Electrode body

Abstract

An electrode body includes a plurality of electrode laminates stacked along a first direction. Each of the plurality of electrode laminates includes a plurality of electrode sheets stacked along the first direction, and a long-size separator extending in a meandering manner among the plurality of electrode sheets. One of the separators in the plurality of electrode laminates is integrally formed with a bundling portion that surrounds the plurality of electrode laminates.

Description

Technical Field

[0001] The technology disclosed in this specification relates to electrode bodies. Background Technology

[0002] Japanese Patent Application Publication No. 2007-305464 describes an electrode body. This electrode body comprises multiple stacked electrode layers. Each of the multiple electrode layers comprises multiple stacked electrode sheets and a long-length diaphragm extending in a zigzag manner between the multiple electrode sheets.

[0003] In the electrode body described above, multiple electrode sheets are stacked one by one while the diaphragm is folded. Errors may occur in the position of the folded diaphragm. Therefore, if the diaphragm is repeatedly folded, these errors gradually accumulate, potentially leading to non-negligible errors in the stacking position of the electrode sheets. Regarding this, as described in Japanese Patent Application Publication No. 2007-305464, if the electrode body is divided into multiple electrode stacks, and the diaphragms are made independent of each other among the multiple electrode stacks, the accumulation of the aforementioned errors can be suppressed. Summary of the Invention

[0004] However, if the electrode body is divided into multiple electrode stacks, no constraint force is generated between the multiple electrode stacks, which may lead to undesirable positional shifts between the multiple electrode stacks. In view of the above, this specification provides a technique for improving the manufacturing quality of an electrode body employing a tortuous diaphragm.

[0005] The technology disclosed in this specification is specifically embodied in an electrode body. In a first embodiment of this electrode body, the electrode body comprises a plurality of electrode stacks stacked along a first direction. Each of the plurality of electrode stacks comprises a plurality of electrode sheets stacked along the first direction and an elongated diaphragm extending in a zigzag manner between the plurality of electrode sheets. In one of the plurality of electrode stacks, the diaphragm integrally forms a binding portion that surrounds the plurality of electrode stacks together.

[0006] In the aforementioned electrode body, a binding portion is integrally formed on the diaphragm of one electrode stack. This binding portion surrounds multiple electrode stacks, thereby generating a restraining force between the multiple electrode stacks and suppressing positional displacement between them. Furthermore, in each electrode stack, positional displacement of the electrode sheet is also suppressed by the restraining force based on the binding portion. Therefore, in at least one of the electrode stacks, it is sufficient to provide a binding portion on the diaphragm, thus avoiding complicating the structure of the electrode body.

[0007] In the second approach, as in the first approach, the distance between the centers of gravity of two adjacent electrode stacks in a second direction orthogonal to the first direction is less than a predetermined reference value. In other words, when stacking multiple electrode stacks during electrode fabrication, the stacking position can be adjusted based on the center of gravity of the electrode stacks. This allows for the high-precision stacking of multiple electrode stacks.

[0008] In a third approach, as in the first or second approach, the diaphragms are joined together between adjacent electrode stacks. This structure helps suppress positional shifts between adjacent electrode stacks.

[0009] In the fourth approach, or any of the first to third approaches, the bundling portion integrally formed with the diaphragm may at least wrap around the periphery of the plurality of electrode stacks once, with the front end of the bundling portion engaging with it. With this structure, the bundling portion has a ring-shaped configuration wrapping around the periphery of the plurality of electrode stacks, thus improving the constraint force on the plurality of electrode stacks.

[0010] In the fifth approach, or in any of the first to fourth approaches, the diaphragms can be directly adjacent to each other between two adjacent electrode stacks of the plurality of electrode stacks. That is, electrode sheets may not be disposed between two adjacent electrode stacks of the plurality of electrode stacks. Attached Figure Description

[0011] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and wherein:

[0012] Figure 1 This is a diagram that roughly shows the structure of battery 100;

[0013] Figure 2 This is a diagram illustrating that an electrode body 10 is housed within an external component 102;

[0014] Figure 3 This is a diagram that schematically illustrates the structure of the electrode body 10 in the embodiment;

[0015] Figure 4A Show Figure 3 Enlarged view of section IV(A) in the image; and

[0016] Figure 4B Show Figure 3 Enlarged view of section IV(B) in the image. Detailed Implementation

[0017] Referring to the accompanying drawings, the electrode stack 10 and the battery 100 using the same embodiment will be described. The battery 100 is, for example, a lithium-ion secondary battery. The battery 100 has a rectangular flat plate shape. Hereinafter, the thickness direction of the battery 100 will be referred to as the Z direction, the length direction of the battery 100 will be referred to as the X direction, and the direction orthogonal to the Z direction and the X direction will be referred to as the Y direction.

[0018] like Figure 1 , Figure 2 As shown, the battery 100 includes an outer casing 102. Within the outer casing 102, the electrode body 10 and the electrolyte (not shown) are sealed together. The outer casing 102 is made of a thin film. For example, the outer casing 102 is a laminated film on both surfaces of an aluminum foil, with resin-coated films disposed thereon.

[0019] like Figure 1 As shown, the battery 100 also includes a positive terminal 104 and a negative terminal 106. One end of the positive terminal 104 protrudes outside the outer casing 102, and the other end of the positive terminal 104 is inside the outer casing 102 connected to the positive current collector foils 22 of the electrode body 10 (see reference). Figure 4A The negative terminal 106 is connected to the outer casing 102 at one end. The other end of the negative terminal 106 is connected to the negative current collector foils 32 of the electrode body 10 (see reference 102) inside the outer casing 102. Figure 4B The positive terminal 104 can be connected to each positive current collector foil 22 via a tab integrally formed with each positive current collector foil 22, or via a tab joined to each positive current collector foil 22 by welding or the like. Similarly, the negative terminal 106 can be connected to each negative current collector foil 32 via a tab integrally formed with each negative current collector foil 32, or via a tab joined to each negative current collector foil 32 by welding or the like.

[0020] like Figure 2 , Figure 3 As shown, the electrode body 10 includes two electrode stacks 12 and 14. The two electrode stacks 12 and 14 are stacked along the Z direction. That is, the Z direction is consistent with the stacking direction of the two electrode stacks 12 and 14. The two electrode stacks 12 and 14 include a first electrode stack 12 and a second electrode stack 14. The second electrode stack 14 is disposed on one of the first electrode stacks 12 along the Z direction (in this case, the -Z direction).

[0021] like Figure 3As shown, electrode stacks 12 and 14 each include a plurality of electrode sheets 20 and 30 and a separator 40. The plurality of electrode sheets 20 and 30 are stacked along the Z direction. The plurality of electrode sheets 20 and 30 have a rectangular shape when viewed along the Z direction. The plurality of electrode sheets 20 and 30 include a plurality of positive electrode sheets 20 and a plurality of negative electrode sheets 30. The separator 40 is an elongated sheet. The separator 40 extends in a zigzag manner between the plurality of positive electrode sheets 20 and the plurality of negative electrode sheets 30. That is, the separator 40 is folded alternately and repeatedly by alternating mountain folds and valley folds at predetermined intervals. Between the separators 40, the positive electrode sheets 20 and negative electrode sheets 30 are stacked alternately one by one. Furthermore, the number of electrode sheets 20 and 30 included in each of the electrode stacks 12 and 14 is not particularly limited.

[0022] like Figure 4A As shown, each of the plurality of positive electrode sheets 20 has a positive electrode current collector foil 22 and a positive electrode active material layer 24. The positive electrode current collector foil 22 and the positive electrode active material layer 24 each have a rectangular shape when viewed along the Z direction. The positive electrode current collector foil 22 is, for example, an aluminum foil. The positive electrode active material layer 24 is disposed on both sides of the positive electrode current collector foil 22. The positive electrode active material layer 24 contains a positive electrode active material. Examples of positive electrode active materials include lithium nickel composite oxides, lithium cobalt composite oxides, and lithium manganese composite oxides. The positive electrode active material can be composed of a single type of material or multiple materials. The positive electrode active material layer 24 may further include a binder, conductive additives, etc. Furthermore, the positive electrode active material layer 24 does not necessarily have to be disposed on both sides of the positive electrode current collector foil 22. That is, in other embodiments, the positive electrode active material layer 24 may also be disposed on one side of the positive electrode current collector foil 22.

[0023] like Figure 4B As shown, each of the plurality of negative electrode sheets 30 has a negative electrode current collector foil 32 and a negative electrode active material layer 34. The negative electrode current collector foil 32 and the negative electrode active material layer 34 each have a rectangular shape when viewed along the Z direction. The negative electrode current collector foil 32 is, for example, a copper foil. The negative electrode active material layer 34 is disposed on both sides of the negative electrode current collector foil 32. The negative electrode active material layer 34 contains a negative electrode active material. Examples of negative electrode active materials include carbon materials such as graphite, hard carbon, and soft carbon; materials that form alloys with lithium, such as silicon (Si); and lithium alloys. The negative electrode active material can be composed of a single type of material or multiple materials. The negative electrode active material layer 34 may further include an adhesive, etc. Furthermore, the negative electrode active material layer 34 does not necessarily have to be disposed on both sides of the negative electrode current collector foil 32. That is, in other embodiments, the negative electrode active material layer 34 may also be disposed on one side of the negative electrode current collector foil 32.

[0024] The separator 40 is configured to allow charge carriers (in this case, lithium ions) to pass through. The separator 40 is made of insulating materials such as polypropylene or polyethylene. Examples of separators 40 include porous polyethylene membranes and porous polypropylene membranes.

[0025] like Figure 3 As shown, the diaphragms 40 are directly adjacent to each other between the two electrode stacks 12 and 14. That is, no electrode sheets 20 and 30 are disposed between the two electrode stacks 12 and 14. Moreover, the diaphragms 40 are joined to each other between the two electrode stacks 12 and 14 via a first joint 44. Furthermore, the dimensions of the directly adjacent diaphragms 40 between the two electrode stacks 12 and 14 in the Y direction may be equal or different.

[0026] In the two electrode stacks 12 and 14, the distance between their respective centers of gravity in the X direction is less than or equal to a predetermined reference value. This predetermined reference value is, for example, less than 20% of the dimension in the X direction of the active material layers 24 and 34 of the electrode sheets 20 and 30, and less than 10% of the dimension in the X direction of the active material layers 24 and 34 of the electrode sheets 20 and 30. Similarly, in the two electrode stacks 12 and 14, the distance between their respective centers of gravity in the Y direction is less than or equal to a predetermined reference value. This predetermined reference value is, for example, less than 20% of the dimension in the Y direction of the active material layers 24 and 34 of the electrode sheets 20 and 30, and less than 10% of the dimension in the Y direction of the active material layers 24 and 34 of the electrode sheets 20 and 30.

[0027] like Figure 3 As shown, the diaphragm 40 of the first electrode stack 12 has a binding portion 42. The binding portion 42 is integrally formed with the diaphragm 40. The binding portion 42 is made of the same material as the diaphragm 40. The binding portion 42 surrounds the two electrode stacks 12 and 14 together. In this embodiment, the binding portion 42 surrounds the two electrode stacks 12 and 14, and the front end 42a of the binding portion 42 is joined to the binding portion 42 via a second joining portion 46 at the Z-direction end face (here, the +Z-direction end face) of the first electrode stack 12.

[0028] In the electrode body 10 described above, a binding portion 42 is integrally formed on the diaphragm 40 of the first electrode stack 12. This binding portion 42 surrounds both electrode stacks 12 and 14, thereby generating a restraining force between the two electrode stacks 12 and 14 and suppressing positional displacement between them. Furthermore, in each electrode stack 12 and 14, positional displacement of the electrode sheets 20 and 30 is also suppressed by the restraining force based on the binding portion 42. Therefore, in at least one of the electrode stacks 12 and 14, only the binding portion 42 needs to be provided on the diaphragm 40, thus avoiding complicating the structure of the electrode body 10.

[0029] In the above embodiment, the distance in the X direction between the centers of gravity of two adjacent electrode stacks 12, 14 is less than or equal to a predetermined reference value. Furthermore, the distance in the Y direction between the centers of gravity of two adjacent electrode stacks 12, 14 is less than or equal to a predetermined reference value. In other words, when multiple electrode stacks 12, 14 are stacked during the manufacturing of the electrode body 10, the stacking position can be adjusted based on the center of gravity of the electrode stacks 12, 14. Instead, for example, it is considered to stack multiple electrode stacks 12, 14 based on the tabs provided on each electrode stack 12, 14. In this case, the position of the tabs also shifts along with the shift in the stacking position of the electrode sheets 20, 30. Therefore, as described above, by stacking multiple electrode stacks 12, 14 based on the center of gravity of each electrode stack 12, 14, multiple electrode stacks 12, 14 can be stacked with high precision.

[0030] In the above embodiments, the diaphragms 40 are joined to each other via a first joint 44 between two adjacent electrode stacks 12 and 14. This structure suppresses positional shifts between the two adjacent electrode stacks 12 and 14. Furthermore, the method of joining the diaphragms 40 of the first electrode stack 12 and the diaphragms 40 of the second electrode stack 14 is not particularly limited. For example, in some embodiments, the first joint 44 may be made of an adhesive material such as an adhesive or adhesive tape. Alternatively, the first joint 44 may be made of a welded portion formed by thermally fusing the diaphragms 40. However, in other embodiments, the diaphragms 40 may not be joined to each other between the two adjacent electrode stacks 12 and 14.

[0031] In the above embodiments, the binding portion 42, integrally formed with the diaphragm 40, wraps around at least one ring around the two electrode stacks 12, 14, and the front end 42a of the binding portion 42 is joined to the binding portion 42 via the second joining portion 46. With this structure, the binding portion 42 wraps around and surrounds the two electrode stacks 12, 14, thereby generating a binding force between the two electrode stacks 12, 14. Furthermore, the method of joining the front end 42a of the binding portion 42 to the binding portion 42 is not particularly limited. For example, as in some embodiments, the second joining portion 46 may also be made of an adhesive material such as an adhesive or adhesive tape. Alternatively, the second joining portion 46 may also be made of a weld portion formed by thermally fusing the binding portion 42.

[0032] In the above embodiment, the front end 42a of the bundling portion 42 is joined to the bundling portion 42 via the second joining portion 46 at the end face of the first electrode laminate 12 in the Z direction (i.e., the end face in the +Z direction). Alternatively, the front end 42a of the bundling portion 42 may also be joined to the bundling portion 42 via the second joining portion 46 at the end face of the second electrode laminate 14 in the Z direction (i.e., the end face in the -Z direction). In this case, the bundling portion 42 may wrap around the two electrode laminates 12, 14. For example, when the second joining portion 46 is formed by a weld portion formed by thermally welding the bundling portion 42, sometimes the front end 42a is pressed against the bundling portion 42 by a heated component. In this case, pressing the front end 42a along the Z direction (i.e., the stacking direction of the plurality of electrode stacks 12, 14) onto the bundle portion 42, rather than pressing the front end 42a along the Y direction onto the bundle portion 42, can securely attach the front end 42a to the bundle portion 42.

[0033] However, instead of the above, the front end 42a of the bundling portion 42 may be joined to the bundling portion 42 via the second joining portion 46 on the end face of the electrode stack 12, 14 in the Y direction (i.e., the end face in the +Y direction or the end face in the -Y direction). In this case, the bundling portion 42 may also wrap around the two electrode stacks 12, 14.

[0034] In the above embodiments, the diaphragms 40 are directly adjacent to each other between two adjacent electrode stacks 12 and 14. However, in other embodiments, electrode sheets 20 and 30 may be disposed on the end face of the second electrode stack 14, and the diaphragm 40 of the first electrode stack 12 may be located between two adjacent electrode stacks 12 and 14.

[0035] In the above embodiments, the binding portion 42 is integrally formed with the diaphragm 40 of the first electrode stack 12. However, in other embodiments, the binding portion 42 may also be integrally formed with the diaphragm 40 of the second electrode stack 14.

[0036] In the above embodiment, the electrode body 10 includes two electrode stacks 12 and 14. However, the electrode body 10 may also include three or more electrode stacks stacked along the Z direction. That is, the electrode body 10 only needs to include at least two electrode stacks 12 and 14. In this case, the electrode stacks located at the ends in the Z direction may include a binding portion 42. In addition, in any two adjacent electrode stacks, the distance between their respective centers of gravity in the X direction may be less than a predetermined reference value, and the distance between their respective centers of gravity in the Y direction may be less than a predetermined reference value. Furthermore, between any two adjacent electrode stacks, each diaphragm 40 may be joined to each other.

[0037] The above provides detailed examples, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes technologies obtained by various modifications and alterations to the above-described examples. The technical elements illustrated in this specification or drawings contribute to the technical usefulness of the technology, either individually or in combination.

Claims

1. An electrode body comprising a plurality of electrode laminates stacked along a first direction. The plurality of electrode stacks each have: Multiple electrode sheets stacked along the first direction; and A long diaphragm extending in a tortuous manner between the plurality of electrode sheets, One of the plurality of electrode stacks has a diaphragm integrally formed with a binding portion that surrounds the plurality of electrode stacks together.

2. The electrode body according to claim 1, wherein, In two adjacent electrode stacks of the plurality of electrode stacks, the distance between their respective centers of gravity in a second direction orthogonal to the first direction is below a predetermined reference value.

3. The electrode body according to claim 1, wherein, Between two adjacent electrode stacks of the plurality of electrode stacks, the respective diaphragms are joined together.

4. The electrode body according to claim 1, wherein, The bundle portion, integrally formed with the diaphragm, surrounds at least one circumference of the plurality of electrode stacks, and the front end of the bundle portion engages with the bundle portion.

5. The electrode body according to claim 1, wherein, Between two adjacent electrode stacks of the plurality of electrode stacks, the respective diaphragms are directly adjacent.

Images