JP2002208442A - Electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical device with excellent safety, without problem of short circuit between electrodes, and not developing into a hard short even when a cell is deformed, due to high strength of a lamination body. SOLUTION: The electrochemical device, comprising a lamination body laminating positive electrodes and negative electrodes through separators, is formed by strongly integrating at least partial areas of the peripheral part of the separator of the laminated body by making them adhere to each other, or, by arranging a heat shrinkable film so as to wrap the outer periphery of the lamination body, and further, strongly integrating at least partial areas of the peripheral part of the separator of the laminated body by making them adhere to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical device having stacked electrode pairs, and more particularly to a lithium secondary battery and an electric double layer capacitor.

[0002]

2. Description of the Related Art With the spread of portable electronic devices, there is a demand for electrochemical devices such as secondary batteries which are small, lightweight, thin and can be operated continuously for a long time. Conventional secondary batteries have used metal outer cans, but the use of an aluminum laminate film for the outer bag has made it possible to produce thinner and lighter secondary batteries.

As a method of forming an electrode group to be put in an outer bag, there are a method of winding a long electrode and a method of laminating a large number of electrodes.

The winding method can be used as it is as an advanced type of cylindrical battery, but the shape of the battery is limited, and it is difficult to produce a battery having a shape other than a cube, a rectangular parallelepiped or a column. In addition, when an attempt is made to manufacture a thin battery, the electrode may be cracked or cut by winding, so that a thick and dense electrode cannot be used, which is disadvantageous in terms of energy density.

On the other hand, in the lamination method, the shape of the battery can be made relatively free, and since there is no need to wind it, a thick and dense electrode can be used, and a thinner and higher energy density battery can be produced. .

A number of proposals have been made for designing a battery that is difficult to short-circuit by the lamination method. One of them is the bag method. JP-A-6-36801, JP-A-9-2133
As disclosed in JP-A-77-77 and JP-A-10-55795, an electrode is generally sandwiched between two separators, and then a peripheral portion is thermally fused to form a bag-shaped electrode. create. Next, the electrodes are stacked and stored in a metal can or an outer bag to form a battery.

However, in these bag construction methods, since the laminate itself is not fixed even if the electrodes are laminated with high precision, the electrodes move during or after the laminate is stored in the metal can or the outer bag, and the lamination is performed. There is a high possibility that displacement will occur. If the stacking deviation is too large, there is a possibility that a portion where the positive electrode and the negative electrode are not opposed to each other may be formed. In this case, precipitation of lithium metal called lithium dendrite occurs, leading to deterioration of cycle characteristics. In the worst case, lithium dendrite may grow, break through the separator, and cause an internal short circuit. Furthermore, when stored in an outer bag with low strength such as an aluminum laminated film, when the bag swells due to gas generation or any other factor, the strength of this laminate is very weak, and it cannot withstand the deformation of the bag. The body itself is also deformed, and the deformation may cause a hard short, which may cause the battery to burst or ignite.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the problem of short circuit between the positive and negative bipolar sheets, to prevent the electrodes from moving even after lamination, and to increase the strength of the laminate, so that even if the battery is deformed. An object of the present invention is to provide an electrochemical device with excellent safety that does not reach a hard short.

[0009]

That is, the above object is achieved by the following constitution of the present invention. (1) An electrochemical device having a laminate in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, wherein at least a part of the peripheral portion of the separator of the laminate is bonded firmly to each other. . (2) An electrochemical device having a laminate in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, wherein a heat-shrinkable film is arranged so as to surround an outer peripheral portion of the laminate, and at least a separator of the laminate is provided. An electrochemical device that is firmly integrated by bonding with a part of the peripheral part of the device. (3) The electrochemical device according to (2), wherein the heat-shrinkable film is a polyolefin microporous film. (4) The positive electrode and / or the negative electrode are housed in a bag-shaped separator (1) to (3).
Any of the electrochemical devices. (5) The electrochemical device according to any one of (1) to (4), wherein the outer bag has an aluminum laminated film. (6) The electrochemical device according to any one of the above (1) to (5), which is a lithium secondary battery.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An electrochemical device according to the present invention is an electrochemical device having an electrode pair in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, wherein at least a part of a peripheral part of the separator of the laminate is formed. It is bonded and firmly integrated.

Alternatively, there is provided an electrochemical device having a laminate in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, wherein a heat-shrinkable film is arranged so as to surround an outer peripheral portion of the laminate, and And a part of the peripheral part of the separator is firmly integrated with each other.

The electrochemical device thus obtained is not only less likely to cause lamination displacement, but also has good results in a predetermined heat test called a hot oven, and is excellent in safety.

Further, by integrating the laminated body, the handleability is facilitated, and the manufacturing process such as encapsulation in an exterior body is simplified.

Next, the electrochemical device of the present invention will be described in more detail with reference to the drawings.

FIGS. 1 and 2 are a plan view showing a schematic configuration of the electrochemical device of the present invention and a sectional view taken along the line AA '. In each drawing, the exterior body is omitted. In the figure, a laminate 2 includes a positive electrode 4, a negative electrode 5, a separator 3
And are alternately stacked.

The size of the separator 3 is larger than that of the electrode composed of the positive electrode 4 and the negative electrode 5, and is set so as to protrude around the electrodes 4 and 5, particularly on both sides when the layers are laminated.

The separator 3 is preferably formed in a bag shape so as to surround the electrodes 4 and 5. Such a bag-shaped separator is obtained by bending one sheet, sandwiching the positive electrode and / or the negative electrode with the separator, and bonding the peripheral portion, or sandwiching the positive electrode and / or the negative electrode with the two separators, Can be obtained by bonding. In this case, at least the extraction electrodes of the positive electrode and / or the negative electrode are not bonded.

That is, the electrodes 4 and 5 are provided with external lead-out terminals (lead-out electrodes), or the lead-out portions 4a and 5a such that a part thereof protrudes from the outer periphery of the separator so as to constitute an external lead-out terminal by itself. Having.

The separator 3 is bonded at its peripheral portion, that is, at a portion which does not overlap with the electrodes 4 and 5 in a plan view when stacked.

The bonding can be performed by the following two methods.

(1) First, a separator folded in half,
Alternatively, after sandwiching the positive electrode and / or the negative electrode between the two separators, the peripheral portion is bonded, and the electrode-separator composite and the electrode to be paired are laminated, and the side end portion (ear end portion) ) Is adhered again. Alternatively, the electrodes may be laminated with an electrode / separator / electrode / separator and the peripheral portions may be bonded at one time.

(2) First, after a positive electrode and / or a negative electrode are sandwiched between two folded separators or two separators, peripheral portions are bonded to produce a bag housing the electrodes. Further, the electrode-separator composite and the electrode to be paired are laminated, and a heat-shrinkable film is disposed so as to be wound around the outer peripheral portion of the obtained laminated body, particularly around its side end (ear end). Finally, it is bonded to the side end (ear end). Alternatively, it may be laminated with an electrode / separator / electrode / separator, wrapped with a heat-shrinkable film, and finally, the peripheral portion and the heat-sealing film may be bonded at one time.

In the present invention, the term "adhesion" means that the peripheral portion or the edge portions of the separator or the side portions of the laminate and the heat-sealing film wound on the laminate are physically bonded to each other.
It means to fix. Normally, the bonding takes the form of heat fusion, but in addition, an optimum bonding method may be used depending on the material and shape of the separator. For example, an adhesive or a fixture made of a resin material may be used.

The condition for heat-sealing the separator depends on the material of the separator to be used, but usually the heating temperature is preferably about 150 to 350 ° C. The heating time is preferably 0.5 to 5 seconds, particularly preferably 1 to 2 seconds. Further, the pressure when pressurizing is preferably about 7 to ²⁰ kg / cm ² .

It is sufficient that at least two or more peripheral portions are bonded to each other as an adhesive region for integrating the laminated body. As shown in FIGS. You may. Preferably, 10% or more of the entire area of the peripheral portion, particularly about 30 to 80%, is used as the final bonding area. In this case, as described above, bonding for sandwiching (wrapping) one electrode itself may be performed in advance, or bonding may be performed at once.

As a bonding region for obtaining a bag, when one separator is folded to form a bag, x = 0.1
５5 mm, y = about 0.1-1 mm is preferred. When a bag is obtained using two separators, x = 0.1 to
5 mm, y and z are about 0.1 to 1 mm.

It is preferable that the gap between the electrode and the bonding portion is minimized. Usually, it is preferably 150 mm or less, particularly preferably 0.5 mm or less.

There are various modes for manual production of the above-mentioned laminate, but the following two methods are preferred.

(1) In the case where no heat-shrinkable film is arranged on the outer peripheral portion: a separator, a positive electrode, a separator, a negative electrode, a separator
..., and a certain number of layers are precisely stacked so that the negative electrode always faces the positive electrode, and only the periphery of the separator is hot-pressed at the temperature at which the separator is fused, so that the laminated body is integrated. Get.

The positive electrode and / or the negative electrode are sandwiched between separators, and only the periphery of the separator is heat-sealed. Also, the separator at the side portion is slightly larger to be heat-sealed again (this portion is referred to as an ear end portion). Using the bag-like separator with electrodes thus made, as above,
A certain number of layers are precisely stacked so that the negative electrode always faces the positive electrode. Finally, the end portions of the separator ears are again heat-sealed to obtain an integrated laminate.

(2) When a heat-shrinkable film is arranged on the outer peripheral portion First, the positive electrode and / or the negative electrode are sandwiched between two folded separators or two separators, and then the electrodes are housed. Make a bag. Further, as shown in FIG. 3, this electrode-separator composite and a pair of electrodes (a negative electrode in the case of a positive electrode) are laminated, and the outer peripheral part of the obtained laminated body, particularly its side end ( The heat-shrinkable film is arranged so as to be wound around the ear end. At this time,
The heat-shrinkable film is preferably wound one or more times, especially one or two times. The heat-shrinkable film is disposed so as to cover at least 10%, particularly at least 30%, of the projected area of the laminate. Finally, it is bonded to the side end (ear end).
Or electrode / separator / electrode / separator ...
And wrapped in a heat-shrinkable film, and finally adhered to the periphery at once.

The conditions for fusing the heat shrinkable film and the separator are as follows: pressure: a degree at which the laminate is shaped, specifically about 0.5 to ⁵ kg / cm ² , and a temperature of 150 to 150 kg / cm ^2.
About 350 ° C., preferably for 0.5 to 5 seconds, especially 1 to 2
It may be applied for about a second.

The laminate obtained by the above methods (1) and (2) is placed in an outer bag such as an aluminum laminated film to obtain an electrochemical device. In carrying out the present invention, a predetermined part of the fusion-processed portion may be unfused. This has the effect of promoting the penetration of the electrolytic solution into the electrodes and preventing the occurrence of wrinkles. For the fusion bonding of the separator, a method such as a combination of heat and pressure bonding is suitable. The fused portion may be bent, and unnecessary portions may be cut.

The separator sheet forming the separator may be composed of one or more polyolefins such as polyethylene and polypropylene (in the case of two or more polyolefins, there are two or more laminated films).
Examples include polyesters such as polyethylene terephthalate, thermoplastic fluororesins such as ethylene-tetrafluoroethylene copolymer, and celluloses. The form of the sheet is such that the air permeability measured by the method specified in JIS-P8117 is about 5 to 2000 seconds / 100 cc, and the thickness is 5 to 100.
There is a microporous membrane film of about μm, woven fabric, non-woven fabric, etc.

In the present invention, it is particularly desirable to use a so-called shutdown separator as the separator. By using the shutdown separator, as the temperature inside the electrochemical device rises, the micropores of the separator are closed, the conduction of ions is suppressed, the current is suppressed, and thermal runaway can be prevented. Examples of such a shutdown separator include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDP) described in, for example, Japanese Patent No. 2642206.
E) A separator made of a synthetic resin film having micropores containing at least one of the above, containing 1% by weight or more of ultrahigh molecular weight polyethylene having a weight average molecular weight of 7 × 10 5 or more described in JP-A No. It is made of a microporous film composed of a polyethylene composition having an average molecular weight / number average molecular weight of 10 to 300, and has a thickness of 0.1 to 25 μm and a porosity of 40.
To 95%, an average through-hole diameter of 0.001 to 0.1 μm, and a breaking strength of 10 mm width having a breaking strength of 0.5 kg or more, wherein the polyethylene composition is made of an aliphatic hydrocarbon or a cyclic hydrocarbon. Alternatively, the resin is heated and dissolved in a non-volatile solvent composed of a mineral oil fraction to form a uniform solution, and the solution is extruded from a die to form a gel-like sheet. After the non-volatile solvent is removed, stretching is performed at least twice in at least one axial direction. And a separator for a lithium battery.

Also, Japanese Patent Application Laid-Open Nos. 9-219184, 2000-223107, and 2000-10
No. 0408 can also be used.

A gel type polymer may be used for the separator. For example, (1) polyalkylene oxide such as polyethylene oxide and polypropylene oxide;
(2) a copolymer of ethylene oxide and acrylate,
(3) a copolymer of ethylene oxide and glycyl ether, (4) a copolymer of ethylene oxide, glycyl ether and allyl glycyl ether, (5) polyacrylate (6) polyacrylonitrile (7) polyvinylidene fluoride, fluoride Fluorinated materials such as vinylidene-hexafluoropropylene copolymer, vinylidene fluoride-ethylene chloride trifluoride copolymer, vinylidene fluoride-hexafluoropropylene fluororubber, vinylidene fluoride "tetrafluoroethylene-hexafluoropropylene fluororubber, etc. Polymers and the like.

The gel polymer may be mixed with an electrolytic solution, or may be applied to a separator or an electrode. Further, by adding an initiator, the gel polymer may be cross-linked by ultraviolet rays, EB, heating or the like.

As the heat-shrinkable film wrapping the laminate, polyethylene, polypropylene or the like exemplified for the above separator can be used. In addition, PET
A film, a PEN film, an aramid film and the like can also be used.

The thickness of the heat-shrinkable film is not particularly limited, but is usually about 5 to 50 μm.
The shrinkage temperature of the heat-shrinkable film is preferably 9
It is about 0 to 200 ° C.

The electrochemical device of the present invention has a structure in which positive and negative electrodes composed of metal foil such as aluminum foil or copper foil, for example, and separators are alternately laminated. External electrodes (lead-out terminals) are connected to the positive and negative electrodes, respectively. The external electrode is aluminum,
It is composed of a metal foil such as copper, nickel, and stainless steel.

The electrochemical device used for the electrochemical device of the present invention is not limited to a battery such as a lithium secondary battery, and a capacitor having a similar structure can be used.

The electrochemical device of the present invention can be used as a lithium secondary battery or an electric double layer capacitor as described below.

<Lithium Secondary Battery> Although the structure of the lithium secondary battery is not particularly limited, it is generally composed of a positive electrode, a negative electrode, and a separator, and is applied to a stacked battery, a cylindrical battery, and the like.

The electrode to be combined with the solid polymer electrolyte may be appropriately selected from those known as electrodes for a lithium secondary battery, and is preferably used as an electrode active material and a gel electrolyte. Is used.

For the negative electrode, a negative electrode active material such as a carbon material, lithium metal, lithium alloy or oxide material is used. For the positive electrode, an oxide or carbon material capable of intercalating / deintercalating lithium ions is used. It is preferable to use such a positive electrode active material as described above. By using such an electrode, a lithium secondary battery having excellent characteristics can be obtained.

The carbon material used as the electrode active material may be appropriately selected from, for example, mesocarbon microbeads (MCMB), natural or artificial graphite, resin fired carbon material, carbon black, carbon fiber and the like. These are used as powders. Above all, graphite is preferred, and its average particle size is preferably 1 to 30 μm, particularly preferably 5 to 25 μm. If the average particle size is too small, the charge / discharge cycle life tends to be short and the variation in capacity (individual difference) tends to be large. If the average particle size is too large, the dispersion of the capacity becomes extremely large, and the average capacity becomes small. It is considered that the capacity variation occurs when the average particle size is large because the contact between the graphite and the current collector and the contact between the graphites vary.

Lithium ion is intercalated day
Intercalatable oxides include lithium
Complex oxides are preferred, for example, LiCoO_Two, LiM
n_TwoO _Four, LiNiO_Two, LiV_TwoO_FourAnd the like.
The average particle size of these oxide powders is about 1 to 40 μm.
It is preferred that

A conductive assistant is added to the electrode if necessary. Preferred examples of the conductive auxiliary agent include metals such as graphite, carbon black, carbon fiber, nickel, aluminum, copper, and silver. Particularly, graphite and carbon black are preferable.

The composition of the electrode is preferably in the range of 80 to 94: 2 to 8: 2 to 18 in terms of the weight ratio of the active material: the conductive auxiliary agent: the binder in the positive electrode. Agent: Binder = 70-97: 0-25: 3-10 is preferred.

As the binder, a thermoplastic elastomer resin such as a fluororesin, a polyolefin resin, a styrene resin or an acrylic resin, or a rubber resin such as a fluororubber can be used. Specific examples include polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyacrylonitrile, nitrile rubber, polybutadiene, butylene rubber, polystyrene, styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethylcellulose, carboxymethylcellulose and the like.

In the production of an electrode, first, an active material and, if necessary, a conductive auxiliary are dispersed in a binder solution to prepare a coating solution.

Then, this electrode coating solution is applied to a current collector. The means for applying is not particularly limited, and may be determined as appropriate according to the material and shape of the current collector. Generally, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method, a screen printing method, and the like are used.
Thereafter, if necessary, a rolling treatment is performed by a flat plate press, a calender roll, or the like.

The current collector may be appropriately selected from ordinary current collectors according to the shape of the device used by the battery and the method of arranging the current collector in the case. Generally, aluminum or the like is used for the positive electrode, and copper, nickel, or the like is used for the negative electrode.
Note that a metal foil, a metal mesh, or the like is generally used as the current collector. Although the metal mesh has lower contact resistance with the electrode than the metal foil, a sufficiently low contact resistance can be obtained even with the metal foil.

Then, the solvent is evaporated to produce an electrode. The coating thickness is preferably about 50 to 400 μm.

Such a positive electrode, a separator, and a negative electrode are laminated in this order, and pressed to form a battery element.

The electrolytic solution impregnated in the separator generally comprises an electrolyte salt and a solvent. Examples of the electrolyte salt include L
iBF ₄ , LiPF ₆ , LiAsF ₆ , LiSO ₃ CF
₃ , lithium salts such as LiClO ₄ and LiN (SO ₂ CF ₃ ) ₂ can be used.

The solvent of the electrolytic solution is not particularly limited as long as it has good compatibility with the above-mentioned solid polymer electrolyte and electrolyte salt, but in a lithium battery or the like, a polar organic solvent which does not decompose even at a high operating voltage. Solvents, for example, carbonates such as ethylene carbonate (abbreviation EC), propylene carbonate (abbreviation PC), butylene carbonate, dimethyl carbonate (abbreviation DMC), diethyl carbonate, ethyl methyl carbonate, etc., tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like A cyclic ether, a cyclic ether such as 1,3-dioxolan, 4-methyldioxolan, a lactone such as γ-butyrolactone, a sulfolane, and the like are preferably used. 3-Methylsulfolane, dimethoxyethane, diethoxyethane, ethoxymethoxyethane, ethyldiglyme and the like may be used.

When it is considered that the electrolyte is composed of the solvent and the electrolyte salt, the concentration of the electrolyte salt is preferably 0.3 to 5 mol.
l / l. Usually, the highest ion conductivity is exhibited at around 0.8 to 1.5 mol / l.

<Electric Double Layer Capacitor> Although the structure of the electric double layer capacitor used in the present invention is not particularly limited, usually, a pair of polarizable electrodes are arranged via a separator, and the polarizable electrode and the peripheral portion of the separator are arranged. Is preferably provided with an insulating gasket. Such an electric double layer capacitor may be any type called a paper type, a laminated type, or the like.

As the polarizable electrode, activated carbon, activated carbon fiber, or the like is used as a conductive active material, and a fluororesin, a fluororubber, or the like is added as a binder. Then, it is preferable to use the mixture formed on a sheet-like electrode. The amount of the binder is about 5 to 15% by mass. Further, a gel electrolyte may be used as the binder.

The current collector used for the polarizable electrode is platinum,
It may be a conductive rubber such as a conductive butyl rubber or the like, may be formed by spraying a metal such as aluminum or nickel, or may be provided with a metal mesh on one surface of the electrode layer.

In the electric double layer capacitor, the polarizable electrode and the separator as described above are combined. The separator is the same as that described for the lithium secondary battery.

For the separator, for example, PEO
(Polyethylene oxide) -based, PAN (polyacrylonitrile) -based, PVDF (polyvinylidene fluoride) -based microporous membranes can be used.

As the electrolyte salt, (C ₂ H ₅ ) ₄ NB
F ₄ , (C ₂ H ₅ ) ₃ CH ₃ NBF ₄ , (C ₂ H ₅ ) ₄ PB
F _4, and the like.

The non-aqueous solvent used for the electrolytic solution may be any of various known ones, and propylene carbonate, ethylene carbonate, γ-
Butyrolactone, acetonitrile, dimethylformamide, 1,2-dimethoxyethane, sulfolane alone or a mixed solvent is preferred.

The concentration of the electrolyte in such a non-aqueous solvent-based electrolyte solution may be 0.1 to 3 mol / l.

When a microporous polymer film is immersed in such an electrolytic solution, the polymer film absorbs the electrolytic solution and gels to form a solid polymer electrolyte.

When the composition of the solid polymer electrolyte is represented by copolymer / electrolyte, the ratio of the electrolyte is preferably 40 to 90% by mass from the viewpoint of the strength of the membrane and the ionic conductivity.

As the insulating gasket, an insulator such as polypropylene or butyl rubber may be used.

The outer bag is composed of a laminated film in which a polyolefin resin layer such as polypropylene or polyethylene or a heat-resistant polyester resin layer as a heat-adhesive resin layer is laminated on both sides of a metal layer such as aluminum. . The outer bag is formed in a bag shape with one side opened by previously bonding two laminated films to each other by thermally bonding the heat-adhesive resin layers on the three end surfaces thereof to each other. Alternatively, a single laminated film may be folded back and the both end faces may be thermally bonded to form a seal portion to form a bag.

The laminated film has a laminated structure of a heat-adhesive resin layer / polyester resin layer / metal foil / polyester resin layer from the interior side in order to ensure insulation between the metal foil constituting the laminated film and the lead terminals. It is preferable to use a laminate film. By using such a laminated film, the high melting point polyester resin layer remains without melting at the time of thermal bonding, so that a separation distance between the lead terminal and the metal foil of the outer package can be ensured, and insulation can be ensured. Therefore, the thickness of the polyester resin layer of the laminate film is preferably about 5 to 100 μm.

[0073]

The present invention will be described below in more detail with reference to examples and comparative examples. [Example 1] (Production of battery)

[0074]

Separator Polyethylene microporous membrane film

The positive electrode was LiCoO ₂ (C-010, manufactured by Seimi Chemical), carbon black (HS-100, manufactured by Denki Kagaku Kogyo), graphite (KS-6, manufactured by TIMCAL), PV
DF (KF-1300, made by Kureha) was applied to an aluminum foil by a doctor blade method and dried to produce. The negative electrode is composed of mesocarbon microbeads (MCMB, manufactured by Osaka Gas), carbon black (HS-100, manufactured by Denki Kagaku Kogyo), and PVDF (KF-1100, manufactured by Kureha) applied to copper foil by the doctor blade method. It was made by drying. The produced positive and negative electrodes were pressed to have a predetermined thickness, and then punched in a predetermined size.

Next, the two-folded separator (thickness
25μm, polyethylene microporous membrane film, manufactured by Asahi Kasei,
A negative electrode was inserted into a product name: microporous membrane high bore N910), and three sides were heat-sealed to produce a bag-shaped negative electrode surrounded by a separator as shown in FIG. As shown in FIG. 1, the separators on both sides of the electrode are slightly larger (ear ends) because they are heat-sealed again. Next, a predetermined number of positive electrodes and negative electrodes were laminated in this order, and finally, the ear ends were heat-sealed to obtain an integrated laminated body.

A lead wire was welded to the laminate, and then inserted into an outer bag (aluminum laminated film, manufactured by Showa Aluminum). Next, an electrolyte solution of EC / DEC = 4/6 was injected, sealed, pre-charged, and aged to produce a sheet-type non-aqueous electrolyte secondary battery.

[Example 2] Positive and negative electrodes were produced in the same manner as in Example 1, and electrodes of a predetermined size were punched out. Next, a positive electrode, a separator cut into a predetermined size, and a negative electrode were laminated in a predetermined number in this order, and finally, a peripheral portion of the separator was heat-sealed to obtain an integrated laminated body.

A lead wire was welded to the laminate, and then inserted into an outer bag (aluminum laminated film, manufactured by Showa Aluminum). Next, an electrolyte solution of EC / DEC = 4/6 was injected, sealed, pre-charged and aged, thereby producing a sheet-type non-aqueous electrolyte secondary battery.

[Example 3] Positive and negative electrodes were produced in the same manner as in Example 1, and electrodes of a predetermined size were punched out. Next, FIG.
As shown in (2), the negative electrode was sandwiched between two separators, and the four sides (including the region indicated by z in FIG. 1) were heat-sealed to produce a negative electrode housed in the bag separator. A predetermined number of positive electrodes and negative electrodes produced in the same manner are laminated, and wrapped with a heat-shrinkable film (polyethylene microporous film, thickness 16 μm, manufactured by Tonen Corp., trade name: E16MMS) for at least one turn, and finally the heat-shrinkable film and the laminate side The parts were heat-sealed to obtain an integrated laminate as shown in FIG.

For this heat fusion, a fusion device as shown in FIG. 3 was used. That is, the U-shaped heating section 12 of the fusion device having the U-shaped heating section 12 on the base 11.
Inside, a laminate in which the separator 3 and the electrodes 4 and 5 were laminated was arranged. Then, the pressure at which the laminate is shaped into a predetermined shape by the pressurizing cylinder 13, specifically, a pressure of 0.1 mm.
A pressure of about 5 to 5 kg / cm ² was applied. At this time, the size (width) of the U-shaped heating portion 12 is adjusted to a size such that the just-shaped end of the separator 3 contacts. Then, the temperature required for heat fusion to the U-shaped heating unit 12,
Preferably about 150-350 ° C., preferably 0.5
印 加 5 seconds, especially about 1 to 2 seconds. In this way, as shown in FIG.
a was fused and the heat-shrinkable film itself shrunk, and was closed and fixed to obtain an integrated laminate. Such a fusion device can be obtained, for example, by modifying the heater portion of FT130 manufactured by Fuji Impulse Industry Co., Ltd.

A lead wire was welded to this laminate, and then inserted into an outer bag (aluminum laminated film, manufactured by Showa Aluminum). Next, an electrolyte solution of EC / DEC = 4/6 was injected, sealed, pre-charged and aged, thereby producing a sheet-type non-aqueous electrolyte secondary battery.

Comparative Example 1 Positive and negative electrodes were produced in the same manner as in Example 1, and electrodes of a predetermined size were punched out. Next, a positive electrode coated with a small amount of a hot-melt type adhesive (A100, manufactured by Mitsui Chemicals) that does not greatly affect the capacity at the center, a separator cut in a predetermined size, and an adhesive coated in the same manner as the positive electrode A certain number of negative electrodes were stacked in this order, and only the part to which the adhesive was applied was hot-pressed at 90 ° C. for 1 minute to obtain a laminated body.

A lead wire was welded to this laminate, and then inserted into an outer bag (aluminum laminated film, manufactured by Showa Aluminum). Next, an electrolyte solution of EC / DEC = 4/6 was injected, sealed, pre-charged, and aged to produce a sheet-type non-aqueous electrolyte secondary battery.

Comparative Example 2 Positive and negative electrodes were produced in the same manner as in Example 1, and electrodes of a predetermined size were punched out. Next, the negative electrode was inserted into the folded separator, and three sides were heat-sealed to produce a negative electrode surrounded by the separator as shown in FIG. Next, a predetermined number of positive electrodes and the negative electrode are stacked in this order,
The lead wire was welded without heat-sealing the side portions, and then inserted into an outer bag (aluminum laminated film, Showa aluminum foil). Next, an electrolyte solution of EC / DEC = 4/6 was injected, sealed, pre-charged, and aged to produce a sheet-type non-aqueous electrolyte secondary battery.

Evaluation Method The batteries prepared in Examples 1, 2 and 3 and Comparative Examples 1 and 2 were evaluated for cycle characteristics, nailing and hot oven characteristics. -Cycle characteristics Charge / discharge was performed in a voltage range of 3 V to 4.2 V with a current amount of 1 C, and the number of cycles required to reach 80% of the initial capacity was measured.

Nail Penetration A 1.5-mm diameter nail made of stainless steel was pierced into a battery charged to 4.2 V with a current amount of 1 C, and it was confirmed whether the battery smoked, expanded or burst.

Hot oven Place the charged battery in the open until the current reaches 4.2 V with a current of 1 C, and change the battery temperature from room temperature to 150 ° C.
The temperature was raised at a rate of 5 ° C./1 minute until
The sample was kept for one minute, and the sample without rupture and ignition was OK.

Table 1 shows the results.

[0091]

[Table 1]

Table 1 clearly shows the effects of the present invention.

[0093]

As described above, according to the present invention, there is no short-circuit problem between the positive and negative bipolar sheets, the electrodes are hard to move even after lamination, and the strength of the laminate is strong, so that even if the battery is deformed. It is possible to provide an electrochemical device with excellent safety that does not reach a hard short.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration example of an electrochemical device of the present invention.

FIG. 2 is a sectional view taken along the line A-A 'in FIG.

FIG. 3 is a cross-sectional view showing a state of manufacturing an electrochemical device having another configuration of the present invention.

FIG. 4 is a plan view showing another configuration example of the electrochemical device of the present invention.

[Explanation of symbols]

 2 Laminated body 3 Separator 4 Positive electrode 5 Negative electrode

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01M 2/02 H01G 9/00 301C 2/18 301J (72) Inventor Yoshio Kawakami 1-1-13 Nihonbashi, Chuo-ku, Tokyo No. FDC term in TDK Corporation (reference) DJ02 DJ04 EJ01 EJ12 HJ12

Claims (6)

[Claims] 1. An electrochemical device having a laminate in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, wherein at least a part of a peripheral portion of the separator of the laminate is adhered and strongly integrated. Chemical device. 2. An electrochemical device having a laminate in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, wherein a heat-shrinkable film is arranged so as to surround an outer peripheral portion of the laminate, and further comprising at least the laminate An electrochemical device that adheres firmly to a part of the periphery of the separator and is firmly integrated. 3. The electrochemical device according to claim 2, wherein the heat-shrinkable film is a microporous polyolefin membrane. 4. The positive electrode and / or the negative electrode is housed in a bag-shaped separator.
Any of the electrochemical devices. 5. The electrochemical device according to claim 1, wherein the outer bag has an aluminum laminated film. 6. The electrochemical device according to claim 1, which is a lithium secondary battery.