JP2015099723A - Flat type secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat type secondary battery capable of electrically connecting connection tabs of respective electrodes to each other even if a metal foil of a current collector constituting the electrode is constituted of metal which is thin and weak against heat when an electrode group of a laminated structure is constituted.SOLUTION: Disclosed is a flat type secondary battery 1 which has an electrode group 5 formed by arranging a positive electrode plate 7 and a negative electrode plate 8 opposed to each other via a separator 9, and an electrolytic solution 6, and in which the electrode group 5 and the electrolytic solution 6 are included in an outer case 2 in which a first plane 2a serves as an electrode terminal having positive polarity and a sealing case 4 in which a second plane 4a opposite to the first plane 2a serves as the electrode terminal having negative polarity. The positive electrode plate 7 and the negative electrode plate 8 have connection tabs whose respective mutual electrode plates are connected to each other, and the mutual connection tabs are connected by anisotropic conductive films 10a, 10b.

Description

  The present invention relates to a flat secondary battery, and more particularly to a structure for connecting a plurality of electrodes.

  A flat secondary battery accommodates an electrode group in which a positive electrode plate and a negative electrode plate face each other with a separator interposed therebetween, and an electrolyte in a space formed by an outer case, a sealing case, and an insulating gasket. It has the structure. For example, it refers to a shape called a button shape or a coin shape. A battery that uses a non-aqueous electrolyte is sometimes called a flat non-aqueous secondary battery.

  Since flat secondary batteries are small and thin, they are widely used as power sources for small devices such as wristwatches and thin devices such as IC cards. In recent years, the demand for higher capacity, higher performance, and lower cost of the flat secondary battery itself has increased with the enhancement of the functions of the above-described devices.

  In general, in order to increase the capacity of a secondary battery as well as the flat shape, it is necessary to increase the facing area between the positive electrode plate and the negative electrode plate. Therefore, the technique for accommodating in the case of the volume determined while increasing the area which a positive electrode plate and a negative electrode plate oppose in an electrode group sees many proposals.

In particular, the electrode group structure is known in several shapes.
For example, it is a laminated structure in which a plurality of positive and negative electrode plates are laminated via a separator (see, for example, Patent Document 1).
Moreover, it is the winding structure which arrange | positioned the separator between the strip | belt-shaped positive electrode plate and the negative electrode plate, and was wound spirally (for example, refer patent document 2).

  In addition to such a laminated structure and a wound structure, a folding structure is also known in which a separator is disposed between a belt-like positive electrode plate and a negative electrode plate, and both are folded alternately (see, for example, Patent Document 3). .)

Each structure of the electrode group has advantages with respect to the performance and manufacture of the secondary battery, and therefore the structure of the electrode group is often selected in view of the shape and performance of the target secondary battery.
In particular, in the case of a flat secondary battery, since the shape thereof is thin, an electrode group having a laminated structure in which a plurality of electrodes can be easily stacked is often used.

  The positive electrode plate and the negative electrode plate of the flat secondary battery expose a portion of the plate-like metal called a current collector on which one side or both sides of the positive electrode mixture or negative electrode mixture are formed and a part of the plate-like metal. And have a portion that has been By electrically connecting the exposed portion and an exterior case or a sealing case as a battery case, electricity is transmitted to and received from the outside. That is, the outer case and the sealing case serve as the positive electrode side terminal and the negative electrode side terminal of the battery, respectively.

  In the case of a laminated structure as shown in Patent Document 1, a plurality of positive plates and negative plates are prepared, and the plurality of positive plates and negative plates are laminated via a separator. Must be electrically connected. For this reason, each electrode plate is provided with a connection portion that exposes the mixture, which is referred to as a connection tab portion, and the connection tab portions are brought together to establish electrical connection. In the prior art shown in Patent Document 1, the connection tab portions are gathered together by welding.

Japanese Patent No. 4363558 (page 3, FIG. 1) Japanese Patent No. 4768912 (pages 5-6, FIGS. 1 and 4) JP2011-138675A (6th page, FIG. 1)

  By the way, generally, metal foil, such as aluminum and copper, is used for the collector which comprises an electrode plate. The thickness of this metal foil is extremely thin, for example, about 10 to 100 μm. As already described, in the case of the laminated structure as shown in Patent Document 1, it is necessary to weld a plurality of connection tab portions to make electrical connection. However, since the metal foil is extremely thin, the metal foil There arises a problem that a hole is opened before connecting each other.

  In particular, when a metal having a low melting point such as aluminum is used for the metal foil, the metal foil is easily melted during welding, and the connection tab portion may be disconnected as well as a hole is easily opened in the metal foil. Such a problem leads to a decrease in yield at the time of production of flat secondary batteries, and a proposal for a solution has been awaited.

  The object of the present invention has been made in view of the above problems of the prior art. A flat secondary that can electrically connect the connection tabs of each electrode even when the metal foil of the current collector that constitutes the electrode is made of a thin metal that is weak to heat when the electrode group has a laminated structure. To provide a battery.

  The flat secondary battery according to the present invention for achieving the above-described object employs the following configuration.

  A plurality of positive first electrode plates and a plurality of negative second electrode plates are arranged to face each other with a separator interposed therebetween, and an electrolyte solution, and the first plane is a positive electrode In a secondary battery in which an electrode group and an electrolytic solution are included in a case in which a second plane opposite to the first plane also serves as a negative electrode terminal also serving as a negative electrode terminal, the first electrode plate and the second electrode plate Has connection tab portions for connecting the electrode plates to each other, and the connection tab portions are connected by an anisotropic conductive film.

  With such a configuration, even when a heat-sensitive metal foil or a thin metal foil is used for the current collector, electrical connection can be established without destroying the connection tab portions.

  You may make it provide the isolation | separation means which prevents electrolyte solution from contacting an anisotropic conductive film between a connection tab part and an electrode group.

  With such a configuration, even if an electrolyte solution having a poor compatibility with the anisotropic conductive film is used, the properties do not touch each other, and the characteristics deteriorate or the anisotropic conductive film peels off. It does not cause problems such as.

  You may make it provide the sealing means which covers the part which a connection tab part and an anisotropic conductive film contact in a connection tab part so that electrolyte solution may not contact an anisotropic conductive film.

With such a configuration, even if an unexpected impact is applied to the flat secondary battery, the connection tab portion and the anisotropic conductive film are not easily peeled off.
In addition, even if an electrolyte solution that is poorly compatible with the anisotropic conductive film (for example, the anisotropic conductive film melts) is used, it does not touch each other and is partially sealed. Since the stopping means can be used, the configuration of the case can be simplified.

  Since the flat secondary battery according to the present invention uses an anisotropic conductive film for connection at the connection tab portions of the first electrode plate and the second electrode plate, the applied heat is significantly low unlike conventional welding. The occurrence of defects in the production of flat secondary batteries can be significantly reduced.

It is sectional drawing of the flat secondary battery in Example 1 of this invention. It is the top view and sectional drawing of the positive electrode plate of the flat secondary battery in Example 1 of this invention. It is the top view and sectional drawing of the negative electrode plate of the flat secondary battery in Example 1 of this invention. It is sectional drawing of the electrode group of the flat secondary battery in Example 1 of this invention. It is sectional drawing of the flat secondary battery in Example 2 of this invention. It is sectional drawing of the flat secondary battery in Example 3 of this invention.

In the flat secondary battery of the present invention, connection tab portions of a plurality of positive plates and a plurality of negative plates are connected by an anisotropic conductive film.
An anisotropic conductive film is a film obtained by forming a mixture of a thermosetting resin and fine metal particles having conductivity into a film shape. It is also called ACF (Anisotropic Conductive Film).

  For the electrical connection between the connection tab portions, the anisotropic conductive film is sandwiched between the connection tab portions, and pressure is applied while applying some heat with a heater or the like. Thereby, the metal particles dispersed in the anisotropic conductive film are pressed against each other, a conductive path is formed, and the connection tab portions are electrically connected to each other.

  In connection with an anisotropic conductive film, unlike conventional welding, the applied heat is significantly low. For this reason, the connection tab portion, of course, does not cause damage to the exterior case and the sealing case due to heat, and can significantly reduce the occurrence of defects in the production of the flat secondary battery.

Hereinafter, embodiments will be described in detail with reference to the drawings.
First, as Example 1, the structure of an electrode group and a flat secondary battery will be described with reference to FIGS.
Next, as Example 2, an example in which separation means is provided so that the electrolytic solution does not contact the anisotropic conductive film will be described with reference to FIG.
Furthermore, as Example 3, an example in which sealing means is provided so that the electrolytic solution does not contact the anisotropic conductive film will be described with reference to FIG.
In addition, all the drawings used for explanation are schematic diagrams schematically showing the invention so that the invention can be easily explained, and portions that are not related to the invention are omitted as flat secondary batteries.

[Structural description of flat secondary battery: FIGS. 1 to 4]
First, the structure of the flat secondary battery according to Example 1 will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing a cross section of a flat secondary battery. FIG. 2 is a plan view and a cross-sectional view of the positive electrode plate constituting the electrode group. FIG. 2B is a cross-sectional view taken along the cutting line AA ′ of the plan view of FIG. is there. FIG. 3 is a plan view and a cross-sectional view of the negative electrode plate constituting the electrode group. FIG. 3B is a cross-sectional view taken along the cutting line BB ′ of the plan view of FIG. is there. FIG. 4 is a cross-sectional view of an electrode group formed by laminating a plurality of positive and negative electrode plates facing each other.

  As shown in FIG. 1, the flat secondary battery 1 seals a shallow bottomed cylindrical outer case 2 having a first plane 2 a as a bottom surface and an opening of the outer case 2 via a gasket 3. A sealing case 4 is provided. The upper surface of the sealing case 4 is a plane facing the first plane 2a of the exterior case 2, and this is defined as a second plane 4a.

  An electrode group 5 having a structure in which a positive electrode plate 7 corresponding to a first electrode plate and a negative electrode plate 8 corresponding to a second electrode plate are stacked in a case composed of an outer case 2 and a sealing case 4 is accommodated. It is comprised with the electrolyte solution 6 with which the exterior case 2 and the sealing case 4 were filled so that the group 5 might be immersed.

  The shape of such a case is not particularly limited, but in the example shown in FIG. 1, the bottom surface of the outer case 2 has a certain thickness. For this reason, the inner surface 2b is parallel to the first plane 2a. The sealing case 4 is the same, and the upper surface of the sealing case 4 has a certain thickness, and the inner surface 4b thereof is parallel to the second plane 4a.

  The material of the exterior case 2 and the sealing case 4 is not particularly limited as long as it is a conductive material. For example, the exterior case 2 and the sealing case 4 are made of a metal material such as stainless steel, aluminum, or nickel, or a material obtained by applying nickel plating to stainless steel.

  The gasket 3 may be made of an insulating material such as polypropylene (PP), polyethylene terephthalate (PET), or polycarbonate (PC).

The material of the electrolytic solution 6 depends on the type of the secondary battery. For example, in the case of a lithium ion secondary battery, lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium borofluoride ( Lithium salt such as LiBF ₄ ) and a solvent such as ethylene carbonate (EC) and propylene carbonate (PC).

As shown in FIG. 2, the positive electrode plate 7 corresponding to the first electrode plate includes, as its outer shape, a positive electrode main body portion 71 and a positive electrode connection tab portion 72 protruding from the positive electrode main body portion 71 in plan view. Has been.
The positive electrode main body 71 is provided with a positive electrode mixture 74 on the surface of a positive electrode current collector 73 formed of a metal foil. In the example shown in FIG. 2, the positive electrode mixture 74 is provided on both surfaces of the positive electrode current collector 73. Yes. The positive electrode mixture 74 is not formed on the surface of the connection tab portion 72, and the positive electrode current collector 73 is exposed. This is for connecting each positive electrode plate 7 with the anisotropic conductive film 10a mentioned later.

In the case of a lithium ion secondary battery, the positive electrode current collector 73 is made of an aluminum foil, and has a thickness of 20 μm, for example. The positive electrode mixture 74 includes a positive electrode active material such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), lithium cobaltate (LiCoO ₂ ), a conductive agent such as acetylene black, and a binder agent such as polyvinylidene fluoride. Composed of a mixture of

The negative electrode plate 8 corresponding to the second electrode plate shown in FIG. 3 is also similar to the positive electrode plate 7 shown in FIG. 2, and the negative electrode main body 81 and the negative electrode connection tab 82 protruding from the negative electrode main body 81 in plan view. It consists of and. Similarly, a negative electrode mixture 84 is provided on both surfaces of a negative electrode current collector 83 formed of a metal foil. The negative electrode mixture 84 is not formed on the surface of the connection tab portion 82, and the negative electrode current collector 83 is exposed. This is also for connecting each negative electrode plate 8 with an anisotropic conductive film 10b described later.

  In the case of a lithium ion secondary battery, the negative electrode current collector 83 is made of a copper foil, and has a thickness of 20 μm, for example. The negative electrode mixture 84 is composed of a mixture of a negative electrode active material such as graphite and a binder agent such as polyvinylidene fluoride.

  In the example of the positive electrode plate 7 and the negative electrode plate 8 shown in FIGS. 2 and 3, the shapes of the positive electrode main body 71 of the positive electrode plate 7 and the negative electrode main body 81 of the negative electrode plate 8 are shown as circular. It is not limited to a circle. In accordance with the shape of the outer case 2 and the sealing case 4, or in view of battery performance such as the amount of storage as a secondary battery, a polygon such as a rectangle or a hexagon, an ellipse, or the like can be freely set.

FIG. 4 shows a configuration in which a plurality of positive plates 7 and negative plates 8 shown in FIGS. 2 and 3 are provided and stacked to form an electrode group 5.
The electrode group 5 is configured by laminating a positive electrode plate 7 and a negative electrode plate 8 with a separator 9 interposed therebetween. The positive electrode plate 7 and the negative electrode plate 8 are stacked so that the positive electrode main body 71 and the negative electrode main body 81 face each other. At this time, the separator 9 is provided so that the positive electrode main body 71 and the negative electrode main body 81 do not contact each other.

  As a material of the separator 9, a microporous polyethylene film can be used. The positive electrode plate 7 and the negative electrode plate 8 are electrically isolated from each other and are made of a material that allows ions to move through the fine holes.

  The connection tab portion 72 for positive electrode and the connection tab portion 82 for negative electrode are outside the outer periphery of the separator 9, that is, in a portion that is not a portion where the positive electrode main body portion 71 and the negative electrode main body portion 81 are laminated in a plan view. They are arranged so as to overlap.

  As shown in FIG. 4, the overlapping positive electrode connection tab portion 72 and negative electrode connection tab portion 82 are spaced apart from each other with a portion where the positive electrode main body portion 71 and the negative electrode main body portion 81 are stacked. And provided so as to face each other. They are provided on the left and right in the view of FIG. And each connection tab part of the same polarity is connected by the anisotropic conductive film.

  That is, the plurality of positive electrode connection tab portions 72 are stacked so as to sandwich the anisotropic conductive film 10a, and the connection tab portions 72 are electrically connected by the anisotropic conductive film 10a. Similarly, a plurality of negative electrode connection tab portions 82 are also stacked so as to sandwich the anisotropic conductive film 10b, and each connection tab portion 82 is electrically connected.

  A known technique can be used as a method of connecting the plurality of connection tab portions 72 and the connection tab portions 82 with the anisotropic conductive films 10a and 10b, respectively, but an example is as follows.

  That is, the connection tab portions and the anisotropic conductive film are alternately stacked, and the stacked portions are pressed and heated in the direction in which the stacked portions are compressed, that is, in the thickness direction of the flat secondary battery. The temperature at that time is, for example, about 150 to 200 ° C. By applying pressure and heating, metal particles dispersed in the anisotropic conductive film are pressed together to form a conductive path, and a plurality of connection tab portions are electrically connected.

  Thus, since the temperature applied when connecting a plurality of connection tab portions having the same polarity by the anisotropic conductive film is lower than the melting point of the metal foil, the connection tab portion may be damaged. Absent.

  The anisotropic conductive films 10a and 10b may have the same characteristics, or may have different characteristics. Since the anisotropic conductive film is formed by molding a mixture of a thermosetting resin and fine metal particles having conductivity into a film shape, there are many types of thermosetting resins and metal particles used. Depending on the combination of these, there is a difference in hardness and electrical resistance when cured. Since the materials of the positive electrode plate 7 and the negative electrode plate 8 are different from each other, the performance of the secondary battery may be improved by using an anisotropic conductive film suitable for each electrical characteristic. .

  As shown in FIGS. 4 and 1, the electrode group 5 formed by laminating a plurality of positive plates 7 and negative plates 8, when housed in a case, has a positive plate 7 and a negative plate 8, respectively. It arrange | positions so that the 2nd 1st plane 2a and the 2nd plane 4a of the sealing case 4 may be parallel.

  If each positive electrode plate 7 or negative electrode plate 8 constituting the electrode group 5 is inclined and laminated, not only a limited case space is wasted but also the connection between the electrode group 5 and the case described below. Will also be disadvantaged.

  In the electrode group 5, the positive electrode current collector 73a of the positive electrode plate 7a and the negative electrode current collector 83a of the negative electrode plate 8a located at the end portions thereof are provided with the positive electrode mixture 74 and the negative electrode mixture 84 only on one side. With such a configuration, as shown in FIG. 1, the inner surface 2b of the outer case 2 and the inner surface 4b of the sealing case 4 can be brought into surface contact with the positive electrode current collector 73a and the negative electrode current collector 83a.

  That is, when the positive electrode current collector 73a made of metal foil and the negative electrode current collector 83a made of metal foil are exposed at the end of the electrode group 5, the electrode group 5 is placed in the case. Thus, the outer case 2 and the positive electrode current collector 73a can be electrically connected, and the sealing case 4 and the negative electrode current collector 83a can be electrically connected.

  Thereafter, the electrolytic solution 6 is put so that the electrode group 5 is immersed, and the gasket 3 is provided between the outer case 2 and the sealing case 4 and pressed, so that each current collector can be more closely attached to the case. .

  With the above configuration, the positive electrode plate 7, the negative electrode plate 8, the outer case 2, and the sealing case 4 need not be connected separately such as welding, and the positive electrode current collector 73 and the negative electrode current collector 83 are welded. A flat secondary battery with good yield can be obtained, which can prevent destruction due to the generated heat.

  Of course, although not shown, an anisotropic conductive film is further provided and connected between the outer case 2 and the positive electrode current collector 73a and between the sealing case 4 and the negative electrode current collector 83a. It may be. In this way, the current collector and the case can be connected more firmly. As described above, since there are many combinations of the thermosetting resin used and the encapsulated metal particles, it is preferable to select an anisotropic conductive film that is suitable for connection between each current collector and the case.

[Description of structure of flat secondary battery: FIG. 5]
Next, the structure of the flat secondary battery according to Example 2 will be described with reference to FIG.
FIG. 5 is a cross-sectional view showing a cross section of the flat secondary battery 100. The same reference numerals are used for the same components as in the previous embodiment.

This embodiment differs from the first embodiment in that the separating means 11 is provided between the positive electrode main body 71 and the positive electrode current collecting tab 72 and between the negative electrode main body 81 and the negative electrode current collecting tab 82. That is, the anisotropic conductive film is isolated from the electrolytic solution by the separating means inside the case.
By this structure, it can prevent that the electrolyte solution 6 contacts the location connected by anisotropic conductive film 10a, 10b.

  The electrolyte 6 used for the flat secondary battery 100 may be made of a material that affects the anisotropic conductive films 10a and 10b. For example, the anisotropic conductive films 10a and 10b are peeled off or melted by the electrolytic solution 6. Even in such a case, separation and melting can be prevented by separating the area of the electrolytic solution 6 from the anisotropic conductive films 10a and 10b by the separating means 11.

  The separating means 11 is provided with a slit 11a, and the positive electrode current collecting tab 72 and the negative electrode current collecting tab 82 are guided to the outside of the area where the electrolytic solution 6 is provided through the slit 11a. Then, the slit 11 a is closed with the sealing agent 12. Therefore, the electrolytic solution 6 does not reach the anisotropic conductive films 10a and 10b by the separating unit 11. Although the sealing agent 12 is not specifically limited, a fluororesin can be used.

  The structure of the separating means 11 may be polypropylene, fluorine-based resin, packing such as polyethylene terephthalate, ceramic, or the like, but the material is not limited as long as the material has no electrical conductivity.

  It goes without saying that such a separating means 11 is bonded to the outer case 2 and the sealing case 4 so that the electrolyte 6 does not leak from the connection point, but may be integrated with these cases. For example, if it is formed integrally with the outer case 2, it is easy to inject the electrolytic solution from the upper part of FIG. Further, if the outer case 2 or the sealing case 4 and the separating means 11 are fixed, the separating means 11 may move erroneously when the electrode group 5 is inserted into the case and the electrolytic solution 6 is injected thereafter. And easy to manufacture.

  By taking the configuration as described above, in addition to the effects shown in Example 1, there is an advantage that the material can be selected without considering the compatibility between the electrolytic solution and the anisotropic conductive film. For example, the material of the electrolyte solution 6 can be selected with priority given to electrical characteristics such as the amount of electricity stored, and the material of the anisotropic conductive films 10a and 10b can be selected according to the ease of connection of the electrode plates.

[Description of the structure of the flat secondary battery: FIG. 6]
Next, the structure of the flat secondary battery according to Example 3 will be described with reference to FIG.
FIG. 6 is a cross-sectional view showing a cross section of the flat secondary battery 101. The same reference numerals are used for the same components as in the previous embodiment.

This embodiment is different from the previous embodiment 1 and embodiment 2 in that sealing is a sealing means around each positive electrode current collecting tab 72 and the anisotropic conductive film 10a connecting the current collecting tabs. The material 13a is provided, and the sealing material 13b is provided around each negative electrode current collecting tab 82 and the anisotropic conductive film 10b connecting the current collecting tabs. That is, the portion where the anisotropic conductive film is provided is covered by the sealing means inside the case.
By this structure, it can prevent that the electrolyte solution 6 contacts the location connected by anisotropic conductive film 10a, 10b.

  With such a configuration, as in Example 2 already described, the electrolytic solution 6 is made of a material that peels off or melts the anisotropic conductive films 10a and 10b. Even if it exists, it becomes possible to prevent contact with the electrolyte solution 6 and the anisotropic conductive films 10a and 10b by these sealing materials 13a and 13b.

As the sealing materials 13a and 13b, for example, silicon rubber, epoxy resin, and the like are conceivable. However, the material is not limited as long as the material does not have electrical conductivity.
In particular, if an epoxy resin is used, a plurality of positive electrode connection tab portions 72 are connected using the anisotropic conductive film 10a, and a plurality of negative electrode connection tab portions 82 are used using the anisotropic conductive film 10b. This is convenient because only a portion where the stubs are connected can be sealed by applying a known resin potting technique.

By taking the above configuration, in addition to the effects shown in Example 1 and the advantage that the material can be selected without considering the compatibility between the electrolytic solution and the anisotropic conductive film, a predetermined portion Since only sealing is possible, the case can be reduced in size.
Even if an unexpected impact is applied to the flat secondary battery, the anisotropic conductive film is not peeled off because the connecting tab portion is fixed.

  According to this invention, since each electrode plate can be connected without the influence of destruction by heat, an electrode plate can also be made thinner. Therefore, it is suitable for a flat secondary battery that satisfies the demands for higher capacity, higher performance, and lower cost.

DESCRIPTION OF SYMBOLS 1,100,101 Flat secondary battery 2 Exterior case 3 Gasket 4 Sealing case 5 Electrode group 6 Electrolyte solution 7 Positive electrode plate 7a Positive electrode plate located at end 8 Negative electrode plate 8a Negative electrode plate located at end 9 Separator 10a, DESCRIPTION OF SYMBOLS 10b Anisotropic conductive film 11 Separation means 12 Sealing material 13a, 13b Sealing material 71 Positive electrode main body part 72 Connection tab part for positive electrodes 73 Positive electrode current collector 73a Positive electrode current collector located at an end 74 Positive electrode mixture 81 Negative electrode Main body part 82 Connection tab part for negative electrode 83 Negative electrode current collector 83a Negative electrode current collector located at the end 84 Negative electrode mixture

Claims (3)

An electrode group in which a plurality of positive first electrode plates and a plurality of negative second electrode plates are arranged to face each other via a separator, and an electrolyte solution,
A flat secondary in which the first plane also serves as the positive electrode terminal and the second plane opposite to the first plane also serves as the negative electrode terminal includes the electrode group and the electrolyte. In batteries,
The first electrode plate and the second electrode plate each have a connection tab portion for connecting the electrode plates to each other.
The connection tab portions are connected by an anisotropic conductive film. A flat secondary battery, wherein: 2. The flat secondary battery according to claim 1, wherein separation means is provided between the connection tab portion and the electrode group so that the electrolyte does not contact the anisotropic conductive film. . The connecting tab portion is provided with sealing means for covering a portion where the connecting tab portion and the anisotropic conductive film are in contact with each other so that the electrolytic solution does not contact the anisotropic conductive film. Item 2. The flat secondary battery according to Item 1.

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