JP7019124B2 - Power storage device - Google Patents

Description

The present invention relates to a power storage device.

Vehicles such as EVs (Electric Vehicles) and PHVs (Plug in Hybrid Vehicles) are equipped with secondary batteries such as lithium-ion batteries as storage devices for storing the power supplied to the motor as the prime mover. This type of secondary battery is disclosed in, for example, Patent Document 1. As shown in FIG. 7, the secondary battery 150 of Patent Document 1 is configured by accommodating the electrode assembly 152 in the case 151 and connecting the terminal member 153 to the electrode assembly 152. The electrode assembly 152 includes a negative electrode 154 in which a negative electrode active material layer 154b is coated on a metal foil 154a, and a positive electrode 155 in which a positive electrode active material layer 155b is coated on a metal foil 155a. The electrode assembly 152 is formed in a layered manner with a separator 156 interposed between the negative electrode electrode 154 and the positive electrode electrode 155.

In the power storage device provided with the secondary battery 150 as in Patent Document 1, for example, the metal foil 154a of the negative electrode electrode 154 and the metal foil 155a of the positive electrode electrode 155 are not coated with an active material. Tabs are formed. A collection of a plurality of these tabs is connected to the terminal member 153 as a tab group. The tab group is curved or bent from one side to the other side in the stacking direction of the electrode assembly 152, for example, in a state where a plurality of tabs are collected. Then, in the tab group, an extending portion extending from the curved or bent portion to the other side in the stacking direction of the electrode assembly 152 is in contact with and connected to the terminal member 153.

Japanese Unexamined Patent Publication No. 2002-298825

By the way, the tab group is connected by being welded to the terminal member 153. When the tab group and the terminal member 153 are joined by welding, the size of the joining area is reflected in the current collection efficiency of the terminal member 153. That is, the larger the joint area, the lower the electric resistance value, and the smaller the joint area, the higher the electric resistance value. Further, if the number of laminated electrodes to be bonded is increased while maintaining the bonding area, the amount of heat required for bonding also increases according to the number of laminated electrodes. Therefore, when bonding electrodes laminated with the same amount of heat, the bonding area becomes smaller as the number of laminated electrodes is increased.

An object of the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power storage device capable of preventing a decrease in current collection efficiency between a tab and a terminal by increasing the bonding area. ..

Hereinafter, means for achieving the above object and its action and effect will be described.

A power storage device that achieves the above object is a power storage device including an electrode assembly having a laminated structure of electrodes, a conductive member exchanged between the electrode assembly, and a case in which the electrode assembly and the conductive member are housed. It is a device. The power storage device of the present invention has a tab group protruding from the end of the electrode assembly, and the tab group is divided into two in the electrode stacking direction, and is referred to as a first tab group and a second tab group. When viewed from the electrode stacking direction, the first tab group and the second tab group collect foil at the central portion of the electrode assembly, respectively, and bend or bend at the central portion of the conductive member with the first bent portion and the second bent portion. The tab group has a first extension portion and a second extension portion extending from the first bending portion and the second bending portion. The first extension portion and the second extension portion extend toward the inner surface of the case facing the electrode assembly in the electrode stacking direction, and are joined to the conductive member at the first extension portion and the second extension portion. It is characterized by having a joint site.

According to this configuration, when the tab group and the conductive member are joined with the same device and the same amount of heat, the tab group is not divided when the tab group is divided into the first tab group and the second tab group. The joint area can be increased as compared with the above. According to this, it is possible to reduce the electric resistance value of the joint portion by increasing the joint area of the conductive member of the tab group.

According to the present invention, it is possible to provide a power storage device capable of having a larger joint area between a tab and a conductive member.

The exploded perspective view of the secondary electron in this embodiment. The perspective view which shows the appearance of a secondary battery. An exploded perspective view showing the components of the electrode assembly Sectional drawing of electrode assembly. Sectional drawing of the electrode assembly in another embodiment. Sectional drawing of the electrode assembly in another embodiment. Sectional drawing which shows the conventional secondary battery.

Hereinafter, the first embodiment in which the power storage device is embodied will be described with reference to FIGS. 1 to 4.

As shown in FIGS. 1 and 2, the secondary battery 10 as a power storage device contains an electrode assembly 11 in a case 21. The case 21 is composed of a square box-shaped case main body 22 and a rectangular flat plate-shaped lid 23 that closes the opening 22a of the case main body 22. Both the case body 22 and the lid 23 are made of metal (for example, made of stainless steel or aluminum). Further, the secondary battery 10 of the present embodiment is a lithium ion battery, which is a square battery having a square outer shell.

A positive electrode terminal 26 and a negative electrode terminal 27 as electrode terminals for transmitting and receiving electricity to and from the electrode assembly 11 are electrically connected to the electrode assembly 11. The positive electrode terminal 26 and the negative electrode terminal 27 are exposed to the outside of the case 21 through a pair of holes 23a and 23b arranged side by side in the lid 23 at predetermined intervals. Ring-shaped insulating members 26a and 27a for insulating from the case 21 are attached to the positive electrode terminal 26 and the negative electrode terminal 27, respectively. Although not shown, an insulating sheet for insulating the case body 22 and the electrode assembly 11 housed inside the case body 22 is provided on the inner surface of the case body 22 constituting the case 21. It is attached.

As shown in FIG. 3, the electrode assembly 11 includes a positive electrode 12 having a positive electrode active material layer 14 coated with a positive electrode active material on both sides of a positive electrode metal foil 13 (for example, an aluminum foil), and a negative electrode metal foil 17 (for example, an aluminum foil). For example, it has a negative electrode 16 having a negative electrode active material layer 18 coated with a negative electrode active material on both sides of a copper foil). The electrode assembly 11 has a layered laminated structure in which a separator 20 that insulates the positive electrode 12 and the negative electrode 16 is interposed between the positive electrode 12 and the negative electrode 16. The electrode assembly 11 is configured by laminating a plurality of positive electrode electrodes 12 and a plurality of negative electrode electrodes 16. That is, the electrode assembly 11 is provided with a plurality of sets including the positive electrode 12, the negative electrode 16, and the separator 20.

The positive electrode electrode 12 has a positive electrode tab 15 made of a positive electrode metal foil 13 having a shape protruding from the edge portion 12a. The negative electrode electrode 16 has a negative electrode tab 19 composed of a negative electrode metal foil 17 having a shape protruding from the edge portion 16a. The positive electrode tab 15 and the negative electrode tab 19 are provided at positions where the positive electrode tab 15 and the negative electrode tab 19 do not overlap with each other in a state where the positive electrode 12 and the negative electrode 16 are laminated. In the present embodiment, the positive electrode tabs 15 are formed to have the same size, and the negative electrode tabs 19 are formed to have the same size.
The positive electrode 12s constituting the electrode assembly 11 are laminated so that the positive electrode tabs 15 are arranged in a row. Similarly, the negative electrode electrodes 16 constituting the electrode assembly 11 are laminated so that the negative electrode tabs 19 are arranged in a row. Then, on the upper surface 11a of the electrode assembly 11, as shown in FIG. 1, each positive electrode tab 15 is collected in a range from one to the other in the stacking direction in the electrode assembly 11, and a positive electrode tab group 15a is provided. ing. Further, on the upper surface 11a of the electrode assembly 11, each negative electrode tab 19 is similarly collected in a range from one to the other in the stacking direction in the electrode assembly 11, and a negative electrode tab group 19a is provided.
A metal (for example, aluminum) positive electrode conductive member 24 for electrically connecting the electrode assembly 11 and the positive electrode terminal 26 is joined to the positive electrode tab group 15a. Further, a metal (for example, copper) negative electrode conductive member 25 for electrically connecting the electrode assembly 11 and the negative electrode terminal 27 is bonded to the negative electrode tab group 19a. The positive electrode conductive member 24 and the negative electrode conductive member 25 of the present embodiment have a rectangular flat plate shape.

Next, the bonding structure of the positive electrode tab group 15a and the positive electrode conductive member 24, and the negative electrode tab group 19a and the negative electrode conductive member 25 will be described in detail with reference to FIG. Although FIG. 4 shows a bonding structure between the negative electrode tab group 19a and the negative electrode conductive member 25, this bonding structure is the same as the bonding structure between the positive electrode tab group 15a and the positive electrode conductive member 24. Therefore, the bonding structure between the negative electrode tab group 19a and the negative electrode conductive member 25 will be described below. In the following description, the negative electrode tab 19 is read as the positive electrode tab 15, the negative electrode tab group 19a is read as the positive electrode tab group 15a, the tip portion 19b of the negative electrode tab 19 is read as the tip portion 15b of the positive electrode tab 15, and the negative electrode conductive member 25 is read as the positive electrode conductive member 24. On the contrary, it is an explanation of the bonding structure of the positive electrode tab group 15a and the positive electrode conductive member 24.

As shown in FIG. 4, the negative electrode tab group 19a in this embodiment is composed of a first tab group 31 and a second tab group 32. The first tab group 31 and the second tab group 32 are divided into two equal numbers of the total number of negative electrode tabs 19 located within the range from one of the stacking directions L of the electrode assembly 11 to the other. Each of the plurality of negative electrode tabs 19 is provided.

When the total number of negative electrode tabs 19 in the electrode assembly 11 is an even number and the negative electrode electrodes 16 are arranged in the outermost layers in the stacking direction L of the electrode assembly 11, in most cases, the electrode assembly 11 The total number of positive electrode tabs 15 in the above is an odd number. Therefore, when the first tab group 31 and the second tab group 32 are formed by the plurality of positive electrode tabs 15, the positive electrode tabs 15 located within the range from one of the stacking directions L of the electrode assembly 11 to the other. By evenly dividing the entire number of sheets into two, the first tab group 31 and the second tab group 32 having a difference in the number of sheets of one sheet are formed on the constituent positive electrode tabs 15.

In the present embodiment, specifically, in the second tab group 32, the negative electrode tab H1 of one of the negative electrode tabs 19 arranged on the outermost side is the negative electrode located at the center position M in the stacking direction L in the electrode assembly 11. It is formed by gathering the other negative electrode tab H2 of the outermost negative electrode tabs 19 extending from the electrode 16 so as to approach each other. The first tab group 31 extends to the outermost negative electrode tab H4 of one of the negative electrode tabs 19 arranged on the outermost side from the negative electrode electrode 16 at the center position M in the stacking direction L in the electrode assembly 11. It is formed by gathering the other negative electrode tab H3 of the arranged negative electrode tabs 19 so as to approach each other.

The first tab group 31 has a first bent portion 33 curved from the center position M of the stacking direction L in the electrode assembly 11 toward the outside of the stacking direction L, and the first bent portion 33 to the stacking direction L. It is provided with a first extending portion 35 extending toward the outside of the. The second tab group 32 has a second bent portion 34 curved from the center position M of the stacking direction L in the electrode assembly 11 toward the outside of the stacking direction L, and the electrode assembly from the second bent portion 34. It is provided with a second extending portion 36 extending toward the outside of the stacking direction L in 11. In the first tab group 31 and the second tab group 32, the first bent portion 33 and the second bent portion 34 are bent so as to collect foil toward the center position M of the stacking direction L in the electrode assembly 11. .. Then, a part of the first extending portion 35 and the negative electrode conductive member 25 are electrically joined. A part of the second extending portion 36 is also electrically joined to the negative electrode conductive member 25. The negative electrode conductive member 25 is arranged between the first extending portion 35 and the second extending portion 36 and the lid 23 of the case 21.

In this embodiment, the first extension portion 35 and the second extension portion 36 are joined to the negative electrode conductive member 25 by resistance welding, respectively, to form a joining portion W, thereby being electrically connected. Resistance welding is a method in which a joining target (tab groups 31, 32, negative electrode conductive member 25 in FIG. 4) is sandwiched between a pair of welding electrodes and welded.

Hereinafter, the operation of the secondary battery 10 of the present embodiment will be described.

The tab groups 15a and 19a of this embodiment collect foil at the center position M in the stacking direction L in the electrode assembly 11, are bent at the bent portions 33 and 34, and extend outward along the conductive members 24 and 25. The portions 35 and 36 are formed. Then, a part of the extending portions 35 and 36 and the conductive member 25 are directly welded to form a joint portion W. By dividing the tab groups 15a and 19a into two tab groups 31 and 32, when resistance welding is performed and the energy of one resistance welding is the same, the tab groups 15a and 19a are not divided as compared with the case where the tab groups 15a and 19a are not divided. , It becomes possible to increase the joint portion W.

Further, the first tab group 31 and the second tab group 32 are collected at the center position M in the stacking direction L in the electrode assembly 11, pass through the bent portions 33 and 34, and conduct from the center position M toward the case body 22. Extensions 35 and 36 are provided so as to extend along the members 24 and 25. In such tab groups 15a and 19a, the difference in distance between the first tab group 31 and the second tab group 32 between the tabs 15 and 19 from the upper surface 11a of the electrode assembly 11 to the joint portion W is relatively small. .. Therefore, in both the first tab group 31 and the second tab group 32, the tip portions 15b and 19b of the tabs 15 and 19 can be positioned at positions separated from the inner surface of the case body 22 of the case 21. Further, since the conductive members 24 and 25 and the first tab group 31 and the second tab group 32 are directly welded by resistance welding, the case is prevented from electrically contacting the inside of the case body 22 with the tabs 15 and 19. It is not necessary to install inclusions such as insulating members inside the main body 22.

As described above, according to the present embodiment, the following effects can be obtained.

(1) In the first tab group 31 and the second tab group 32, the first extending portion 35 and the second extending portion 36 are electrically welded directly to the conductive members 24 and 25 (joint portion W). It is joined to the conductive members 24 and 25. Welding can only handle welding objects with a thickness that can be sandwiched between a pair of welding electrodes, and as the thickness of the welding object increases, the thickness direction of the bonding portion W increases, and the bonding area decreases accordingly. .. In this embodiment, since the tab group of the electrode assembly 11 is divided into two tab groups 31 and 32 in the stacking direction L, the area of the joint portion W can be increased as compared with the case where the tab group is not divided. This makes it possible to reduce the electrical resistance of the joint portion W.

(2) The tab groups 15a and 19a collect foil at the center position M in the stacking direction L in the electrode assembly 11, are bent at the bending portions 33 and 34, and extend outward along the conductive members 24 and 25. 35 and 36 are formed. Therefore, the difference in the distances between the tabs 15 and 19 from the upper surface 11a of the electrode assembly 11 of the tab groups 15a and 19a to the joint portion W becomes small, and the extension located on the outer peripheral side in the bending direction of the bending portions 33 and 34 becomes small. The amount of protrusion of the portions 35 and 36 can be suppressed. Therefore, it is possible to suppress the occurrence of a short circuit between the tabs 15 and 19 and the case 21.

(3) Regarding the welding of the conductive members 24 and 25 and the tab group, since the tab group of the electrode assembly 11 is divided into two tab groups 31 and 32 in the stacking direction L, compared with the case where the tab group is not divided. It is possible to suppress the positional deviation between the tab groups 15a and 19a and the conductive members 24 and 25 during resistance welding.

The above embodiment may be changed as follows.
○ As shown in FIG. 5, the positions where the first tab group 31 and the second tab group project from the edge portions 12a and 16a do not overlap in the direction along the edge portions 12a and 16a. In the case of this embodiment, the first tab group 31 and the second tab group face the extending portions 35 and 36 in the same direction. When performing resistance welding, welding can be continued on the same surface, so the man-hours for welding can be reduced.
○ As shown in FIG. 6, the positions where the first tab group 31 and the second tab group project from the edge portions 12a and 16a do not overlap in the direction along the edge portions 12a and 16a. In the case of the embodiment of FIG. 5, the first tab group 31 and the second tab group face the extending portions 35 and 36 in the same direction. In the case of the embodiment of FIG. 6, the first tab group 31 and the second tab group face the extending portions 35 and 36 in opposite directions. In the case of this embodiment, when resistance welding is performed, the welding can be continued on the same surface, so that the man-hours in welding can be reduced.
○ A plurality of tabs 15 and 19 may be divided so that the number of tabs 15 and 19 is larger in the first tab group 31 than in the second tab group 32. This is because, for example, the total number of tabs 15 and 19 is an odd number, and when the number of tabs 15 and 19 is evenly divided between the first tab group 31 and the second tab group 32, the first tab group 31 This is because the number of tabs 15 and 19 is one more than that of the second tab group 32. Further, regardless of whether the total number of tabs 15 and 19 is odd or even, the number of tabs 15 and 19 in the first tab group 31 is larger than that in the second tab group 32. May be split.

10 Secondary battery 11 Electrode assembly 12 Electrode assembly 12 Positive electrode 13 Positive metal foil 14 Positive active material layer 15 Positive tab 16 Negative electrode 17 Negative electrode metal foil 18 Negative electrode active material layer 19 Negative tab 20 Separator 21 Case 22 Case body 23 Lid 24 Positive electrode Conductive member 25 Negative electrode Conductive member 26 Positive electrode terminal 27 Negative electrode terminal 31 First tab group 32 Second tab group 33 First bending part 34 Second bending part 35 First extension part 36 Second extension part M Central position L Electrode set Lamination direction of solid 11 W Joining site

Claims (2)

A power storage device including an electrode assembly having a laminated structure of electrodes, a conductive member exchanged between the electrode assembly, and a case in which the electrode assembly and the conductive member are housed.
It has a group of tabs protruding from the end of the electrode assembly and has a group of tabs.
The tab group has a first tab group and a second tab group divided into two in the stacking direction of the electrode assembly, respectively.
The first tab group and the second tab group each have a first bent portion and a second bent portion that collect foil at the center position in the stacking direction in the electrode assembly and are curved or bent at the center position. ,
It has a first extension portion and a second extension portion in which the tab group extends from the first bending portion and the second bending portion.
The first extension portion and the second extension portion extend toward the inner surface of the case facing the electrode assembly in the stacking direction, and extend in the same direction in the stacking direction .
A power storage device characterized in that the first extending portion and the second extending portion have a joining portion that is joined to the conductive member. A claim characterized in that the positions of the first tab group and the second tab group projecting from the end do not overlap in a direction along the end of the electrode assembly in which the tab group protrudes. Item 1. The power storage device according to Item 1.

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