JP2001068074A - Battery - Google Patents

Abstract

(57) [Summary] [Problem] To prevent liquid leakage and gas intrusion,
To provide a battery with low danger of short circuit and high energy density. SOLUTION: In a battery in which a battery element having a positive electrode and a negative electrode is housed in a case whose inside is decompressed, the case has a gas barrier layer containing an inorganic material and having a thickness of 1000 nm or less. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery, and more particularly, to a non-aqueous battery excellent in productivity, high in safety and excellent in durability.

[0002]

2. Description of the Related Art In recent years, the production of batteries has been rapidly increasing with the development of portable electronic devices, and the demand for backup batteries has been steadily increasing due to the spread of personal computers and word processors. As batteries used in these applications, the demand for rechargeable and long-life rechargeable batteries is rapidly increasing, and lithium ion is used as an electromotive substance, and a compound capable of inserting and extracting lithium ions is used as a positive electrode and a negative electrode. The lithium secondary batteries used have attracted attention.

[0003] However, lithium has a very high activity with respect to water, and has problems such as ignition due to liquid leakage or inactivation of lithium due to invasion of air and moisture. You. As means for reducing such troubles, it has been practiced to make the electrolyte filled between the positive electrode and the negative electrode non-fluidized by using a gelling agent or the like to prevent liquid leakage.

[0004] As a result, it is not always necessary to use a rigid container as a case for housing the battery element, and it is possible to use a flexible film, so that the whole battery can be reduced in size and the degree of freedom in shape can be improved. Also increased. However, in a battery used for a long time such as a secondary battery, in addition to the non-fluidization of the electrolyte, the sealing is excellent in durability and there is no risk of breakage, and air and moisture may not enter. There is a need for a coating that does not have the risk of cracking.

Conventionally, a primary battery or a secondary battery is covered with a metal such as stainless steel. However, when sealing with a metal can, insulation between the positive electrode and the negative electrode is required, and the production thereof requires a high level of efficiency. There is a problem that technology and a large-sized device are required, and energy density is reduced as a result of using metal. On the other hand, when a battery element is coated with a flexible sheet material having a high gas barrier property, the coating process is easy, the product can be manufactured with high productivity, and a coating with high impact resistance is formed. And the energy density can be increased.

However, when the battery element is covered and sealed with the sheet, the structure of the sheet becomes a problem. Conventionally, a metal / synthetic resin laminated composite film using a metal layer made of aluminum to prevent intrusion of air and water and providing a heat sealing layer made of a synthetic resin to facilitate sealing during coating is known. However, in this case, there are the following problems.

FIG. 9 is a partial sectional view of a battery using a conventional metal / synthetic resin laminated composite film. The battery element (not shown) is housed in a case composed of upper and lower sheets 91 and 92. A conductive lead 93 electrically connected to the battery element is led to the outside from the bonded portion of the sheet-like materials 91 and 92. Sheets 91 and 9
2 is a metal / synthetic resin laminated composite film having a three-layer structure in which a top and bottom of a metal layer 94 made of aluminum are covered with a protective layer 95 and a heat sealing layer 96, respectively. The sheet materials 91 and 92 and the leads 93 are bonded by heat fusion of a heat sealing layer 96 inside the metal layer 94.

Here, the side portions 97 and 9 of the sheet material
In 8, since the metal layer 94 is exposed, there is a possibility that a short circuit may occur due to contact with the conductive lead 93.
Further, since the sheets 93 and 92 and the leads 93 are bonded by heat fusion of the heat seal layer 96, the metal layer 94 and the leads 93 are brought into contact with each other by the melting of the heat seal layer 96 at this time. Could cause a short circuit.
This problem can be avoided by increasing the thickness of the heat sealing layer 96 to some extent.
6 also becomes thick, so that intrusion of gas such as moisture from this portion becomes a problem. Furthermore, a method of effectively preventing gas intrusion by lengthening the portion to be heat-sealed can be considered, but in this case, unnecessary parts for the battery element increase, so that the entire battery becomes large. As a result, the energy density per weight or volume of the battery is reduced.

When the battery element is housed in the flexible case, the inside of the case is usually depressurized to improve the adhesion between the layers such as the positive electrode and the negative electrode constituting the battery element. The battery is pressed by pressure. That is,
In this case, it is extremely important that the pressure inside the battery does not increase in order to maintain the adhesion between the battery layers. If the pressure inside the case increases, the adhesion of each layer of the battery decreases,
Insufficient and uneven ion conduction and electron conduction between the positive and negative electrodes results in significant degradation of battery performance. However, when a conventional metal / synthetic resin laminated composite film using a metal layer made of aluminum is used, as described below, there is a problem that air tends to enter from the outside and battery performance tends to decrease with time. there were.

FIG. 11 is a partial front view showing the structure of a conventional battery, and is a view of the battery of FIG. 9 viewed from the direction in which the leads protrude. 11 are the same as those in FIG. The case-like objects 91 and 92 are bonded to each other by heat fusion with a heat seal layer 96.
In the portion where 3 exists, the sheet-like materials 91 and 92 do not directly contact, but exist so as to sandwich the lead 93 therebetween. As a result, the sheet materials 91 and 92 are sharply curved at the boundary portions 101 and 102 where the leads are present, respectively.

However, in the above-mentioned conventional sheet-like material, the metal layer 94 is formed of a metal such as aluminum, so that there is a case where the following ability at the boundary portion is insufficient. In such a case, as shown in FIG.
Air gaps 103 and 104 are formed in the side surface portion of the case 3, and as a result, air enters from this portion, and the degree of pressure reduction inside the case is reduced. Of course, if the thickness of the metal layer is made sufficiently thin, the followability is improved on average, but in any case, no void is generated when the sheet-like objects are bonded to each other for the improvement of the followability. It is necessary to stick together carefully. Further, a sealant such as a modified polyolefin is placed between the bonded portions of the sheet-like material, and the sheet-like material is bonded through the sealant layer, so that the seal layer is used as a buffer, so to speak. It is also possible to reduce the curvature of the sheet-like material at the boundary portion or to compensate for the poor followability by filling the gap with a sealant. However, even in this case, since the above-mentioned bending and poor followability are not eliminated,
This does not solve the essential problem, and it is necessary to carefully bond the sheets so that no gap is generated when the sheets are bonded to each other.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a battery which is excellent in productivity, in which liquid leakage and air intrusion are suppressed, danger of short circuit is low, and deterioration of battery performance is suppressed. It is in. Another object of the present invention is to provide a battery that can be reduced in size and has a high energy density.

[0013]

SUMMARY OF THE INVENTION The present invention is based on the finding that the above object can be solved by providing an extremely thin layer containing an inorganic material in a case, and has the following constitution as its gist. [1] A battery in which a battery element having a positive electrode and a negative electrode is housed in a case whose internal pressure is reduced, wherein the case has a gas barrier layer containing an inorganic material and having a thickness of 1000 nm or less. [2] The battery according to [1], wherein the battery element has a thin plate shape, and the case is composed of two sheet-like objects sandwiching the battery element from above and below. [3] The battery according to [2], wherein at least a part of the sheet-like material is mutually fused by heat fusion to form a case. [4] The battery of [1] to [3], wherein the case has a substrate layer on at least one of the upper and lower sides of the gas barrier layer.

[5] The battery of [4], wherein the base layer contains polyvinyl alcohol. [6] The battery of [4] or [5], wherein the base layer contains polyester. [7] The battery of [1] to [6], wherein a heat sealing layer made of a polyolefin resin is provided inside the gas barrier layer. [8] The battery of [1] to [7], wherein a protective layer made of at least one resin selected from the group consisting of polyester and polyamide is provided outside the gas barrier layer.

[9] The battery of [1] to [8], wherein the battery element is a lithium secondary battery using lithium as an electromotive substance. [10] A positive electrode and a negative electrode are laminated via a non-fluid electrolyte layer [1] to

The battery according to [9]. [11] The battery of [1] to [10], wherein the gas barrier layer is formed by vacuum evaporation. [12] The inorganic material is an oxide of at least one element selected from the group consisting of aluminum, silicon, tin, zinc, iridium, titanium and zirconium [1]
~ The battery of [11].

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A battery according to the present invention comprises a battery element having a positive electrode and a negative electrode housed in a case. The electromotive substance for the function of the battery element is a metal component that normally becomes ions and electrochemically participates in the charging and discharging of the secondary battery to generate an electromotive force, and lithium is usually used. Hereinafter, the present invention will be described using a lithium secondary battery as an example. The positive electrode 1 or the negative electrode 2 is usually formed in a plate shape using the current collector 5 as a base material as shown in FIG. However, only one side of the current collector 5 may be provided depending on the purpose.

As the current collector 5, a metal foil such as an aluminum foil or a copper foil can be generally used. The thickness is appropriately selected, but is preferably 1 to 30 μm. If the thickness is too small, the mechanical strength becomes weak, which causes a problem in production. If it is too thick, the capacity of the battery as a whole decreases. It is preferable that the surface of the current collector be subjected to a surface roughening treatment in advance, since the adhesive strength of the electrode is increased. As the surface roughening method, mechanical polishing method,
An electrolytic polishing method or a chemical polishing method may be used. Examples of the mechanical polishing method include a method of polishing the surface of the current collector with a polishing cloth paper having abrasive particles fixed thereon, a grindstone, an emery buff, a wire brush provided with a steel wire, or the like. Further, an intermediate layer may be formed on the surface of the current collector to increase the adhesive strength and the conductivity. Further, the shape of the current collector 5 may be a plate shape,
It may be a mesh or a punched metal.

As the active material used for the positive electrode, an inorganic compound or an organic compound can be used as long as it can occlude and release lithium ions. Examples of the inorganic compound include a transition metal oxide, a composite oxide of lithium and a transition metal, and a transition metal sulfide. Here, as the transition metal, Fe, C
o, Ni, Mn, etc. are used. Specifically, MnO,
Transition metal oxides such as V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ ; composite oxides of lithium and transition metals such as lithium nickelate, lithium cobaltate and lithium manganate; Ti
Transition metal sulfides such as S ₂ , FeS, and MoS ₂ are exemplified. These compounds may be partially substituted with elements in order to improve their properties. Examples of the organic compound include polyaniline, polypyrrole, polyacene, disulfide-based compounds, and polysulfide-based compounds. These inorganic compounds and organic compounds may be mixed and used as the positive electrode active material. Preferably,
A composite oxide of lithium and a transition metal, in particular, a composite oxide containing lithium and manganese, such as lithium cobaltate, lithium manganate and lithium nickelate, and cobalt or nickel, particularly lithium and cobalt or nickel. Complex oxide.

The average particle size of the positive electrode active material may be appropriately selected depending on the balance with the other components of the battery. The average particle size is usually 1 to 30 μm, and particularly preferably 1 to 10 μm, such as the initial efficiency and cycle characteristics. It is preferable because the battery characteristics are improved. Examples of the negative electrode active material capable of inserting and extracting lithium ions that can be used for the negative electrode include a carbon-based material such as graphite and coke. Such a carbon-based material can also be used in the form of a mixture or coating with a metal, a metal salt, an oxide, or the like. Examples of the negative electrode material include oxides and sulfates of silicon, tin, zinc, manganese, iron, nickel and the like, metallic lithium, Li-Al, Li-Bi-C
d, lithium alloys such as Li-Sn-Cd, lithium transition metal nitrides, silicon and the like can also be used. Preferably, it is graphite or coke in terms of capacity. The average particle size of the negative electrode active material is usually 12 μm or less, preferably 10 μm or less, from the viewpoint of improving battery characteristics such as initial efficiency, rate characteristics, and cycle characteristics. If the particle size is too large, the electron conductivity deteriorates. Also, usually 0.5 μm
The thickness is preferably 7 μm or more.

Since these positive electrode active material and negative electrode active material are usually bound on the current collector, it is preferable to use a binder. As the binder, inorganic compounds such as silicate and glass, and various resins mainly composed of polymers can be used. Examples of the resin include alkane-based polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone. Acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide; polyfluorinated vinyl,
Fluorinated resins such as polyvinylidene fluoride and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; polyvinyl alcohol-based polymers such as polyvinyl acetate and polyvinyl alcohol; polyvinyl chloride and polyvinylidene chloride Halogen-containing polymers other than fluorine; conductive polymers such as polyaniline and the like can be used. Further, a mixture of the above-mentioned polymers and the like, a modified product, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer and the like can also be used. The weight average molecular weight of these resins is preferably 10,000 to 3,000,000, and more preferably 100,000 to 1,000,000.
If it is too low, the strength of the coating film decreases, which is not preferable. If it is too high, the viscosity becomes high, and it becomes difficult to form an electrode.

The electrodes may contain additives, such as conductive materials and reinforcing materials, which exhibit various functions, powders, fillers, and the like, if necessary. The conductive material is not particularly limited as long as it can impart conductivity by being mixed in an appropriate amount with the active material, but usually, acetylene black, carbon black, carbon powder such as graphite, and various metal fibers,
Foil and the like. As additives, trifluoropropylene carbonate, vinylene carbonate, 1,6-
Dioxaspiro [4,4] nonane-2,7
-Dione, 12-crown-4-ether and the like can be used to increase the stability and life of the battery. As the reinforcing material, various inorganic or organic spherical or fibrous fillers can be used.

The compounding amount of the binder with respect to 100 parts by weight of the active material is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight. If the amount of the resin is too small, the strength of the electrode decreases. If the amount of the resin is too large, the amount of voids in the electrode decreases, and the proportion of the ion mobile phase described below decreases. As a method of forming the electrode on the current collector, for example, a powdery active material mixed with a solvent together with a binder, ball mill, sand mill, a twin-screw kneader and the like to form a dispersion paint, on the current collector And a method of drying it. In this case, the type of the solvent used is not particularly limited as long as it is inert to the active material and can dissolve the binder. For example, any of commonly used inorganic and organic solvents such as N-methylpyrrolidone and the like can be used. Can also be used.

Alternatively, the active material may be formed by a method in which the active material is mixed with a binder and heated so as to be softened by pressure bonding or spraying on a current collector. Furthermore, it can be formed by firing the active material alone on the current collector. A composite electrode can be formed as an ion mobile phase by allowing an electrolyte to be present in the space between the electrodes. The higher the ratio of the ion mobile phase in the electrode, the easier the ion migration. The higher the ratio, the better in terms of rate characteristics, while the lower the ratio, the higher the capacitance. Preferably 10
50% by volume. As the material for the ion mobile phase, the same material as the material for the electrolyte layer described later can be used.

It is preferable that the positive electrode and the negative electrode are thicker in terms of capacity and thinner in terms of rate. Film thickness is usually 10
μm or more, preferably 20 μm or more, more preferably 30 μm or more, and most preferably 50 μm or more. On the other hand, the upper limit of the electrode film thickness is usually 200 μm or less, preferably 150 μm or less. As the electrolyte layer 3 interposed between the positive electrode 1 and the negative electrode 2, a normal electrolytic solution may be used, but similarly, it has a function of electrochemically bonding the positive electrode and the negative electrode, and has a low fluidity. A non-fluid electrolyte having shape retention is preferably used. As a result, electrolyte leakage can be effectively prevented.

The electrolyte layer usually has a supporting electrolyte. As the supporting electrolyte used in the electrolyte layer, any substance can be used as long as the electrolyte is stable with respect to the positive electrode and the negative electrode, and is capable of moving lithium ions to perform an electrochemical reaction with the positive electrode active material or the negative electrode active material. Can also be used. Specifically, LiPF ₆ , L
iAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCl
O ₄ , LiI, LiBr, LiCl, LiAlCl, L
Lithium salts such as iHF ₂ , LiSCN, and LiSO ₃ CF ₂ are mentioned. Of these, LiPF ₆ , L
iClO ₄ is preferred.

When these supporting electrolytes are used in the state of being dissolved in a non-aqueous solvent, the concentration is generally 0.5 to 2.5 m
ol / L. The nonaqueous solvent in which these supporting electrolytes are dissolved is not particularly limited, but a solvent having a relatively high dielectric constant is preferably used. Specifically, ethylene carbonate, cyclic carbonates such as propylene carbonate, dimethyl carbonate, diethyl carbonate, acyclic carbonates such as ethyl methyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, glymes such as dimethoxyethane, γ-butyrolactone and the like Examples thereof include lactones, sulfur compounds such as sulfolane, and nitriles such as acetonitrile. One or two of these
Mixtures of more than one species can also be used.

Among these, one or more solvents selected from cyclic carbonates such as ethylene carbonate and propylene carbonate, and acyclic carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are particularly preferred. is there. In addition, those in which a part of hydrogen atoms in these molecules are substituted with halogen or the like can also be used. Further, additives and the like may be added to these solvents. As additives, for example, trifluoropropylene carbonate, vinylene carbonate,
1,6-Dioxaspiro [4,4] nonane
-2,7-done, 12-crown-4-ether and the like can be used for the purpose of enhancing the stability, performance and life of the battery.

As the non-fluid electrolyte layer, a gel electrolyte can be used. The gel electrolyte is mainly composed of an electrolyte containing a supporting electrolyte and a solvent, and contains a polymer for gelation, and the electrolyte is held in a polymer network, so that the fluidity as a whole is significantly reduced. Things. The properties such as ionic conductivity are similar to those of a normal electrolytic solution, but the fluidity, volatility and the like are significantly suppressed, and the safety is enhanced. The ratio of the polymer in the gel electrolyte is preferably 1 to 50%. If the temperature is too low, the electrolyte cannot be held, and a liquid leak may occur. If it is too high, the ionic conductivity may decrease, and the battery characteristics may deteriorate.

In order to form a gel electrolyte layer,
(1) A method of using an electrolyte raw material containing a monomer and polymerizing the same to form a polymer can be mentioned.
Polymers capable of performing such a reaction include those produced by polycondensation of polyester, polyamide, polycarbonate, polyimide, etc., those produced by polyaddition such as polyurethane, polyurea, etc., and acrylics such as polymethyl methacrylate. Derivative polymers and polyvinyl acetates such as polyvinyl acetate and polyvinyl chloride are also produced by addition polymerization, etc., but the polymerization is easy to control and the high polymerization produced by addition polymerization does not generate by-products during polymerization. It is desirable to use molecules. In particular, a method of polymerizing a monomer having a reactive unsaturated group is preferable because of its high productivity.

Examples of such a monomer having a reactive unsaturated group include acrylic acid, methyl acrylate, ethyl acrylate, ethoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxyethyl acrylate, polyethylene glycol monoacrylate, and ethoxyethyl methacrylate. , Methoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, polyethylene glycol monomethacrylate, N, N diethylaminoethyl acrylate, N, N dimethylaminoethyl acrylate, glycidyl acrylate, allyl acrylate, acrylonitrile, N-vinylpyrrolidone, diethylene glycol diacrylate, triethylene glycol Diacrylate, tetraethylene glycol diacrylate, poly Chi glycol diacrylate,
Diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, and the like can be used, and those which are preferable in terms of reactivity, polarity, safety, and the like may be used alone or in combination. Preferably, a monomer having an acryloyl group and / or a methacryloyl group is used.

As a method for polymerizing these monomers, there are methods using heat, ultraviolet rays, electron beams, etc., but from the viewpoint of high productivity, a method using ultraviolet rays or heat is effective. In this case, in order to make the reaction proceed effectively, a polymerization initiator that reacts with ultraviolet light may be added to the electrolytic solution. Usable UV polymerization initiators include benzoin, benzyl, acetophenone, benzophenone, Michler's ketone, biacetyl, benzoyl peroxide and the like, and those which are preferable in terms of reactivity, polarity, safety and the like may be used alone or in combination. In the case of polymerization by heat, it is easy to control the reaction rate. In particular, by changing the type and amount of thermal polymerization initiator, the amount of monomer and the number and type of reactive groups in the monomer, the structure of the gel can be controlled and the ionic conductivity etc. Can be improved. Further, since the whole reaction proceeds uniformly, a uniform gel can be formed.

At the time of thermal polymerization, a polymerization initiator may be added to control the reaction. Available thermal polymerization initiators include 1,1-di (tert-butylperoxy) -3,3,5-trimethylcyclohexane,
2-bis- [4,4-di (tert-butylperoxycyclohexyl) propane], 1,1-di (tert-butylperoxy) -cyclohexane, tert-butylperoxy-3,5,5-trimethylhexa Nonate, tertiary butyl peroxy-2-ethyl hexanonate, dibenzoyl peroxide and the like can be used,
Those which are preferable in terms of reactivity, polarity, safety and the like may be used alone or in combination.

In order to form a gel electrolyte layer, (2) a method in which an electrolyte material containing a polymer which can be gelled by cooling is used and the polymer is cooled to room temperature can be adopted. In this case, as a polymer that can be used,
Any material can be used as long as it forms a gel with respect to the electrolytic solution and is stable as a battery material. Examples thereof include polymers having a ring such as polyvinylpyridine and poly-N-vinylpyrrolidone; polymethacryl. Methyl acid,
Acrylic polymers such as polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide; fluorinated resins such as polyvinyl fluoride and polyvinylidene fluoride; poly Examples thereof include CN group-containing polymers such as acrylonitrile and polyvinylidene cyanide; polyvinyl alcohol-based polymers such as polyvinyl acetate and polyvinyl alcohol; and halogen-containing polymers excluding fluorine such as polyvinyl chloride and polyvinylidene chloride. In addition, a mixture of the above polymers, a modified product,
Derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers and the like can also be used.
Preferred are CN group-containing polymers such as polyacrylonitrile.

Since the electrolyte and the electrolyte used in the lithium battery usually have polarity, the above (1),
(2) Regardless of the method, it is preferable that the polymer has a certain degree of polarity. The weight average molecular weight of these polymers is preferably in the range of 10,000 to 5,000,000. If the molecular weight is low, it is difficult to form a gel. If the molecular weight is high, the viscosity becomes too high and handling becomes difficult. The concentration of the polymer in the electrolytic solution may be appropriately selected according to the molecular weight, but is preferably from 0.1% by weight to 30% by weight. If the concentration is 0.1% by weight or less, it is difficult to form a gel, the retention of the electrolytic solution is reduced, and problems of flow and liquid leakage may occur. If the concentration is 30% by weight or more, the viscosity becomes too high, causing difficulty in the process, and the proportion of the electrolytic solution is reduced, the ionic conductivity is reduced, and the battery characteristics such as rate characteristics may be deteriorated.

A solid electrolyte layer can be used as the non-fluid electrolyte layer. As the solid electrolyte, various known solid electrolytes can be used.
For example, it can be formed by mixing the polymer used in the gel electrolyte and the supporting electrolyte salt at an appropriate ratio.
In this case, in order to increase the conductivity, it is preferable to use a polymer having a high polarity and to have a skeleton having many side chains. As the non-fluid electrolyte layer, a gel electrolyte or a solid electrolyte impregnated in a spacer such as a porous film or a nonwoven fabric may be used. The thickness of the electrolyte layer is usually 1-2.
The thickness is 00 μm, preferably 5 to 100 μm, and more preferably 10 to 50 μm.

The battery element having the positive electrode 1, the negative electrode 2, and the electrolyte layer 3 can have a structure according to the purpose. For example, as shown in FIG. 1, a positive electrode material composition is laminated on a current collector 5 to obtain a plate-shaped positive electrode 1. The negative electrode 2 is formed in a plate shape by the same method, and the positive electrode 1 and the negative electrode 2 formed in the plate shape are laminated via the non-fluid electrolyte layer 3 to obtain a thin plate battery.

When increasing the battery capacity or increasing the output potential, as shown in FIG.
Are alternately stacked via the non-fluid electrolyte layer 3. The number of the positive electrode 1 and the negative electrode 2 to be laminated is arbitrary, but the number of the positive electrode 1 and the negative electrode 2 is generally the same. In this case, as shown in FIG. 3, the current collector 5 of the positive electrode 1 forms a protruding piece 5a protruding from the positive electrode 1 on one side of one side of the electrode.
A protrusion 5b is formed on the other side of the same side also in the current collector 5 of
As shown in FIG. 4, the protruding protruding pieces 5a and 5b are respectively connected up and down to form a positive electrode and a negative electrode lead wire connection terminal, whereby a secondary battery having a large capacity can be obtained. . Usually, the lead wires 55a and 55b are further connected to the lead wire coupling terminal, and a part of the leads 55a and 55b is led to the outside of the case.

The battery of the present invention has the battery element 4 configured as described above housed in a flexible case whose inside is decompressed. Preferably, the case is composed of two film-like sheets sandwiching the thin battery element. In the present invention, the case has a gas barrier layer containing an inorganic material. As the sheet-like material 6 constituting the case, a material in which a base material layer 8 made of a resin is stacked in contact with the gas barrier layer 7 as shown in FIG. 5A can be used.
The base material layer 8 is usually laminated on the outer surface of the gas barrier layer 7, but can also be provided on the inner surface, and is preferably laminated on both surfaces as shown in FIG. 5 (B). As a result, the gas barrier layer can be protected more effectively.

In the present invention, the inner surface refers to a surface which is inner when the battery element 4 is covered with the sheet-like material 6, and the opposite side is an outer surface. The gas barrier layer 7 contains an inorganic material, and such a layer can be manufactured by performing, for example, vacuum deposition, CVD, sputtering, ion plating, or the like on the base material layer. Preferably, the gas barrier layer 7 is formed by a vacuum deposition of an inorganic material. Of course, the gas barrier layer 7 may contain a substance other than the inorganic material, but preferably 50% by weight or more, particularly 70% by weight or more, and more preferably 90% by weight or more of the entire gas barrier layer is made of an inorganic oxide. The inorganic materials used include silicon, aluminum, tin, zinc, iridium,
Examples include oxides or nitrides of at least one element selected from the group consisting of titanium and zirconium. Among them, a preferable inorganic material is a silicon oxide and / or an aluminum oxide.

The thickness of the gas barrier layer 7 is usually at least 1 nm, preferably at least 10 nm, and
Or less, preferably 500 nm or less. If the gas barrier layer is too thin, the gas barrier property may be deteriorated. If the thickness is too thick, cracks are easily formed in the gas barrier layer itself, and the followability is deteriorated, and the adhesion of each layer of the battery is deteriorated. The base layer 8 is usually made of various synthetic resins, and its thickness is usually about 0.1 to 500 μm, preferably about 1 to 200 μm.

In the sheet-like material, it is preferable that a heat sealing layer is provided inside the gas barrier layer and a protective layer is provided outside. The sheet material 6 can be easily sealed by the heat sealing layer. Further, the gas barrier layer can be more strongly protected against external force by the protective layer. More specifically,
As shown in FIG. 6, a heat sealing layer 9 made of a synthetic resin is formed on the inside of the gas barrier layer 8 in order to further seal it, and on the outer surface, the gas barrier layer or the base material layer is protected. It is preferable that the protective layer 10 is laminated. Also,
As shown in FIG. 10, when a plurality of portions each composed of the base material layer 8 and the gas barrier layer 7 are laminated, a heat seal layer 9 is provided inside thereof, and a sheet-like material provided with a protective layer outside is used.
Further, the gas barrier property is improved, which is preferable. In each of the embodiments shown in FIGS. 6 and 10, the heat sealing layer is provided in contact with the gas barrier layer, and the protective layer is provided on the opposite side. A protective layer may be provided, and a heat seal layer may be provided on the opposite side. The thicknesses of the heat sealing layer and the protective layer are each usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 80 μm or less. The heat sealing layer 9 and the protective layer 10 are preferably formed using a synthetic resin.

In the present invention, the base material layer 8 and the heat seal layer 9
The elastic modulus and the tensile elongation of the synthetic resin used for the protective layer 10 are not limited. Therefore, the synthetic resin in the present invention includes what is generally called an elastomer. As the synthetic resin, a thermoplastic resin, a thermoplastic elastomer, a thermosetting resin, or a plastic alloy is used. These resins include those in which a filler such as a filler is mixed.

The thermoplastic resin includes polyethylene, polypropylene, modified polyolefin, ionomer, polyvinyl alcohol, ethylene-vinyl acetate copolymer (EV
A), ethylene-vinyl acetate-vinyl alcohol terpolymer (EVOH), polyvinylidene chloride, polyvinyl chloride, amorphous polyolefin (transparent, for example, Nippon Zeon / trade name: ZEONEX), polyamide, polyethylene terephthalate, poly Butylene terephthalate, polycarbonate, polystyrene, styrene copolymer (AB
S resin, AS resin, SMA resin, ACS resin, ASA resin, etc.), polyacrylonitrile, polyoxymethylene,
Polymethyl methacrylate, polyphenylene ether,
Polyphenylene sulfide, polyetheretherketone (PEEK), polyetherketone, polyimide, polyetherimide, polyamideimide, fluororesin (polytetrafluoroethylene, tetrafluoroethylene-propylene hexafluoropropylene copolymer, vinylidene fluoride, etc.) ), Liquid crystal polymers (for example, aromatic polyester-based Mitsubishi Engineering Plastics / trade name: Novaculate), polyarylate, polymethylpentene, polysulfone, and norbornene-based resins (for example, JSR / trade name: Arton).

A thermoplastic elastomer can be processed in the same manner as a thermoplastic resin, and is a general term for a material whose molded article exhibits rubber elasticity, and has a hard segment (hard phase) and a soft segment (soft phase) in its molecular structure. In the styrene system, polystyrene is used for the hard phase, butadiene, isoprene and the like are used for the soft phase. In the case of polyester, a hard phase is polyester and the soft phase is polyether. In the case of polyamide, a hard phase is polyamide and a soft phase is polyether. In addition, there are olefin type, polyvinyl chloride type, urethane type and chlorinated polyethylene.

Thermosetting resins include phenol resins, phenol aralkyl resins, furan resins, amino resins (urea resins, melamine resins, benzoguanamine resins), unsaturated polyester resins, diallyl phthalate resins, epoxy resins, vinyl ester resins, and phenoxy resins. , Polyurethane, silicone resin. Plastic alloys
The above thermoplastic materials are arbitrarily melt-mixed. Examples of commercialized products include polycarbonate and ABS resin, alloys of polyamide, polyphenylene ether, polybutylene terephthalate, and the like, and polyamide and polyamide resin and ABS resin,
Alloys with polyphenylene ether and polyolefin are known.

The synthetic resin used in the sheet material is as follows:
Depending on the purpose, it can be selected and used depending on the heat sealing property, mechanical strength and the like. Specific examples of the resin used for the base layer 8 include polyolefins such as homopolymers or copolymers of ethylene, propylene, and butene;
Amorphous polyolefins such as cyclic polyolefins, polyester resins such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyamides such as nylon 6, nylon 12, and copolymerized nylon, polyvinyl alcohol, and ethylene-vinyl acetate copolymer partially hydrolyzed Decomposed product (EVOH), polyimide, polyetherimide, polysulfone, polyethersulfone, polyetheretherketone, polycarbonate (PC), polyvinylbutyral, polyarylate, ethylene-tetrafluoroethylene copolymer, ethylene trifluoride chloride , Ethylene tetrafluoride-
Perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride, polyvinyl fluoride, fluorine resin such as perfluoroethylene-perfluoropropylene-perfluorovinylether terpolymer, and acrylate compound having radically reactive unsaturated compound A resin composition, a resin composition comprising the acrylate compound and a mercapto compound having a thiol group, and a resin composition in which oligomers such as epoxy acrylate, urethane acrylate, polyester acrylate, and polyether acrylate are melted in a polyfunctional acrylate monomer. Curable resins, mixtures thereof, and the like are included. Among them, polyester, polypropylene, polyamide, polyvinyl alcohol and ethylene-vinyl acetate copolymer partial hydrolyzate are preferable, and polyester and polyvinyl alcohol are particularly preferable. When using polyvinyl alcohol, the degree of saponification is 98% or more, especially 99%.
% Or more is preferable.

The resin used for the protective layer is preferably polyethylene, polypropylene, modified polyolefin, ionomer, amorphous polyolefin, polyester such as polyethylene terephthalate, nylon 6, nylon 66.
It is desirable to use a resin such as polyamide having excellent chemical resistance and puncture resistance. Particularly preferred is polyester or polyamide. Relatively low temperature (200 ° C or less) for heat seal layer
, A resin that melts in the above, for example, polyethylene, polypropylene, modified polyolefin, ionomer, ethylene-vinyl acetate copolymer and the like can be used. Particularly preferred are polyolefin resins such as polyethylene, polypropylene, modified polyolefin and amorphous polyolefin. When the base layer 8 and the protective layer 10 are in contact with each other, or when the base layer 8 and the heat sealing layer 9 are in contact with each other,
The same material may be used for both layers. In the present invention, it is preferable to provide a gas barrier layer formed by vapor deposition on the base material layer and further provide an inorganic material layer by coating or the like. Examples of such an inorganic material include silicate and the like. The thickness of the inorganic material layer is usually 0.1 to 500 μm, preferably 1 to 500 μm.
200 μm.

The lamination of each layer can be performed by extrusion lamination, dry lamination, vapor deposition, adhesion using a sputtering adhesive, or the like. The thickness of the obtained sheet is usually 1 μm or more, preferably 10 μm.
m or more, more preferably 20 μm or more, and usually 1000 μm or less, preferably 500 μm, more preferably 200 μm or less. The method of covering and sealing the battery element 4 using the sheet-like material 6 is not particularly limited, but for example, the case is formed by at least part of the sheet-like materials being mutually fused by heat fusion. It can be coated by the following method. That is,
The covering of the battery element 4 is, as shown in FIG.
Is bent at the central portion 6a to form two sheets, an upper sheet 66b and a lower sheet 66c. After the battery element 4 is loaded between the two, the upper sheet and the lower sheet are joined, and the bent side 6a is formed. The lead wires 55a and 55b are provided so as to protrude from the opposing sides, and the side 6 orthogonal to the bent side 6a
b, 6c and the protruding sides 6 of the lead wires 55a, 55b
The peripheral portion of d is sealed under reduced pressure, and the sealed portions 12b, 12c,
12d and the structure shown in FIG.
Thin sheet-shaped battery element 4 with two sheet-like objects 66b and 66c
Are sandwiched from above and below to form a secondary battery. The sealing method is not particularly limited, and a heat seal bar, an ultrasonic sealer, or the like can be used. Further, instead of the sealing, bonding with an adhesive may be used. At this time, the inside of the case can be reduced in pressure by performing the sealing under vacuum.

In the present invention, in order to further reduce the adverse effect due to the intrusion of moisture, it is preferable that the battery further has a moisture absorbent. As the hygroscopic agent, a material having a high hygroscopic property such as synthetic zeolite (molecular sieve), silica gel, calcium chloride, calcium oxide, phosphorus pentoxide, barium oxide, magnesium perchlorate, barium perchlorate and the like is used. Preferably high adsorption capacity even at high temperatures, no deliquescence, synthetic zeolite, phosphorus pentoxide, barium oxide,
Calcium oxide is used. However, when mixed or carried on a carrier such as resin or pulp, a deliquescent drying agent (for example, calcium chloride) may be used.

These moisture absorbents can be used in the form of powder, pellets, or a simple substance formed into a sheet, or can be kneaded in the synthetic resin used in the above-described case. Further, it is also possible to attach the moisture absorbent powder to one side of the double-sided pressure-sensitive adhesive tape and attach it to the inner surface of the case, but preferably, a molded article molded using the moisture absorbent powder with a binder is used. . The shape is generally a sheet shape, but may be a rod shape, a ring shape or the like according to the purpose. As the binder resin of the moisture absorbent, for example, a thermoplastic resin, a thermoplastic elastomer,
Thermosetting resins, plastic alloys, and natural polymers (vegetable fibers, pulp) can be used.

[0050]

According to the present invention, since the gas barrier layer contains an inorganic material, intrusion of a gas such as water vapor can be effectively prevented. In addition, the gas barrier layer is 1000 n
m, which is extremely thin, so that it is flexible and highly flexible, so that the adhesion of each layer of the battery is improved. In addition, since the inorganic material generally has extremely low electric conductivity, the possibility that a short circuit will occur between the battery element and the portion where the gas barrier layer is exposed can be reduced even in a battery having the configuration shown in FIG. . Furthermore, when the sheet-like material constituting the case is heat-sealed, there is no possibility of short-circuiting due to melting of the heat-sealed portion, so that the thickness of the heat-sealed portion can be made as thin as possible. As a result, it is possible to more effectively prevent gas such as water vapor from entering. Further, the thickness of the heat-sealed portion can be made as small as possible, so that the battery can be further reduced in size and the energy density can be improved. Similarly, the width of the heat-sealed part can be reduced,
The size of the battery can be further reduced, and the energy density can be improved.

Further, since the case used in the present invention can be reduced in weight as compared with a conventional laminated film using aluminum, the weight of the battery can be further reduced and the energy density can be improved. . Further, in the case of a conventional laminated film using aluminum, there is a problem that a residue remains during the incineration treatment, but in the case of the present invention containing an inorganic material, the incineration treatment is easy.

[0052]

EXAMPLES Example 1 (Evaluation of Gas Barrier Property) Polyvinyl alcohol having a thickness of 12 μm (a saponification degree of 99%)
A silicon oxide vapor-deposited film was formed on one side of the above film by vacuum vapor deposition by heating and evaporating silicon oxide at 150 °. A low-density polyethylene film having a thickness of about 55 μm was further adhered to the surface of the laminated body on which the vapor-deposited film was formed, and a polyethylene terephthalate film having a thickness of 12 μm was adhered to the opposite surface by an adhesive.

The heat seal layer (low density polyethylene), gas barrier layer (silicon oxide),
The moisture permeability and oxygen permeability of a sheet (laminated film 1) composed of a base material layer (polyvinyl alcohol) and a protective layer (polyethylene terephthalate) were measured. The moisture permeability was measured at 40 ° C. in an environment of 90% RH, and the oxygen permeability was measured at 25 ° C. in an environment of 90% RH. The results are shown in Table 1. For comparison, a similar sheet-like material was manufactured (laminate film 2) except that the vapor-deposited film portion of the above-mentioned sheet-like material was made of aluminum foil having a thickness of 9 μm. It was measured. The results are shown in Table 1.

[0054]

[Table 1]

Table 1 shows that the film using silicon oxide has gas barrier properties comparable to those of the conventional film using aluminum.

Example 2 (Production of Battery) Lithium cobaltate and polyvinylidene fluoride (PVd)
F) and a positive electrode composed of acetylene black (thickness: 40 μm)
m) with an aluminum current collector having a protruding piece (thickness 25 μm)
m), and a negative electrode (25 μm) made of graphite and PVdF was similarly formed on a copper current collector (thickness: 25 μm) having protrusions by coating. As an electrolyte, a non-fluid electrolyte obtained by gelling an electrolyte solution composed of LiPF ₆ and a mixed solvent of propylene carbonate / ethylene carbonate with an acrylic-modified polyethylene oxide-based polymer is used, and is filled in the voids of the nonwoven fabric (thickness: 60 μm). This was interposed between the positive electrode and the negative electrode as an electrolyte layer. The positive electrode and the negative electrode were impregnated with the above non-fluid electrolyte, and the gap between the positive electrode and the negative electrode was filled with the non-fluid electrolyte as an ion mobile phase.

A plurality of the thus obtained thin plate-shaped unit battery elements are stacked in the thickness direction, the protruding pieces of the respective current collectors are vertically connected, and further connected to a lead wire to form a battery. Elements. Polypropylene is used as the heat sealing layer and polyvinyl alcohol (saponification degree 99) is used as the base layer.
% Or more), and the above battery element was encapsulated using a laminated film having the same layer configuration as that of FIG. 10 using polyamide as the protective layer. That is, as shown in FIG. 7, the laminated film is bent at the central portion 6a to form the upper sheet 66b.
And the lower sheet 66c, and the battery element 4
After the sheet is loaded, the upper sheet and the lower sheet are joined, and the lead wires 55a and 55b are arranged so as to protrude from the sides facing the bending side 6a, and the sides 6 orthogonal to the bending side 6a are arranged.
b, 6c and the side 6d from which the lead wires 55a, 55b protrude
Was sealed under vacuum to obtain a battery having the structure shown in FIG.

At this time, the thickness of each layer of the laminated film used was 15 μm for the heat sealing layer, 150 ° for the gas barrier layer containing silicon oxide, 12 μm for the base material layer, and 25 μm for the protective layer.
m. The obtained lithium secondary battery was extremely lightweight and small, had little intrusion of gas such as water vapor, had no short circuit, and had extremely excellent performance. Also, it had excellent durability even when used repeatedly.

Example 3 A lithium secondary battery was produced in the same manner as in Example 2, except that a moisture absorbent sheet having a synthetic zeolite was sandwiched between the battery element and the sheet when the battery element was encapsulated. Was manufactured and evaluated. As a result, the deterioration of the battery performance due to the penetration of water vapor was further reduced, and the durability of the battery was further improved. The hygroscopic sheet was prepared by blending a pulverized synthetic zeolite (molecular sieves 3A) with a high-density polyethylene pellet in a dry room so that the weight fraction was 20%, and cut out a sheet formed by a press. Manufactured. Example 4 As a sheet-like material, lithium was formed in the same manner as in Example 3 except that an inorganic material layer made of silicate was formed between the heat sealing layer and the base material layer by further coating the base material layer. A secondary battery was manufactured and evaluated. As a result, the deterioration of the battery performance due to the penetration of water vapor was further reduced, and the durability of the battery was further improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of an electrode used in the present invention.

FIG. 2 is a longitudinal sectional view showing an example of a battery element used in the present invention.

FIG. 3 is a plan view of the battery element of FIG. 2;

FIG. 4 is a perspective view showing a lead terminal portion of a current collector.

FIGS. 5A and 5B are longitudinal sectional views of a sheet used in the present invention.

FIG. 6 is a longitudinal sectional view showing another example of a sheet-like material used in the present invention.

FIG. 7 is a perspective view showing the assembly of the battery of the present invention.

FIG. 8 is a plan view showing an example of the battery of the present invention.

FIG. 9 is a partial cross-sectional view showing the structure of a conventional battery.

FIG. 10 is a longitudinal sectional view showing still another example of the sheet-like material used in the present invention.

FIG. 11 is a partial front view showing a battery having a conventional structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Non-fluid electrolyte layer 4 Battery element 5 Current collector 5a, 5b Current collecting piece 6 Sheet 7 Gas barrier layer 8 Base layer 9 Heat seal layer 10 Protective layer 12b, 12c, 12d Sealed Department

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H011 AA09 AA10 AA17 CC02 CC05 CC10 DD13 DD18 DD21 5H029 AJ12 AJ14 AJ15 AK02 AK03 AK05 AK16 AL01 AL02 AL06 AL07 AL12 AM00 AM02 AM03 AM04 AM05 AM07 AM16 CJ24 DJ02 EJ05EJ

Claims (12)

[Claims] 1. A battery in which a battery element having a positive electrode and a negative electrode is housed in a case whose inside is decompressed, wherein the case has a gas barrier layer containing an inorganic material and having a thickness of 1000 nm or less. battery. 2. The battery according to claim 1, wherein the battery element has a thin plate shape, and the case is formed of two sheet-like members sandwiching the battery element from above and below. 3. The battery according to claim 2, wherein at least a part of the sheet-like material is mutually fused by heat fusion to form a case. 4. The battery according to claim 1, wherein the case has a base material layer on at least one of the upper and lower sides of the gas barrier layer. 5. The battery according to claim 4, wherein the base layer contains polyvinyl alcohol. 6. The battery according to claim 4, wherein the base layer contains polyester. 7. The battery according to claim 1, wherein a heat sealing layer made of a polyolefin resin is provided inside the gas barrier layer. 8. The battery according to claim 1, wherein a protective layer made of at least one resin selected from the group consisting of polyester and polyamide is provided outside the gas barrier layer. 9. The battery according to claim 1, wherein the battery element is a lithium secondary battery using lithium as an electromotive substance. 10. The battery according to claim 1, wherein the positive electrode and the negative electrode are laminated via a non-fluid electrolyte layer. 11. The battery according to claim 1, wherein the gas barrier layer is formed by vacuum deposition. 12. The inorganic material is aluminum, silicon,
The battery according to any one of claims 1 to 11, wherein the battery is an oxide of at least one element selected from the group consisting of tin, zinc, iridium, titanium, and zirconium.