JP2000077044A - Sheet battery - Google Patents

Abstract

(57) [Problem] To provide a sheet battery capable of suppressing leakage of an electrolytic solution, intrusion of moisture, and the like, and stabilizing battery characteristics, despite having a thickness equal to or less than a conventional thickness. It is in. SOLUTION: Two sheet-like exterior members (1, 2) are joined at their peripheral edges, and at least a positive electrode 3 is provided between the exterior members.
a, a separator 3c, and a negative electrode 3b are stacked, and a stack 3 is accommodated, and lead terminals (4a, 4b) protruding to the outside of the battery are connected to the positive electrode 3a and the negative electrode 3b, respectively.
Further, the cross section of the end of the lead terminal (4a, 4b) on the surface direction side of the exterior member is tapered to the outside of the lead terminal to complete the sheet battery 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a sheet battery.

[0002]

2. Description of the Related Art With the development of electronic technology in recent years, various electronic devices have been reduced in size and weight. In particular, this is remarkable in the fields of notebook personal computers, mobile phones, digital cameras, and the like, and in these devices, batteries that serve as power sources are required to be further reduced in size and weight. Further, in these devices, the internal surplus space is reduced along with the miniaturization, and it may be difficult to secure a space for a power supply. Therefore, recently, various types of sheet batteries which are not affected by the shape and size of the space inside the electronic device have been developed.

FIG. 3 is a view showing a conventional sheet battery.
FIG. 1A is a perspective view. FIGS. 7B and 7C are cross-sectional views, and only lines appearing in the cross section are shown. As shown in FIG. 1A, the sheet battery 20 has a stacked body 23 in which a positive electrode 23a, a separator 23c, and a negative electrode 23b are sequentially stacked between a sheet-shaped exterior member 21 and an exterior member 22. It is formed by injecting an electrolytic solution. Peripheral part of exterior member 21 and exterior member 22
Are joined by heat sealing. Positive electrode 2
The exterior member 21 and the exterior member 2
2 and a lead terminal 24a for the positive electrode and a lead terminal 24b for the negative electrode that protrude to the outside of the battery from each other. The positive electrode 23a and the positive lead terminal 24a
And the connection between the negative electrode 23b and the lead terminal 24b for the negative electrode are schematically shown.
Only the outer shape of the laminate 23 is indicated by a dotted line.

FIGS. 1B and 1C are partially enlarged views of a cross section taken along a line BB in a thickness direction, and show peripheral portions of an exterior member 21 and an exterior member 22. FIG.
Shows a state before heat sealing, and FIG. 3C shows a state after heat sealing. As shown in FIGS. 8B and 8C, the exterior member 21 and the exterior member 22 are respectively provided with an adhesive layer (21
a, 22a). Lead terminals (24a, 24
b) is sandwiched between the exterior member 21 and the exterior member 22.
The cross section of the lead terminals (24a, 24b) is rectangular (rectangular). The adhesive layers (21a, 22a) are formed of a hot melt adhesive. This adhesive layer 21
(a) and the adhesive layer 22a are heat-sealed and fused as shown in FIG. 3 (c), whereby the peripheral edge of the exterior member 21 and the peripheral edge of the exterior member 22 are joined.

[0005]

However, hot-melt adhesives usually used for sheet batteries have low fluidity during heat sealing, and the thickness of the adhesive layer is usually about 50 μm to 100 μm. The thickness of the electrode lead is about 50 μm to 100 μm. for that reason,
As shown in FIG. 4B, the adhesive layer (21a, 22a) does not extend to the side surfaces of the lead terminals (24a, 24b) during heat sealing, and the side surfaces of the lead terminals (24a, 24b) after heat sealing. May form a gap S. When such a gap S is formed, the electrolyte inside the battery leaks from the gap S, or water or the like intrudes into the battery from the gap S. I will. On the other hand, the formation of the gap S can be eliminated by increasing the thickness of the adhesive layer. However, in this case, the thickness of the sheet battery itself increases, which is not preferable.

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems and to suppress leakage of electrolyte and intrusion of moisture and the like, and to stabilize battery characteristics even though the thickness is equal to or less than the conventional thickness. An object of the present invention is to provide a sheet battery.

[0007]

According to the present invention, there is provided a sheet battery comprising:
It has the following features. (1) A structure in which two sheet-like exterior members are joined at their peripheral edges, and a laminate formed by laminating at least a positive electrode, a separator, and a negative electrode is accommodated between the exterior members. Are connected to lead terminals protruding outside of the battery from between the one exterior member and the other exterior member in the peripheral portion, respectively, and the lead terminal is connected to the exterior member at least in the joined peripheral portion. A sheet battery, wherein a cross-sectional shape of an end portion on a side in a plane direction is formed so as to be tapered outside a lead terminal.

(2) The sheet battery according to the above (1), wherein the cross section of the lead terminal has a shape selected from an ellipse, a hexagon, a parallelogram, an arc, a trapezoid, a rhombus, and an oval. .

[0009]

As described above, in the sheet battery of the present invention, the lead terminals are formed such that the cross-sectional shape of the end on the surface side of the exterior member is tapered outside the lead terminals. I have. That is, in the present invention, the cross-sectional shape of the lead terminal is not a rectangle as in the related art, but is, for example, an ellipse, a hexagon, a parallelogram, an arc, a trapezoid, a rhombus, an oval, or the like. Therefore, at the peripheral portion where the two exterior members are joined, the material forming the exterior member can easily wrap around to the side surface of the lead terminal. Note that the transverse section in the present invention refers to a section perpendicular to the longitudinal axis of the lead terminal. According to the present invention, formation of a gap between the side surface of the lead terminal and the exterior member can be suppressed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an example of the sheet battery of the present invention. FIG. 3A is a perspective view, and FIG.
Is shown in a sectional view. As shown in the example of FIG.
The sheet battery 10 includes two sheet-like exterior members (1, 2).
2) are joined at the peripheral edges of each other, and have a structure in which a laminate 3 formed by laminating at least the positive electrode 3a, the separator 3c, and the negative electrode 3b is housed between the exterior members. Lead terminals (4a for the positive electrode and 4b for the negative electrode) protruding outside the battery from between the outer member 1 and the outer member 2 in the peripheral portion are connected to the positive electrode 3a and the negative electrode 3b. The positive electrode 3
The connection between a and the lead terminal 4a for the positive electrode and the connection between the negative electrode 3b and the lead terminal 4b for the negative electrode are schematically shown. In FIG. 3A, only the outer shape of the laminate 3 is indicated by a dotted line. An electrolytic solution is further injected between the exterior members.

FIG. 1B is a cross-sectional view taken along a line AA in the thickness direction, and shows a peripheral portion where the exterior member 1 and the exterior member 2 are joined. As shown in the example of FIG. 3B, the lead terminals (4a, 4b) are at least at the peripheral edge where the exterior members 1 and 2 are joined to each other at the surface side of the exterior member (1, 2). The cross section of the portion is formed so as to be tapered outside the lead terminal.

In the example of FIG. 1B, the lead terminals (4a,
The cross section 4b) has an elliptical shape and tapers at the ends. The exterior members (1, 2) each have an adhesive layer (1a, 2a) on the side facing each other, and the adhesive layers (1a, 2a) are connected to the lead terminals (4a, 2a).
4b). Further, the adhesive layer (1
a, 2a) are formed of a hot melt adhesive.
The periphery of the exterior member 1 and the periphery of the exterior member 2 are joined by heat sealing the adhesive layer 1a and the adhesive layer 2a and fusing them together.

If the cross-sectional shape of the lead terminals (4a, 4b) is not a rectangular shape as in the prior art but an elliptical shape as described above, the adhesive layer (1) is formed during heat sealing.
a, 2a) sufficiently reaches the side surfaces of the lead terminals (4a, 4b). Therefore, the lead terminals (4a, 4a,
The formation of a gap between b) and the adhesive layer (1a, 2a) can be suppressed.

In the present invention, as shown in FIG. 1, the cross section, that is, the cross section perpendicular to the longitudinal axis of the lead terminal, of the terminal at the end on the surface direction side of the exterior member has the shape of the terminal. Any material may be used as long as it is tapered outward. The lead terminal only needs to have such a tapered cross-sectional shape only at the peripheral portion where the exterior member is joined, and does not need to have such a cross-sectional shape throughout.

In the present invention, the shape of the cross section of the end portion of the lead terminal is tapered, specifically, when the cross section of the lead terminal has an elliptical shape, a hexagonal shape, or the like as shown in FIG. It refers to the case of a parallelogram, bow, trapezoid, diamond, or oval. However, it is preferable that the shape of the cross section of the lead terminal be elliptical or elliptical from the viewpoint of easy production of the lead terminal. In the present invention, an ellipse refers to a shape represented by a quadratic curve, and an oval refers to a shape formed by attaching a rectangle between two semicircles.

FIG. 2 is a sectional view showing another example of the sheet battery of the present invention. FIG. 3A shows an example in which the cross section of the lead terminal has a hexagonal shape. FIG. 2B shows an example in which the cross section of the lead terminal has a parallelogram shape. FIG. 3C shows an example in which the cross section of the lead terminal has an arcuate shape.
FIG. 3D shows an example in which the cross section of the lead terminal has a trapezoidal shape. FIG. 7E shows an example in which the cross section of the lead terminal has a rhombic shape. FIG.
Shows an example in which the cross section of the lead terminal has an oblong shape.

The material for forming the lead terminal of the present invention may be any material that does not dissolve due to the local battery reaction inside the battery. Aluminum is preferably used for the positive electrode, and nickel or copper is preferably used for the negative electrode.

The exterior member used in the present invention has a sheet shape and forms an exterior of a sheet battery. The exterior member may be formed of a single material, or may be formed of a plurality of materials. Further, it may have a single-layer structure or a multilayer structure as shown in FIG. Further, those conventionally used for sheet batteries can also be used. The structure and material of the exterior member may be different between one and the other.

A preferred example of the exterior member has a multilayer structure in which a protective layer containing a resin material, a metal layer containing a metal material, and an adhesive layer containing an adhesive are laminated. When the exterior member has a multilayer structure as described above, resistance to external damage can be increased, and moisture resistance can be further improved. In particular, by including the metal layer, the moisture-proof effect is further enhanced.

Specifically, examples of the material for forming the protective layer include films of polyester, nylon, polycarbonate, polyarylate, liquid crystal polyester, polyphenylene sulfide, polysulfone, polyether ether ketone, and the like. Examples of the material for forming the metal layer include metal foils such as aluminum, copper, and stainless steel. Examples of the material for forming the adhesive layer include ethylene vinyl acetate copolymer (EVA), ethylene acrylic acid copolymer (EAA), and ethylene ethyl acrylate copolymer (E
EA) and olefin hot melt adhesives such as modified polypropylene resin.

The thickness of the exterior member is 60 regardless of its structure.
It may be set to about μm to 300 μm. Further, the thickness of the exterior member may be different between one and the other. When the exterior member is a laminate comprising the above-described protective layer, metal layer, and adhesive layer, the protective layer is
μm ~ 100μm, metal layer 15μm ~ 100μm
And the thickness of the adhesive layer is preferably about 30 μm to 100 μm.

The laminate sandwiched between the exterior members may be a laminate in which at least a positive electrode, a separator, and a negative electrode are laminated. As the electrolytic solution injected between the positive electrode, the separator, the negative electrode, and the exterior member, those composed of the same materials as those conventionally used for lithium ion batteries can be used. The sheet battery of the present invention can be used as a lithium ion battery.

[0023]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 A sheet battery shown in FIG. 1 was manufactured according to the following procedure. First, outer shape 100mm × 100mm, thickness 16μ
m and a 20 μm-thick aluminum metal foil having the same outer shape as described above and a dry-laminating method using a urethane-based adhesive. A hot melt adhesive made of a copolymer (EVA) having a thickness of 0.
Extrusions 1 and 2 were prepared by bonding in advance a film formed so as to have a thickness of 050 mm by thermal bonding.

The laminate housed between the exterior members was made of a material conventionally used for a lithium ion battery, and was manufactured so as to have a total thickness of 1 mm. The positive electrode was connected to a lead terminal having an oval cross section (width 3 mm, thickness 100 μm), length 100 mm, and aluminum material. The negative electrode has an oval cross section (width 4 mm,
A lead terminal having a thickness of 50 μm) and a length of 100 mm and made of nickel was connected.

Next, the exterior member 1 and the exterior member 2 obtained above
Were superimposed on each other, and heat sealing was performed only on two sides of the four peripheral parts to house the laminate. Note that the heat sealing is performed at a position within 10 mm inward from the outer periphery of the exterior member. Further, one of the two sides that were not joined was heat-sealed under the same conditions as above, and 3.5 ml of the electrolyte was injected from the other side. The remaining unbonded side was heat-sealed under the same conditions as above to obtain a sheet battery of the present invention.

Comparative Example As the lead terminal for the positive electrode, the shape of the cross section was rectangular (3
mm × 100 μm), a length of 100 mm, and a material of aluminum.
A sheet battery was produced in the same manner as in Example 1 except that a material having a thickness of 0 mm and a nickel material was used.

Evaluation With respect to the sheet batteries obtained in the above Examples and Comparative Examples,
A charge-discharge cycle test was performed under general conditions performed for a conventional lithium-ion battery, and a change in discharge capacity after a lapse of the cycle and a change in weight of the battery were examined. Table 1 shows the results.

[0028]

[Table 1]

According to Table 1, the sheet batteries obtained in the examples are as follows.
Compared with the sheet battery obtained in the comparative example, the decrease in discharge capacity with an increase in the number of cycles is small, and it can be said that the battery characteristics are excellent. Further, in the sheet battery obtained in the example, since the weight change with the increase in the number of cycles is small, it can be said that the leakage of the electrolytic solution to the outside of the battery is suppressed.

[0030]

According to the present invention as described above,
The generation of a gap between the lead terminal and the exterior member can be suppressed. Therefore, in the sheet battery of the present invention, the sealing performance is improved as compared with the conventional sheet battery, and the battery characteristics (particularly, the cycle characteristics) can be stabilized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a sheet battery of the present invention.

FIG. 2 is a diagram showing another example of the sheet battery of the present invention.

FIG. 3 is a view showing a conventional sheet battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exterior member 2 Exterior member 3 Laminated body 3a Positive electrode 3b Negative electrode 3c Separator 4a Lead terminal (positive electrode) 4b Lead terminal (negative electrode) 10 Sheet battery

Claims (2)

[Claims] 1. A structure in which two sheet-like exterior members are joined at their peripheral edges, and a laminated body formed by laminating at least a positive electrode, a separator, and a negative electrode is accommodated between the exterior members. The negative electrode is connected to lead terminals projecting to the outside of the battery from between the one exterior member and the other exterior member at the peripheral portion, and the lead terminal is provided at least at the joined peripheral portion at the outer peripheral portion. The cross-sectional shape of the end on the surface side of the member is
A sheet battery formed so as to be tapered outside a lead terminal. 2. A cross section of the lead terminal has an elliptical shape.
The sheet battery according to claim 1, wherein the sheet battery has a shape selected from a hexagon, a parallelogram, an arc, a trapezoid, a rhombus, and an oval.