ends are fastened. Thus, the positive electrode external electrode terminal 8P and the positive electrode current collector 14P are integrally fixed to the battery cover 6, and the negative electrode external electrode terminal 8N and the negative electrode current collector 14N are integrally fixed to the battery cover 6.

[0050] Here, a gasket 15 is provided between the positive electrode terminal 8P and the negative electrode terminal 8N and the battery cover 6. Furthermore, an insulating plate 16 is provided between the positive electrode current collector 14P and the negative electrode current collector 14N and the battery cover 6. The gasket 15 and the insulating plate 16 are used to electrically insulate the positive electrode terminal 8P and the negative electrode terminal 8N, as well as the positive electrode current collector 14P and the negative electrode current collector 14N, from the battery cover 6.

[0051] In addition, an injection port 10 is formed on the battery cover 6. After electrolyte is injected into the battery casing 11 through the injection port 10, a sealing plug 9 is welded to the injection port 10 to seal the secondary battery 20.

[0052] In addition, the battery casing 11, battery cover 6, positive electrode side current collector 14P and positive electrode side external electrode terminal 8P are made of aluminum-based materials (including aluminum), and the negative electrode side current collector 14N and negative electrode side external electrode terminal 8N are made of copper-based materials (including copper).

[0053] As described above, the positive electrode side current collector 14P and the negative electrode side current collector 14N are ultrasonically welded to the positive electrode side convergent plate portion 301d and the negative electrode side convergent plate portion 302d, respectively, while being mounted and fixed on the battery cover 6. Therefore, the mechanical vibration generated by the ultrasonic amplitude transformer used for ultrasonic welding is transmitted to the battery cover 6 via the positive electrode side current collector 14P and the negative electrode side current collector 14N. Consequently, the mechanical vibration acting on the battery cover 6 acts as a mechanical force on the gas discharge valve 7.

[0054] Therefore, it is conceivable that the gas discharge valve 7 might be damaged due to this mechanical force, rendering it unable to perform its intended function. Consequently, in this situation, the secondary battery would be deemed defective, leading to an increased defect rate.

[0055] To solve this problem, this embodiment is characterized by employing the following structure: the joining regions of the positive-side current collector 14P, the negative-side current collector 14N, and the positive-side flat plate portion 301d and the negative-side flat plate portion 302d of the electrode body 13 are formed close to the front end of the other end side (the end opposite to the fixed side of the external electrode terminal) of the positive-side current collector 14P and the negative-side current collector 14N. In other words, the joining region where the current collector 14N joins the electrode body 13 is formed in the end region on the other side of the current collector 14N in a direction away from one side of the current collector 14N.

[0056] Furthermore, in this embodiment, the formation positions of the aforementioned bonding regions are specified for the positive electrode side current collector 14P and the negative electrode side current collector 14N. However, depending on the different metal materials of the positive electrode side current collector 14P and the negative electrode side current collector 14N, there may be cases where it is not necessary to specifically specify the formation positions of the bonding regions. In such cases, bonding can also be performed at the conventional formation positions of the bonding regions.

[0057] According to the inventor's insight, it has been determined that the influence of mechanical vibration in the negative electrode side current collector 14N made of copper-based material is not that great. Therefore, it is not necessary to specifically specify the formation position of the joint area for the negative electrode side current collector 14N made of copper-based material.

[0058] This is because copper-based materials have a higher specific gravity compared to aluminum-based materials. As a result, copper-based materials are less prone to vibration during ultrasonic welding, and the vibration energy is lower. Therefore, mechanical vibration is not as significant a problem in copper-based materials as it is in the case of aluminum-based materials.

[0059] Therefore, in this case, it is sufficient to specify the formation position of the aforementioned bonding region for the positive electrode side current collector 14P made of aluminum-based materials. Of course, this embodiment can also be applied to the negative electrode side current collector 14N made of copper-based materials in the presence of mechanical vibration.

[0060] Figure 5 This indicates that the battery cover 6 is separated from the positive electrode current collector 14P and the negative electrode current collector 14N. Figure 6 This indicates that the positive electrode current collector 14P and the negative electrode current collector 14N are integrally mounted on the battery cover 6.

[0061] exist Figure 5 In this battery cover 6, an insulating plate 16 corresponding to the positive electrode terminal 8P and the negative electrode terminal 8N is installed on the inner wall 6W (fixed to one side of the battery housing 11) on the inner surface side. Furthermore, the positive electrode current collector 14P and the negative electrode current collector 14N are mounted on the inner wall 6W on the inner surface side of the battery cover 6 by clamping the insulating plate 16.

[0062] Then, as Figure 6 The battery cover 6, assembled in this manner, along with the positive electrode side current collector 14P and the negative electrode side current collector 14N, is overlapped with the positive electrode side convergent plate-shaped portion 301d and the negative electrode side convergent plate-shaped portion 302d of the electrode body 13 and mounted on the joining fixture. Regarding this state, using... Figure 7 Please provide an explanation.

[0063] Next, the structures of the positive-side current collector 14P and the negative-side current collector 14N will be described. Here, the positive-side current collector 14P and the negative-side current collector 14N have substantially the same structure; therefore, the positive-side current collector 14P, made of an aluminum-based material, will be described below. However, for the negative-side current collector 14N, the "P" in the reference numerals can be replaced with "N".

[0064] like Figure 5 , Figure 6 As shown, the positive electrode side current collector 14P is formed to include: a flat mounting base 41P that is fixed to the inner wall 6W on the inner surface side of the battery cover 6 via an insulating plate 16; and a current collector 44P extending from the mounting base 41P in a vertical or substantially vertical direction. Therefore, the positive electrode side current collector 14P is shaped to extend in a vertical or substantially vertical direction relative to the inner wall 6W on the inner surface side of the battery cover 6.

[0065] The current collector 44P has an inclined portion 45P extending inwards towards the storage space of the battery casing 11, and a current collector body portion 46P extending continuously from the inclined portion 45P. The current collector body portion 46P refers to the portion from the connection point connected to the inclined portion 45P to the front end portion 47P. Furthermore, the inclined portion 45P is for... Figure 3 As shown, the current collector body 46P is joined to the positive electrode side flat plate 301d, which is formed so that the current collector body 46P is close to the positive electrode side flat plate 301d.

[0066] The current collector body 46P has an overlapping area that coincides with the positive electrode side converged plate 301d in a manner that contacts the positive electrode side converged plate 301d. A joining area 42P is formed in a portion of this overlapping area. This joining area 42P is formed near the front end portion 47P of the current collector body 46P. That is, it is an end region formed on the other side of the current collector plate 14P in a direction away from one side of the current collector plate 14P. Furthermore, the end region is the area near the front end portion 47P and has a size that allows the joining area 42P to be formed. As described later, the joining area 42P roughly corresponds to the area that contacts the anvil.

[0067] By setting the joint area 42P to the side close to the front end 47P of the current collector body 46P as described above, the distance between the joint area 42P and the fixed base 41P in the current collector 44P can be increased, that is, the propagation distance of mechanical vibration can be increased.

[0068] When the width and thickness of the current collector 44P are constant, the attenuation of mechanical vibration energy depends on the propagation distance, and therefore tends to increase the attenuation as the propagation distance increases. One reason for this is that, in the region between the joint area 42P and the fixed base 41P of the current collector 44, a longer distance between the joint area 42P and the fixed base 41P increases the area that can move freely, thereby attenuating the mechanical vibration.

[0069] In other words, it can be considered that during the propagation of mechanical vibration from the joint area 42P to the fixed base 41P during ultrasonic welding, the vibration energy expands to a wider range as the distance increases, and the energy per unit area decreases. Therefore, the mechanical vibration at the fixed base 41P is reduced.

[0070] As described above, by increasing the distance between the joining area 42P and the fixed base 41P, mechanical vibration can be attenuated more efficiently. Therefore, even if mechanical vibration generated by the ultrasonic amplitude transformer used for ultrasonic welding propagates to the battery cover 6 via the current collector 44P, this mechanical vibration is attenuated, thus preventing mechanical vibration acting on the battery cover 6 from damaging the gas discharge valve 7. Furthermore, the location definition and area of ​​the joining area 42P will be discussed using... Figure 8 Please provide an explanation.

[0071] Next, use Figure 7 This describes the ultrasonic welding process used to join the positive electrode side current collector 14P to the positive electrode side flat plate 301d of the electrode body 13. The same applies to the negative electrode side current collector 14N and the exposed negative electrode foil 302c of the electrode body 13.

[0072] In ultrasonic welding, as... Figure 6 With the battery cover 6 integrated with the positive electrode current collector 14P, the anvil 51 of the ultrasonic welding device is brought into contact with the positive electrode current collector 14P by clamping the positive electrode current collector 14P and the positive electrode converging plate 301d, and the ultrasonic amplitude transformer 50 is brought into contact with the positive electrode converging plate 301d.

[0073] Then, after pressing the positive electrode side current collector 14P and the positive electrode side collapsible plate 301d together using the anvil 51 and the ultrasonic amplitude transformer 50, the ultrasonic amplitude transformer 50 is vibrated to join the positive electrode side current collector 14P to the positive electrode foil exposed portion 301c of the electrode body 13.

[0074] Figure 7 This is a schematic representation of the current collector 14P and... Figure 3 A diagram showing the process of joining electrode body 13. Additionally, in Figure 7 The process for the positive electrode side is described, but the process for the negative electrode side is the same.

[0075] like Figure 7 As shown, on one surface 301df of the positive electrode side flat plate 301d formed by gathering the positive electrode foil exposed portion 301c of the electrode body 13 into a flat plate, the current collector body 46P of the positive electrode side current collector plate 14P is disposed. With the flat portions of the positive electrode foil exposed portion 301c of the electrode body 13 and the current collector body 46P of the positive electrode side current collector plate 14P respectively abutting each other, they are pressed in the direction of the hollow arrow to join them.

[0076] Specifically, based on the position where the positive electrode side of the electrode body 13 abuts against the flat portion of the positive electrode side of the current collector plate 14P 46P, an ultrasonic amplitude transformer 50 is disposed on the opposite side of the positive electrode side of the positive electrode side of the abutment plate 301d, and an anvil 51 is disposed on the positive electrode side of the current collector plate 14P 46P. Here, the cross-sectional shape of the anvil 51, which is at least orthogonal to the pressing direction of the anvil 51, is formed to be rectangular.

[0077] Then, using the ultrasonic amplitude transformer 50 and the anvil 51, the positive electrode side of the electrode body 13, the collapsible plate 301d and the current collector body 46P, are pressed and clamped in the direction of the hollow arrow, and the ultrasonic amplitude transformer 51 is mechanically vibrated in this state. Using the frictional heat generated by this mechanical vibration, the positive electrode side collapsible plate 301d and the current collector body 46P are joined to form a joining region 42P. Furthermore, as described above, the joining region 42P is formed to correspond to the area where the anvil 51 contacts the current collector body 46P.

[0078] In this embodiment, in order to form the engagement area 42P close to the front end portion 47P of the current collector body 46P, the anvil 51 and the ultrasonic amplitude transformer 50 are arranged close to the front end portion 47P of the current collector body 46P.

[0079] In other words, frictional engagement occurs in the area of ​​high clamping force between the anvil 51 and the ultrasonic amplitude transformer 50. Therefore, the anvil 51 is preferably positioned as close as possible to the front end 47P side of the current collector body 46P. This is because, as described above, by increasing the distance between the engagement area 42P and the fixed base 41P, mechanical vibration can be attenuated more efficiently.

[0080] Here, the engagement area 42P has a shape similar to the contact shape when the anvil 51 is pressed onto the current collector body 46P. In this case, the shape of the engagement area 42P may be larger or smaller than the contact shape of the anvil, but in either case, its shape is similar.

[0081] Therefore, when confirming the shape of the joined area 42P after joining, one can infer the shape by observing the joining marks of the anvil 51 formed on the surface of the current collector body 46P by the pressing of the anvil 51. The joining marks are uneven indentations formed by the plastic deformation of the surface of the current collector body 46P by the contact / pressing of the anvil 51.

[0082] Furthermore, by observing the joint mark, it is possible to determine the position of the anvil 51 in contact. In other words, the position of the joint area 42P in the current collector body 46P can be deduced by analogy.

[0083] Furthermore, mechanical vibrations can propagate to the battery cover 6 via the positive electrode side current collector 14P. Therefore, the current collector body 46P is preferably pressed by the anvil 51. This is because, assuming that the current collector body 46P is pressed by the ultrasonic amplitude transformer 50, the mechanical vibration of the ultrasonic amplitude transformer 50 would directly act on the current collector body 46P, which is therefore not preferred.

[0084] Next, use Figure 8 The positive electrode side current collector 14P shown will be described, focusing on the structure of the front end portion 47P, which is a feature of this embodiment, where the joining region 42P is close to the front end portion 46P of the current collector body 46P. Here, Figure 8 Only the positive electrode side current collector plate 14P after it is joined with the electrode body 13 is shown. Therefore, a joint mark 52P for the anvil 51 used in the welding operation is formed on the front end 47P side of the current collector body 46P.

[0085] In this embodiment, as described above, the main objective is to attenuate mechanical vibration energy by increasing the distance between the engagement area 42P and the fixed base 41P.

[0086] Therefore, it is important that the joining area 42P formed in the current collector body 46P is formed close to the front end portion 47P on the other side of the current collector body 46P (the side opposite to the fixing base). In this case, the formation position of the joining area 42P, in other words, the position where the anvil 51 contacts the current collector body 46P, is determined according to the idea described below.

[0087] First, the area of ​​the joint region 42P that provides the required joint force in the design is determined, and the front end shape of the anvil 51 corresponding to this area is then determined. For example, as... Figure 7 As shown, the cross-sectional shape of the anvil 51, which is orthogonal to the pressing direction of the anvil 51, is determined to be rectangular. This is because the current collector body 46P is formed into a long and thin strip shape, and therefore the front end shape of the anvil 51 is determined according to this shape.

[0088] Next, ultrasonic welding is performed using the anvil 51. In this case, as... Figure 7 As shown, the positive electrode side current collector 14P and the electrode body 13 are overlapped for bonding. However, as mentioned above, in order to attenuate mechanical vibration, it is necessary to increase the distance between the bonding area 42P and the fixed base 41P.

[0089] Therefore, as Figure 7As shown, the side wall 51R, which is opposite to the side wall 51F of the anvil 51 facing the fixed base 41P, is positioned close to the front end portion 47P of the current collector body 46P. In this case, the side wall 51R of the anvil 51 is positioned so as not to extend outward beyond the front end portion 47P. The length between the front end portion 47P and the side wall 51R of the anvil 51 is formed to a length permissible by design.

[0090] Regarding the positional relationship between the anvil 51 and the ultrasonic amplitude transformer 50, in order to efficiently transmit the mechanical vibration of the ultrasonic amplitude transformer 50, the contact portion between the anvil 51 and the current collector body 46P is formed to overlap with the contact portion between the ultrasonic amplitude transformer 50 and the positive electrode side convergent plate-shaped portion 301d. That is, when the joint mark 52P is projected in the direction of the joint mark formed by the ultrasonic amplitude transformer 50, the two joint marks overlap.

[0091] Furthermore, the side wall 50R of the ultrasonic amplitude transformer 50 extends beyond the side wall 51R of the anvil 51 and is located at the front end 47P. This allows for efficient transmission of mechanical vibrations to the anvil 51. Additionally, the side wall 50R of the ultrasonic amplitude transformer 50 and the side wall 51R of the anvil 51 can be located on the same plane (a so-called coplanar relationship) when viewed in their respective pressing directions (the direction of the hollow arrow). In either case, the ultrasonic amplitude transformer 50 is positioned close to the front end 47P of the current collector body 46P. This allows for efficient transmission of mechanical vibrations to the anvil 51.

[0092] In this embodiment, the key is that the distance between the engagement area 42P and the fixed base 41P can be set to a length that allows mechanical vibration to be attenuated to the point that the gas discharge valve 7 will not be damaged. For this purpose, the side wall 51R of the anvil 51 is arranged close to the front end 47P of the current collector body 46P.

[0093] Back Figure 8 , Figure 8 This is an example of a joint mark 52P when the anvil 51 is pressed against the current collector body 46P in the direction of the hollow arrow. Furthermore, the joint mark 52P and the joint area 42P are positioned relative to each other below, and therefore will be described as substantially synonymous.

[0094] When the total length of the current collector body 46P (the length of the current collector body 46P from the connection portion connected to the inclined portion 45P to the front end portion 47P) is “L”, the joint mark 52P is formed close to the front end portion 47P within a range of “L / 2” as seen from the front end portion 47P after dividing the current collector body 46P into two equal parts.

[0095] Therefore, the length from the side opposite to the edge of the joining area 42P opposite to the front end 47P to the fixed base 41P is approximately "L / 2" plus the length of the inclined portion 45P and the connecting portion 48P that connects the fixed base 41P and the inclined portion 45P.

[0096] Here, "approaching the front end portion 47P" means approaching the front end portion 47P on the premise that the edge of the rectangular joint 52P, or in other words, the joint area 42P opposite to the front end portion 47P, does not extend beyond the front end portion 47P. Of course, the distance between the edge of the joint area 42P opposite to the front end portion 47P and the front end portion 47P is set to the length required by the design.

[0097] However, when the area of ​​the joint region 42P is large, it is conceivable that the length of the joint mark 52P from the front end 47P side exceeds "L / 2", as shown by the joint mark 52P indicated by the dashed line.

[0098] Even in this case, because the anvil 51 is configured close to the front end portion 47P, a large portion of the area of ​​the joint mark 52P exists within a range of "L / 2" from the front end portion 47P. For example, more than 50% of the joint mark 52P exists within a range of "L / 2" from the front end portion 47P.

[0099] Therefore, the distance between the joining area 42P and the fixing base 41P can be made as long as possible. Here, the distance between the joining area 42P and the fixing base 41P is the distance between the farthest edge of the joining area 42P and the fixing base 41P when viewed from the front end 47P. That is, it is the distance from the side opposite to the front end 47P of the rectangular-shaped joining area 42P.

[0100] This allows for maximizing the propagation distance of vibration and effectively attenuating mechanical vibration. As a result, even if the mechanical vibration generated by the ultrasonic amplitude transformer 50 used for ultrasonic welding propagates to the battery cover 6 via the current collector 44P, the mechanical vibration is attenuated, thus preventing the mechanical vibration acting on the battery cover 6 from damaging the gas discharge valve 7.

[0101] The above description shows that by making the length between the joint area 42P and the fixed base 41P as long as possible, the mechanical vibration in the current collector 44P is attenuated.

[0102] By reducing the contact area between the anvil 51 and the current collector 46P, the energy of mechanical vibration input to the current collector 44P can be reduced, thereby reducing the mechanical force acting on the gas discharge valve 7.

[0103] like Figure 7 As shown, the area (Sa) of the contact between the anvil 51 and the current collector 46P is set to be smaller than the area (Sh) of the contact between the ultrasonic amplitude transformer 50 and the positive electrode-side convergent plate 301d. According to the inventor's understanding, when the ratio of Sa / Sh is less than 1.0 (Sa / Sh < 1.0), the energy of mechanical vibration input to the current collector 44P can be effectively reduced. Furthermore, the areas (Sa) and (Sh) can also be described as the areas of the joint formed by the anvil 51 and the ultrasonic amplitude transformer 50.

[0104] Furthermore, when the contact area of ​​the anvil 51 can be reduced, it can also indirectly help to increase the distance between the mating area 42P and the fixed base 41P.

[0105] Next, a modified example of the positive electrode current collector 14P will be described. This modified example is... Figure 8 The example shown is where the connecting inclined portion 45P and the connecting portion 48P of the fixed base 41P in the positive electrode side current collector 14P are changed to a buffer connecting portion 49P. Furthermore, the buffer connecting portion can be formed as a "flexible structure," and the structure other than the buffer connecting portion 49P is similar to... Figure 8 The structures are the same, so the explanation is omitted.

[0106] exist Figure 9 In the positive electrode side current collector plate 14P, a buffer connection portion 49P is integrally formed as a connection portion connecting the inclined portion 45P and the fixed base portion 41P. This buffer connection portion 49P extends convexly in the same direction as the inclined portion 45P. That is, the cross-sectional shape in the direction orthogonal to the planar portion 53P forming the joint line 52P of the current collector body portion 46P is formed as an arc shape. Here, it is formed as a semi-circle. Furthermore, the width and thickness of the buffer connection portion 49P are formed to be the same as the width and thickness of the inclined portion 45P and the current collector body portion 46P.

[0107] The arc-shaped buffer connection 49P increases the distance between the fixed base 41P and the engagement area 42P, thereby reducing mechanical vibration. More importantly, the buffer connection 49P is also elastic, allowing the current collector 44P to move more significantly, which further effectively reduces mechanical vibration.

[0108] As described above, in this modified example, a buffer connection 49P is formed between the fixed base 41P and the inclined portion 45P, thereby further suppressing mechanical vibration.

[0109] As described above, the present invention is a secondary battery, characterized in that it comprises: an electrode body including a positive electrode material and a negative electrode material; a battery container housing the electrode body and a battery cover sealing the battery container; a current collector plate disposed inside the battery container and joined to the electrode body by ultrasonic welding; and external electrode terminals disposed on the outer surface of the battery cover and connected to the current collector plate, and a gas exhaust valve disposed on the battery cover, one side of the current collector plate being electrically connected to the external electrode terminals and fixed to the battery cover, the other side of the current collector plate being joined to the electrode body, and the joining area where the current collector plate and the electrode body are joined being formed near the front end of the other side of the current collector plate.

[0110] This structure increases the propagation distance from the connection area of ​​the current collector to its fixed position on the battery cover. The longer propagation distance of the current collector can be used to reduce or absorb the mechanical force generated by the mechanical vibration of the ultrasonic welding acting on the battery cover. Therefore, damage to the gas discharge valve can be suppressed, thereby reducing the defect rate.

[0111] Furthermore, the present invention is not limited to the above-described embodiments, but includes various modifications. The embodiments described above have been detailed to facilitate understanding of the invention and are not necessarily limited to all described constituent elements. In addition, a portion of the constituent elements of one embodiment may be replaced with constituent elements of other embodiments, or constituent elements of other embodiments may be added to the constituent elements of one embodiment. Other constituent elements may also be added, deleted, or replaced in the constituent elements of each embodiment.

[0112] Explanation of reference numerals in the attached figures

[0113] 6…Battery cover, 6W…Inner wall, 7…Gas exhaust valve, 8P…Positive side external electrode terminal, 8N…Negative side external electrode terminal, 9…Sealing plug, 10…Injection port, 11…Battery casing, 13…Electrode body, 14P…Positive side current collector, 14N…Negative side current collector, 41P, 41N…Fixing base, 42P, 42N…Connecting area, 44P, 44N…Current collector, 45P, 45N…Inclined part, 46P, 46N…Current collector body, 47P, 47N…Front end, 48P…Connecting part, 50…Ultrasonic amplitude transformer, 51…Anvil.

Claims

1. A secondary battery, characterized in that, have: Electrode bodies including positive electrode materials and negative electrode materials; A battery container for housing the electrodes and a battery cap for sealing the battery container; A current collector plate disposed inside the battery container; as well as External electrode terminals are disposed on the outer surface of the battery cover, and a gas exhaust valve is disposed on the battery cover. One side of the current collector is electrically connected to the external electrode terminal and is fixed to the battery cover, while the other side of the current collector is engaged with the electrode body. The junction area where the current collector plate and the electrode body are joined is formed on the other side of the current collector plate in an end region located in a direction away from said side.

2. The secondary battery according to claim 1, characterized in that: The joining area is formed at a position that allows it to contact the anvil used for ultrasonic welding.

3. The secondary battery according to claim 1, characterized in that: The current collector plate has: a fixing base disposed on one side of the current collector plate; and a current collector extending on the other side of the current collector plate in a direction away from the fixing base. The current collector has a main body portion with the end regions provided thereon. The joining area is formed within the range of the end region of the current collector body.

4. The secondary battery according to claim 3, characterized in that: When the current collector body is divided into two equal parts towards the front end, the joining area is formed in the area after the two parts are divided on the front end side.

5. The secondary battery according to claim 3, characterized in that: When the current collector body is divided into two equal parts towards the front end, more than 50% of the joining area is formed in the area after the two parts are divided on the front end side.

6. The secondary battery according to claim 2, characterized in that: When the contact area between the anvil, which is pressed against the current collector plate, and the current collector plate is denoted as Sa, and the contact area between the ultrasonic amplitude transformer, which is pressed against the electrode body, and the electrode body is denoted as Sh, the relationship Sa / Sh < 1.0 exists.

7. The secondary battery according to claim 6, characterized in that: The position in contact with the ultrasonic amplitude transformer used for ultrasonic welding is set in the end region on the other side of the current collector.

8. The secondary battery according to claim 7, characterized in that: The joint mark formed by the anvil and the joint mark formed by the ultrasonic amplitude transformer overlap when projected onto each other in the direction in which the anvil and the ultrasonic amplitude transformer are pressed.

9. The secondary battery according to claim 3, characterized in that: A buffer connection portion capable of reducing or absorbing mechanical vibrations generated by the ultrasonic welding is formed between the fixing base portion fixed to the battery cover and the current collecting body portion.

10. The secondary battery according to claim 9, characterized in that: The buffer connection is formed with an elastic shape for reducing or absorbing the mechanical vibration.

11. The secondary battery according to claim 10, characterized in that: The buffer connection is formed in an arc shape that is bent in a direction orthogonal to the planar portion of the current collector body and protrudes.

12. The secondary battery according to any one of claims 1 to 11, characterized in that: The current collector is a positive electrode side current collector made of aluminum-based materials.

13. A battery pack, characterized in that: The battery pack is constructed by stacking multiple secondary batteries. Each secondary battery includes: an electrode body comprising a positive electrode material and a negative electrode material; a battery container housing the electrode body and a battery cover sealing the battery container; a current collector plate disposed inside the battery container and joined to the electrode body by ultrasonic welding; external electrode terminals disposed on the outer surface of the battery cover and connected to the current collector plate; and a gas vent valve disposed on the battery cover. The secondary battery used is the secondary battery according to any one of claims 1 to 11.

14. A method for bonding the current collector plate of a secondary battery, characterized in that: The secondary battery includes: an electrode body comprising a positive electrode material and a negative electrode material; a battery container housing the electrode body and a battery cover sealing the battery container; a current collector plate disposed inside the battery container and joined to the electrode body by ultrasonic welding; external electrode terminals disposed on the outer surface of the battery cover and connected to the current collector plate; and a gas vent valve disposed on the battery cover. The ultrasonic welding is performed by pressing the anvil of the current collector and the battery cover together, while the current collector and the battery cover are fixed as a whole. The anvil is positioned close to the front end of the current collector on the opposite side of the side fixed to the battery cover, and the ultrasonic amplitude transformer is positioned corresponding to the anvil. In this state, the ultrasonic amplitude transformer is mechanically vibrated, forming a junction area between the current collector and the electrode body at the location where the anvil is located.

15. The current collector bonding method for a secondary battery according to claim 14, characterized in that: The current collector includes a fixing base that can be fixed to the battery cover, and a current collector extending from the fixing base to the front end. The current collector includes a current collector body portion that extends toward the front end and contacts the electrode body. The anvil is configured such that when the current collector body is bisected towards the front end, the engagement area is formed in the bisected area on the front end side.

16. The current collector bonding method for a secondary battery according to claim 14, characterized in that: The current collector includes a fixing base that can be fixed to the battery cover, and a current collector extending from the fixing base to the front end. The current collector includes a current collector body portion that extends toward the front end and contacts the electrode body. The anvil is configured such that when the current collector body is bisected towards the front end, more than 50% of the engagement area is formed in the bisected area on the front end side.

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