Electrode group, method for manufacturing an electrode group, and secondary battery

Abstract

The objective is to provide an electrode group that suppresses short circuits caused by cracking of the positive or negative electrode at the innermost circumference of the electrode group, a method for manufacturing the electrode group, and a secondary battery. [Solution] The electrode group of the embodiment has a wound body formed in a flat shape by winding a first positive electrode and a first negative electrode via a first separator. It also has a laminate formed by stacking a second positive electrode and a second negative electrode via a second separator. Furthermore, the laminate is arranged on the inner circumference of the wound body.

Description

Technical Field

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[0001] Embodiments of the present invention relate to an electrode group, a method for manufacturing the electrode group, and a secondary battery.

Background Art

[0002] In recent years, secondary batteries such as lead-acid batteries and nickel-metal hydride batteries have been used as power sources represented by electric vehicles, hybrid vehicles, electric motorcycles, and forklifts. In order to adopt lithium-ion secondary batteries with high energy density, development has been carried out while considering long life, safety, etc.

[0003] An electrode group used in a lithium-ion secondary battery (hereinafter referred to as a secondary battery) is, for example, manufactured by winding an electrode member composed of a positive electrode, a negative electrode, and a separator and pressing the whole into a flat shape. In such a type of secondary battery, when the positive electrode or the negative electrode is sharply bent by pressure molding at the innermost peripheral portion of the electrode group, there is a possibility that the positive electrode or the negative electrode may crack. And there is a risk that this cracked portion may break through the separator and come into electrical contact with the opposing positive electrode or negative electrode, causing a short circuit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide an electrode group, a method for manufacturing the electrode group, and a secondary battery that suppress a short circuit caused by cracking of the positive electrode or the negative electrode at the innermost peripheral portion of the electrode group.

Means for Solving the Problems

[0006] To solve the above problems, the electrode group of the embodiment has a wound body formed in a flat shape by winding a first positive electrode and a first negative electrode via a first separator, and a laminate formed by stacking a second positive electrode and a second negative electrode via a second separator. The laminate is arranged on the inner circumference of the wound body. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic perspective view showing the electrode group according to the first embodiment. [Figure 2] A partially unfolded perspective view of the wound body included in the electrode group according to the first embodiment, viewed from above. [Figure 3] A partially unfolded perspective view of the laminate included in the electrode group according to the first embodiment, viewed from above. [Figure 4] A schematic cross-sectional view showing the electrode group according to the first embodiment. [Figure 5] A schematic cross-sectional view showing a modified example of the electrode group according to the first embodiment. [Figure 6] A schematic perspective view showing a secondary battery according to the second embodiment. [Modes for carrying out the invention]

[0008] The electrode group, the method for manufacturing the electrode group, and the secondary battery of the embodiment will be described below with reference to the drawings.

[0009] (First embodiment) The electrode group 5 of the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic perspective view of the electrode group 5 according to the first embodiment, and Figure 2 is a partially unfolded perspective view of the wound body 5a included in the electrode group 5 according to the first embodiment, viewed from above.

[0010] As shown in Figure 1, the electrode group 5 has a laminate 5b and a wound body 5a, with the laminate 5b positioned on the inner circumference 80 of the wound body 5a. The wound body 5a is manufactured, for example, as shown in Figure 2, by winding a first positive electrode 13 and a first negative electrode 15 around a first separator 4, and then press-molding the entire structure into a flattened shape in the stacking direction (Y direction) of the first positive electrode 13 and the first negative electrode 15. Here, the inner circumference 80 of the wound body 5a is defined as the portion around which the separator 4, positioned inside the winding, is wrapped.

[0011] Pressure molding involves, for example, applying pressure to the coiled body 5a by sandwiching it between coil presses made of heated metal plates. This pressure molding reduces the space within the coiled body 5a, so that, for example, when the coiled body 5a is housed in a case (not shown) of a secondary battery, more first positive electrodes 13 and first negative electrodes 15 can be housed in the limited space within the case. Note that the manufacturing method of the coiled body 5a is not limited to these methods; it is sufficient that the first positive electrode 13 and first negative electrode 15 are wound and formed into a flattened shape.

[0012] The first positive electrode 13 has a strip-shaped positive electrode current collector 13a having a long side 90 (Z direction) and a short side 92 (X direction). On the positive electrode current collector 13a, there is a positive electrode mixture layer 130 in which the positive electrode mixture is applied parallel to the long side 90, and an uncoated portion 70a of the positive electrode mixture layer where the positive electrode mixture is not applied. The first negative electrode 15 has a strip-shaped negative electrode current collector 15a having a long side 90 and a short side 92. On the negative electrode current collector 15a, there is a negative electrode mixture layer 150 in which the negative electrode mixture is applied parallel to the long side 90, and an uncoated portion 70b of the negative electrode mixture layer where the negative electrode mixture is not applied.

[0013] In the wound body 5a of this embodiment, the uncoated portion 70a of the positive electrode mixture layer protrudes in the opposite direction to the protruding direction of the uncoated portion 70b of the negative electrode mixture layer and is provided at both ends of the electrode group 5. However, the protruding directions of the uncoated portion 70a of the positive electrode mixture layer and the uncoated portion 70b of the negative electrode mixture layer are not limited to these. The uncoated portion 70a of the positive electrode mixture layer and the uncoated portion 70b of the negative electrode mixture layer may protrude in the same direction, and both may be provided at one end of the wound body 5a.

[0014] In the electrode group 5, the laminate 5b, which is arranged on the inner circumference 80 of the wound body 5a, will be described with reference to Figure 3. Figure 3 is a partially unfolded perspective view from above of the laminate 5b included in the electrode group 5 according to the first embodiment.

[0015] The second positive electrode 13' has a rectangular positive electrode current collector 13a' having a long side 90' ​​(X direction) and a short side 92' (Z direction), as shown in Figure 3. On the positive electrode current collector 13a', there is a positive electrode mixture layer 130' where the positive electrode mixture is applied parallel to the short side 92', and an uncoated portion 70a' of the positive electrode mixture layer where the positive electrode mixture is not applied. The second negative electrode 15' has a strip-shaped negative electrode current collector 15a' having a long side 90' ​​and a short side 92'. On the negative electrode current collector 15a', there is a negative electrode mixture layer 150' where the negative electrode mixture is applied parallel to the short side 92', and an uncoated portion 70b' of the negative electrode mixture layer where the negative electrode mixture is not applied.

[0016] In the laminate 5b of this embodiment, the uncoated portion 70a' of the positive electrode mixture layer protrudes in the opposite direction to the protruding direction of the uncoated portion 70b' of the negative electrode mixture layer and is provided at both ends of the laminate 5b. However, the protruding directions of the uncoated portion 70a' of the positive electrode mixture layer and the uncoated portion 70b' of the negative electrode mixture layer are not limited to these. The uncoated portion 70a' of the positive electrode mixture layer and the uncoated portion 70b' of the negative electrode mixture layer may protrude in the same direction, and both may be provided at one end of the laminate 5b.

[0017] The electrode group 5 of this embodiment will be further described with reference to Figure 4. Figure 4 is a schematic cross-sectional view (cross-section II shown in Figure 1) of the electrode group 5 according to the first embodiment.

[0018] As shown in FIG. 4, in the electrode group 5 of the present embodiment, the laminate 5b is disposed on the inner peripheral portion 80 of the wound body 5a. Here, since the first separator 4 is wound around the inner peripheral portion 80 of the wound body 5a, it is preferable that the second positive electrode 13' or the second negative electrode 15' of the laminate 5b is disposed at a position facing the first separator 4 in the inner peripheral portion 80 of the wound body 5a. In the wound body 5a of the present embodiment, since the first positive electrode 13 is wound on the outer side of one turn of the first separator 4 in the inner peripheral portion 80 of the wound body 5a, the second negative electrode 15' of the laminate 5b is disposed at a position facing the first separator 4 in the inner peripheral portion 80 of the wound body 5a. On the other hand, when the first negative electrode 15 is wound on the outer side of one turn of the first separator 4 in the inner peripheral portion 80 of the wound body 5a, the first positive electrode 13' of the laminate 5b is disposed at a position facing the first separator 4 in the inner peripheral portion 80 of the wound body 5a.

[0019] In the electrode group 5 of the present embodiment, since the laminate 5b is disposed on the inner peripheral portion 80 of the wound body 5a, the bending curvature of the inner peripheral portion 80 of the wound body 5a becomes larger as compared with the case where the laminate 5b is not disposed on the inner peripheral portion 80 of the wound body 5a. Thereby, for example, after winding the first positive electrode 13 and the first negative electrode 15, even when the first positive electrode 13 in the inner peripheral portion 80 of the wound body 5a is bent by pressing and molding the whole wound body 5a in the stacking direction (Y direction) of the first positive electrode 13 and the first negative electrode 15, cracking of the first positive electrode 13 in the inner peripheral portion 80 of the wound body 5a can be suppressed. And, in the inner peripheral portion 80 of the wound body 5a, it is possible to suppress the cracked first positive electrode 13 from piercing through the separator 4 and making electrical contact with the opposed first negative electrode 15.

[0020] Here, the laminate 5b is composed of a total of five sheets including two second negative electrodes 15', two second separators 4', and one second positive electrode 13'. From the viewpoint of increasing the bending curvature in the inner peripheral portion 80 of the wound body 5a, it is preferably composed of at least five or more second positive electrodes 13', second negative electrodes 15', and second separators 4'.

[0021] The length in the Z direction of the second positive electrode 13' and the second negative electrode 15' used in the laminate 5b is preferably equal to the length in the Z direction of the flat portion 60 in the cross section of the wound body 5a. The wound body 5a of the present embodiment is flat, and in the cross section of the wound body 5a, there are a flat portion 60 and curved portions 62 provided on both sides of the flat portion 60. By making the length in the Z direction of the second positive electrode 13' and the second negative electrode 15' used in the laminate 5b equal to the length in the Z direction of the flat portion 60 of the wound body 5a, it is possible to obtain an electrode group 5 that ensures sufficient battery capacity as the entire electrode group 5. Further, it is possible to suppress the end portions of the second positive electrode 13' and the second negative electrode 15' used in the laminate 5b from contacting the second separator 4' in the inner peripheral portion 80 of the wound body 5a and piercing through the second separator 4'.

[0022] A modified example of the electrode group 5 of the first embodiment will be described with reference to FIG. 5. FIG. 5 is a cross-sectional view (the I-I cross section shown in FIG. 1) schematically showing a modified example of the electrode group 5 according to the first embodiment. The difference between FIG. 5 and FIG. 4 is the number of laminations of the second positive electrode 13' and the second negative electrode 15' of the laminate 5b.

[0023] The laminate 5b shown in FIG. 4 was composed of a total of five sheets including two second negative electrodes 15', two second separators 4', and one second positive electrode 13', whereas the laminate 5b shown in FIG. 5 is composed of a total of nine sheets including three second negative electrodes 15', four second separators 4', and two second positive electrodes 13'. As a result, the curvature of the inner peripheral portion 80 of the wound body 5a becomes even larger. For example, after winding the first positive electrode 13 and the first negative electrode 15, even when the first positive electrode 13 in the inner peripheral portion 80 of the wound body 5a is bent by pressure molding the entire wound body 5a in the lamination direction (Y direction) of the first positive electrode 13 and the first negative electrode 15, cracking of the first positive electrode 13 in the inner peripheral portion 80 of the wound body 5a can be suppressed. And in the inner peripheral portion 80 of the wound body 5a, it is possible to suppress the cracked first positive electrode 13 from piercing through the separator 4 and making electrical contact with the opposed first negative electrode 15.

[0024] Here, the manufacturing method of the electrode group 5 of this embodiment will be described. The electrode group 5 is manufactured by winding the first positive electrode 13 and the first negative electrode 15 via the first separator 4 (winding body manufacturing step), then placing the laminate 5b on the inner circumference 80 of the winding body 5a (first placement step), and then forming the winding body 5a with the laminate 5b on it into a flat shape (first winding body forming step). Alternatively, the first positive electrode 13 and the first negative electrode 15 may be wound via the first separator 4 to form a flat winding body 5a (second winding body forming step), and then placing the laminate 5b on the inner circumference 80 of the flat winding body 5a (second placement step). Then, the laminate 5b is manufactured (laminated body manufacturing process) by laminating a second positive electrode 13' and a second negative electrode 15' via a second separator 4', as shown in Figure 3.

[0025] In the electrode group 5 and the manufacturing method of the electrode group 5 of the first embodiment described above, the laminate 5b is placed on the inner circumference 80 of the wound body 5a. As a result, the curvature of the inner circumference 80 of the wound body 5a becomes larger compared to the case where the laminate 5b is not placed on the inner circumference 80 of the wound body 5a. Therefore, even if, for example, after winding the first positive electrode 13 and the first negative electrode 15, the entire wound body 5a is pressure-molded in the stacking direction (Y direction) of the first positive electrode 13 and the first negative electrode 15, and the first positive electrode 13 in the inner circumference 80 of the wound body 5a is bent, cracking of the first positive electrode 13 in the inner circumference 80 of the wound body 5a can be suppressed. Then, in the inner circumference 80 of the wound body 5a, the broken first positive electrode 13 pierces the separator 4, resulting in an electrode group in which electrical contact with the opposing first negative electrode 15 is suppressed.

[0026] (Second embodiment) The secondary battery 1 of the second embodiment will be described with reference to Figure 6. Figure 6 is a schematic perspective view showing the secondary battery 1 according to the second embodiment.

[0027] As shown in Figure 6, the secondary battery 1 has an outer case 3, and the electrode group 5 of the first embodiment is housed inside the outer case 3. Inside the outer case 3, the electrode group 5 is impregnated with an electrolyte (not shown), and the electrolyte is injected, for example, through an injection port (not shown) provided on the lid member 7, and the injection port is sealed with a sealing plate 19 after the electrolyte has been injected. The electrolyte used is a non-aqueous electrolyte prepared by dissolving an electrolyte (e.g., a lithium salt) in a non-aqueous solvent. The non-aqueous solvent may be used alone or in a mixture of two or more types.

[0028] A gas discharge valve 21 may be provided on the surface of the lid member 7 together with the sealing plate 19. Furthermore, for example, a pair of positive electrode external terminals 23a and negative electrode external terminals 23b are attached to the surface of the lid member 7, and the external terminals 23a and 23b are electrically connected to the uncoated portion 70a of the positive electrode mixture layer and the uncoated portion 70b of the negative electrode mixture layer of the electrode group 5, respectively. A terminal insulator 35 may be provided between the external terminals 23a and 23b and the lid member 7 to maintain insulation between them.

[0029] The secondary battery 1 of the second embodiment described above is equipped with the electrode group 5 of the first embodiment. As a result, the curvature of the inner circumference 80 of the wound body 5a is larger than when the laminate 5b is not placed on the inner circumference 80 of the wound body 5a. Therefore, even if, for example, after winding the first positive electrode 13 and the first negative electrode 15, the entire wound body 5a is pressure-molded in the stacking direction (Y direction) of the first positive electrode 13 and the first negative electrode 15, and the first positive electrode 13 on the inner circumference 80 of the wound body 5a is sharply bent, cracking of the first positive electrode 13 on the inner circumference 80 of the wound body 5a can be suppressed. In this way, a secondary battery 1 is obtained in which the cracked first positive electrode 13 on the inner circumference 80 of the wound body 5a does not pierce the separator 4 and electrical contact with the opposing first negative electrode 15 is suppressed.

[0030] According to the electrode group 5 of at least one embodiment described above, the laminate 5b is arranged on the inner circumference 80 of the wound body 5a. As a result, the curvature of the inner circumference 80 of the wound body 5a is larger than when the laminate 5b is not arranged on the inner circumference 80 of the wound body 5a. Therefore, even if, for example, after winding the first positive electrode 13 and the first negative electrode 15, the entire wound body 5a is pressure-molded in the lamination direction (Y direction) of the first positive electrode 13 and the first negative electrode 15, and the first positive electrode 13 in the inner circumference 80 of the wound body 5a is bent, cracking of the first positive electrode 13 in the inner circumference 80 of the wound body 5a can be suppressed. As a result, an electrode group is obtained in which the cracked first positive electrode 13 in the inner circumference 80 of the wound body 5a does not pierce the separator 4 and electrical contact with the opposing first negative electrode 15 is suppressed.

[0031] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0032] 1...Secondary battery, 3...Outer case, 4...First separator, 4'...Second separator, 5...Electrode group, 5a...Wound body, 5b...Laminate, 7...Lid member, 13...First positive electrode, 13'...Second positive electrode, 13a...Positive electrode current collector, 15...First negative electrode, 15'...Second negative electrode, 15a...Negative electrode current collector, 19...Sealing plate, 21...Gas discharge valve, 23a...Positive electrode external terminal, 23b...Negative electrode external terminal, 35...Terminal insulator, 60...Flat part, 62...Curved part, 70a...Uncoated part of positive electrode mixture layer, 70b...Uncoated part of negative electrode mixture layer, 80...Inner circumference, 90...Long side, 92...Short side, 130...Positive electrode mixture layer, 150...Negative electrode mixture layer.

Claims

1. A first positive electrode and a first negative electrode are wound around a first separator, forming a flattened wound body, A laminate in which a second positive electrode and a second negative electrode are stacked via a second separator, Equipped with, The laminate is a group of electrodes arranged on the inner circumference of the wound body.

2. A winding body manufacturing process in which a first positive electrode and a first negative electrode are wound around a first separator to produce a winding body, A laminate manufacturing process for producing a laminate by stacking a second positive electrode and a second negative electrode via a second separator, A first arrangement step involves arranging the laminate on the inner circumference of the winding body, A method for manufacturing an electrode group, comprising: a first winding body forming step of forming the winding body on which the laminate is arranged into a flat shape.

3. A second winding body forming step involves winding a first positive electrode and a first negative electrode via a first separator to form a flattened winding body, A laminate manufacturing process for producing a laminate by stacking a second positive electrode and a second negative electrode via a second separator, A method for manufacturing an electrode group, comprising: a second arrangement step of arranging the laminate on the inner circumference of the flattened wound body.

4. The electrode group according to claim 1, A rechargeable battery equipped with an electrolyte.

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