Secondary battery

Abstract

This invention provides a technique for reducing external loads such as vibration and impact applied to the boundary between the electrode body and the current collector tab. The disclosed secondary battery includes an electrode body, a housing body, and a cover. The cover has a current collector terminal mounted via an insulating material. The electrode body has a current collector tab. The current collector tab has an extension extending from the electrode body and a branch extending from a front end region of the extension in a direction different from the extension. The branch has a portion that engages with the current collector terminal.

Description

Technical Field

[0001] This invention relates to secondary batteries. Background Technology

[0002] Japanese Patent Application Publication No. 2018-94559 discloses a secondary battery in which a power generation element having a positive electrode and a negative electrode are housed inside a battery casing. In the secondary battery disclosed herein, the positive electrode and the negative electrode protruding from the power generation element are engaged with current collector terminals of the same polarity disposed inside the battery casing. Through this engagement, the positive electrode and the negative electrode are electrically connected to electrode terminals disposed outside the battery casing.

[0003] Furthermore, Japanese Patent Application Publication No. 2020-167010 discloses a secondary battery comprising: an electrode body having electrode plates; an outer casing having the electrode body; and a sealing plate sealing the outer casing and having terminals. In the secondary battery disclosed herein, a current collector is mounted to the sealing plate via an insulating member. The electrode plates are electrically connected to the terminals via this current collector.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2018-94559

[0005] Patent Document 2: Japanese Patent Application Publication No. 2020-167010

[0006] However, the inventors considered it desirable to reduce external loads such as vibration and impact applied to the boundary between the electrode body and the collector ear when connecting the collector ear to the collector terminal. Summary of the Invention

[0007] According to the technology disclosed herein, a secondary battery is provided, comprising: an electrode body; a housing body having an opening for receiving the electrode body; and a cover mounted on the opening of the housing body. In this secondary battery, the cover has a current collector terminal mounted via an insulating material. The electrode body has a current collector tab. The current collector tab has an extension extending from the electrode body and a branch extending from a front end region of the extension in a direction different from the extension. The branch has a portion that engages with the current collector terminal.

[0008] The collector tab has an extension extending from the electrode body and a branch extending from the front end region of the extension in a direction different from the extension, which engages with a collector terminal. That is, the collector tab and the collector terminal are engaged at a position deviating from the extending direction of the extension. Therefore, when engaging the collector tab with the collector terminal, the external load applied at the point where the extension begins to extend from the electrode body (the boundary between the electrode body and the collector tab) can be reduced. By reducing the external load applied at the point where the extension begins to extend from the electrode body during engagement, the risk of damage to the collector tab is reduced.

[0009] In a preferred embodiment of the secondary battery disclosed herein, the aforementioned branch extends from the front end region of the extension in a direction substantially perpendicular to the direction in which the extension extends from the electrode body. According to this structure, it is less likely to apply external loads at the point where the extension begins to extend, thus reducing the risk of damage to the current collector tab.

[0010] In another preferred embodiment, the aforementioned branch includes a first branch and a second branch. The first branch extends from the front end region of the extension in a direction substantially perpendicular to the direction in which the extension extends from the electrode body, and the second branch extends in a direction opposite to the direction in which the first branch extends. According to this structure, the extension is supported by the first branch and the second branch, which respectively engage with the current collector terminal on both sides. Therefore, it is less likely to apply external loads to the portion from which the extension begins, thus reducing the risk of damage to the current collector tab. Furthermore, the engagement area between the current collector tab and the current collector terminal can be increased, thereby further reducing the resistance of the secondary battery.

[0011] In another preferred embodiment, the front end region of the extension has a joining portion on the front end side that engages with the current collector terminal. According to this structure, by engaging a portion of the front end side of the extension's front end region with the current collector terminal, the joining area is increased, thereby reducing the resistance of the secondary battery. Furthermore, this prevents the extension from detaching from the surface of the current collector terminal. Attached Figure Description

[0012] Figure 1 This is a partial cross-sectional view of the secondary battery 10.

[0013] Figure 2 yes Figure 1 Sectional view II-II.

[0014] Figure 3 This is a top view showing the construction of the inner surface of cover 14.

[0015] Figure 4 This is a schematic diagram illustrating the ultrasonic connection between the negative collector ear 122 and the negative collector terminal 43.

[0016] Figure 5 This is a top view showing the state in which the positive collector terminal 33 and the negative collector terminal 43 are connected to the electrode body 20.

[0017] Figure 6 This is a top view illustrating the state in which the negative collector tab 122 is engaged with the negative collector terminal 43 in another embodiment.

[0018] Figure 7 This is a top view illustrating the state in which the negative collector tab 322 is connected to the negative collector terminal 43.

[0019] Explanation of reference numerals in the attached figures

[0020] 10…Secondary battery; 12…Outer casing; 14…Cover; 15…Injection hole; 16…Sealing component; 17…Gas vent valve; 20…Electrode body; 29…Insulating film; 21…Positive plate; 22…Negative plate; 23…Separator; 30…Positive terminal; 31…Positive external terminal; 32…Connecting component; 33…Positive current collector terminal; 40…Negative terminal; 41…Negative external terminal; 42…Connecting component; 43…Negative current collector terminal; 50…External insulating component; 60…Internal insulating component; 90, 290, 390…Joint (pre-joined portion); 121, 321…Positive current collector ear; 122, 322…Negative current collector ear. Detailed Implementation

[0021] The following describes one embodiment of the secondary battery disclosed herein. This embodiment is not intended to specifically limit the invention. Unless otherwise specified, the technology disclosed herein is not limited to the embodiment described herein. The accompanying drawings are schematic and do not necessarily reflect the actual object. Furthermore, components and parts that perform the same function are appropriately labeled with the same reference numerals, and repeated descriptions are omitted. Also, unless otherwise specified, expressions indicating numerical ranges such as "A to B" mean "A or more and B or less," and include "above A and below B."

[0022] In this specification, "secondary battery" generally refers to an energy storage device that undergoes a charging and discharging reaction by the movement of charge carriers between a pair of electrodes (positive and negative electrodes) via an electrolyte. This secondary battery includes not only so-called storage batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, but also capacitors such as electric double-layer capacitors. The following describes an embodiment using a lithium-ion secondary battery as an example.

[0023] Implementation Method 1

[0024] <Secondary Battery 10>

[0025] Figure 1This is a partial cross-sectional view of the secondary battery 10. Figure 1 In the middle, along a wide surface on one side of the roughly rectangular outer shell 12, the state in which the interior is exposed is depicted. Figure 2 yes Figure 1 Sectional view II-II. Figure 2 The image schematically depicts a partial cross-sectional view of the engagement between the negative collector tab 122 and the negative collector terminal 43, viewed from a narrow section of the generally rectangular housing 12. Figure 1 , 2 As shown, the secondary battery 10 has a housing body 12, a cover 14, and an electrode body 20.

[0026] <Electrode 20>

[0027] The electrode body 20 is the power generation element of the secondary battery 10, and includes a positive electrode, a negative electrode, and an insulating member that separates the positive electrode from the negative electrode. Additionally, the electrode body 20 has a current collector tab for external electrical connection. Figure 2 As shown, in this embodiment, the secondary battery 10 has two adjacently arranged electrode bodies 20. Figure 1 , 2 As shown, the two adjacent electrode bodies 20 are housed within the outer casing 12 while covered by an insulating film 29. Figure 1 As shown, the electrode body 20 includes a positive electrode plate 21 as a positive electrode element, a negative electrode plate 22 as a negative electrode element, and a separator plate 23 as a separator. The positive electrode plate 21 and the negative electrode plate 22 have a stacked structure with the separator plate 23 separating them. Here, the electrode body 20 illustrates a so-called stacked electrode body in which the positive electrode plate 21 and the negative electrode plate 22, which are formed in a predetermined shape, overlap with the separator plate 23 separating them.

[0028] <Positive Plate 21>

[0029] like Figure 1 As shown, the positive electrode plate 21 includes a generally rectangular positive electrode current collector foil 21a and a positive electrode active material layer 21b formed on the positive electrode current collector foil 21a. The positive electrode active material layer 21b is formed on both sides of the positive electrode current collector foil 21a. In this embodiment, the formation area of ​​the positive electrode active material layer 21b is rectangular. The positive electrode plate 21 has a positive electrode current collector tab 121 protruding from one side of the formation area of ​​the positive electrode active material layer 21b (see reference). Figure 5 The positive electrode collector tab 121 is part of the positive electrode current collector foil 21a, and is the portion where the active material layer 21b is not formed on the surface. In this embodiment, a positive electrode protective layer 21p is formed at the boundary between the positive electrode active material layer 21b and the positive electrode collector tab 121 (see reference). Figure 5Here, the positive electrode protective layer 21p is formed at the end of the positive electrode active material layer 21b in the protruding direction of the positive electrode current collector tab 121, and is adjacent to the positive electrode current collector tab 121. Furthermore, the formation of the positive electrode protective layer 21p is not necessary.

[0030] The positive electrode current collector foil 21a can be, for example, aluminum foil. The positive electrode active material layer 21b is a layer containing the positive electrode active material. The positive electrode active material is, for example, a material in a lithium-ion secondary battery, such as a lithium transition metal composite material, that can release lithium ions during charging and absorb lithium ions during discharging. Generally speaking, various materials other than lithium transition metal composite materials are proposed for the positive electrode active material, and there is no particular limitation. The positive electrode protective layer 21p is, for example, a layer containing inorganic fillers such as alumina.

[0031] <Negative Plate 22>

[0032] like Figure 1 As shown, the negative electrode plate 22 includes a generally rectangular negative electrode current collector foil 22a and a negative electrode active material layer 22b formed on the negative electrode current collector foil 22a. The negative electrode active material layer 22b is formed on both sides of the negative electrode current collector foil 22a. In this embodiment, the formation area of ​​the negative electrode active material layer 22b is rectangular. The negative electrode plate 22 has a negative electrode current collector tab 122 protruding from one side of the formation area of ​​the negative electrode active material layer 22b (see reference). Figure 5 The negative electrode current collector tab 122 is part of the negative electrode current collector foil 22a, and is the part where the active material layer 22b has not been formed on the surface.

[0033] The negative electrode current collector foil 22a can be, for example, copper foil. The negative electrode active material layer 22b is a layer containing the negative electrode active material. The negative electrode active material is, for example, a material like natural graphite that can absorb lithium ions during charging and release the lithium ions absorbed during charging during discharging, which is found in lithium-ion secondary batteries. Generally speaking, various materials other than natural graphite are proposed for the negative electrode active material, and there is no particular limitation.

[0034] <Isolation Panel 23>

[0035] In this embodiment, the separator 23 is generally rectangular and is formed to be slightly larger than the negative electrode active material layer 22b in a manner that allows it to cover the negative electrode active material layer 22b. The separator 23 can be, for example, a porous resin plate with the required heat resistance that allows electrolyte passage. Various forms of the separator 23 are proposed and are not particularly limited.

[0036] like Figure 1As shown, the width W2 of the negative electrode active material layer 22b along the long side of the bottom surface 12a is wider than the width W1 of the positive electrode active material layer 21b along the same direction. The width W3 of the separator 23 along the long side of the bottom surface 12a is wider than the width W2 of the negative electrode active material layer 22b. The positive electrode collector tab 121 and the negative electrode collector tab 122 have the required lengths by extending from the separator 23 (see reference). Figure 5 ).like Figure 1 As shown, the positive electrode plate 21, the negative electrode plate 22, and the separator plate 23 are overlapped in such a manner that the positive electrode active material layer 21b is covered by the negative electrode active material layer 22b with the separator plate 23 in between, and the positive electrode current collector tab 121 and the negative electrode current collector tab 122 extend from the separator plate 23, respectively. In this embodiment, in the rectangular region formed by overlapping the positive electrode plate 21 and the negative electrode plate 22 with the separator plate 23 in between, the positive electrode active material layer 21b is formed on both sides of the positive electrode plate 21, and the negative electrode active material layer 22b is formed on both sides of the negative electrode plate 22. Furthermore, at one end of the rectangular region, a plurality of positive electrode current collector tabs 121 protrude in an overlapping state. Similarly, at the same end, a plurality of negative electrode current collector tabs 122 protrude in an overlapping state.

[0037] like Figure 1 , 2 As shown, the main body of the electrode body 20, excluding the positive electrode collector tab 121 and the negative electrode collector tab 122, is a flat cubic shape with a pair of wide rectangular surfaces 20a. In this embodiment, the end faces of each electrode plate and the separator plate 23 in the stacking direction Z constitute the wide rectangular surfaces 20a. The four sides of the main body of the electrode body, excluding the pair of wide rectangular surfaces 20a, are the stacked surfaces of the positive electrode plate 21, the negative electrode plate 22, and the separator plate 23.

[0038] <Outer shell body 12>

[0039] like Figure 1 As shown, the outer casing 12 houses the electrode body 20 and has an opening 12h for housing the electrode body 20. The outer casing 12 has a generally rectangular shape with an opening on one side. Figure 1 , 2 As shown, the outer casing 12 has a generally rectangular bottom surface 12a, a pair of wide surfaces 12b, and a pair of narrow surfaces 12c. The pair of wide surfaces 12b rise from the long sides of the bottom surface 12a. The pair of narrow surfaces 12c rise from the short sides of the bottom surface 12a. The opening 12h is formed by being surrounded by the long sides of the pair of wide surfaces 12b and the short sides of the pair of narrow surfaces 12c. Furthermore, in this embodiment, from the viewpoint of lightweight design and ensuring the required rigidity, the outer casing 12 and the cover 14, described later, are respectively formed of aluminum or an aluminum alloy mainly composed of aluminum.

[0040] Additionally, the outer casing 12 can also accommodate an electrolyte (not shown) other than the electrode body 20. As the electrolyte, a non-aqueous electrolyte that dissolves the supporting salt in a non-aqueous solvent can be used. Examples of non-aqueous solvents include carbonate-based solvents such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Examples of supporting salts include fluorinated lithium salts such as LiPF6.

[0041] <Gastaut 14>

[0042] The cover 14 is installed in the opening 12h of the housing body 12. Furthermore, the periphery of the cover 14 engages with the edge of the opening 12h of the housing body 12. This engagement can be achieved, for example, by a seamless, continuous weld. This weld can be achieved, for example, by laser welding. The housing body 12 and the cover 14 have a number (one or more) of electrode bodies. Figure 2 In the illustrated embodiment, two corresponding sizes are shown. An injection hole 15 and a gas discharge valve 17 are provided on the cover 14. The injection hole 15 is used to inject electrolyte after the cover 14 is joined to the outer casing 12. The injection hole 15 is sealed by a sealing member 16. The gas discharge valve 17 is a thin-walled portion configured to rupture when the internal pressure of the secondary battery 10 exceeds a predetermined value, thereby discharging gas from the secondary battery 10 to the outside.

[0043] In this embodiment, a positive terminal 30 and a negative terminal 40 are mounted on the cover 14. The positive terminal 30 includes a positive external terminal 31, a connecting member 32, and a positive current collector terminal 33. The negative terminal 40 includes a negative external terminal 41, a connecting member 42, and a negative current collector terminal 43. The positive external terminal 31 and the negative external terminal 41 are respectively mounted on the outside of the cover 14 via external insulating members 50. The connecting member 32 and the positive current collector terminal 33, and the connecting member 42 and the negative current collector terminal 43 are mounted on the inside of the cover 14 via internal insulating members 60 provided on each pole side. The connecting member 32 and the positive current collector terminal 33, and the connecting member 42 and the negative current collector terminal 43 are arranged along the inner surface of the cover 14. The positive current collector terminal 33 is connected to the positive pole (specifically, the positive plate 21) of the electrode body 20 via a positive current collector tab 121. The negative current collector terminal 43 is connected to the negative electrode (specifically the negative electrode plate 22) of the electrode body 20 via the negative current collector ear 122.

[0044] like Figure 1 As shown, the positive collector tab 121 and negative collector tab 122 of the electrode body 20 are respectively mounted on the positive collector terminal 33 and negative collector terminal 43 mounted on both sides of the cover 14 along its long side. The electrode body 20 is housed in the outer casing 12 in this state, mounted on the cover 14 via the collector tabs. Figure 1 , 2As shown, the electrode body is housed in the housing body 12 with its wide rectangular surface 20a facing the wide surface 12b of the housing body 12. Furthermore, the connection between the collector terminal and the collector ear will be described in more detail later.

[0045] The following description, using the negative electrode side as an example, details the terminal structure of the secondary battery 10 and the connection between the electrode body 20 and the cover 14. Figure 1 As shown, the cover 14 has a mounting hole 19 for mounting the negative external terminal 41. The mounting hole 19 penetrates the cover 14 at a predetermined position. The negative external terminal 41 is mounted in the mounting hole 19 of the cover 14, with the external insulating member 50 clamped between them.

[0046] <Negative External Terminal 41>

[0047] Here, the negative external terminal 41 has a head 41a and a shaft 41b. The head 41a is a portion disposed on the outside of the cover 14. The head 41a is a generally flat portion larger than the mounting hole 19. The shaft 41b is a portion that is fitted into the mounting hole 19 via an external insulating member 50. The shaft 41b extends downward from approximately the center of the head 41a (in... Figure 1 The inner side of the outer shell body 12 protrudes in the middle. Figure 1 As shown, the front end of the shaft portion 41b is riveted to the connecting member 42 inside the cover 14. The front end of the shaft portion 41b is bent and then riveted to the connecting member 42 while being inserted into the mounting hole 19 of the cover 14 and the through hole 42a of the connecting member 42.

[0048] <External insulation component 50>

[0049] like Figure 1 As shown, the external insulating member 50 is a component mounted on the inner side of the mounting hole 19 of the cover 14 and the outer surface of the cover 14. In this embodiment, the external insulating member 50 includes a base portion 50a, a cylindrical portion 50b, and a sidewall 50c. The base portion 50a is a portion fitted onto the outer surface surrounding the mounting hole 19 of the cover 14. The base portion 50a has a surface that matches this outer surface (in this embodiment, it is a generally flat surface). The cylindrical portion 50b protrudes from the bottom surface of the base portion 50a. The cylindrical portion 50b has a shape that follows the inner side of the mounting hole 19 of the cover 14 so that it can be fitted into the mounting hole 19. The inner side of the cylindrical portion 50b forms a mounting hole for mounting the shaft portion 41b of the negative external terminal 41. The sidewall 50c rises upward from the periphery of the base portion 50a. The head 41a of the negative external terminal 41 is fitted into the portion surrounded by the sidewall 50c of the external insulating member 50.

[0050] An external insulating component 50 is disposed between the cover 14 and the negative external terminal 41, ensuring insulation between them. Furthermore, the external insulating component 50 ensures the airtightness of the mounting hole 19 of the cover 14. From this viewpoint, it is preferable to use a material with excellent chemical resistance and durability. In this embodiment, the external insulating component 50 is made of PFA. PFA is a copolymer of tetrafluoroethylene and perfluoroalkylvinylether. However, the material used for the external insulating component 50 is not limited to PFA.

[0051] <Internal Insulation Component 60>

[0052] The internal insulating component 60 is a component fitted inside the cover 14 around the mounting hole 19 of the cover 14. The internal insulating component 60 includes a flat portion 60a, a hole 60b, and a sidewall 60c. The flat portion 60a is a portion disposed along the inner surface of the cover 14. In this embodiment, the flat portion 60a is a generally flat portion. The flat portion 60a is disposed along the inner surface of the cover 14 and is sized to not protrude from the cover 14, so that it is housed within the housing body 12. The hole 60b is a hole corresponding to the mounting hole 19. In this embodiment, the hole 60b is located approximately at the center of the flat portion 60a. The sidewall 60c rises downward from the periphery of the flat portion 60a. Since the internal insulating component 60, which houses the connecting component 42 and the negative current collector terminal 43, is disposed inside the housing body 12, it is preferable that the flat portion 60a possesses the required chemical resistance. In this embodiment, the internal insulating component 60 uses PPS. PPS stands for polyphenylene sulfide resin. However, the material used for the internal insulation component 60 is not limited to PPS.

[0053] <Connecting component 42>

[0054] Figure 3 This is a top view showing the construction of the inner surface of cover 14. (Example) Figure 1 , 3As shown, the connecting member 42 is generally flat and has a through hole 42a and a protrusion 42b. The connecting member 42 is a component fitted to the flat portion 60a of the internal insulating member 60, connecting the negative external terminal 41 to the negative current collector terminal 43. The shaft portion 41b of the negative external terminal 41 is inserted through the through hole 42a. The shaft portion 41b is riveted around the through hole 42a. The protrusion 42b is a portion that engages with the through hole 43a1 provided in the first plate portion 43a of the negative current collector terminal 43. The shape of the protrusion 42b is such that it can engage with the through hole 43a1. In this embodiment, the planar shape of the protrusion 42b viewed from the inner surface side of the cover 14 is elliptical. The connecting member 42 is, for example, made of copper or a copper alloy.

[0055] <Negative collector terminal 43>

[0056] like Figures 1-3 As shown, the negative current collector terminal 43 is mounted on the cover 14 via an insulating material (e.g., the flat portion 60a of the internal insulating member 60). The negative current collector terminal 43 includes a first plate portion 43a, a second plate portion 43b, and a stepped portion 43c. The first plate portion 43a is a portion disposed along the surface of the connecting member 42. In this embodiment, the first plate portion 43a is a generally flat portion. The first plate portion 43a has a through hole 43a1. The protrusion 42b of the connecting member 42 fits into the through hole 43a1. The through hole 43a1 is formed in a shape that allows the protrusion 42b to fit. The second plate portion 43b is a portion disposed on the flat portion 60a of the internal insulating member 60. In this embodiment, the second plate portion 43b is a generally flat portion. The negative current collector ear 122 is engaged at the second plate portion 43b. The stepped portion 43c is the part that rises from one end of the first plate portion 43a toward one end of the second plate portion 43b, connecting the two plate portions. In this embodiment, the stepped portion 43c is arranged along the side wall of the connecting member 42. The negative current collector terminal 43 is formed, for example, of copper or a copper alloy.

[0057] like Figures 1-3 As shown, in this embodiment, the negative electrode collector ear 122 protruding from the electrode body 20 is engaged with the second plate portion 43b of the negative electrode collector terminal 43.

[0058] In addition, ultrasonic bonding can be cited as a bonding method for connecting the collector tab to the collector terminal. Figure 4 This is a schematic diagram illustrating the ultrasonic connection between the negative collector tab 122 and the negative collector terminal 43. (See diagram for example.) Figure 4As shown, in the ultrasonic bonding of the negative collector tab 122 and the negative collector terminal 43, a plurality of negative collector tabs 122, which are formed by protruding from one end of the electrode body 20 and stacked, overlap with the negative collector terminal 43. Then, the welding head H and anvil A of the ultrasonic bonding apparatus clamp the predetermined bonding portion 90 in the overlapping area. In this embodiment, the welding head H abuts against the negative collector tab 122, and the anvil A abuts against the negative collector terminal 43. Then, the two components are bonded by applying pressure to the two components and vibrating the welding head H.

[0059] In the aforementioned ultrasonic bonding, an external load, such as vibration of the welding head H, is applied to the base B of the negative collector tab 122. The base B will be described later. The inventors considered reducing the external load applied to the base of the collector tab during bonding (e.g., ultrasonic bonding). The inventors believed that this would reduce the risk of collector tab damage during the aforementioned bonding process, and investigated the shape of the collector tab and the formation location of the bonding portion between the collector tab and the collector terminal.

[0060] Figure 5 This is a top view showing the state in which the electrode body 20 is connected to the positive collector terminal 33 and the negative collector terminal 43. (Example) Figure 5 As shown, the positive current collector terminal 33 and the negative current collector terminal 43 are spaced apart and arranged with the mating surfaces of the connecting current collector ears facing upwards. In this embodiment, the positive current collector terminal 33 and the negative current collector terminal 43 are configured such that, after being installed on the cover 14, the second plate portion 33b and the second plate portion 43b are positioned to the side of the gas discharge valve 17 provided on the cover 14. The two electrode bodies 20 are arranged symmetrically with the positive current collector ear 121 and the negative current collector ear 122 facing the positive current collector terminal 33 and the negative current collector terminal 43. Furthermore, the positive current collector ear 121 and the negative current collector ear 122 are overlapped and connected to the positive current collector terminal 33 and the negative current collector terminal 43.

[0061] The connection between the negative collector tab 122 and the negative collector terminal 43 will be described below. In this embodiment, as... Figure 5 As shown, the front ends of the negative electrode collector ears 122, which extend from the two electrode bodies 20 symmetrically arranged relative to the negative electrode collector terminal 43, are disposed in the aforementioned mating surface in the second plate portion 43b in an opposing manner. At least a portion of the negative electrode collector ears 122 is mated to the second plate portion 43b at the predetermined mating portion 90 (see reference). Figure 4 A joint 90 is formed, as detailed later. Furthermore, after two negative collector tabs 122 are connected to the negative collector terminal 43, the negative collector terminal 43 with the negative collector tabs 122 connected is mounted on the cover 14. After the negative collector terminal 43 is mounted on the cover 14, the wide surfaces of the electrode body 20 are overlapped and stored in the outer casing body 12 (see reference). Figure 2).

[0062] <Negative collector ear 122>

[0063] like Figure 5 As shown, the negative current collector tab 122 has an extension 122a extending from the electrode body 20, and a branch 122b extending from the front end region E of the extension 122a in a direction different from that of the extension 122a. The branch 122b has a portion (joint portion 90) that engages with the negative current collector terminal 43. In this embodiment, as... Figure 5 As shown, the extension 122a and the branch 122b are strip-shaped. Figure 5 In the figure, the extension 122a extends from the electrode body 20. In the same figure, arrow P indicates the direction in which the extension 122a extends from the electrode body 20, and is hereinafter referred to as the "first extension direction P". For example, the first extension direction P can be defined by the line La connecting the center R in the width direction of the base end B of the extension 122a and the center S in the width direction of the base end B side of the front end region E of the extension 122a. Here, the base end B of the extension 122a refers to the boundary between the negative electrode collector terminal 43 and the outer edge of the electrode body 20. The outer edge of the electrode body 20 is, for example, the periphery of the wide rectangular surface 20a of the electrode body 20. The front end region E refers, for example, to the region of the extension 122a where the branch 122b is provided, and the base end B side of the front end region E of the extension 122a refers to the base end B side of the region of the extension 122a where the branch 122b is provided.

[0064] In addition, Figure 5 In the diagram, arrow Q indicates the direction in which the branch 122b extends, and is referred to below as the "second extension direction Q". For example, the second extension direction Q can be defined by the line Lb connecting the center T of the width direction of the branch 122b (the center T on the first extension direction P of the branch 122b) and the center U of the first extension direction P of the front end region E of the extension 122a. Moreover, "the branch 122b extends from the front end region E of the extension 122a in a direction different from the direction in which the extension 122a extends from the electrode body 20" means, for example, that when the angles formed by the line La along the first extension direction P and the line Lb along the second extension direction are set as α and β (where α ≥ β, α + β = 180°), β is greater than 10°.

[0065] —Extension 122a—

[0066] In this embodiment, such as Figure 5 As shown, the extension 122a is the portion extending from the electrode body 20 toward the second plate portion 43b of the negative collector terminal 43. In this embodiment, the extension 122a has the same width We from the base end B of the negative collector tab 122 to the front end region E. A branch 122b extending in the second extending direction is provided in the front end region E. Figure 2 , 5 As shown, the extension 122a is housed in the housing body 12 in a bent state, with the support 122b arranged along the negative current collector 43 mounted on the cover 14.

[0067] Branch 122b

[0068] In this embodiment, such as Figure 5 As shown, branch 122b has a first branch 122x and a second branch 122y extending from the front end region of extension 122a in a direction different from extension 122a. The first branch 122x and the second branch 122y are respectively oriented in a direction substantially perpendicular to the direction in which extension 122a extends from electrode body 20 (in this embodiment, the first extending direction P). Figure 2 , 5 The extension extends along the long side of the cover 14. In this embodiment, "approximately perpendicular" means that the line La along the first extending direction P intersects the line Lb along the second extending direction at approximately a right angle, and that the angles α and β formed by the lines La and Lb are both 90° ± 10°. Furthermore, the second branch 122y extends from the front end region of the extension 122a in the direction opposite to the direction of the first branch 122x. Moreover, the first branch 122x and the second branch 122y are joined to the negative current collector terminal 43 (forming the joint 90).

[0069] In the secondary battery 10, the negative electrode current collector tab 122 has an extension 122a extending from the electrode body 20, and a branch 122b extending from the front end region E of the extension 122a in a direction different from that of the extension 122a. The branch 122b is connected to the negative electrode current collector terminal 43. In other words, in the extending direction of the extension 122a (in... Figure 5 The negative collector tab 122 is joined to the negative collector terminal 43 at a position offset from the first extension direction P. Therefore, when the negative collector tab 122 and the negative collector terminal 43 are joined, for example by ultrasonic bonding, the amount of material in the extension portion 122a extending from the electrode body 20 can be reduced. Figure 4 , 5 The external load applied at the base end (B) is reduced. By reducing the external load applied during engagement at the portion of the extension 122a that extends from the electrode body 20 (base end B), the risk of damage to the negative electrode collector ear 122 is reduced.

[0070] Furthermore, as described above, by providing the joining portion 90 at a position offset from the extension portion 122a, even after the negative electrode collector ear 122 is joined to the negative electrode collector terminal 43, the external load (e.g., vibration, impact, etc. applied during the manufacturing or use of the secondary battery) applied to the portion of the extension portion 122a extending from the electrode body 20 can be reduced, thereby reducing the risk of damage to the negative electrode collector ear 122.

[0071] The first branch 122x and the second branch 122y extend from the front end region E of the extension 122a in a direction substantially perpendicular to the direction in which the extension 122a extends from the electrode body 20. Therefore, it is not easy to apply an external load to the part that extends from the extension 122a, thereby preventing damage to the negative electrode collector tab 122.

[0072] In this embodiment, such as Figure 5 As shown, the branch 122b has a first branch 122x and a second branch 122y. The first branch 122x extends from the front end region E of the extension 122a in a direction substantially perpendicular to the direction in which the extension 122a extends from the electrode body 20, and the second branch 122y extends in the opposite direction to the direction in which the first branch 122x extends. In this case, the extension 122a is supported by the first branch 122x and the second branch 122y, which are respectively joined to the negative current collector terminal 43 on both sides. Therefore, it is not easy to apply an external load to the part extending from the extension 122a, so that the current collector tab is not easily damaged. In addition, the joint area between the negative current collector tab 122 and the negative current collector terminal 43 can be increased, so the resistance of the secondary battery 10 can be further reduced.

[0073] <Joint 90>

[0074] In this embodiment, such as Figure 5 As shown, the first branch 122x and the second branch 122y of the branch 122b extending from the extension 122a (in this embodiment, the second extending direction Q) are joined to the negative collector terminal 43, forming a joint 90 at this location. By joining the first branch 122x and the second branch 122y to the negative collector terminal 43, the negative collector tab 122 and the negative collector terminal 43 can be joined at a position that deviates from the extending direction of the extension 122a (the first extending direction P) and is further away from the base end B of the negative collector tab 122. This allows for better reduction of external load and reduction of the risk of damage to the collector tab.

[0075] Furthermore, in this embodiment, a joint portion 90 is provided on both the first branch 122x and the second branch 122y, increasing the area where the joint portion is formed. This increases the contact area between the negative current collector tab 122 and the negative current collector terminal 43, further reducing the resistance of the secondary battery 10. Additionally, at least a portion of the branch 122b needs to be connected to the negative current collector terminal 43. Alternatively, there may be a portion of the branch 122b that is not connected to the negative current collector terminal 43. While not particularly limited, the area of ​​the joint portion 90 should be approximately 30% or more of the area of ​​one branch 122b. Furthermore, although the planar shape of the negative current collector tab 122 in this embodiment is slightly more complex, it can still be manufactured using a negative current collector foil punching process, so the manufacturing difficulty of the negative current collector tab 122 can be considered relatively low.

[0076] The shape of the joint is not particularly limited as long as the technical effects disclosed here can be achieved. Figure 5 The shape of the joint 90 shown is generally rectangular, but it can also be circular, elliptical, or other shapes. The desired shape can be achieved by appropriately changing the settings of the ultrasonic welding device (e.g., the shape of the workpiece-facing surface of the welding head and anvil).

[0077] The above description, using the negative electrode side as an example, explains the structure near the terminals of the secondary battery 10 and the connection between the current collector tab and the current collector terminal. Regarding the structure near the terminals of the secondary battery 10, as... Figure 1 As shown, on the positive electrode side, a fuse component 70 is disposed between the connecting component 32 and the first plate portion 33a of the positive electrode current collector terminal 33. A flat plate-shaped terminal protection component 80 is disposed between the positive electrode external terminal 31 and the electrode body 20. Figure 1 , 3 As shown, a cylindrical opening 60a1 protruding towards the inner side of the outer casing 12 is provided on the flat portion 60a of the internal insulating member 60 disposed on the positive electrode side. The cylindrical opening 60a1 is disposed directly below the injection hole 15. A through hole 33a1 for mounting the protrusion 32a of the connecting member 32 and a through hole 33a2 for mounting the protrusion 70a of the fuse member 70 are provided on the first plate portion 33a of the positive electrode current collector terminal 33. A through hole 33b1 for mounting the cylindrical opening 60a1 is provided on the second plate portion 33b of the positive electrode current collector terminal 33. The positive electrode external terminal 31, the connecting member 32, and the positive electrode current collector terminal 33 can all be formed of aluminum or an aluminum alloy. Furthermore, in Figure 1 In the attached drawing, reference numeral 18 indicates a mounting hole on the positive side, and reference numeral 33c indicates a stepped portion of the positive collector terminal 33. Figure 3In the accompanying drawings, reference numeral 31b indicates the shaft portion of the positive external terminal 31, and reference numeral 32b indicates the protrusion of the connecting member 32. Apart from this, it is essentially the same as the negative side, therefore description is omitted here. Furthermore, for structures of the fuse components and terminal protection components, and structures different from those of the negative side and not specifically described in this specification, no features are assigned to the technology disclosed herein, therefore description is omitted.

[0078] The connection between the collector tab and the collector terminal on the positive side is the same as that on the negative side, so the explanation here is omitted. Figure 5 , 6 In the accompanying drawings, reference numeral 121 indicates the positive electrode current collector, reference numeral 121a indicates an extension of the positive electrode current collector 121, reference numeral 121b indicates a branch of the positive electrode current collector 121, reference numeral 121x indicates the first branch, and reference numeral 121y indicates the second branch. Furthermore, the secondary battery 10 may have at least one of the aforementioned connections between the current collector and the current collector terminal. From the viewpoint of better achieving the technical effects disclosed herein, it is preferable that the secondary battery 10 has the aforementioned connection between the current collector and the current collector terminal at both the positive and negative electrodes.

[0079] The above describes one embodiment of the technology disclosed herein. Furthermore, the first embodiment described above represents an example of a secondary battery applying the technology disclosed herein and is not intended to limit the technology disclosed herein. Other embodiments of the technology disclosed herein will be described below. In addition, in the following description, except for points specifically mentioned, a structure substantially equivalent to the secondary battery 10 according to the first embodiment described above can be adopted.

[0080] Implementation Method 2

[0081] In the first embodiment described above, the branch 122b is engaged with the negative current collector terminal 43, while the extension 122a is not engaged with the negative current collector terminal 43. However, this is not a limitation. Figure 6 This is a top view illustrating the state in which the negative collector tab 122 is engaged with the negative collector terminal 43 in another embodiment. Figure 6As shown, the front end region E of the extension 122a has a joining portion that engages with the negative current collector terminal 43 at the front end side. In this embodiment, a joining portion 290 is formed to engage the first branch 122x, the second branch 122y, and a portion of the front end side of the front end region E of the extension 122a with the negative current collector terminal 43. On the other hand, a portion of the base end B side of the front end region E of the extension 122a is not engaged with the negative current collector terminal 43. In addition to the branch 122b, a portion of the front end side of the front end region E of the extension 122a is engaged with the negative current collector terminal 43, thereby increasing the joining area and reducing the resistance of the secondary battery 10. Furthermore, this can prevent the extension 122a from floating off the surface of the negative current collector terminal 43. Moreover, since a portion of the base end B side of the front end region E of the extension 122a is not engaged with the negative current collector terminal 43, there is a degree of freedom for deformation at that location, thereby reducing the risk of damage to the negative current collector tab 122 after external load is applied. Furthermore, when the length of the first extending direction P of the front end region E of the extension 122a is set to 1, a portion of 1 / 4 to 1 / 2 of the length from the front end side of the front end region E can be connected to the negative current collector terminal 43.

[0082] Third Implementation Method

[0083] Furthermore, in the first embodiment described above, the branch 122b of the negative collector tab 122 is composed of a first branch 122x and a second branch 122y. However, it is not limited to this. Figure 7 This is a top view illustrating the state in which the negative collector tab 322 is connected to the negative collector terminal 43. (See attached image.) Figure 7 As shown, the negative collector tab 322 has an extension 322a and a branch 322b. In this embodiment, the negative collector tab 322 has a branch 322b provided only on one side of the front end region E3 of the extension 322a in the second extending direction Q. The extension 322a in this embodiment has the same structure as the extension 122a of the negative collector tab 122 in the first embodiment described above. The branch 322b in this embodiment has the same structure as the first branch 122x of the negative collector tab 122 in the first embodiment described above. Therefore, detailed descriptions of the extension 322a and branch 322b of the negative collector tab 322 are omitted here. Figure 7As shown, in the second extending direction Q, the front end of the branch 322b is joined to the negative current collector terminal 43 (forming the joint 390). In this embodiment, the aforementioned effects of reducing external load and reducing the risk of damage to the negative current collector ear 322 can also be achieved. Furthermore, if it is desirable to achieve the above effects and further reduce the area of ​​the negative current collector ear 122 disposed on the negative current collector terminal 43, the shape of the negative current collector ear 322 is preferred. Moreover, the location where the branch 322b is formed is not limited to the above-described case. The branch 322b may also be formed on the side of the gas exhaust valve 17 provided on the cover 14. Additionally, Figure 7 Reference numeral 321 in the figure is the positive electrode collector tab, reference numeral 321a is the extension of the positive electrode collector tab 321, and reference numeral 321b is the branch of the positive electrode collector tab 321.

[0084] Other implementation methods

[0085] Furthermore, in the first embodiment described above, both the first branch 122x and the second branch 122y extend from the extension 122a in a substantially vertical direction. However, this is not a limitation. Specific illustrations are omitted, but for example, the angle formed between the first branch 122x or the second branch 122y and the extension 122a can be set to a range exceeding 100° and less than 150° (e.g., 110° to 130°). In this case, the technical effects disclosed herein can also be achieved.

[0086] Alternatively, branch 122b may also include a third branch in addition to the first branch 122x and the second branch 122y described in the first embodiment. Detailed illustrations are omitted, but the third branch could, for example, be a portion extending in the direction of the extension 122a described in the first embodiment (see reference). Figure 5 In the direction in which the third branch extends, the third branch can engage with the negative collector terminal 43. In this embodiment, the aforementioned effects of reducing external load and reducing the risk of damage to the collector ear can also be achieved.

[0087] Furthermore, the electrode body 20 of the secondary battery 10 according to the first embodiment described above is a stacked electrode body, but a wound electrode body can also be used. In addition, the joining means between the current collector tab and the current collector terminal is not limited to ultrasonic joining, but can also be conventional joining means such as laser welding or resistance welding.

Claims

1. A secondary battery, wherein, The secondary battery has the following characteristics: Electrode body; The outer casing has an opening for receiving the electrode body; as well as The cover is installed at the opening of the outer casing body. The cover has current collector terminals mounted via insulating material. The electrode body has a current collector ear. The current collector ear has an extension extending from the electrode body and a branch extending from the front end region of the extension in a direction different from the extension, the branch having a portion that engages with the current collector terminal. The branch extends from the front end region of the extension in a direction substantially perpendicular to the direction in which the extension extends from the electrode body. The branch comprises a first branch and a second branch. The first branch extends from the front end region of the extension in a direction substantially perpendicular to the direction in which the extension extends from the electrode body. The second branch extends in the opposite direction to the direction in which the first branch extends. The front end region of the extension has a mating portion on the front end side that engages with the current collector terminal. A portion of the base side of the front end region of the extension is not engaged with the current collector terminal. When the length of the front end region of the extension portion in the direction extending from the electrode body is set to 1, a portion of 1 / 4 to 1 / 2 of the length from the front end side of the front end region is joined to the current collector terminal. Thus, a joint is formed in which a portion of 1 / 4 to 1 / 2 of the length of the front end region of the first branch, the second branch, and the extension is joined to the current collector terminal, and the joint is U-shaped in a top view.

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