JP2000260411A - Lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify an initial charging process and release a pressure when a battery internal pressure is abnormally increased by charging a power generating element in a bag-shaped exterior body having a through hole, providing a clearance communicated with the inside and the outside of the exterior body respectively in an exhaust means arranged on a through hole, and providing organic liquid filling the clearance. SOLUTION: A power generating element constructed of a positive electrode 21, a solid electrolyte 22 serving also as a separator, and a negative electrode 23 is sealed inside a bag-shaped exterior body 3. A through hole 31 is arranged in a part of the exterior body 3, and above the through hole 31, an exhaust means 4 is arranged. The exhaust means 4 is provided with a clearance communicated with the inside and the outside of the exterior body 3 respectively and filled with organic liquid 5. The exhaust means 4 releases gas generated inside the exterior body 3 in an initial charging time via the organic liquid 5, while in the initial charging time and the following using time, the exhaust means 4 prevents invasion of water, oxygen gas and the like into the inside of the exterior body 3 from the outside. Therefore, expansion of the exterior body 3 in the initial charging time is prevented and battery reliability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sheet-type lithium secondary battery having a bag-shaped outer package.

[0002]

2. Description of the Related Art At present, various batteries are used in the field of electronics from automobiles. Since many of these batteries contain a liquid electrolyte, a strong seal is required to prevent leakage of the liquid electrolyte. Even in lithium-ion secondary batteries, which are widely used as driving power supplies for portable devices due to their high energy density, etc., since a strong metal can is used as the outer can without exception to prevent liquid leakage, The advantage of being suitable for weight reduction cannot be fully utilized. Although it is inevitable to reduce the weight and thickness of current devices in general, devices using current lithium-ion rechargeable batteries are occupying a larger weight in the entire device,
Also, the thickness of the battery has been limiting the thickness of the device. Therefore, it is no exaggeration to say that one key to the future development of the lithium ion secondary battery lies in its light weight and thinness.

[0003] Under such circumstances, lithium polymer secondary batteries are being developed. In a lithium polymer secondary battery, a gelled solid electrolyte obtained by swelling a polymer with an electrolyte solution is used, so that there is no free liquid in the battery. Therefore, there is no fear of liquid leakage. Further, the gelled solid electrolyte has plasticity in addition to high electrical conductivity equivalent to that of the liquid electrolyte. As described above, the lithium polymer secondary battery has attracted attention as a next-generation type battery because it can be made into a sheet and thinned, can be stacked and miniaturized, and has a high degree of freedom in shape selection. .

[0004]

The lithium polymer secondary battery usually has a structure in which a positive electrode and a negative electrode are laminated via a separator made of a gelled solid electrolyte, and the laminated body is sealed in a sheet-shaped package. You. A bag-like body such as an aluminum laminate pack is generally used for the sheet-like exterior body.

By the way, in a lithium ion secondary battery,
Charging must be performed at the final stage of the manufacturing process. During this charging (hereinafter, referred to as initial charging), gas is generated inside the battery. In the case of a sheet-type battery, since the exterior body has plasticity or flexibility, the exterior body swells due to generation of this gas,
The battery thickness increases. In sheet-type batteries, the greatest effect is to be made thin, so it is necessary to prevent the battery thickness from increasing due to initial charging. For this reason, a method has been proposed in which the generated gas is released to the outside by performing initial charging without sealing the outer package of the battery, and thereafter, the outer package is sealed.

However, the lithium ion secondary battery has a problem that a non-aqueous electrolyte is used, and this electrolyte dislikes moisture. Therefore, if the exterior body is not sealed, it is necessary to perform the initial charging in a dry atmosphere, which complicates the process and increases the cost.

Under such circumstances, for example, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 308240 proposes a method described below. In this method, a housing having a storage space for storing a power generation element and a spare space that communicates with the storage space and stores gas at the time of initial charging is prepared in advance,
After the power generation element is stored in the storage space from the opening of the housing, a first step of closing the opening, initial charging of the power generation element, and aging are performed. Second to store gas in the spare space
And a third step of cutting off the spare space from the storage space after blocking a communication portion between the storage space and the spare space. That is, in this method, a housing (aluminum laminate pack or the like) that is larger than a battery to be finally manufactured is used, and a power generation element is sealed in the housing to perform initial charging and aging. After the gas to be sealed is sealed in the spare space in the housing, the spare space is cut off to obtain a battery.

However, even the method described in the above publication has a problem that the number of steps is large and the housing is cut off.

Incidentally, in the case of a sheet-type battery, it has been proposed to provide a pressure-releasing mechanism on the sheet-like exterior body in order to release a rapid rise in internal pressure. For example, Japanese Patent Laid-Open No. 9-1
Japanese Patent Application Laid-Open No. 99099 discloses a lithium ion battery in which a power generation element is housed in a bag-shaped storage body made of a functional film member, wherein a pressure release means having an operating pressure of 1.2 to 20 kg / cm ² is provided. It is described that it is attached to. In this battery, a rupture film (made of the same member as the bag-shaped storage body and formed with a kerf for breakage) is configured to be broken only when the internal pressure of the storage body becomes a predetermined value or more as a pressure release valve. ) Is used. In this publication, a nail penetration test is performed to confirm the operation of the pressure release valve. The nail piercing test is a test in which an internal short circuit is generated by piercing a battery with a nail, and the internal pressure of the container is increased by rapid heat generation and gas generation. The pressure relief valve described in the publication is for releasing such a sudden rise in internal pressure, and does not return once broken. Therefore, this pressure release valve cannot be used as a gas relief valve at the time of the initial charging described above.

Japanese Patent Application Laid-Open No. H10-55792 discloses that in a thin battery in which a power generation element is encapsulated by adhering exterior films to each other, a portion having a small peeling strength is partly bonded to the exterior film. There is described a thin battery in which a portion having a small peel strength is provided outside the bonding portion and small inside the bonding portion. In this battery, a portion having a small peeling strength is provided so that when the internal pressure of the battery rises, the internal pressure is concentrated at this portion and gas is released smoothly. That is, in this battery, a portion having a small peel strength is used as a non-return type valve. Therefore, the invention described in the publication cannot be applied to a gas relief valve at the time of initial charging.

In the method described in Japanese Patent Application Laid-Open No. H10-308240, the gas generated during the initial charging can be released.
It is not possible to release the rapidly rising internal pressure during a short circuit.

An object of the present invention is to provide a highly safe lithium secondary battery capable of simplifying the initial charging step and releasing the pressure when the internal pressure of the battery is abnormally increased.

[0013]

The above object is achieved by the following (1).
This is achieved by the present invention of (9). (1) The power generation element is enclosed in a bag-like outer body,
A through-hole is provided in the exterior body, and an exhaust unit is provided on the through-hole. The exhaust unit includes a gap communicating with the inside and the outside of the exterior body, and an organic liquid filled in the gap. Rechargeable lithium battery. (2) The above-mentioned (1), wherein the exhaust means is constituted by a laminate of a plurality of films including an annular film, and a center hole of the annular film constitutes the gap, and the gap is filled with an organic liquid. Lithium secondary battery. (3) The exhaust means is composed of a laminate of a plurality of films, an adhesive layer is formed except for a part so as to form a gap between adjacent films, and the gap is filled with an organic liquid. The lithium secondary battery according to the above (1). (4) The lithium secondary battery according to the above (1), wherein the exhaust means has a porous film having air permeability and an organic liquid filled in a void of the porous film. (5) The viscosity of the organic liquid is 0.1 to 25 ° C.
The lithium secondary battery according to any one of the above (1) to (4), which is 10,000 mPa · s. (6) The lithium secondary battery according to any one of (1) to (4), wherein the organic liquid has photocurability, and has a viscosity before curing of 10,000 mPa · S or less at 25 ° C. (7) The lithium secondary battery according to any one of (1) to (4), wherein the organic liquid has moisture curability, and has a kinematic viscosity before curing of not more than 3,000 cSt at 20 ° C. (8) The lithium secondary battery according to (6) or (7), wherein the organic liquid is cured after the initial charge. (9) The lithium secondary battery according to any one of (1) to (8), wherein the organic liquid contains a fluorine-based compound.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A schematic structure of a lithium secondary battery of the present invention is shown in FIG. FIG. 1B is an enlarged sectional view of the vicinity of the exhaust means 4 in FIG.
Shown in

In the lithium secondary battery shown in FIG.
A power generating element including a positive electrode 21, a solid electrolyte 22 also functioning as a separator, and a negative electrode 23 is sealed in a bag-shaped exterior body 3. A through hole 31 is provided in a part of the exterior body 3, and the exhaust unit 4 is provided on the through hole 31. Note that, in FIG. 1A, the illustration of the lead wire drawn from the exterior body 3 is omitted.

The exhaust means 4 is, as shown in FIG.
There is a gap communicating with the inside and the outside of the exterior body 3, and the gap is filled with the organic liquid 5.

The exhaust means 4 is used to cover the exterior body 3 during initial charging.
While the gas generated inside escapes through the organic liquid 5,
At the time of initial charging and subsequent use, it is possible to prevent moisture, oxygen gas, and the like from entering the exterior body 3 from outside. Therefore, it is possible to prevent the outer package 3 from expanding at the time of initial charging, and to increase the reliability of the battery.

Further, when a short circuit occurs due to an impact or the like during use of the battery, a large amount of gas is generated in the exterior body 3 and the internal pressure rises rapidly and may burst, but the exhaust means 4 is provided. For example, when the internal pressure rises, the gas in the exterior body 3 can be released through the organic liquid 5 or by the destruction of the exhaust means 4 itself or falling off from the surface of the exterior body 3, that is, Because it works as a safety valve, it has excellent safety.

The exhaust means 4 shown in FIG.
It is formed by laminating a first film 41, a second film 42, and a third film 43. The first film 41 and the second film 42 are annular. First film 41
The inner diameter of the liquid is to suck up the organic liquid 5 in the void by capillary action and to support it by surface tension.
It is set relatively small. On the other hand, the second film 42
Has a diameter corresponding to the filling amount of the organic liquid 5 because the central hole constitutes the void. As shown in FIG.
The second film 42 is provided with a notch in the radial direction for communicating the center hole with the outside. The third film 43 is provided as a lid for the gap. The filling of the organic liquid 5 into the space is preferably performed by sucking up the organic liquid from the center hole of the first film 41 by utilizing the capillary phenomenon. Even when the center hole of the first film 41 is set to be large, the first film 41 and the third film 4 can be formed by making the second film 42 relatively thin.
The organic liquid can be sucked up and held in the gap between the organic liquid 3 and the liquid crystal 3 by utilizing the capillary phenomenon.

The inner diameter of the first film 41 is small enough to hold the organic liquid 5 sufficiently and large enough to allow the gas inside the outer package 3 to sufficiently escape according to various properties such as the viscosity of the organic liquid 5. It may be set, but usually 1 to 15
mm. The inner diameter 42 of the second film may be determined according to the filling amount required for the organic liquid 5, but is usually 1 to 15 mm. Each film may be made of a resin, and any of a resin such as polyethylene terephthalate (PET) and various fluorine-based resins may be used.

FIG. 2A shows another example of the structure of the exhaust means. The exhaust means 4 shown in FIG. 3 includes a first film 41, a second film 42, and a third film 43 shown in plan views in (b), (c), and (d) of FIG. It is formed by lamination. The first film 41 and the second film 42 are annular. An adhesive layer 91 is applied to the back surface of the first film, and is adhered to the exterior body 3. On the back surface of the second film 42, an adhesive layer 92 is formed except for a band near the center. The organic liquid 5 is filled in the space where the adhesive layer 92 is not formed, and the inside of the exterior body 3 and the outside communicate with each other through the organic liquid 5.
Since the adhesive layer 92 is thin, the space formed by the first film 41, the second film 42, and the adhesive layers 92 on both sides can suck up and hold the organic liquid 5 by capillary action. Note that a pair of third films 43 having the same shape as the pair of adhesive layers 92 is provided as a reinforcing material, and is bonded to the second film 42 by the adhesive layer 93.

FIG. 3 shows another example of the structure of the exhaust means 4.
The exhaust means 4 shown in FIG. 3 has a first film 41 made of a porous film having air permeability, and a second film 42 having air permeability is provided thereon to protect the porous film. 92. The second film 42 is preferably made of a nonwoven fabric or a net. The organic liquid 5 is filled in the voids of the porous film, that is, in the pores. The specific configuration of the porous film is not particularly limited, as long as it has a through-hole capable of holding an organic liquid, and is usually made of a resin film. As the resin, a fluorine-based resin such as polytetrafluoroethylene is preferable, but other resins can also be used. The pore size and the density of the pores are not particularly limited. That is, in the configuration examples shown in FIGS. 1 and 2, only one hole is provided, but in the configuration of FIG. 3, at least two holes may be provided. The hole diameter may be appropriately determined according to the density of the holes so that sufficient exhaust performance can be obtained. However, generally, various commercially available porous films having both waterproofness and moisture permeability (for example, Microtex manufactured by Nitto Denko) may be used. In such a porous film, for example, the pore diameter is about 0.1 to 10 μm, the existing density of pores is about several hundred million / cm ² , and the thickness is about 50 to 500 μm.

As each film constituting the exhaust means 4, an organic polymer film may be generally used. At least one of the films, especially the film provided on the uppermost surface, is made of a metal or metal oxide having a high gas barrier property. Is also preferred. As such a film, for example, Al
Alternatively, a film made of Al ₂ O ₃ or SiO ₂ can be used. Bonding of each film and exhaust means 4 and exterior body 3
There is no particular limitation on the means for bonding to the substrate, and any means capable of sealing with high airtightness may be used. For example, an adhesive may be used, or thermal welding may be used.

The organic liquid can be filled into the space inside the exhaust means 4 by utilizing the capillary action, and is low enough to release gas from the exterior body 3 in the presence of a pressure gradient. It is necessary to have a viscosity, and to have such a high viscosity that an organic liquid does not flow out of the void and that a gas (water vapor, oxygen) from the outside can be shut off in the absence of a pressure gradient. is necessary. Specifically, the optimum viscosity may be set according to the type of the organic liquid, but is usually 0.1 to 10,000 mPa at 25 ° C.
-It is preferable to select from the range of s.

However, in the case where the organic liquid 5 has curability, gas is released at the time of initial charging before the organic liquid 5 is cured, and the organic liquid 5 is cured after the initial charging.
The viscosity before curing is preferably low, and the viscosity after curing is preferably relatively high. That is, first, at the time of the initial charge, the organic liquid 5 is used with a low viscosity, so that the gas generated by the initial charge is easily permeated. Since the initial charging is normally completed in about 10 hours or less, even if the viscosity of the organic liquid 5 is low, intrusion of moisture, oxygen, and the like into the exterior body 3 can be sufficiently suppressed. If the organic liquid 5 is cured after the initial charge, the intrusion of moisture, oxygen, and the like from the outside can be substantially blocked, and the electrolytic solution in the exterior body 3 can be prevented from volatilizing through the organic liquid 5. Moreover, it functions as a safety valve when the battery internal pressure rises sharply,
There is no problem with safety.

As the curable organic liquid, those containing a photo-curable or moisture-curable compound are preferred. At least the third film 4 among the films constituting the exhaust means 4
If 3 is transparent to curing light such as ultraviolet light, the organic liquid 5 can be cured after initial charging. Also,
In the case of using a moisture-curable organic liquid, even if the initial charge is performed in the air, the curing hardly proceeds due to a short time, so that sufficient gas permeability can be expected. On the other hand, if the battery is left in the air after the initial charge, the curing proceeds due to the moisture in the air, so that it is possible to prevent moisture and oxygen from entering the battery from the exhaust means 4 when the battery is used. When the organic liquid 5 has photocurability, the viscosity before curing is preferably 1 at 25 ° C.
It is less than 000 mPa · s. When the organic liquid has moisture curability, the kinematic viscosity before curing is preferably 3,000 cSt or less at 20 ° C.

The type of the organic liquid is not particularly limited, and the gas in the outer package 3 generated at the time of initial charging can be discharged to the outside, that is, the gas can permeate according to the pressure gradient, and the water vapor in the air can be discharged. It is possible to select an organic liquid capable of suppressing entry of oxygen and oxygen into the exterior body 3, that is, an organic liquid capable of suppressing gas permeation when there is no pressure gradient. Examples of such an organic liquid include an oil containing silicone or a fluorine-based compound. Particularly, a fluorine-based compound has strong water repellency, and thus has an excellent effect of suppressing water vapor transmission. Further, if a fluorine-based compound is used, it is possible to prevent the electrolyte solution from leaking out of the inside of the exterior body 3 when the battery is used.

However, when a curable compound is used as the organic liquid and the organic liquid is cured after the initial charge, the cured organic compound generally has extremely low gas permeability, so that a sufficient effect can be obtained without using a fluorine-based compound. Is obtained.

As the liquid fluorine compound, various compounds having a fluoroalkylene are preferred. Of these, perfluoro compounds have the property of dissolving oxygen gas, and therefore have high oxygen gas barrier properties.

Specific examples of preferred liquid fluorine compounds include polyethers having fluoroalkylenes and derivatives thereof, particularly perfluoropolyethers and derivatives thereof (for example, Fomblin, Galden, and Daikin Industries, manufactured by Ausimont). Demnum), a trifluorinated ethylene polymer (for example, Daifoil manufactured by Daikin Industries, Ltd.). Derivatives of polyethers having fluoroalkylenes are those obtained by introducing various functional groups such as hydroxyl groups, carboxyl groups, and isocyanate groups into the ends of the polyethers, and performing isocyanate modification, carboxyl group modification, alcohol modification, ester modification, and the like. Is mentioned.

The photocurable organic liquid may be a substituted or unsubstituted saturated hydrocarbon compound having at least one (meth) acryloyl group having a double bond and exhibiting ultraviolet sensitivity in one molecule. The oligomer may be used. Such compounds include, for example, trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3
4,4,4-hexafluorobutyl methacrylate, perfluorooctylethyl methacrylate, perfluorooctylethyl acrylate and the like can be mentioned.

Such a photocurable compound is charged into the exhaust means 4 together with the photopolymerization initiator. As the photopolymerization initiator, a normal photopolymerization initiator that generates radicals by irradiation with ultraviolet rays may be used, and examples thereof include benzoin ethers such as benzoin isopropyl ether and benzoin isobutyl ether, benzophenone, p-methoxybenzophenone, and p-bromo. Benzophenones such as benzophenone, benzyl methyl ketal, acetophenones such as 2,2-diethoxyacetophenone and 1,1-dichloroacetophenone, thioxanthones such as 2-chlorothioxanthone, quinones such as anthraquinone and phenanthraquinone, benzyl Sulfides such as disulfide and tetramethylthiuram monosulfide may be used.

Examples of the water-curable organic liquid include various compounds having an isocyanate group. Specifically, the above-mentioned isocyanate-modified perfluoropolyether is preferable, but a compound containing no fluorine can also be preferably used.

The average molecular weight of the organic liquid used in the present invention is not particularly limited and may be determined so as to fall within the preferable viscosity range described above.
About 0 to 10,000, 1 before curing type
It is about 00 to 3,000.

By the way, in place of using a curable organic liquid, or in addition to this, the structure of the exhaust means is, for example, as shown in FIG. In addition, it is possible to prevent the electrolytic solution in the exterior body from volatilizing through the organic liquid. In addition, it can function as a safety valve when the battery internal pressure rises sharply.

The exhaust means 4 provided in the lithium secondary battery shown in FIG. 4 is different from each of the above exhaust means in having a seal 10. However, the structure excluding the seal 10 may be the same as the exhaust means shown in FIGS. In the illustrated example, the structure is similar to that of FIG. Seal 10
Is provided for the purpose of blocking the organic liquid 5 from the outside of the battery. Since the seal 10 is open at the time of initial charging, it does not hinder the release of gas generated at the time of initial charging to the outside. Then, after the initial charge, the seal 10 is closed by an adhesive or heat welding, so that invasion of moisture or oxygen from the outside through the organic liquid 5 can be prevented, and volatilization of the electrolyte can be prevented. Further, when the internal pressure of the battery rises rapidly, the seal 10 is opened or the exhaust means 4 itself breaks or falls off, and thus functions as a safety valve. Seal 1
0 may be made of resin. In FIG. 4, the area filled with the organic liquid 5 extends for a long time, and the seal 10 is provided at the end of the exterior body 3 in order to avoid the area where the power generation element 2 is present to perform sealing.

The exterior body 3 is formed of a bag-like film. As this film, a functional film which is a package material described in JP-A-9-199099 may be used. The functional film is a generic name of a film that does not cause a chemical change upon contact with a power generation element, can prevent leakage of an electrolyte solution and gas permeation, and is hard to be damaged. Specifically, a gas barrier layer composed of an inorganic foil composed of an inorganic material such as metal (Al or the like), glass, ceramics, etc., a reinforcing layer composed of a synthetic resin, and an adhesive layer are generally laminated. However, the present invention is not limited to such a laminate type, and any material having a feature as a functional film can be used without any particular limitation. In order to form a bag-shaped exterior body using such a film, the films may be thermally welded to each other, or the films may be bonded to each other with an adhesive or a joining member.

The power generating element enclosed in the exterior body 3 is composed of a separator, an electrode and an electrolyte. The present invention
The present invention can be widely applied to a conventional lithium secondary battery having a bag-shaped exterior body, for example, the battery described in the above-mentioned Japanese Patent Application Laid-Open No. 9-199099. The battery described in the publication, in the positive electrode, using a lithium compound as an active material, acetylene black as a conductive additive, using polyvinylidene fluoride as a binder, and in the negative electrode, using graphite as an active material and styrene butadiene rubber as a binder These are combined with a separator made of a microporous polyethylene membrane. Then, the positive electrode, the negative electrode and the separator are wound in a flat spiral shape to form a wound electrode group,
These are laminated as a flat plate to form a laminated electrode group, and these electrode groups are sealed in an exterior body. Also in the present invention, the configuration of the electrode plate group may be appropriately selected from any one of these, but it is preferable to use a stacked electrode plate group because thinning is easy.

However, in the present invention, it is preferable to use a polymer substance which gels by impregnation with an electrolytic solution as a separator, since it is easy to reduce the thickness and there is no fear of liquid leakage. It is preferable to use a polymer substance which gels by impregnation with an electrolytic solution. The gelled polymer substance holds the electrolyte solution inside,
Works as a solid electrolyte. That is, the present invention is suitable for the polymer battery described above. Hereinafter, the power generation element will be described using a polymer battery as an example.

The polymer materials usable as the solid electrolyte include: 1) a polymer of an acrylate containing a photopolymerizable monomer, ethylene oxide, and a polyfunctional acrylate, 2) polyacrylonitrile, 3) polyethylene oxide, polypropylene oxide. 4) polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-ethylene trifluoride ethylene chloride (CTFE) copolymer [P (VDF-CTFE)], Vinylidene fluoride-hexafluoropropylene fluoro rubber, vinylidene fluoride-
Fluoropolymers such as tetrafluoroethylene-hexafluoropropylene fluororubber [P (VDF-TFE-HFP)] and vinylidene fluoride-tetrafluoroethylene-perfluoroalkylvinylether fluororubber are exemplified. As the vinylidene fluoride polymer,
In particular, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene (HFP), a copolymer of vinylidene fluoride and ethylene trifluoride chloride [P
(VDF-CTFE)]. VDF-CTFE
For example, the copolymer is available from Central Glass Co., Ltd. under the trade name “Sefuralsoft (G150, G180)” (VDF-
CTFE as the main chain and VDF as the side chain) from Solvay Japan, Ltd.
8 "and the like. In addition, VDF-HFP copolymer is commercially available from Elf Atochem under the trade name “KynarFlex2”.
750 (VDF: HFP = 85: 15wt%) '', `` KynarFlex2801 (VDF: HFP = 9
0:10 wt%) ", sold by Japan Solvay Co., Ltd. under the trade names" Solef 11008 "," Solef 11010 "," Solef 21508 "," Solef 21510 "and the like. In the vinylidene fluoride-based polymer, the ratio of vinylidene fluoride is 50% by weight or more, particularly 7% by weight.
It is preferably at least 0% by weight.

As a solvent for dissolving the polymer substance, for example, acetone, tetrahydrofuran, methyl acetate and the like can be used.

As the electrode active material, for the negative electrode, for example, a carbon material, lithium metal, lithium alloy or oxide material is used, and for the positive electrode, those capable of intercalating / deintercalating lithium ions, for example, oxides Substance or carbon may be used. The carbon material used as the electrode active material is, for example, mesocarbon microbeads (MCM
B), natural or artificial graphite, resin-fired carbon material, carbon black, carbon fiber, or the like. These are used as powders. As the oxide capable of intercalating / deintercalating lithium ions, a composite oxide containing lithium is preferable. For example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiV
₂ O _{4 and the} like. The average particle size of the oxide powder is preferably about 1 to 40 μm.

Examples of the conductive additive used for the electrode include graphite, carbon black, carbon fiber, nickel, aluminum, copper, silver and the like, and graphite is particularly preferred.

The method for molding the polymer substance is not particularly limited. For example, when manufacturing a film-shaped molded body,
What is necessary is just to apply a polymer solution on a base material. This substrate may be any smooth material. For example, polyester film, glass, polytetrafluoroethylene film and the like can be mentioned. The means for applying the polymer solution to the substrate is not particularly limited, and may be appropriately determined according to the material and shape of the substrate. Generally, a metal mask printing method, an electrostatic coating method, a dip coating method, A coating method, a roll coating method, a doctor blade method, a gravure coating method, a screen printing method, or the like may be used. Thereafter, the solvent is removed by evaporation. The removal of the solvent can be performed at room temperature, or may be performed by heating. Further, if necessary, pressing is performed by a flat plate press, a calender roll, or the like. When manufacturing an electrode, a compact containing the active material is thermocompression-bonded to a current collector. Note that a film-shaped molded product may be obtained by directly applying a polymer solution containing an active material to a current collector. In that case, after applying to the current collector, pressing may be performed.

As the current collector, a metal foil, a metal mesh, or a punching metal is used. As a constituent material of the current collector,
For example, aluminum is used for the positive electrode, and copper and nickel are used for the negative electrode.

[0046]

Example 1 A lithium secondary battery was manufactured in the following procedure.

Polymer: PVDF [KynarFlex 2801
(Manufactured by Elf Atochem Co.)], (copolymer of polyvinylidene fluoride and propylene hexafluoride), 1 M of LiPF ₆ in a mixed solvent of electrolytic solution: ethylene carbonate: dimethyl carbonate = 1: 2 (volume ratio)
Solvent: acetone in a weight ratio of polymer: electrolyte: solvent = 3: 7: 20
To prepare a first solution.

In the first solution, an active material: LiCoO ₂ and a conductive auxiliary agent: acetylene black were added in a weight ratio of the first solution: active material: conductive auxiliary agent = 2: 7.
5: 1.2, and dispersed to obtain a positive electrode slurry.

Further, polymer substance: electrolyte solution: solvent = 3:
A graphite was added as an active material to the second solution prepared in the same manner as in the first solution except that the ratio was 7: 5 so that the second solution: active material = 2: 1. This was dispersed to obtain a negative electrode slurry.

Using the first solution, the slurry for the positive electrode, and the slurry for the negative electrode, an electrode group consisting of a positive electrode, a gelled solid electrolyte, a negative electrode, a gelled electrolyte, a positive electrode,... It was placed in a bag-like outer package (aluminum laminate pack) and sealed with a sealer. The plane dimensions of the exterior body were 60 mm × 70 mm. As shown in FIG. 2, a through-hole 31 having a diameter of 1 mm was formed in the exterior body 3, and the exhaust means 4 was bonded so as to cover the through-hole 31. This exhaust means 4 has the structure shown in FIG. The first film 41 is made of PET, has an outer diameter of 20 mm,
The inner diameter is 7 mm and the thickness is 100 μm. The adhesive layer 91 applied to the first film 41 has a thickness of 50 μm. The second film 42 is made of PET and has a diameter of 20 mm and a thickness of 75 μm.
m. Each of the pair of adhesive layers 92 applied to the second film 42 has a width of 4 mm and a thickness of 20 μm. Each of the third films 43 has a width of 4 mm and a thickness of 100 μm.
It is. The adhesive layer 93 applied to the third film 43 is
The thickness is 20 μm. The organic liquid 5 includes a trifluorinated ethylene polymer (Daifoil # 1 manufactured by Daikin Industries, Ltd.).
0) was used. Its viscosity at 25 ° C. is 19
The molecular weight was 900 from 0 to 490 mPa · s.

Example 2 As a polymer substance, a thermoplastic fluororesin having a main chain composed of a copolymer of vinylidene fluoride and chlorofluoroethylene and a side chain composed of polyvinylidene fluoride (Cefralsoft manufactured by Central Glass Co., Ltd.) A battery was fabricated in the same manner as in Example 1, except that

Example 3 When laminating a positive electrode, a solid electrolyte and a negative electrode, no electrolyte was added, that is, the electrolyte was removed from the first solution and the electrolyte was removed from the second solution. A negative electrode-polymer film-negative electrode... Laminate was formed by using the removed material. The laminate was impregnated with an electrolytic solution to form an electrode group. Otherwise, the procedure of Example 1 was repeated to prepare a battery.

Example 4 A battery was prepared in the same manner as in Example 3 except that the exhaust means 4 having the structure shown in FIG. 4 was used.

Example 5 As an organic liquid 5, a water-curable isocyanate-modified perfluoropolyether (Fomblin: FOMBLIN Z DISOC, manufactured by Ausimont Co., kinematic viscosity 160 ° C. at 20 ° C.)
A battery was fabricated in the same manner as in Example 1 except that St) was used.

Example 6 As the organic liquid 5, a photocurable 2,2,3,3-tetrafluoropropyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd., viscosity of 1.8 mPa · s or less) and a photopolymerization initiator (manufactured by BASF) were used. IR
A battery was prepared in the same manner as in Example 1 except that a mixture with GACURE 1700) was used.

Example 7 Silicone oil (viscosity of 10,000) was used as the organic liquid 5.
mPa · s or less), and a battery was fabricated in the same manner as in Example 3.

[0057] without providing comparative example exhaust means 4, also, in addition to not providing a through hole in the outer body 3 A battery was fabricated in the same manner as in Example 1.

Each of the batteries thus produced was initially charged using a lead wire drawn out of the outer package 3, and the thickness increase of the outer package 3 before and after the initial charging was examined. Table 1 shows the results. The time required for the initial charging was 7.5 hours.

The batteries of Examples 1, 5, and 7 were
The initial capacity and the capacity after storage at room temperature for 77 days were measured, and the capacity retention after storage was determined. Table 2 shows the results.
However, in the battery using the photocurable organic liquid, the organic liquid 5 was cured by irradiating ultraviolet rays from above the exhaust unit 4 immediately after the initial charging.

[0060]

[Table 1]

[0061]

[Table 2]

From Table 1, it can be seen that the battery of the present invention provided with the exhaust means 4 has an outer casing 3 by initial charging compared to the battery of the comparative example.
It can be seen that the increase in thickness is small. Also, from Table 2, it can be seen that when a fluorine-based compound was used as the organic liquid 5, the capacity reduction due to storage was small, and when the curable compound was cured after the initial charge, the capacity retention rate was further increased. It turns out that it becomes high. The silicone oil used in Example 7 has a lower water repellency and a higher water vapor transmission rate than the fluorine-based compound, so that water vapor in the atmosphere enters the inside of the battery to increase self-discharge, thereby increasing the capacity retention. It is thought that this led to a decline.

[0063]

According to the present invention, the gas generated during the initial charging can be easily released, so that the atmosphere control is not required in the initial charging process, and the process can be simplified. In addition, the exhaust means provided in the present invention functions as a safety valve when the internal pressure of the battery rises sharply, so that a highly safe lithium secondary battery is realized.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view illustrating a configuration example of a lithium secondary battery of the present invention having an exhaust unit. (B)
FIG. 3 is an enlarged cross-sectional view illustrating the vicinity of an exhaust unit 4 of the lithium secondary battery illustrated in FIG. (C) is a plan view of the second film 42 in (b).

FIG. 2A is a cross-sectional view illustrating a configuration example of an exhaust unit 4. (B) is a plan view of the first film 41 in (a), (c) is a plan view of the second film 42 in (a), and (d) is a plan view of the third film 43 in (a). It is.

FIG. 3 is a cross-sectional view illustrating a configuration example of an exhaust unit.

FIG. 4 is a plan view showing a configuration example of a lithium secondary battery of the present invention having an exhaust means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Positive electrode 22 Solid electrolyte 23 Negative electrode 3 Package 3 31 Through-hole 4 Exhaust means 41 1st film 42 2nd film 43 3rd film 5 Organic liquid 91, 92, 93 Adhesive layer 10 Seal

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (9)

[Claims] 1. A power generating element is enclosed in a bag-shaped outer body, a through hole is provided in the outer body, and exhaust means is provided on the through hole, and the exhaust means is provided inside the outer body. And a gap communicating with the outside and an organic liquid filled in the gap. 2. The exhaust means comprises a laminate of a plurality of films including an annular film, wherein a center hole of the annular film constitutes the space, and the space is filled with an organic liquid. 1. The lithium secondary battery. 3. The exhaust means is composed of a laminate of a plurality of films, an adhesive layer is formed except for a part so as to form a gap between adjacent films, and an organic liquid is formed in the gap. 2. The lithium secondary battery according to claim 1, wherein 4. The lithium secondary battery according to claim 1, wherein said exhaust means includes a porous film having air permeability, and an organic liquid filled in voids of said porous film. 5. The lithium secondary battery according to claim 1, wherein said organic liquid has a viscosity of 0.1 to 10,000 mPa · s at 25 ° C. 6. The lithium secondary battery according to claim 1, wherein the organic liquid has photocurability, and has a viscosity before curing of 10,000 mPa · S or less at 25 ° C. 7. The lithium secondary battery according to claim 1, wherein the organic liquid has moisture curability, and has a kinematic viscosity before curing of not more than 3,000 cSt at 20 ° C. 8. The lithium secondary battery according to claim 6, wherein the organic liquid is cured after the initial charge. 9. The lithium secondary battery according to claim 1, wherein said organic liquid contains a fluorine compound.