JP2013073755A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery reducing a portion where a potential difference occurs between layers of a positive electrode or a negative electrode, in the entire electrode body as possible, thereby uniforming electrode reactions as the entire electrode body.SOLUTION: Layers of a positive electrode 12 forming each of bent parts 21, 22 are electrically connected with each other via each of contact parts 42 of a metal member 40a by bringing the contact parts 42 into contact with each other so that at least two layers of the positive electrode 12 forming each of the bent parts 21, 22 are stepped over, the metal member being bonded to an uncoated part 12b of the positive electrode 12 forming both bent parts 21, 22 at both ends in the winding axial direction of an electrode body 11.

Description

  The present invention relates to a secondary battery including an electrode body that is formed by insulating a positive electrode and a negative electrode and winding or laminating them.

  In general, a secondary battery is known that includes an electrode body that is formed by interposing a strip-shaped separator between a strip-shaped positive electrode and a strip-shaped negative electrode and winding them in a spiral shape. The positive electrode and the negative electrode are formed with a coated portion where the active material is applied and an uncoated portion where the active material is not applied. The positive electrode and the negative electrode are stacked while being shifted in the width direction via the separator, and are wound in a spiral shape with the uncoated portions of the positive electrode and the negative electrode protruding outward from both end edges of the separator. And after a positive electrode, a negative electrode, and a separator are wound by the spiral shape, a flat electrode body is formed by compressing a positive electrode, a negative electrode, and a separator from radial direction both sides. The electrode body is formed of both bent portions that are bent so as to be curved in an arc shape located at both ends in the long diameter direction, and a connecting portion that extends in the long diameter direction and connects the two bent portions. A current collecting terminal is joined to a part of the uncoated portion of the positive electrode and the negative electrode forming the connecting portion. And the secondary battery is comprised by accommodating the electrode body to which each current collection terminal was joined in the case where electrolyte solution was inject | poured inside (for example, refer patent document 1).

JP-A-10-261441

  By the way, in the electrode body of such a secondary battery, since a current collecting terminal is joined to a part of the connecting part, a potential difference is hardly generated between the positive electrode or negative electrode layers forming the connecting part. Thus, the electrode reaction at the connecting portion is performed uniformly. However, since the positive electrode or negative electrode layers forming the bent portions are separated from each other, a potential difference is generated between the positive electrode or negative electrode layers forming the bent portions, so that the electrode reaction at the bent portions is caused. It becomes non-uniform, and the output density of the electric power generated as a whole electrode body will fall.

  The present invention has been made in order to solve the above-described problems, and the object of the present invention is to reduce as much as possible the potential difference between positive electrode and negative electrode layers in the entire electrode body, and as a whole electrode body. An object of the present invention is to provide a secondary battery that can make the electrode reaction uniform.

  In order to achieve the above object, an invention according to claim 1 includes an electrode body formed by insulating a positive electrode and a negative electrode and winding or laminating them, and collecting each of the positive electrode and the negative electrode. In the secondary battery provided with an electrical terminal, the electrode body is formed with at least one bent portion where the positive electrode and the negative electrode forming the electrode body are bent, and the bent portion includes: The gist is that a metal member having at least one contact portion that contacts at least two layers of the positive electrode or the negative electrode is provided.

  According to the present invention, the contact portion of the metal member is in contact with at least two positive or negative electrode layers forming the bent portion, so that the positive or negative electrode layers forming the bent portion are in contact with each other. It can be electrically connected through the section. Therefore, compared to the case where no metal member is provided in the bent portion, it is possible to suppress the occurrence of a potential difference between the positive electrode and negative electrode layers forming the bent portion, and the electrode reaction at the bent portion is uniform. Can be. As a result, it is possible to reduce as much as possible the potential difference between the positive and negative electrode layers in the entire electrode body, and to make the electrode reaction uniform in the entire electrode body.

The gist of the invention according to claim 2 is that, in the invention according to claim 1, a plurality of the contact portions are provided.
According to this invention, compared with the case where a contact part is single, the site | part which contacts so that the layer of the positive electrode or negative electrode which forms a bending part may be straddled can be increased. Therefore, the positive or negative electrode layers forming the bent portion can be electrically connected to each other through the contact portions, and a potential difference is generated between the positive or negative electrode layers forming the bent portion. Further, it can be easily prevented.

The gist of the invention described in claim 3 is that, in the invention described in claim 1 or 2, the contact portions are arranged radially.
According to this invention, since each contact part is arranged radially, each layer of the positive electrode or negative electrode forming the bent part and each contact part can be easily crossed, and the positive electrode or negative electrode forming the bent part. It is possible to facilitate the contact of each layer with each contact portion.

  According to a fourth aspect of the invention, in the invention of the second or third aspect, the metal member is formed with a gap penetrating in the thickness direction, and each contact portion sandwiches the gap. The main point is that a plurality of them are arranged on both sides.

  For example, it is conceivable to join the metal member and the positive electrode or negative electrode layer forming the bent portion by indirect welding. In this case, one welded joint used for indirect welding is brought into contact with a portion of a metal member that overlaps with one contact located on one side across the gap, and the other welded joint Is brought into contact with the other contact portion located on the other side across the gap and a portion of the metal member to be polymerized, and a current flows between the weld joint portions. At this time, since a gap is formed in the metal member, it is possible to make it difficult for the current flowing from one weld joint to flow toward the other weld joint through the metal member. The flowing current can flow in the order of the metal member, one contact portion, the positive electrode or the negative electrode, the other contact portion, the metal member, and the other weld joint portion. As a result, the metal member and the positive or negative electrode layer forming the bent portion can be joined by indirect welding.

  According to the present invention, it is possible to make the electrode reaction uniform for the entire electrode body by reducing as much as possible the potential difference between the positive and negative electrode layers in the entire electrode body.

The longitudinal cross-sectional view of the secondary battery in embodiment. The perspective view which expands and shows a part of electrode body. The top view of a metal member. AA line sectional view in FIG. The perspective view which shows the state which attached the metal member to the electrode body typically. The figure which shows typically the relationship between a contact part and an electrode body. The perspective view which shows a collector terminal and a part of electrode body. The top view which shows the metal member in another embodiment. BB sectional drawing in FIG.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS.
As shown in FIG. 1, the secondary battery 10 includes an electrode body 11, a case C that houses the electrode body 11, and a lid F of the case C. Case C has a bottomed rectangular box shape with one side opened, and an electrolyte is injected therein. A positive terminal F1 and a negative terminal F2 are attached to the lid F.

  As shown in FIG. 2, the electrode body 11 is configured by interposing a strip-shaped separator 14 between a strip-shaped positive electrode 12 and a strip-shaped negative electrode 13, and winding these in a spiral around the winding axis L. ing. The positive electrode 12 is made of aluminum, and the negative electrode 13 is made of copper. The positive electrode 12 and the negative electrode 13 are formed with coated portions 12a and 13a to which the active material is applied and uncoated portions 12b and 13b to which the active material is not applied.

  The positive electrode 12 and the negative electrode 13 are stacked while being shifted in the width direction via the separator 14, and the uncoated portions 12 b and 13 b of the positive electrode 12 and the negative electrode 13 are protruded outward from both end edges 14 a and 14 b of the separator 14, respectively. In this state, it is wound around the winding axis L in a spiral shape. Then, after the positive electrode 12, the negative electrode 13, and the separator 14 are wound in a spiral shape, the flat electrode body 11 is formed by compressing the positive electrode 12, the negative electrode 13, and the separator 14 from both sides in the radial direction. The electrode body 11 includes both bent portions 21 and 22 that are bent so as to be curved in an arc shape located at both ends in the major axis direction (the direction of the arrow Y1 shown in FIG. 2), and the bent portions 21 and 22 that extend in the major axis direction. It forms from the connection part 23 to connect. Here, the bent portions 21 and 22 refer to portions where the curvature is larger than other portions in the electrode body 11.

  As shown in FIG. 1, at both ends of the electrode body 11 in the winding axis L direction, a metal member 40 a is joined to an uncoated portion 12 b of the positive electrode 12 that forms both bent portions 21 and 22. Further, a metal member 40b is joined to the uncoated portion 13b of the negative electrode 13 that forms both the bent portions 21 and 22. The metal member 40a joined to the uncoated part 12b of the positive electrode 12 is made of aluminum, and the metal member 40b joined to the uncoated part 13b of the negative electrode 13 is made of copper.

  Hereinafter, the metal member 40a joined to the uncoated portion 12b of the positive electrode 12 will be described in detail. In addition, since the metal member 40b joined to the uncoated part 13b of the negative electrode 13 has the same configuration as the metal member 40a joined to the uncoated part 12b of the positive electrode 12, detailed description thereof is omitted.

  As shown in FIG. 3, each metal member 40 a is arranged radially from the center of each metal plate 41 on a disk-shaped metal plate 41 and a back surface 41 a on the uncoated portion 12 b side of the positive electrode 12 in the metal plate 41. And a plurality of contact portions 42 (12 in this embodiment). As shown in FIG. 4, each contact portion 42 tapers as the distance from the back surface 41 a of the metal plate 41 increases, and the tip 42 a is pointed.

  As shown in FIG. 3, the metal plate 41 is formed with two slits 43 as gaps penetrating in the thickness direction. Each slit 43 is formed so as to extend along the radial direction along a straight line L1 passing through the center of the metal plate 41. A plurality (6 in this embodiment) of the contact portions 42 are arranged on both sides of the slits 43.

  As shown in FIG. 5, the metal member 40 a is indirect welded at a portion where the edge 121 b of the uncoated portion 12 b of the positive electrode 12 forming the bent portions 21 and 22 contacts the tip 42 a of the contact portion 42. It is joined by doing. Specifically, for example, the weld joint portions T1 and T2 are brought into contact with the portions of the metal plate 41 that overlap with the contact portions 421 and 422 on both sides of the slit 43 among the contact portions 42, and the weld joints. A current is passed between the portions T1 and T2.

  At this time, since the slits 43 are formed in the metal plate 41, it is difficult for the current flowing from the weld joint portion T <b> 1 to flow toward the weld joint portion T <b> 2 through the metal plate 41. Therefore, the current that flows from the welded joint portion T1 flows in the order of the metal plate 41, the contact portion 421, the uncoated portion 12b of the positive electrode 12, the contact portion 422, the metal plate 41, and the welded joint portion T2. Then, resistance heat is generated at a portion where the edge 121b of the uncoated portion 12b and the tip 42a of the contact portion 42 are in contact with each other. And by this resistance heat, the contact part with the front end 42a of the contact part 42 in the edge 121b of the uncoated part 12b, and the contact part with the edge 121b of the uncoated part 12b in the front end 42a of the contact part 42 Is heated and melted. Further, the melted part of the edge 121b of the uncoated part 12b and the melted part of the tip 42a of the contact part 42 are cooled, respectively, so that the edge 121b of the uncoated part 12b and the tip of the contact part 42 are cooled. 42a is joined to each other.

  As shown in FIG. 6, among the layers of the positive electrode 12, the tips 42a of all the contact portions 42 except for the two contact portions 42 arranged so as to be polymerized in the inner region of the innermost layer, Contact is made so as to straddle at least two layers of the positive electrode 12 forming the bent portions 21 and 22. The layer of the positive electrode 12 forming each bent portion 21, 22 is in contact with at least one of the contact portions 42. In FIG. 6, for convenience of explanation, only the tip 42 a of each contact portion 42 is illustrated by a broken line.

  As shown in FIG. 1, at both ends in the winding axis L direction of the electrode body 11, current collecting terminals 31 are joined to the uncoated portion 12 b of the positive electrode 12 that forms the connecting portion 23. As shown in FIG. 7, the current collecting terminal 31 is formed by bending a metal plate. The current collecting terminal 31 is formed at one end thereof and connected to the uncoated portion 12b of the positive electrode 12, and the terminal connecting portion 33 formed at the other end and connected to the positive electrode terminal F1. It is comprised from the connection part 34 which connects the connection part 32 and the terminal connection part 33. FIG.

  The connecting portion 32 and the connecting portion 34 extend along the major axis direction of the electrode body 11, and a stepped portion 35 extending along the winding axis L direction of the electrode body 11 is provided between the connecting portion 32 and the connecting portion 34. Is formed. A pair of connection allowances 32 a are erected along the winding axis L direction of the electrode body 11 at both side edges of the connection portion 32. The terminal connecting portion 33 is continuous with the connecting portion 34 and extends along the winding axis L direction of the electrode body 11.

  The connection portion 32 is buried inside the innermost layer of the positive electrode 12 layer forming the connection portion 23, and the outer surface of the connection allowance 32 a and the inner peripheral surface of the uncoated portion 12 b of the positive electrode 12 are opposed to each other. To be arranged. And the electrode body 11 is pressurized from both sides in the compression direction, and joined by ultrasonic welding in a state where the outer surface of the connection allowance 32a and the inner peripheral surface of the uncoated portion 12b of the positive electrode 12 are in close contact. Thereby, the current collection terminal 31 is connected over each layer of the positive electrode 12 which forms the connection part 23.

  As shown in FIG. 1, the connecting portion 34 is located on the outer side in the winding axis L direction than the end portion of the positive electrode 12, and more than the bent portion 21 while passing the outer side in the winding axis L direction than the metal member 40 a. It extends to the outside in the major axis direction. The terminal connection part 33 is connected to the positive terminal F1. The description on the negative electrode 13 side is the same as the description on the positive electrode 12 side in the above description, and thus the detailed description thereof is omitted. For this reason, in the description of the negative electrode 13 side, the “positive electrode 12” in the above description is “negative electrode 13”, the “uncoated part 12b” is “uncoated part 13b”, and the “edge 121b” is “ The description will be made by replacing “metal member 40a” with “metal member 40b” and “positive terminal F1” with “negative terminal F2” in the end edge 131b.

  Then, the electrode body 11 in which the positive electrode 12 or the negative electrode 13 and the positive electrode terminal F1 or the negative electrode terminal F2 are connected via the current collecting terminals 31 is accommodated in the case C, and the opening of the case C is closed with the lid F and sealed. Thus, the secondary battery 10 is configured.

Next, the operation of this embodiment will be described.
Since each contact portion 42 of the metal member 40a is in contact with at least two layers of the positive electrode 12 forming the bent portions 21, 22, the layer of the positive electrode 12 forming the bent portions 21, 22 They are electrically connected to each other through the contact portions 42. Therefore, the current flowing through each layer of the positive electrode 12 forming the bent parts 21 and 22 flows uniformly between the respective layers of the positive electrode 12 forming the respective bent parts 21 and 22 via the respective contact parts 42. . Furthermore, the current collection terminal 31 is connected over each layer of the positive electrode 12 which forms the connection part 23. Therefore, the current flowing through each layer of the positive electrode 12 that forms the connecting portion 23 flows uniformly between the layers of the positive electrode 12 that forms the connecting portion 23 via the current collecting terminal 31. Therefore, as a whole, the part where the potential difference is generated between the layers of the positive electrode 12 is eliminated as much as possible in the electrode body 11. In addition, since the same effect | action as the said effect | action can be acquired also about the negative electrode 13 side, the detailed description is abbreviate | omitted.

In the above embodiment, the following effects can be obtained.
(1) The contact portions 42 of the metal members 40a and 40b are brought into contact so as to straddle at least two layers of the positive electrode 12 or the negative electrode 13 forming the bent portions 21 and 22. Therefore, it is possible to prevent a potential difference from occurring between the layers of the positive electrode 12 or the negative electrode 13 that form the bent portions 21 and 22, and to make the electrode reaction at each bent portion uniform. As a result, as compared with the case where the metal members 40a and 40b are not provided in the bent portions 21 and 22, the portion where the potential difference is generated between the positive electrode 12 or the negative electrode 13 layers in the entire electrode body 11 is reduced as much as possible. Thus, the electrode reaction can be made uniform for the entire electrode body 11.

  (2) A plurality of contact portions 42 are provided. Therefore, compared with the case where the contact part 42 is single, the site | part which contacts so that the layer of the positive electrode 12 or the negative electrode 13 which forms each bending part 21 and 22 may be straddled, and each bending part 21 and 22 is formed. Thus, it is possible to further prevent the potential difference from occurring between the positive electrode 12 and the negative electrode 13 layers.

  (3) The contact portions 42 are arranged radially. Therefore, each layer of the positive electrode 12 or the negative electrode 13 that forms the bent portions 21 and 22 and each contact portion 42 can be easily crossed, and each layer of the positive electrode 12 or the negative electrode 13 that forms the bent portions 21 and 22 Each contact part 42 can be made to contact easily.

  (4) The slits 43 penetrating in the thickness direction are formed in the metal plate 41 of the metal members 40 a and 40 b, and a plurality of contact portions 42 are arranged on both sides of the slit 43. Therefore, when performing indirect welding, it is possible to make it difficult for the current flowing from the welded joint portion T1 to flow toward the welded joint portion T2 via the metal plate 41. Accordingly, the current flowing from the welded joint portion T1 is made to flow in the order of the metal plate 41, the contact portion 421, the uncoated portions 12b and 13b of the positive electrode 12 or the negative electrode 13, the contact portion 422, the metal plate 41, and the welded joint portion T2. Can do. As a result, the metal members 40a and 40b and the layer of the positive electrode 12 or the negative electrode 13 forming the bent portions 21 and 22 can be joined by indirect welding.

In addition, you may change the said embodiment as follows.
In the embodiment, the configuration of the metal members 40a and 40b may be changed. For example, as shown in FIG. 8, the metal member 60 extends linearly to a flat metal plate 61 and a back surface 61 a of the positive electrode 12 or the negative electrode 13 on the uncoated portions 12 b and 13 b side of the metal plate 61. A plurality of (eight in this embodiment) contact portions 62 are formed. Each contact portion 62 extends in parallel. As shown in FIG. 9, each contact portion 62 tapers as the distance from the back surface 61 a of the metal plate 61 increases, and the tip 62 a is pointed. As shown in FIG. 8, two slits 63 are formed in the metal plate 61 as gaps penetrating in the thickness direction. A plurality of contact portions 62 are arranged on each side of the slits 63 (four in this embodiment).

  In the embodiment, the slits 43 are formed as gaps in the metal plate 41, but not limited to this, for example, arranged side by side on a straight line L 1 that passes through the thickness direction of the metal plate 41 and passes through the center of the metal plate 41. A plurality of holes may be formed as voids.

  In the embodiment, for example, the insulating member may be embedded so as to extend on the straight line L1 passing through the center of the metal plate 41 without forming the slit 43 in the metal plate 41. Also in this case, when performing indirect welding, the insulating member can make it difficult for the current flowing from the welded joint portion T1 to flow toward the welded joint portion T2 via the metal plate 41.

  In the embodiment, for example, the end edges 121b and 131b of the uncoated portions 12b and 13b and the tip 42a of the contact portion 42 may be joined by solder, or may be joined by a conductive adhesive.

(Circle) in embodiment, the number of the contact parts 42 is not specifically limited.
In embodiment, you may provide the metal members 40a and 40b only in one bending part 21, for example.

  In the embodiment, the electrode body 11 constituted by interposing a strip-shaped separator 14 between the strip-shaped positive electrode 12 and the negative electrode 13 and spirally winding them around the winding axis L is used. For example, an electrode body configured by laminating a strip-shaped separator between a strip-shaped positive electrode and a negative electrode may be used. Then, the stacked electrode body may be bent to form a bent portion, and a metal member may be disposed in the bent portion.

  In embodiment, although the electrode body 11 was formed in the flat shape (elliptical shape) which has a major axis direction, you may form not only in this but in circular shape, for example. In this case, since the curvature of the circumferential portion of the electrode body is substantially constant, the bent portion may be any portion. Preferably, the two bent portions are arranged to face each other on both sides of a center line of a circle connecting the centers of the circular electrode bodies.

  In the embodiment, the electrode body 11 may be formed in a rectangular shape or a square shape. In this case, one bent portion may be formed on one side of the rectangular or square shape, and the other bent portion may be formed on the side facing the one side.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery, 11 ... Electrode body, 12 ... Positive electrode, 13 ... Negative electrode, 21, 22 ... Bending part, 31 ... Current collecting terminal, 40a, 40b, 60 ... Metal member, 42, 421, 422, 62 ... Contact Part, 43, 63... Slit as a gap.

Claims (4)

A secondary battery comprising an electrode body formed by insulating between a positive electrode and a negative electrode and winding or laminating them, and a collector terminal provided on each of the positive electrode and the negative electrode,
The electrode body has at least one bent portion where the positive electrode and the negative electrode forming the electrode body are bent,
The secondary battery, wherein the bent portion is provided with a metal member having at least one contact portion that contacts at least two layers of the positive electrode or the negative electrode.   The secondary battery according to claim 1, wherein a plurality of the contact portions are provided.   The secondary battery according to claim 1, wherein the contact portions are arranged radially.   The said metal member is formed with the space | gap which penetrates the thickness direction, and each contact part is multiply arranged by the both sides which pinched | interposed the said space | gap, The Claim 2 or Claim 3 characterized by the above-mentioned. Secondary battery.

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