JP2011009118A - Coin type secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent peeling-off between the upper and lower films to form a separator while making sure to exhaust air residual in the bag-shaped separator.SOLUTION: As for a coin-shaped secondary battery, a laminate type electrode body 3 in which a positive electrode 7 and a negative electrode housed in the round bag-shaped separator 9 are alternately laminated is housed in a flat and round battery container. From a positive electrode current collector of the positive electrode 7, a positive electrode lead 71a is led out from the separator 9 extending toward one side of the electrode body 3. From a negative current collector of the negative electrode, a negative electrode lead 81a is extended toward the other side of the electrode body 3. In the peripheral part 14 of the bag-shaped separator 9, three pieces of non-adhered parts 15A, 15B are installed in a dispersed state at positions except the counter position 9c of the negative electrode lead 81a in order to exhaust the air in the bag-shaped separator 9.

Description

  The present invention relates to a coin-type secondary battery in which a laminated electrode body and a non-aqueous electrolyte are accommodated in a flat round battery container.

  For example, Patent Document 1 is known as a coin-type secondary battery of this type. In that case, a sealing plate (sealing can) is attached to the opening of the battery can (exterior can) via a gasket, and a flat round battery container is constructed by caulking and sealing the periphery of the opening. A battery case and a non-aqueous electrolyte are accommodated in the battery container. The electrode body has a positive electrode in which a positive electrode active material such as lithium cobaltate is applied on both sides of a positive electrode current collector made of aluminum foil, and a negative electrode active material such as a coke baked product applied to a negative electrode current collector made of copper foil. The negative electrodes thus formed are alternately laminated via sheet-like polyethylene separators. In addition, the positive electrode lead extended from each positive electrode current collector is electrically connected to the inner surface of the battery can, and the negative electrode lead extended from each negative electrode current collector is electrically connected to the inner surface of the sealing plate.

  As another structure of the electrode body having a laminated structure, for example, as shown in Patent Document 2, a separator is formed in a flat bag shape, and a positive electrode is accommodated in the bag-shaped separator. Specifically, after sandwiching the positive electrode between two polypropylene films, which are separator materials, and then bonding (welding) the peripheral edges of the films together, Contains the positive electrode. When the positive electrode is accommodated in the bag-like separator as described above, the contact between the positive electrode and the negative electrode is more reliably compared to the configuration in which a sheet-like separator is sandwiched between the positive electrode and the negative electrode as in Patent Document 1. Can be prevented.

  By the way, in the case where the positive electrode is accommodated in the bag-shaped separator, air (dry air not containing moisture) may remain in the separator. When the battery is assembled with air remaining in this way, the contact area between the positive electrode active material and the electrolytic solution is reduced by the amount of the air, the battery reaction is inhibited, and the battery capacity is reduced. Further, lithium may be deposited at the boundary between the air and the positive electrode.

  As a countermeasure, it is conceivable to provide 10 or more non-adhesive portions (14 in Patent Document 2) when the peripheral edges of the upper and lower films are bonded to each other as in Patent Document 2. According to this, since the air in a separator is discharged | emitted from a non-bonding part, it can prevent that air remains in a separator.

Japanese Patent Laying-Open No. 2005-310577 (FIG. 1-2) JP 2008-091100 A (paragraph number 0026, FIG. 1)

  However, when the number of non-adhered portions is 10 or more as in Patent Document 2, the adhesiveness between the upper and lower films is lowered, and there is a possibility that peeling occurs between these films. In this case, the positive electrode and the negative electrode may be short-circuited.

  The present invention addresses such problems, and can reliably prevent the air remaining in the bag-shaped separator from being discharged while suppressing the occurrence of peeling between the upper and lower films forming the separator. The purpose is to.

  In order to achieve the above object, a coin-type secondary battery according to the present invention has a sealed can 6 attached to an opening of an outer can 4 via a gasket 5 as shown in FIG. The battery container 2 has a flat round battery container 2 sealed by caulking the peripheral edge, and a plurality of stages of positive electrodes 7 and negative electrodes 8 accommodated in a circular bag-shaped separator 9 are alternately arranged in the battery container 2. A laminated electrode body 3 and a non-aqueous electrolyte are accommodated, and the positive electrode 7 is formed by forming a positive electrode active material layer 72 on both surfaces of a positive electrode current collector 71, A positive electrode lead 71 a extends from the body 71 toward one side of the electrode body 3 and is led out from the separator 9, and the negative electrode 8 is formed by forming a negative electrode active material layer 82 on a negative electrode current collector 81. The negative electrode lead 81 a extends from the negative electrode current collector 81 toward the other side of the electrode body 3. The bag-shaped separator 9 is formed by sandwiching the positive electrode 7 between two films 12 and 12 that are the material of the separator 9 and bonding the peripheral edges of the films 12 and 12 to each other. 2 to 5 non-adhesive portions 15A and 15B for discharging air in the bag-like separator 9 are dispersed on the peripheral edge portion 14 of the separator 9 in a position excluding the opposing position 9c of the negative electrode lead 81a. It is characterized by being provided in a shape. The air here includes, for example, dry air not containing moisture, inert gas, and the like. Adhering the peripheral portions of the films 12 and 12 includes directly adhering the peripheral portions of the upper and lower films 12 and 12 and adhering them with a synthetic resin film or the like interposed therebetween. The adhesion includes adhesion by heat welding, adhesion by an adhesive, and the like.

  One of the non-adhesive portions 15A and 15B can also serve as a lead-out portion 9b for leading the positive electrode lead 71a out of the separator 9.

  The binding tape 13 is wound around the outer periphery of the electrode body 3 in a direction orthogonal to the extending direction of the positive electrode lead 71a and the negative electrode lead 81a, and the non-adhesive portions 15A and 15B are bound at the peripheral portion of the bag-like separator 9. The tape 13 may be provided at a position other than the arrangement position 9d.

  In the coin-type secondary battery according to the present invention, two to five non-adhesive portions 15A and 15B are dispersed in the peripheral portion 14 of the bag-shaped separator 9 at positions excluding the facing position 9c of the negative electrode lead 81a. Provided. According to this, even when air remains in the separator 9 during the operation of housing the positive electrode 7 in the bag-shaped separator 9, the non-adhesive portions 15A, 15A,. It can be quickly and reliably discharged out of the separator 9 through 15B. Therefore, due to the assembly of the coin-type secondary battery 1 with air remaining in the separator 9, the contact area between the positive electrode active material layer 72 and the non-aqueous electrolyte decreases due to the residual air, and the battery reaction It is possible to eliminate the inconvenience that is hindered and to reliably prevent the battery capacity from decreasing. Further, it is possible to prevent lithium from being deposited at the boundary portion between the air and the positive electrode active material layer 72 of the positive electrode 7.

  In addition, since the number of non-adhesive portions 15A and 15B is two or more, the residual air in the separator 9 can be reliably discharged. In addition, by making the number five or less, the size of the adhesive portion 16 becomes too small, the adhesiveness between the upper and lower films 12 and 12 is deteriorated, and the peeling between these films 12 and 12 is surely prevented. can do. When the non-adhesive portions 15A and 15B are provided at positions excluding the facing position 9c of the negative electrode lead 81a, the non-adhesive portion 15B is not blocked by the negative electrode lead 81a. Therefore, there is no inconvenience that the discharge of residual air in the separator 9 is hindered by the presence of the negative electrode lead 81a.

  When one of the non-adhesive portions 15A and 15B also serves as a lead-out portion 9b essential for leading the positive electrode lead 71a out of the separator 9, the lead-out portion 9b can also be used for discharging air in the separator 9. The residual air in 9 can be discharged more quickly.

  When the non-adhesive portions 15A and 15B are provided in the peripheral portion 14 of the bag-like separator 9 except for the arrangement position of the binding tape 13, the non-adhesive portions 15A and 15B are closed by the binding tape 13. It is possible to reliably prevent the residual air in the separator 9 from being easily discharged.

It is a top view of the bag-shaped separator which concerns on the coin-type secondary battery of this invention. It is a longitudinal cross-sectional view which shows the whole structure of a coin-type secondary battery. It is a longitudinal cross-sectional view which shows a part of coin-type secondary battery. It is an exploded view of a coin-type secondary battery. It is a perspective view which shows the state before forming a separator in a bag shape.

  1 to 5 show an embodiment in which a coin-type secondary battery of the present invention is applied to a lithium ion secondary battery. As shown in FIGS. 2 and 3, the coin-type secondary battery 1 contains a vertically stacked electrode body 3 and a non-aqueous electrolyte (not shown) in a flat round battery container 2. Has been.

  The battery container 2 is sealed (crimped) by attaching a sealing can 6 to the opening of the outer can 4 via a gasket 5 and caulking the peripheral edge of the opening. That is, the battery container 2 includes a flat round dish-shaped outer can 4 whose peripheral edge 4a is bent upward in FIG. 2, and a flat round dish-shaped sealing can 6 whose peripheral edge 6a is bent downward in FIG. The outer can 4 and the sealing can 6 are caulked and sealed through a gasket 5 disposed between the peripheral portions 4a and 6a of the both. The lower end portion of the peripheral edge portion 6a of the sealing can 6 is processed into an inner and outer double helix fold. The outer can 4 and the sealed can 6 are made of stainless steel. The gasket 5 is formed of a synthetic resin that is an insulator.

  The electrode body 3 is configured by laminating a plurality of substantially circular positive electrodes 7 accommodated in a substantially circular flat bag-shaped separator 9 and a substantially circular negative electrode 8 alternately in the vertical direction. Each separator 9 is made of a microporous thin film made of polyethylene having excellent insulating properties, and is capable of transmitting lithium ions. In the illustrated example, the number of stacked layers of the positive electrode 7 and the negative electrode 8 is drawn only for the sake of simplicity, but in actuality, approximately seven stacked layers are employed. However, it is needless to say that the number of stages is not limited to this.

  Negative electrodes 8A and 8B are disposed at both ends (upper and lower ends in FIG. 3) of the electrode body 3 in the stacking direction. Except for the negative electrodes 8A and 8B located at the upper and lower ends, the negative electrode 8 is provided with a negative electrode active material layer 82 containing a negative electrode active material such as graphite on both upper and lower surfaces of a negative electrode current collector 81 made of copper foil. Yes. Specifically, in the negative electrode 8A located at the upper end of the electrode body 3 in the state of FIG. 3, the negative electrode active material layer 82 is provided only on the lower surface side of the negative electrode current collector 81, and the upper surface on the opposite side is exposed. In contact with the inner surface of the sealing can 6. In the negative electrode 8 </ b> B located at the lower end of the electrode body 3, the negative electrode active material layer 82 is provided only on the upper surface side of the negative electrode current collector 81. Between the negative electrode current collector 81 of the negative electrode 8 </ b> B on the lower end side of the electrode body 3 and the inner bottom surface 4 b of the outer can 4, an insulating seal 10 made of tape or the like formed of polyethylene terephthalate (PET) or polyimide is disposed. Has been.

  Each positive electrode 7 is provided with a positive electrode active material layer 72 containing a positive electrode active material such as lithium cobaltate on both upper and lower surfaces of a positive electrode current collector 71 made of aluminum foil. Then, as shown in FIG. 5, the positive electrode 7 is sandwiched from above and below by two polyethylene films 12 and 12 which are materials of the separator 9, and punched into a substantially circular shape in that state, and the punched top and bottom Each of the positive electrodes 7 is accommodated in a bag-like separator 9 by bonding the peripheral portions of the films 12 and 12 directly or by heat welding or the like with a film made of polyethylene terephthalate (PET) interposed therebetween (FIG. 1). State). In each positive electrode current collector 71, a positive electrode lead 71 a made of an aluminum foil integrated with the positive electrode current collector 71 extends toward one side of the electrode body 3 (left side in FIG. 2). It is derived from the separator 9. The tips of the positive leads 71a are electrically connected to the inner bottom surface 4b of the outer can 4 in the illustrated coin-type secondary battery 1 by an ultrasonic welding method or the like (see FIG. 3).

  From the negative electrode current collector 81 of each of the negative electrodes 8, 8A and 8B, a negative electrode lead 81a made of copper foil integral with the negative electrode current collector 81 is on the other side of the electrode body 3 (on the opposite side to the lead-out direction of the positive electrode lead 71a). To the right). These negative electrode leads 81a are connected to each other by an ultrasonic welding method or the like in a state where their tips are grouped together. As described above, the negative electrode current collector 81 of the negative electrode 8 </ b> A on the upper end side of the electrode body 3 is in contact with the inner surface of the sealing can 6, whereby the negative electrodes 8, 8 </ b> A and 8 </ b> B are electrically connected to the sealing can 6. .

  As shown in FIGS. 1 and 4, a binding tape 13 made of polypropylene having chemical resistance is disposed on the outer periphery of the electrode body 3 in a direction orthogonal to the direction in which the leads 71 a and 81 a extend (hereinafter, this orthogonal direction is The free end is bonded to the outer periphery of the electrode body 3 in this state. By attaching the binding tape 13, the bag-shaped separator 9 and the negative electrode 8 that accommodate the positive electrode 7 are prevented from being displaced.

  In the peripheral portion 14 of the bag-shaped separator 9, as shown in FIG. 1, a non-adhesive portion 15A is formed in a lead-out portion (left side in FIG. 1) 9b for leading the positive electrode lead 71a out of the separator 9. . Further, in the peripheral portion 14 of the separator 9, the portion between the facing position (right side in FIG. 1) 9 c facing the negative electrode lead 81 a and the arrangement position (front and rear positions in FIG. 1) 9 d and 9 d of the binding tape 13 is A pair of non-adhesive portions 15B and 15B are formed. That is, three non-adhesive portions 15A and 15B that are not bonded are dispersedly formed on the peripheral edge portion 14 of the separator 9. Of the peripheral edge portion 14 of the separator 9, the portions (adhesive portions) 16 excluding the three non-adhesive portions 15A and 15B are all adhered. The total size of the outer edges 17 of the three non-adhesive portions 15 </ b> A and 15 </ b> B is set to about 20% of the total dimensions of the outer edge 9 a of the separator 9.

  Assembling the coin-type secondary battery 1 with the flat circular dish-shaped sealing can 6 facing down (in other words, with the opening of the sealing can 6 facing upward) in reverse to the state of FIG. 5 and then inject non-aqueous electrolyte. Subsequently, after assembling the outer can 4 in which the electrode body 3 is previously attached in a predetermined state, the caulking is sealed. Specifically, this is performed as follows.

  First, the gasket 5 is attached to the peripheral edge 6 a of the sealing can 6 with the opening of the sealing can 6 facing upward. Then, the electrode body 3 is temporarily fixed to the inner bottom surface 4 b side of the outer can 4 with an insulating seal 10. At this time, the positive electrode lead 71 a of the electrode body 3 is ultrasonically welded to the inner bottom surface 4 b of the outer can 4. Next, after injecting a non-aqueous electrolyte into the sealing can 6 fitted with the gasket 5, the outer can 4 with the opening facing downward is fitted on the outer side of the gasket 5, and then the peripheral edge of the outer can 4 Caulking is performed with the portion 4a facing inward.

With this caulking process, the gasket 5 is compressed, and the gap between the outer can 4 and the sealing can 6 is sealed by the gasket 5. Further, air remaining in the bag-like separator 9 (dry air not containing moisture) is discharged out of the separator 9 through the three non-adhesive portions 15A and 15B, and the gasket 5 and the outer can 4 It is discharged out of the battery through the gap. Thus, the outer can 4 and the sealing can 6 are caulked and sealed with the gasket 5 interposed therebetween, and the coin-type secondary battery 1 of the present invention shown in FIG. 2 can be obtained. As the non-aqueous electrolyte solution, for example, it can be used those obtained by dissolving LiPF ₆ in a solvent mixture of ethylene carbonate and methyl ethyl carbonate.

  As described above, when the non-adhesive portions 15A and 15B are provided on the peripheral edge portion 14 of the separator 9, even if air remains in the separator 9, the residual air passes through the non-adhesive portions 15A and 15B during the caulking process. Can be discharged out of the separator 9. Therefore, due to the assembly of the coin-type secondary battery 1 with air remaining in the separator 9, the contact area between the positive electrode active material layer 72 and the non-aqueous electrolyte decreases due to the residual air, and the battery reaction It is possible to eliminate the trouble that hinders the battery capacity and to reliably prevent the battery capacity from decreasing. Further, it is possible to prevent lithium from being deposited at the boundary between the air and the positive electrode active material layer 72 of the positive electrode 7.

  In order to avoid the non-adhesive portion 15B from being blocked by the binding tape 13, the non-adhesive portion 15B was formed avoiding the arrangement position 9d of the binding tape 13. Further, in order to prevent the non-adhesive portion 15B from being blocked by the negative leads 81a connected to each other in a state where the tips are grouped together, the non-adhesive portion 15B is formed so as to avoid the opposing position 9c of the negative lead 81a. did. If two or more non-adhesive portions 15A and 15B are provided including the lead-out portion 9b from which the positive electrode lead 71a is led out from the bag-like separator 9, the air in the separator 9 can be reliably discharged. On the other hand, by setting the number to 5 or less, it is possible to prevent the size of the adhesive portion 16 from becoming too small and the adhesiveness between the upper and lower films 12 and 12 to be lowered, and peeling between these films 12 and 12 can be prevented. . That is, it is preferable that two to five non-adhesive portions 15A and 15B are provided in a distributed manner in the peripheral edge portion 14 of the separator 9.

  The total dimension of the outer edges 17 of the non-adhesive portions 15A and 15B is preferably set to 15 to 60% (15% or more and 60% or less) of the entire dimensions of the outer edge 9a of the separator 9. This is combined with the fact that the total size of the outer edges 17 of the non-adhesive portions 15A and 15B is set to 15% or more of the total size of the outer edge 9a of the separator 9, thereby reducing the number of non-adhesive portions 15A and 15B to two or five. Thus, it is possible to more reliably prevent the air in the separator 9 from being properly discharged during the caulking process. By setting it to 60% or less, combined with two or five non-adhesive portions 15A and 15B, the size of the adhesive portion 16 becomes too small, and the upper and lower films 12 and 12 are bonded to each other. It is possible to prevent the positive electrode 7 from protruding from the non-adhesive portions 15A and 15B to the outside of the separator 9 and to contact the negative electrode 8.

  Of the peripheral edge portion 14 of the separator 9, a non-adhesive portion may be formed at a portion between the lead-out portion 9b and the arrangement positions 9d and 9d of the binding tape 13. In the illustrated example of the coin-type secondary battery 1, the outer can 4 is on the positive electrode side and the sealing can 6 is on the negative electrode side, but the coin can is on the positive electrode side and the outer can 4 is on the negative electrode side. Needless to say, the present invention can also be applied to the secondary battery 1.

DESCRIPTION OF SYMBOLS 1 Coin type secondary battery 2 Battery container 3 Electrode body 4 Exterior can 5 Gasket 6 Sealing can 7 Positive electrode 8 Negative electrode 9 Separator 9b Lead-out part 9c Opposite position 12 Film 13 Binding tape 15A / 15B Non-adhesive part 16 Adhesive part 71 Positive electrode current collection Body 71a positive electrode lead 72 positive electrode active material layer 81 negative electrode current collector 81a negative electrode lead 82 negative electrode active material layer

Claims (3)

It has a flat round battery container sealed by attaching a sealing can to the opening of the outer can via a gasket and caulking the peripheral edge of the opening,
In the battery container, a stacked electrode body and a non-aqueous electrolyte solution, in which a plurality of positive and negative electrodes stored in a circular bag-shaped separator are stacked, are stored,
The positive electrode is formed by forming a positive electrode active material layer on both surfaces of a positive electrode current collector, and a positive electrode lead extends from the positive electrode current collector toward one side of the electrode body and is led out from the separator. And
The negative electrode is formed by forming a negative electrode active material layer on a negative electrode current collector, and a negative electrode lead extends from the negative electrode current collector toward the other side of the electrode body,
The bag-shaped separator is formed by sandwiching the positive electrode with two films that are materials of the separator, and bonding the peripheral portions of the films to each other.
Two to five non-adhesive portions for discharging the air in the bag-shaped separator are provided in a distributed manner on the periphery of the bag-shaped separator at positions other than the position where the negative electrode lead is opposed. A coin-type secondary battery characterized by having   2. The coin-type secondary battery according to claim 1, wherein one of the non-adhesive portions also serves as a lead-out portion for leading the positive electrode lead out of the separator. On the outer periphery of the electrode body, a binding tape is wound in a direction orthogonal to the extending direction of the positive electrode lead and the negative electrode lead,
3. The coin-type secondary battery according to claim 1, wherein the non-adhesive portion is provided at a position excluding a position where the binding tape is arranged at a peripheral portion of the bag-shaped separator.

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