JP4830267B2 - Laminated battery - Google Patents

Description

  The present invention relates to a battery in which a power generation element is sealed with a laminate film (hereinafter referred to as “laminate battery”). More specifically, the present invention relates to a laminate battery having high peel strength at the seal portion of the laminate film.

  In recent years, laminated batteries are attracting attention as power sources not only for electronic devices such as portable PCs and mobile phones, but also for hybrid vehicles and electric vehicles. In this laminate battery, a power generation element (electrode body, electrolyte, etc.) is sealed with a laminate film. FIG. 9 is a diagram illustrating a state before sealing the laminated battery. The laminate film 2 is provided with a storage portion 21 for storing the power generation element 1 and a flange portion 25 for sealing the power generation element 1 by heat welding. The power generation element 1 is disposed in the storage portion 21, and the power generation element 1 is sealed by sealing the flange portion 25 along the edge of the storage portion 21 without a gap.

  Specifically, as shown in FIG. 10, the power generating element 1 is wrapped with a laminate film 2 from the front surface and the back surface, and a seal head is set along the edge of the storage portion 21 of the laminate film 2. Then, the flange portion 25 of the laminate film 2 is heated and pressed by the seal head, whereby the adhesive layer of the laminate film 2 is melted and sealed (hereinafter, the heat-welded portion is referred to as a “heat seal portion”). ).

  As a battery in which the power generation element is sealed with the laminate film as described above, for example, there is a battery disclosed in Patent Document 1. In this battery, the laminate film is sealed by a seal head provided with a step. For this reason, the thickness of the adhesive layer of the heat seal portion is thick on the inner side (power generation element storage space side) and thin on the outer side (laminate film end side). As a result, the moisture resistance of the laminate battery and the peel strength of the laminate film are improved.

  In addition, the power generation element may generate a large amount of gas when there is an abnormality such as overcharge or short circuit, and the storage space pressure (hereinafter referred to as “internal pressure”) may increase rapidly. Also, the internal pressure may increase due to changes in the operating environment temperature. Therefore, in the laminated battery, a gas discharge part is provided in a part of the flange part as a safety mechanism for safely discharging the generated gas. This gas discharge part has a structure that can release the generated gas when the internal pressure rises to a predetermined value or more by the generated gas. As a result, when the internal pressure rises due to an overcharged state, the gas discharge unit is opened and the gas filled in the storage space of the power generation element can be safely discharged.

As such a laminated battery provided with a gas discharge part, there is a battery disclosed in Patent Document 2, for example. In this battery, as shown in FIG. 11, the seal width of a part of the heat seal portion 22 (shaded portion in FIG. 11) of the laminate film 2 is narrower than the other heat seal portions 22. A portion of the flange portion of the laminate film 2 where the seal width is narrow is used as the gas discharge portion 40. And when the internal pressure of a laminated battery rises, the heat seal part 22 of the gas discharge part 40 peels off rapidly, and it is supposed that it will be in an open state. As a result, the gas filled in the storage space of the power generation element can be safely discharged.
JP 2001-199413 A JP 2001-93483 A

  However, the laminate battery shown in FIG. 10 has the following problems. That is, when the laminate film 2 is thermally welded, the adhesive resin of the laminate film 2 is extruded from the edge of the heat seal portion 22. For this reason, when the laminate film 2 is sealed without any gap along the edge of the storage portion 21, a large amount of adhesive resin is extruded from the end of the heat seal portion 22 toward the inside. FIG. 12 is a diagram illustrating a state within a broken line frame B of the laminated battery illustrated in FIG. 10. As shown in FIG. 12, the resin portion 8 formed by extruding the adhesive resin protrudes greatly to the inner side. In order to improve the moisture resistance of the heat seal part 22, it is necessary to make the layer thickness of the adhesive layer as thin as possible, and when the laminate film 2 is thermally welded, the layer thickness of the adhesive layer should be made as thin as possible. Pressure. Therefore, the amount of protrusion of the resin portion 8 increases as the thickness of the adhesive layer is reduced.

  When the resin portion 8 protrudes to the inner side, a notch-shaped portion 28 is formed by the protruding portion of the resin portion 8 and the laminate film 2. When the internal pressure increases, stress concentrates on the notch-shaped portion 28. Therefore, the peel strength of the heat seal portion 22 is lowered because of the notched portion 28. In the laminated battery disclosed in Patent Document 1, the amount of the adhesive resin protruding is small by the level difference of the seal head, but the protrusion itself is not suppressed. For this reason, it has not yet been possible to suppress a decrease in peel strength.

  Further, as shown in FIG. 11, even if a gas discharge portion 40 having a narrow seal width compared to other portions is provided in a part of the heat seal portion 22, the gas discharge portion 40 is surely secured when the internal pressure increases. It is not always open. This is considered to be because, if there is a notch-shaped part (see FIG. 12) due to protrusion of the adhesive resin in a part other than the gas discharge part 40, the peel strength is lower than that in the gas discharge part 40 at that part. . Therefore, when the internal pressure of the laminated battery rises, an unexpected part may be opened, making it difficult to collect exhaust gas.

  The present invention has been made to solve the problems of the conventional laminate battery described above. That is, an object of the present invention is to provide a laminate battery that can improve the peel strength of the heat seal part and reliably recover the gas generated inside the battery.

A laminate battery made for the purpose of solving this problem has a power generation element and a laminate film that wraps the power generation element, wraps the power generation element from its front and back surfaces with a laminate film, and seals the edges of the laminate film. A laminated battery for sealing a power generation element by means of a laminate film, wherein the laminate film has a storage part for storing the power generation element and a flange part located at the edge of the storage part, and the flange part is on the edge of the flange part. Positioned, enclosing the power generation element from at least 3 sides, and sealed processing part that is sealed with adhesive resin, and is located closer to the storage part than the seal processing part, and encloses the power generation element from at least 3 directions and is not sealed a non-sealing processing unit, a part of the flange portion, the second seal pressurizing the sealed fabricated from edge of the flange portion to the edge of the housing part And a part, the resin portion by protruding from the sealing processing of the adhesive resin to the power generating element side, non-sealing process located in portion, the second by extrusion of the power generating element side from the second seal processing portion of the adhesive resin The resin part is located in a storage space by the storage part .

  That is, in the laminated film battery of the present invention, the power generating element is sealed by performing a sealing process such as heat welding on the flange portion. The flange portion is provided with a seal processing portion that is sealed and a non-seal processing portion that is positioned closer to the power generation element than the seal processing portion. That is, when sealing the flange portion, a non-sealed portion that is not pressurized is provided by performing a sealing process with a gap between the storage portion and the seal head. This gap is at least 1.5 mm. By providing such a gap, that is, a non-sealed portion, it is possible to prevent the resin portion due to the protrusion of the adhesive resin from protruding into the storage space of the power generation element. Therefore, a decrease in the peel strength at the sealed portion is suppressed.

  More specifically, it has a resin part in which the adhesive resin of the laminate film protrudes from the seal processing part to the storage part side, and the end of the resin part on the power generation element side is located in the non-seal process part. The seal processing is done. By performing such a sealing process, the protruding portion of the adhesive resin, that is, the resin portion does not protrude into the storage space of the power generation element. Therefore, a notch-shaped portion due to the protrusion of the resin portion is not formed, and a decrease in the peel strength of the sealed portion is suppressed.

In addition, a part of the flange portion of the laminate film battery of the present invention is provided with a second seal processing portion that is sealed from the edge of the flange portion to the edge of the storage portion, and power generation from the second seal processing portion of the adhesive resin. The 2nd resin part by the protrusion to the element side is located in the storage space by a storage part .

  That is, in the laminated film battery of the present invention, the second sealing portion is provided with a portion where the width of the non-sealing portion is narrower than the width of the non-sealing portion of other portions. That is, when sealing the flange portion, the second seal processing portion is sealed by narrowing the gap between the storage portion and the heat seal portion. As a result, the adhesive resin is pushed out to the storage space of the power generation element for the second seal processing portion. Therefore, the peel strength of the seal processing portion is reduced for the second seal processing portion. That is, a part having a low peel strength is intentionally provided in the flange part. By using this second sealing portion as a gas discharge portion, the internal gas can be reliably recovered when the internal pressure of the laminated battery increases.

  More specifically, there is a second resin portion in which the adhesive resin of the laminate film protrudes from the second seal processing portion to the storage portion side, and the end of the second resin portion on the power generation element side is the storage portion. The seal processing is made so as to be located in the storage space. Since the sealing process is performed as described above, the protruding portion of the adhesive resin, that is, the second resin portion protrudes from the storage space of the power generation element at the second sealing portion. Therefore, a notch-shaped portion is formed by the protrusion of the second resin portion, and the peel strength is reduced in the second seal processing portion. Therefore, the gas generated inside the battery can be reliably recovered by using the second seal processing part as the gas discharge part.

  According to the present invention, by providing the non-sealing part between the sealing part and the power generation element, it is possible to suppress the adhesive resin of the laminate film from protruding into the storage space of the power generation element. Therefore, the peel strength of the sealed portion is improved. In addition, by providing a portion where the width of the non-sealed portion is narrower than the width of the non-sealed portion of the other portion as the second sealed portion, a portion having a lower peel strength than the sealed portion is intended. Can be provided. By using this second sealing part as a gas discharge part, it is possible to provide a gas discharge part that reliably opens when the internal pressure increases. Therefore, a laminate battery has been realized that can improve the peel strength of the heat seal part and reliably recover the gas generated inside the battery.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, the present invention is applied to a laminated battery in which a secondary battery such as a lithium battery is enclosed in a laminated film.

  As shown in FIG. 1, the laminate battery 100 of this embodiment includes a power generation element 1 and bipolar terminals 12 and 13 protruding from the power generation element 1, and these are wrapped in a laminate film 2. The power generation element 1 is formed in a flat shape by winding a bipolar sheet with a separator interposed therebetween. Bipolar terminals 12 and 13 are connected to the bipolar sheets of the power generation element 1, respectively. Further, the bipolar terminals 12 and 13 also protrude from the laminate film 2. The laminate film 2 has a resin coated on both surfaces of a metal foil, and one resin layer functions as an adhesive layer and the other resin layer functions as a surface protective layer. Moreover, the edge of the laminate film 2 is heat-welded, and the power generation element 1 is sealed. These configurations are common for laminated batteries.

  Specific examples of each member constituting the power generation element 1 include, for example, lithium cobalt oxide as a positive electrode sheet, graphitized carbon material as a negative electrode sheet, a resin such as polyethylene as a separator, and a lithium salt as an electrolytic solution. Organic solvents are used. The laminate film 2 has an aluminum foil with a thickness of about 40 μm as a substrate, an adhesive layer of polypropylene (PP) or polyethylene (PE) with a thickness of about 80 μm on one side, and a thickness of about 25 μm on the other side. Each is coated with a surface protective layer such as polyamide. The laminate film 2 is disposed so that the inner side (the side where the power generation element 1 is accommodated) is an adhesive layer and the outer side is a surface protective layer.

  FIG. 2 is a side view of the laminated battery 100 shown in FIG. As shown in FIG. 2, the laminate film 2 of the laminate battery 100 is provided with a storage portion 21 formed by embossing and a flange portion 25 located on the edge of the storage portion 21. That is, the power generation element 1 is sealed by wrapping the power generation element 1 from the front and back surfaces in the storage portion 21 and thermally welding the flange portion 25. In the flange portion 25, a portion where the heat welding is performed is referred to as a heat seal portion 22 (shaded portion in FIG. 1), and a portion where the heat welding is not performed is referred to as a non-sealing portion 23.

  Specifically, in this embodiment, heat pressing is performed on the flange portion 25 of the laminate film 2. Further, pressurization is performed until the film thickness of the entire heat seal portion 22 reaches 200 μm. Thereby, the adhesive layers of the laminate film 2 are thermally welded. And in this form, as shown in FIG. 3, the clearance gap L is provided between the accommodating part 21 and the heat seal part 22 (seal head) of the laminate film 2, and it pressurizes. The size of the gap L is adjusted by the thickness of the adhesive layer of the laminate film 2 and the pressure applied by the seal head. In this embodiment, the range of 1.5 mm to 3.0 mm is appropriate.

  FIG. 4 shows a state in a broken line frame A of the laminated battery shown in FIG. As shown in FIG. 4, the adhesive resin protrudes from the heat seal portion 22 to form the resin portion 8. An end 81 on the inner side of the resin 8 is located in the gap L, that is, in the non-sealed portion 23. Further, the size of the gap L is such that after the laminate film 2 is sealed, the resin 8 does not protrude into the storage space of the power generation element 1, that is, a notch-shaped portion (see FIG. 12) due to the protrusion of the resin 8 is not formed. Designed to. Since the shape of the end 81 on the inner side of the resin layer 8 is an arc shape, the flatness is higher than that of the notch shape. Moreover, since the laminate film 2 bends to the outside when the internal pressure increases, the flatness becomes higher. For this reason, concentration of stress is avoided, and a decrease in peel strength of the heat seal portion 22 is suppressed.

  Further, as shown in FIG. 1, a gas discharge portion 4 is provided in a part of the flange portion 25 of the laminate film 2. The gas discharge unit 4 has a structure in which the heat seal portion of the gas discharge unit 4 is torn when the internal pressure reaches a predetermined value (in this embodiment, 0.55 MPa, hereinafter referred to as “open pressure”). . Thereby, when the decomposition gas of the electrolyte is generated due to the overcharge state, the gas discharge part 4 is opened when the internal pressure reaches the open pressure, and the gas filled in the storage space of the power generation element 1 is safely released. be able to.

  Specifically, the gas discharge part 4 of this embodiment is a part that is a part of the flange part 25 and is sealed to the edge of the storage part 21. That is, the laminate film 2 is sealed with a gap L of about 1.5 mm to 3.0 mm with respect to the edge of the storage portion 21 at a portion other than the gas discharge portion 4 of the flange portion 25. Therefore, there is an unsealed portion 23 having a width of about 1.5 mm to 3.0 mm. On the other hand, the gas discharge part 4 is sealed without providing such a gap. Therefore, the width of the non-sealed portion 23 is very narrow. Therefore, the resin part 8 due to the protrusion of the adhesive resin does not protrude toward the storage space in the part other than the gas discharge part 4 (see FIG. 4), and the peel strength of the heat seal part 22 is high. On the other hand, in the gas discharge part 4, the resin part 8 protrudes to the storage space side (see FIG. 12), and its peel strength is low. Therefore, in the flange part 25, a location with a low peel strength and a location with a high peel strength can be reliably created.

  Next, the results of peel strength experiments on the laminate battery of this embodiment and the conventional laminate battery will be described. In this experiment, the sealed laminate film was pulled from both ends, and the force required for adhesive failure was measured. The test laminated battery was sealed by applying a pressure of 1 MPa from both sides of the heat seal part at 190 ° C. for 4 seconds. The width of the non-sealed part shall be 2.0 mm.

  FIG. 5 shows the results of the peel strength test. In the case of a type in which a gap is not provided between the laminate film storage portion and the heat seal portion as in the conventional laminate battery (see FIG. 11), a force of about 7.4 kgf / 15 mm is required. On the other hand, in the case of a type in which a gap is provided between the laminate film storage portion and the heat seal portion as in the laminate battery of this embodiment (see FIG. 1), a force of about 12.3 kgf / 15 mm is required. there were. From this result, it was found that the laminate battery of this embodiment had higher tensile strength, that is, peel strength than the conventional laminate battery.

  Next, the results of the breakdown voltage experiment on the laminate battery of this embodiment and the conventional laminate battery will be described. In this experiment, we confirmed the function and function of the gas discharge part by confirming the destruction pressure and the destruction part of the laminate battery. The test laminate battery was sealed by applying pressure from the both sides of the heat seal part to 200 μm until the film thickness of the entire heat seal part was 200 μm (approximately 30 seconds). It is. The width of the non-sealed portion is 3.0 mm.

  FIG. 6 is a diagram showing an outline of the destructive pressure test. In the destructive pressure test, the test laminate battery 50 is disposed at a predetermined position, and the test laminate battery 50 and the air pipe 54 are connected. As shown in FIG. 7, the test laminate battery 50 is sandwiched between a pair of aluminum restraint plates 51 and 52, and the squares of the aluminum restraint plates 51 and 52 are fastened with bolts and fixed. It is in the state. Of the laminate battery 50 to be tested, the flange portion 55 is open.

  In the destructive pressure test, the test laminate battery 50 and the air pipe 54 are connected, and then the test laminate battery 50 is covered with a safety cover 53 and gradually pressurized with a pressure regulator. Then, the internal pressure of the test laminate battery 50 gradually increases, and the test laminate battery 50 is destroyed. And the pressure at the time of destruction of the test laminated battery 50 is measured with a pressure sensor, and the pressure value is displayed on the pressure indicator. Thereby, the breakdown pressure value and the variation of the test laminate battery 50 were verified. Further, the broken portion of the laminate battery 50 to be tested is checked by visual observation by separating the aluminum restraint plates 51 and 52. As a result, it was verified whether or not destruction occurred in the gas discharge section.

  FIG. 8 shows the result of this breakdown voltage test. In the type of conventional laminated battery (see FIG. 11), the heat seal part is provided with no gap with respect to the storage part, the non-seal part is provided in a part of the heat seal part, and the part is a gas discharge part. , Opening rate at the gas discharge part was very low at 40%. This is because the resin part protrudes from the inside of the part other than the gas discharge part and a notch-shaped part is formed. On the other hand, the width of the heat seal part is narrowed as the gas discharge part and the non-seal part is It is thought that this is because the decrease in peel strength is suppressed by increasing the width.

  On the other hand, as in the laminated battery of this embodiment (see FIG. 1), a non-sealed portion is provided between the laminate film storage portion and the heat seal portion, and the portion sealed to the edge of the storage portion is part of the flange portion. In the type in which the part is provided and the part is used as the gas discharge part, the open rate at the gas discharge part is 100%. From this experiment, it was found that the laminate battery of this embodiment has a smaller variation in open pressure than the conventional laminate battery, and can reliably release the internal gas from the gas discharge part.

  As described above in detail, in the laminated battery 100 of this embodiment, when the flange portion 25 is sealed, the non-sealed portion 23 having a predetermined width is provided between the storage portion 21 and the heat seal portion 22. Specifically, the width of the non-sealing portion 23, the thickness of the adhesive layer of the laminate film 2, the thickness of the sealing head so that the resin portion 8 protruding from the heat sealing portion 22 is accommodated in the non-sealing portion 23. The applied pressure is adjusted. Thereby, the resin portion 8 due to the protrusion of the adhesive resin is suppressed from protruding into the storage space by the storage portion 21, and the formation of the notch-shaped portion is suppressed. Therefore, a decrease in the peel strength of the heat seal part 22 is suppressed.

  Further, in the laminate battery 100 of this embodiment, as the gas discharge part 4, a part sealed to the edge of the storage part 21 is provided in a part of the flange part 25. That is, in the gas discharge part 4, the peel strength is lowered by intentionally projecting the resin part 8 toward the storage space and providing a notch-shaped part. Therefore, when the internal pressure of the laminate battery 100 rises, the gas discharge part 4 is opened very quickly. Therefore, a laminate battery has been realized that can improve the peel strength of the heat seal portion 22 and reliably recover the gas generated inside the laminate battery.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, a laminated battery is not limited to a lithium ion battery. That is, the battery in the present invention may be any element that converts chemical energy into electrical energy, and can be applied to nickel-metal hydride batteries, nickel-cadmium batteries, fuel cells, electrolytic capacitors, and the like.

  In addition, as a method of wrapping the power generation element, one laminate film may be folded and the power generation element may be disposed inside and sealed in three directions other than the crease, or may be disposed between the two laminate films. Four sides may be sealed.

It is a front view which shows the outline of the laminated battery which concerns on this form. It is a side view which shows the outline of the laminated battery shown in FIG. It is sectional drawing which shows the heat seal part at the time of the heat welding of the laminated battery shown in FIG. It is sectional drawing which shows the state in the broken-line frame of the laminated battery shown in FIG. It is a graph which shows the result of a peel strength test. It is a figure which shows the outline of a breakdown pressure test. It is a figure which shows the state of the test laminated battery at the time of a breakdown pressure test. It is a table | surface which shows the result of a breakdown pressure test. It is a figure which shows the structure of the laminated battery which concerns on the conventional form. It is sectional drawing which shows the heat seal part at the time of the heat welding of the laminated battery which concerns on the conventional form. It is a figure which shows the structure of the gas discharge part of the laminated battery which concerns on the conventional form. It is sectional drawing which shows the state in the broken-line frame of the laminated battery shown in FIG.

Explanation of symbols

1 Power generation elements (power generation elements)
2 Laminate film (laminate film)
4 Gas discharge part (second seal processing part)
8 Resin part (resin part, second resin part)
21 Storage section (storage section)
22 Heat seal part (sealed part)
23 Non-sealed parts (non-sealed parts)
25 Flange (Flange)
100 Laminated battery

Claims (2)

A laminate that has a power generation element and a laminate film that wraps the power generation element, wraps the power generation element from its front and back surfaces with the laminate film, and seals the power generation element by sealing an edge of the laminate film In batteries,
The laminate film is
A storage section for storing the power generation element;
A flange portion located on an edge of the storage portion;
The flange portion is
A sealing portion that is located on the edge of the flange portion, surrounds the power generation element from at least three sides, and is sealed with adhesive resin;
An unsealed portion that is located closer to the housing than the sealed portion, surrounds the power generation element from at least three sides, and is not sealed ;
A second sealing portion that is a part of the flange portion and is sealed from an edge of the flange portion to an edge of the storage portion;
Have
The resin part by the protrusion of the adhesive resin from the sealing part to the power generation element side is located in the non-sealing part ,
The laminated battery , wherein the second resin portion by the protrusion of the adhesive resin from the second seal processing portion to the power generation element side is located in a storage space by the storage portion . The laminated battery according to claim 1,
The non-sealed portion has a width of at least 1.5 mm.

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