JP2015103291A - Laminate battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate battery which allows for local peeling strength adjustment of a laminate film, without narrowing the heat seal width affecting the water vapor barrier.SOLUTION: In a laminate battery 12 including a battery element 4 formed by laminating a positive electrode plate 1 for connecting a positive electrode terminal 9 and a negative electrode plate 2 for connecting a negative electrode terminal 8 via a separator 3, and two laminate films 5, 6 having recesses 7a, 7b for housing the battery element 4 and sealing an outer peripheral edge 11 of the recesses 7a, 7b, the positive electrode terminal and negative electrode terminal are provided on the outer peripheral edge via a tab film 10, so that the ends of them project outward from the outer peripheral edge. On the battery element side face of the tab film, an unfinished part 13 is formed by making the surface of any one or both of the positive electrode terminal and negative electrode terminal adhere to the fusion parts 5c, 6c of the laminate film.

Description

  The present invention relates to a battery using a laminate film for an exterior, and particularly to a form for sealing a battery element of a laminate film.

  Lithium ion batteries having a large charge / discharge capacity are widely used in portable battery-powered devices such as mobile phones. In addition, high output secondary batteries are also required in applications such as electric vehicles, electric bicycles, electric tools, and power storage.

  In these high output batteries, in order to increase the energy density per unit volume or mass of the battery, at least a thermoplastic film and a metal foil are used instead of an aluminum material such as a tube type or a square type as a battery outer container. Laminate type batteries using a laminate film that can be thinned by laminating are widely used. The outer peripheral edge of the laminate film is sealed by heat fusion or the like to form a laminate container, which seals the battery element.

  However, since the battery element generates Joule heat during operation (during charging / discharging), the temperature of the inside of the laminate container rises to around 60 ° C. Furthermore, when there is a short circuit or abnormal charge / discharge, the internal temperature may exceed 100 ° C. By this temperature increase, the electrolyte solution constituting the battery element is vaporized, and the internal pressure of the laminate container is rapidly increased by the vaporized material. And when the intensity | strength of a laminate container cannot endure this internal pressure, there exists a possibility that a laminate container may burst.

  As a technique for solving this problem, for example, there is a technique disclosed in Patent Document 1. The bag body for storing the power generation element for a thin battery described in Patent Document 1 has a peripheral edge formed in the heat seal part, and a part of the heat seal part is narrower than the seal width of the other heat seal part. It is formed in a cutout shape from the inner edge toward the outer edge.

JP 2001-93483 A

  However, when a notch is provided in a part of the peripheral edge of the heat seal as in the prior art described above, the water vapor barrier property of that part is inferior because the heat seal width of the notch is narrow. As a result, moisture enters from the outside and reacts with the electrolytic solution, so that the internal pressure of the laminate container is increased. Moreover, since local stress concentration occurs by forming the notch, the laminate container itself may be distorted when the internal pressure is increased, and the battery element may be short-circuited.

  The present invention has been made in view of the above-described problems, and provides a laminate type battery that enables local peel strength adjustment of a laminate film without reducing the heat seal width that affects the water vapor barrier. With the goal.

  In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that a positive electrode plate (1) for connecting a positive electrode terminal (9) and a negative electrode plate (2) for connecting a negative electrode terminal (8) are separated. (3) a battery element (4) formed by stacking, and a recess (7a, 7b) for housing the battery element (4), and an outer peripheral edge (11) outside the recess (7a, 7b). In the laminate type battery (12) provided with two laminated films (5, 6) to seal the positive electrode terminal and the negative electrode terminal, both ends protrude outward from the outer peripheral edge. As described above, the outer peripheral edge is provided through the tab film (10), and the surface of one or both of the positive electrode terminal and the negative electrode terminal and the fused portion (5c, 6c) of the laminate film are provided. The notch (13) formed in close contact with the tab fill Wherein the of provided on the side surface side of the battery element side.

  According to this configuration, the positive electrode terminal and the negative electrode terminal are provided on the outer peripheral edge via the tab film (10) so that both ends protrude outward from the outer peripheral edge. A notch portion (13) formed by closely contacting one or both surfaces of the terminal and the fused portion (5c, 6c) of the laminate film is provided on the side surface side of the tab film on the battery element side.

  Therefore, it is possible to reduce the adhesive strength of the notch portion that causes the peeling of the laminate film, and even when the internal pressure of the laminate container is relatively low, the laminate film is easily peeled off to reliably release the internal pressure of the laminate container. There is an excellent effect of being able to. In addition, since the notch portions can be provided at any one of the four positions together with the positive and negative electrode terminals, the internal pressure can be released more reliably and the peel strength can be easily adjusted.

It is a perspective view which shows the inside of the lamination film which cut | disconnected the external appearance and one part of the lamination type battery of this invention. It is an expanded sectional view which shows in detail between positive and negative electrodes by the II-II line of FIG. It is sectional drawing which shows the outline | summary when laminating films are heat-seal | fused. It is an expanded sectional view which shows the condition where the notch part was peeled and the internal pressure of the laminate container was released. It is a graph which shows the form from which the behavior of peeling strength changes with the presence or absence of a notch part. It is a figure which shows the internal pressure releasing part of each Example, an opening location, and determination.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, parts corresponding to each other in all the drawings in this specification are denoted by the same reference numerals, and description of the overlapping parts will be omitted as appropriate.

  As shown in FIGS. 1 and 2, a laminate type battery 12 is provided with a battery element 4 disposed between two laminate films 5 and 6 and sealed together with an electrolyte in which an electrolyte is dissolved in a non-aqueous solvent. It becomes. The battery element 4 is housed in recesses 7a and 7b formed on one or both of the laminate film 5 and the laminate film 6 by a method such as embossing. 1 and 2 show examples in which the laminate film 5 is provided with a recess 7a and the laminate film 6 is provided with a recess 7b.

  The battery element 4 is formed by further laminating a plurality of sets in which a positive electrode plate 1 and a negative electrode plate 2 are laminated via a separator 3. The battery element 4 has a rectangular parallelepiped shape including a rectangular surface that is slightly smaller than the rectangular shape of the bottom surface of the recesses 7a and 7b. The outer peripheral edge 11 of the laminate films 5 and 6 is a surface where the two laminate films 5 and 6 come into contact with each other outside the outer periphery of the recesses 7a and 7b, and is sealed by a method such as heat fusion. The positive electrode terminal 9 connected to the positive electrode plate 1 and the negative electrode terminal 8 connected to the negative electrode plate 2 are sealed through the tab film 10 at the outer peripheral edge 11 of the laminate films 5 and 6, and both ends are the outer peripheral edge 11. Protrudes outward.

  The tab film 10 is made of acid-modified polypropylene and has polarity, and therefore has adhesiveness. The tab film 10 can take a single layer or a multilayer structure of two or more layers.

  The positive electrode plate 1 is obtained by suspending and mixing a positive electrode mixture composed of a positive electrode active material, a conductive agent and a binder in an appropriate solvent, applying a slurry to one or both sides of the positive electrode current collector, and drying. It can produce by doing.

  The negative electrode plate 2 is prepared by suspending and mixing a negative electrode mixture composed of a negative electrode active material, a conductive agent and a binder in an appropriate solvent, and applying a slurry to one or both sides of the negative electrode current collector, followed by drying. It can produce by doing.

  The positive electrode terminal 9 is a tab-like member that guides the electric power extracted from each positive electrode plate 1 to the outside of the laminate films 5 and 6 and is made of an aluminum plate having a thickness of 400 μm. The negative electrode terminal 8 is a tab-like member that guides the electric power extracted from each negative electrode plate 2 to the outside of the laminate films 5 and 6 and is a copper plate having a thickness of 200 μm. The copper plate can be nickel-plated to improve adhesion. The positive electrode terminal 9 and the negative electrode terminal 8 can be subjected to chemical conversion treatment in order to improve corrosion resistance. Although FIG. 1 shows that the positive electrode terminal 9 and the negative electrode terminal 8 are provided on the laminate films 5 and 6 on both short sides of the recesses 7a and 7b, both lengths of the recesses 7a and 7b are shown. It may be provided on each of the side laminate films 5 and 6. Further, the positive electrode terminal 9 and the negative electrode terminal 8 may be provided side by side on the laminate films 5 and 6 corresponding to one of the short side and the long side of the recesses 7a and 7b.

  The separator 3 has a role of electrically insulating the positive electrode plate 1 and the negative electrode plate 2 and holding an electrolytic solution. As the separator 3, for example, a porous synthetic resin film, in particular, a porous film of polyolefin polymer (polyethylene, polypropylene) can be used. The separator 3 preferably has a larger outer shape than the positive electrode plate 1 and the negative electrode plate 2 in order to ensure insulation between the positive electrode plate 1 and the negative electrode plate 2.

  Laminate films 5 and 6 are made of exterior parts 5a and 6a made of biaxially stretched polyester resin (polyethylene terephthalate) and biaxially stretched polyamide resin (nylon), core parts 5b and 6b made of aluminum foil, etc., unstretched polyolefin The fused portions 5c and 6c made of resin (polypropylene) or the like are bonded together by heat fusion or an adhesive in the order described above. The exterior portions 5a and 6a reinforce the tensile strength, piercing strength, bending weakness, and the like of a core portion that generally has spreadability. The core portions 5b and 6b achieve an airtight / liquidtight structure in the direction of transmitting the film surface (the thickness direction of the laminate film) by using a material without holes. The fused portions 5c and 6c have corrosion resistance to the electrolytic solution, and heat-seal the laminate films 5 and 6 that house the battery element 4 together. The fused portions 5c and 6c are made of unmodified polypropylene and have no polarity and are not adhesive. However, since they are not stretched, heat fusion is possible. As an example, the thickness of each part is 30 μm for the exterior parts 5a and 6a, 40 μm for the core parts 5b and 6b, and 80 μm for the fused parts 5c and 6c.

  Next, based on FIG. 3, the sealing method by the heat sealing | fusion of the laminate films 5 and 6 is demonstrated. Although FIG. 3 shows only the positive electrode terminal 9 side, the negative electrode terminal 8 side can be similarly implemented.

  The fusion part 5c of the outer peripheral edge 11 of the laminate film 5 and the fusion part 6c of the outer peripheral edge 11 of the laminate film 6 are arranged to face each other so as to sandwich the positive electrode terminal 9 with the tab film 10 attached to both surfaces. At this time, the positive electrode terminal 9 is disposed so that the side surface of the tab film 10 on the battery element 4 side is positioned on the opposing surface of the outer peripheral edge 11 slightly outside the opening angle of the recesses 7a and 7b.

  In this state, a pair of heat seal bars 14 adjusted to an appropriate temperature at which the fused portions 5c and 6c are melted are moved closer to each other from both outer sides of the opposed outer peripheral edges 11, and come into contact with the outer peripheral edges 11. Let And the outer periphery 11 of the part in which the positive electrode terminal 9 of the laminate films 5 and 6 is not provided is heat-seal | fused by clamp | tightening the heat seal bars 14 with an appropriate pressure. The outer peripheral edge 11 of the portion of the laminate films 5 and 6 where the positive electrode terminal 9 is provided is in close contact with the tab film 10.

  At this time, the unmodified polypropylene in the fused portions 5 c and 6 c melts and flows and adheres closely to the side surface of the tab film 10 on the battery element 4 side and the surface of the positive electrode terminal 9. As a result, as shown in FIG. 2, the unmodified property that forms the fused portions 5c and 6c of the laminate films 5 and 6 between the side surface of the tab film 10 on the battery element 4 side and the vicinity of the opening angles of the recesses 7a and 7b. A notch portion 13 is formed in which the polypropylene is in close contact with the side surface of the tab film 10 and the surface of the positive electrode terminal 9. The notch 13 can be provided on either or both of the front and back surfaces of the positive electrode terminal 9. Further, the notch 13 can be provided on either or both of the front and back surfaces of the negative electrode terminal 8. Furthermore, the notch 13 can be provided on either the positive electrode terminal 9 or the negative electrode terminal 8. That is, the notch portion 13 can be provided at any one of the four locations together with the positive and negative electrode terminals.

  As shown in FIGS. 2 and 4, the notch 13 is formed from the surface of the positive electrode terminal 9 when the pressure in the laminate container formed by sealing the recesses 7 a and 7 b rises to a predetermined value. Is extended with an appropriate width L in the axial direction of the positive electrode terminal 9. The dimension of the width L is preferably 100 μm or more.

  And the peeling of the notch part 13 becomes a cut, and the tab film 10 is easily peeled from the surface of the positive electrode terminal 9, and the gap G is formed. As a result, the pressure in the laminate container is released.

  Here, based on FIG. 5, the form of internal pressure release of a laminate container is demonstrated. FIG. 5 shows the present invention having a notch 13 and a conventional one not having a notch 13 with the displacement (elongation) of the laminate film caused by internal pressure as the abscissa and the peel strength (load) as the ordinate. It is a graph which compares and shows the behavior of the peeling strength with a thing.

  In the prior art that does not have the notch portion 13, the tab film extends from the corner of the recess so as to protrude toward the battery element. Therefore, a notch part will be located in the middle of the core part of a laminate film, and the electrode terminal surface, and stress will be disperse | distributed. Further, since the notch portion is between the fusion film portion and the tab film, both of which are made of polypropylene-based resin, the adhesion is strong.

  Therefore, even if the internal pressure of the laminate container rises, it does not peel off at the notched portion, and the portions other than the outer peripheral edge of the laminate film are broken. This point is indicated by A in FIG. An example of the peel strength (load) in A is 170 N per 15 mm length of the laminate film, which corresponds to an internal pressure of 1.1 MPa of the laminate container.

  On the other hand, in the thing of this invention which has the notch part 13, as shown in FIG. 2, the side surface by the side of the battery element 4 of the tab film 10 is located in a little outward rather than the recessed part 7a, 7b opening angle. . Therefore, the portion where the notch portion 13 is biased toward the surface side of the positive electrode terminal 9 or the negative electrode terminal 8 between the core portions 5b and 6b of the laminate films 5 and 6 and the surface of the positive electrode terminal 9 or the negative electrode terminal 8 The stress concentrates on the notch 13. Further, the notch portion 13 is formed between the fused portions 5c and 6c made of unmodified polypropylene (nonpolar) and the positive electrode terminal 9 or the negative electrode terminal 8 made of aluminum or copper (polarity). Since each has a different material and polarity, the adhesion between them is weak.

  Therefore, if the internal pressure of the laminate container rises to a relatively low predetermined value, the notch 13 is easily peeled off. This point is indicated by B in FIG. An example of the peel strength in B is 90 N per 15 mm length of the laminate film, which corresponds to an internal pressure of 0.6 MPa in the laminate container. For this reason, it is preferable that the peeling strength of the notched portion 13 is 100 N / 15 mm or less.

  In this way, by providing the notch 13, it is possible to realize a reduction in the peel strength indicated by D in FIG. 5, so that it can be selectively opened as a safety valve for the laminate container.

  As an example of the notch portion 13, as shown in FIG. 6, examples 1 to 5 show an internal pressure releasing portion, an opening location, and determination. Moreover, the comparative example 1 is shown as what does not have a notch part.

  According to FIG. 6, as a result of setting the notch portion 13 to various internal pressure release portions and opening locations as in Examples 1 to 5, the internal pressure of the laminate container was released at 0.6 MPa or less in all of them, and was good (◯ ) Is made. On the other hand, in Comparative Example 1, since there was no notched portion, the laminate container was not released even when the internal pressure of the laminate container became 1.1 MPa or more, and the laminate container broke and some of the battery elements were scattered. Therefore, the comparative example 1 is determined to be defective (x).

  By the way, although the above-mentioned notch is provided on the positive and negative electrode terminals, it is similar to the notch of the present invention on the voltage detection line, the temperature detection line, etc. arranged at a different position from them. A hook can be provided.

  In addition, this invention includes what can be implemented in the aspect which added various change, correction, improvement, etc. based on the knowledge of those skilled in the art. Further, it goes without saying that any of the embodiments to which the above-mentioned changes are added is included in the scope of the present invention without departing from the gist of the present invention.

  For example, the recesses 7 a and 7 b have been described as having a shape that is symmetrical with respect to the outer peripheral edge 11, but each recess may have an asymmetric shape with respect to the outer peripheral edge 11. At that time, the notched portion on the side of the concave portion having a deep depth is more easily peeled off.

  As is clear from the above detailed description, according to the laminated battery 12 of the present embodiment, the positive electrode terminal 9 and the negative electrode terminal 8 are such that both ends protrude outward from the outer peripheral edge 11. It is provided on the outer peripheral edge 11 with the tab film 10 interposed therebetween, and the surface of one or both of the positive electrode terminal 9 and the negative electrode terminal 8 and the fused portions 5c and 6c of the laminate films 5 and 6 are formed in close contact with each other. Is provided on the side surface of the tab film 10 on the battery element 4 side.

  Therefore, since the adhesive force of the notch portion 13 that is the starting point for peeling the laminate films 5 and 6 can be reduced, the laminate film can be easily peeled even when the internal pressure of the laminate container is relatively low, and the internal pressure of the laminate container is released. There is an excellent effect that can be carried out reliably. Moreover, since the notch part 13 can be provided in one to four arbitrary places together with the positive and negative electrode terminals, the internal pressure can be released more reliably and the peel strength can be easily adjusted.

  Moreover, since the tab film 10 consists of acid-modified polypropylene, the peeling strength of the notch part 13 can be reduced effectively.

  Moreover, since the fused parts 5c and 6c are made of unmodified polypropylene, the peel strength of the notched part 13 can be effectively reduced.

  Moreover, since the notch part 13 has a width | variety of 100 micrometers or more in the axial direction of the positive electrode terminal 9 or the negative electrode terminal 8, the peeling strength of the laminate films 5 and 6 can be adjusted optimally.

  Moreover, since the peeling strength of the notch part 13 is 100 N / 15 mm or less, the laminate films 5 and 6 can be peeled safely and reliably.

  Moreover, since each recessed part 7a, 7b is asymmetrical shape with respect to the outer periphery 11, the notch part by the side of a recessed part with a deep depth becomes easier to peel, and adjustment of peeling strength becomes easy.

DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Negative electrode plate 3 Separator 4 Battery element 5, 6 Laminate film 5c, 6c Fusion part 7 Recessed part 8 Negative electrode terminal 9 Positive electrode terminal 10 Tab film 11 Outer periphery 12 Laminated battery 13 Notch part

Claims (7)

A battery element (4) formed by laminating a positive electrode plate (1) connecting a positive electrode terminal (9) and a negative electrode plate (2) connecting a negative electrode terminal (8) with a separator (3) interposed therebetween; Two laminate films (5, 6) having recesses (7a, 7b) for accommodating the battery element (4) and having the outer peripheral edges (11) outside the recesses (7a, 7b) sealed. In the laminated battery (12),
The positive electrode terminal and the negative electrode terminal are provided on the outer peripheral edge via a tab film (10) so that both ends protrude outward from the outer peripheral edge,
A notch portion (13) formed by adhering the surface of one or both of the positive electrode terminal and the negative electrode terminal and the fused portion (5c, 6c) of the laminate film is formed on the tab film. A laminate type battery comprising a battery element side surface side.   The laminate type battery according to claim 1, wherein the tab film is made of acid-modified polypropylene.   The laminate type battery according to claim 1, wherein the fused portion is made of unmodified polypropylene.   The laminate type battery according to any one of claims 1 to 3, wherein the fused portion is in close contact with a side surface of the tab film on the battery element side.   5. The laminate type battery according to claim 1, wherein the notch portion has a width of 100 μm or more in an axial direction of the positive electrode terminal or the negative electrode terminal.   The laminate type battery according to any one of claims 1 to 5, wherein a peeling strength of the notched portion is 100 N / 15 mm or less.   The laminated battery according to any one of claims 1 to 6, wherein each of the recesses has an asymmetric shape with respect to the outer peripheral edge.

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