JP2003303577A - Enclosed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an enclosed battery having an outer casing material free from pin holes and having a deep (over 3 mm and not more than 10 mm) rectangular draw forming part. <P>SOLUTION: In this enclosed battery comprising a power generation element, and the outer casing material accommodating the power generation element, and formed by drawing a metal laminate resin film including a soft metallic sheet and a sealant layer, into the rectangular shape, the sealant layer of the metal laminate resin film is composed of a thermoplastic resin including granulated antiblocking agent. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed battery using a draw-formed metal laminated resin film as an exterior material.

[0002]

2. Description of the Related Art In recent years, there have been remarkable improvements in the performance and miniaturization of electronic devices such as video cameras and headphone stereos, and the demand for higher energy secondary batteries as the power source for these electronic devices has increased. There is. Therefore, non-aqueous electrolyte secondary batteries using a substance capable of inserting and extracting lithium, such as lithium metal, lithium alloy, or carbonaceous material, as an anode material have been actively developed.
Above all, reducing the volume occupied by elements other than the power generation element of the battery is advantageous for increasing the energy and downsizing of the battery.

From the above, a battery in which a metal laminate resin film capable of being thinned is used instead of the metal can such as iron or aluminum which has been used as the exterior material until now is drawing attention. .

The exterior material is made of a metal laminate resin film containing a soft metal sheet such as aluminum foil and a thermoplastic film such as nylon, polyethylene or polypropylene which is a sealant layer. It is common that the layers are heat-sealed and sealed.

There are roughly two types of forms of the exterior material using such a metal laminated resin film. One is a form in which the metal laminated resin film is directly stored in a bag shape to accommodate the power generating element, and the other is. One is a form in which a metal laminate resin film is subjected to rectangular draw forming, and the power generating element is housed in the draw forming portion. The latter form has a rectangular draw-forming portion that matches the shape of the power generating element to be housed, and therefore has the advantage that the proportion of the power generating element in the battery volume can be increased compared to the former form.

[0006] When the metal resin laminate film is subjected to draw forming to produce an exterior material, there is a limit to the draw depth and it cannot be applied to all battery sizes required by the market, and the draw depth is limited. When molding in the area close to
There arises a problem that there is a risk that a small hole called a pin hole, such as a pin pierced, is opened in the soft metal sheet of the metal laminated resin film. The occurrence of pinholes is
The moisture proof property of the exterior material is lost, and there arises a problem that water enters the interior of the power generation element. Therefore, when manufacturing the exterior material, the metal laminated resin film should be deeper,
It is important to perform stable draw forming from the viewpoint of increasing the battery capacity and improving reliability.

[0007]

When performing the deep and stable rectangular draw-forming described above, one of the conditions is that the material has good slidability, but a sealant resin used for a metal laminate resin film is required. Has poor sliding properties, and is not suitable for extreme deep drawing.

Generally, it is possible to improve lubricity by using a lubricant, but the surface formed by drawing becomes the inner surface side, that is, the storage portion side of the power generation element and the electrolyte when used as an exterior material. Therefore, if the lubricant remains, the battery may swell due to a chemical reaction with the electrolyte contained in the exterior material,
There arises a problem such that the fusion bonding strength of the sealant layer is reduced or caused. In order to solve this problem, it is necessary to remove the lubricant adhering to the inner surface of the exterior material before accommodating the power generation element and the electrolyte in the exterior material, which leads to an increase in manufacturing cost due to the complicated process. .

An object of the present invention is to provide a hermetically sealed battery provided with an exterior material having a deep rectangular draw forming portion without pinholes.

[0010]

SUMMARY OF THE INVENTION A sealed battery according to the present invention includes a power generating element and an outer casing that houses the power generating element and is formed by drawing a metal laminated resin film including a soft metal sheet and a sealant layer into a rectangular shape. The sealant layer of the metal laminated resin film is made of a thermoplastic resin to which a granular antiblocking agent is added.

In the sealed battery according to the present invention, the granular antiblocking agent having an average diameter of 3 μm or more is contained in the sealant layer in an amount of 1 mm in the sealant layer.
It is preferable to add 100 or more per ² units.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a sealed battery according to the present invention,
For example, a thin lithium secondary battery will be described with reference to FIGS.

FIG. 1 is a perspective view showing a thin lithium secondary battery according to the present invention, FIG. 2 is a perspective view showing a power generating element incorporated in the secondary battery shown in FIG. 1, and FIG. 3 is a view showing the secondary battery shown in FIG. It is a perspective view which shows the exterior material used.

As shown in FIG. 2, the power generation element 1 has, for example, a positive electrode in which a positive electrode active material layer is supported on a current collector and a separator, and a negative electrode in which a negative electrode active material layer is supported on a current collector and a separator in a spiral shape. It is rolled into a flat, rectangular shape. External lead terminals 2 and 3 connected to the positive and negative electrodes
Are respectively extended to the outside from the same side surface of the power generation element 1.

The power generating element 1 has a bent portion in which the outer lead terminals 2 and 3 of the power generating element 1 are extended in a rectangular draw-molded portion 5 of a two-folded exterior material 4 shown in FIG. It is wrapped so that it is located on the side of the side opposite to the side where The exterior material 4 is made of a metal laminated resin film including a soft metal sheet and a sealant layer, and
2 of the power generation element 1 excluding the bent portion as shown in FIG.
Three side portions corresponding to one long side surface and one short side surface are heat-sealed with the sealant layer to form horizontally extending seal portions 6a, 6b, 6c, and these seal portions 6a, 6b, 6c are formed. The power generation element 1 is sealed by The external terminals 2 and 3 connected to the positive electrode and the negative electrode of the power generating element 1 are extended to the outside through the seal portion 6b on the side opposite to the bent portion. A non-aqueous electrolyte solution is impregnated and contained in the inside of the power generation element 1 and the exterior film 11 sealed by the seal portions 6a, 6b, 6c.

The power generating element is not limited to the one described above which is wound into a spiral shape and then pressure-molded into a flat shape.
You may make it the structure which laminated | stacked the positive electrode, the separator, and the negative electrode.

The draw forming portion of the exterior material is formed, for example, by the following draw forming shown in FIG. That is,
A metal-laminated resin film 11 is used as a rectangular punch 12
The resin film 11 is placed on the wrinkle holding base 13 from which the
The sealant layer is placed on the punch 12 so as to contact the punch 12. Subsequently, a die 15 having a rectangular recess 14 is formed.
Are lowered so that the concave portions 14 thereof match the punch 12, and the metal laminated resin film 11 is sandwiched between the wrinkle holding base 13 and the die 15 to prevent wrinkles from being generated in the metal laminated resin film 11. At the same time, the metal laminate resin film 11 is drawn by the punch 12 and the recess 14 to form a rectangular draw-forming portion 16 as shown in FIG.

Next, the positive electrode, the negative electrode and the separator, the exterior film, and the non-aqueous electrolytic solution which compose the power generating element will be described in detail.

1) Positive Electrode This positive electrode has a structure in which a positive electrode active material layer containing an active material binder, a binder and a conductive agent is formed on one surface or both surfaces of a current collector.

Examples of the current collector include aluminum, nickel or stainless steel plates, aluminum, nickel or stainless steel meshes, and the like.

As the positive electrode active material, various oxides,
For example, manganese dioxide, lithium manganese composite oxide,
Examples thereof include lithium-containing nickel oxide, lithium-containing cobalt compound, lithium-containing nickel-cobalt oxide, lithium-containing iron oxide, lithium-containing vanadium oxide, and chalcogen compounds such as titanium disulfide and molybdenum disulfide. Among them, lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (L
iNiO ₂ ), lithium manganese oxide (LiMn ₂ O
₄ or LiMnO ₂ ) is preferable because a high voltage can be obtained.

As the binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), etc. may be used. it can.

Examples of the conductive agent include acetylene black, carbon black, graphite and the like.

2) Negative Electrode This negative electrode has, for example, a structure in which a negative electrode active material layer containing an active material and a binder is formed on at least one surface of a current collector.

Examples of the current collector include a copper plate and a copper mesh.

The negative electrode active material is not particularly limited,
Metallic lithium, lithium alloys, coke, carbon fiber, which reversibly absorbs and desorbs lithium ions during charge and discharge, or intercalates and deintercalates.
Examples of the material include carbonaceous materials such as graphite, mesophase pitch carbon, pyrolytic vapor-phase carbonaceous material, and fired resin.

The binder preferably contains, for example, a binder such as polytetrafluoroethylene, polyvinylidene fluoride, ethylene-propylene-diene copolymer, styrene-butadiene rubber, carboxymethyl cellulose and the like.

3) Separator Examples of the separator include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-
It is made of a microporous membrane made of butene copolymer or a woven or non-woven fabric having fibers of these materials.

4) Exterior material As the metal laminate resin film constituting this exterior material, a sealant film made of a thermoplastic resin to which a granular antiblocking agent is added, and aluminum (A
1) or a soft metal sheet such as an aluminum alloy (Al alloy) and a resin film having rigidity may be laminated to form a laminated film. However, the method for laminating the thermoplastic resin on the soft metal sheet is not limited to laminating, and the thermoplastic resin may be laminated on the soft metal sheet by means such as coating.

As the thermoplastic resin, for example, polyethylene (PE), polypropylene (PP), polypropylene-polyethylene copolymer, ionomer, ethylene vinyl acetate (EVA) and the like can be used.

As the above-mentioned granular antiblocking agent,
For example, inorganic materials such as silica, talc and diatomaceous earth are preferable.

The particulate antiblocking agent is preferably added to the thermoplastic resin of the sealant layer so that 100 or more particles having an average diameter of 3 μm or more are present per 1 mm ^{2 of the} sealant layer. When the average particle size of the granular anti-blocking agent is less than 3 μm, the slipperiness of the surface of the sealant layer to which the anti-blocking agent is added cannot be sufficiently enhanced, and the metal laminate resin film having the sealant layer is more preferable. It may be difficult to perform deep and stable drawing. More preferably, the average particle size of the granular antiblocking agent is 10 to 30 μm.
Is.

When the number of the granular anti-blocking agents present per 1 mm ^{2 of the} sealant layer is less than 100, the slipperiness of the surface of the sealant layer to which the anti-blocking agent is added cannot be sufficiently enhanced, and the sealant layer is not formed. There is a possibility that it may be difficult to deeper and stably draw the metal-laminated resin film having the above. More preferably the sealant layer of the particulate anti-blocking agent 1 mm
The existing number per ² is 300 to 600.

As the organic resin having rigidity, for example, nylon, polyethylene terephthalate (PET) or the like can be used.

Specific examples of the metal laminated resin film include a laminated film of polyethylene (PE) film / Al sheet / nylon film laminated from the inner surface side to the outer surface, PE film / Al sheet / PET.
A laminated film of ionomer film / Al sheet foil / nylon film, etc. can be used.

5) Nonaqueous Electrolyte Solution The nonaqueous electrolyte solution has a composition in which an electrolyte is dissolved in a nonaqueous solvent.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ) and lithium tetrafluoroborate (LiB).
F ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), LiN (CF
₃ SO ₂ ) _{2 and the} like can be used.

As the non-aqueous solvent, for example, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, sulfolane, 3-methylsulfolane, tetraethylene glycol dimethyl ether,
Triethylene glycol dimethyl ether, methyl triglyme, butyl diglyme and the like can be used.
These non-aqueous solvents can be used in the form of one kind or a mixture of two or more kinds.

The non-aqueous electrolyte is usually used in the form of a solution, but may be in a solid form (for example, sol form, gel form, etc.) or a mixed form of solid form and solution form.

As described above, the sealed battery of the present invention comprises a power generating element and an exterior material that houses the power generating element and is formed by drawing a metal laminated resin film including a soft metal sheet and a sealant layer into a rectangular shape. The sealant layer of the metal laminated resin film is made of a thermoplastic resin to which a granular anti-blocking agent is added.

According to such a constitution, the granular anti-blocking agent added to the sealant layer is incompatible with the thermoplastic resin such as polypropylene or polyethylene and forms microscopic roughness on the surface of the sealant layer. Therefore, the slipperiness of the surface of the sealant layer can be improved. Since the sealant layer is brought into contact with the punch 12 shown in FIG. 4 described above when drawn in the state of the metal laminate resin film, the metal laminate resin film is improved by improving the slipperiness of the sealant layer surface. Deep and stable drawing is possible. As a result, it is possible to obtain an exterior material having a deep rectangular draw forming portion of more than 3 mm and 10 mm or less without generating pinholes and the like.

Particularly, an average diameter of 3 μm is contained in the sealant layer.
By adding 100 or more of the granular antiblocking agent having a size of m or more per 1 mm ² of the sealant layer, the slipperiness of the surface of the sealant layer can be further improved. A deeper and more stable draw forming of a metal laminated resin film having a layer is possible, and there is no occurrence of pinholes, etc., and an exterior having a deep rectangular draw forming portion of more than 3 mm (particularly more than 6 mm) and 10 mm or less. The material can be obtained.

Therefore, according to the present invention, the exterior material having a deep (more than 3 mm and less than 10 mm) rectangular draw-forming portion without pinholes is provided to maintain stable quality and meet various size requirements. It is possible to realize a high-capacity, highly reliable sealed battery that can also be used.

[0044]

The preferred embodiments of the present invention will be described in detail below.

Example 1 A three-layer metal laminated resin film prepared by laminating a nylon film having a thickness of 25 μm, a soft aluminum sheet having a thickness of 40 μm and a polyethylene film having a thickness of 30 μm as a sealant layer in this order is prepared. did. The polyethylene film has silica added as an anti-blocking agent,
When the surface of the film was observed by a scanning electron microscope (SEM), 10 to 30 silica particles having a diameter of 3 to 15 μm were present in the visual field of 1 mm ² .

Comparative Example 1 A metal laminated resin film similar to that of Example 1 was prepared except that a polyethylene layer containing no antiblocking agent was used.

The metal laminated resin films of Example 1 and Comparative Example 1 were cut into a size of 200 mm long and 150 mm wide, and these metal laminated resin films were placed on the wrinkle holder 13 as shown in FIG. Then, the polyethylene film (sealant layer) was placed so as to contact the rectangular punch 12 side, and rectangular drawing was performed to confirm the presence or absence of pinholes.

The dimensions of the rectangular punch 12 subjected to the draw forming were 55 mm in length and 33 mm in width, and the curvature radii of all corners and sides were 2.0 mm. In addition, the rectangular recess 1 formed in the die 15 combined with the punch 12.
The dimension of 4 was 55.5 mm in length and 33.5 mm in width, and the radii of curvature of all corners and sides were also 2.0 mm. The size of the die 15 for inserting the metal laminated resin film and the size of the wrinkle holder 13 are both 200 mm in length and 150 mm in width, and the whole of the metal laminated resin film cut is sandwiched and formed so that the depth of the drawing portion is 4 mm in outer dimension. did.

Table 1 below shows the number of pinholes generated in the 500 metal laminated resin films of Example 1 and Comparative Example 1.

[0050]

[Table 1]

As is clear from Table 1, in Example 1, it was confirmed that no pinholes were generated in all 500 sheets in the drawing with a depth of 4 mm.

On the other hand, in Comparative Example 1, it was confirmed that pinholes were generated in 55 out of 500 sheets in the draw forming at a depth of 4 mm, which shows that the draw formability is inferior to that in Example 1.

Example 2 A three-layer metal laminated resin film was prepared by laminating a nylon film having a thickness of 25 μm, a soft aluminum sheet having a thickness of 40 μm and a polyethylene film having a thickness of 30 μm as a sealant layer in this order. did. The polyethylene film has silica added as an anti-blocking agent,
When the surface of the film was observed by a scanning electron microscope (SEM), 100 to 150 silica particles having a diameter of 3 to 15 μm were present in the visual field of 1 mm ² .

(Example 3) Polyethylene film (see
As the runt layer), the surface of the film is scanned with an electron microscope.
Blockin with a diameter of 3 to 15 μm as observed with a mirror (SEM)
1mm anti-corrosion agent ²There are 500 to 600 in the field of view of
The same metal laminae as in Example 2 except that the same one was used.
A resin film was prepared.

A metal laminate resin film (Comparative Example 2) similar to that of Example 2 was used except that the metal laminate resin films of Examples 2 and 3 and the polyethylene layer containing no antiblocking agent were used. 150
The metal laminated resin film is cut into a size of mm and placed on the wrinkle holder 13 so that the polyethylene film (sealant layer) contacts the rectangular punch 12 side as shown in FIG. The rectangular draw forming was performed under the same conditions as in Example 1 except that the outer dimension of the draw forming portion was set to 6 mm, and the presence or absence of pinholes was confirmed.

Table 2 shows the number of pinholes in the 500 metal laminated resin films of Examples 2 and 3 and Comparative Example 2.

[0057]

[Table 2]

As is clear from Table 2 above, Examples 2, 3
Then, it was confirmed that pinholes were not generated in all 500 sheets in the deep drawing of 6 mm deeper than in Example 1.

On the other hand, in Comparative Example 2, 12 out of 500 sheets
Generation of pinholes was confirmed with 0 sheets, and it is understood that the draw formability is inferior to Examples 2 and 3.

As described above, the metal laminated resin film having the sealant layer to which the granular anti-blocking agent is added as in Example 1 can be deeply and stably formed by drawing, so that there is no pinhole and the like, and a large volume of power generation is possible. It is possible to obtain an exterior material having a draw forming part capable of accommodating elements. In particular, an average diameter of 3 in the sealant layer
A metal laminate resin film having a sealant layer in which the granular anti-blocking agent having a size of μm or more is added so that 100 or more are present per 1 mm ^{2 of} the sealant layer is deeper and stable drawing is possible,
As a result, it is possible to obtain an exterior material having no draw hole and the like, which has a draw-formed portion capable of accommodating a power generating element having a larger volume.

[0061]

As described above in detail, according to the present invention, an exterior material having a deep rectangular draw forming portion without pinholes is provided, stable quality is maintained, and various size requirements are met. It is possible to provide a high-capacity, highly reliable sealed battery capable of achieving.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a thin lithium secondary battery which is a sealed battery according to the present invention.

FIG. 2 is a perspective view showing a power generation element incorporated in the secondary battery of FIG.

FIG. 3 is a perspective view showing an exterior material used in the secondary battery of FIG.

FIG. 4 is a perspective view showing an embodiment for performing draw forming on a metal laminated resin film.

[Explanation of symbols]

1 ... power generation element, 4 ... Exterior material, 5, 16 ... Rectangular draw forming part, 11 ... Metal laminated resin film, 12 ... Rectangular punch, 13 ... Wrinkle holder, 14 ... Rectangular recess, 15 ... Dice.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 9, 2002 (2002.9.9)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

The power-generating element is not limited to the above-described spiral-shaped coil which is pressure-molded into a flat shape.
You may make it the structure which laminated | stacked the positive electrode, the separator, and the negative electrode.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

1) Positive Electrode This positive electrode has an active material on one or both sides of the current collector, for example.
It has a structure in which a positive electrode active material layer containing a quality, a binder and a conductive agent is formed.

Continued front page    F-term (reference) 5H011 AA09 BB04 CC02 CC06 CC10                       DD01 KK01                 5H029 AJ14 AK02 AK03 AK05 AL06                       AL07 AL08 AL12 AM03 AM04                       AM05 AM07 BJ04 DJ02 EJ01                       EJ12 HJ04

Claims (3)

[Claims] 1. A sealed battery comprising: a power generating element; and an exterior material that houses the power generating element and is formed by drawing a metal laminated resin film including a soft metal sheet and a sealant layer into a rectangular shape, wherein the metal is The sealed battery, wherein the sealant layer of the laminated resin film is made of a thermoplastic resin to which a granular antiblocking agent is added. 2. The sealant layer has an average diameter of 3 μm.
The sealed battery according to claim 1, wherein the granular antiblocking agent having a size of m or more is added so that 100 or more are present per 1 mm ^{2 of the} sealant layer. 3. The exterior material exceeds 3 mm and 10 mm
The sealed battery according to claim 1, which is drawn by a rectangular shape having the following depth.