JP2002075324A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery wherein 7 or more thin film unit battery elements formed by laminating positive electrodes formed by forming a positive electrode material layer on metallic foil for the positive electrode and negative electrodes formed by forming a negative electrode layer on metallic foil for the negative electrode are laminated in its thickness direction, the battery element has a terminal part formed by mutually bonding tabs of the metal foil for each positive electrode and tabs of the metal foil for each negative electrode, and the tabs for the positive electrode and the negative electrode are bonded by high bonding strength without producing a defective part such as a short-circuited part. SOLUTION: The tabs 4a of the metallic foil for the positive electrode, which constitutes each laminated unit battery element, are mutually bonded, the tabs 4b of the metallic foil 26 for the negative electrode are mutually bonded, and a lead 21 is also bonded to them by resistance welding. The laminated body of the unit battery element is vacuum-enclosed in amoring materials 2, 3. The lead 21 is extended to the outside from the joint surface of the amoring materials 2, 3.

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 thin film unit battery element comprising a positive electrode having a metal foil for a positive electrode and a negative electrode having a metal for a negative electrode laminated through an electrolyte layer. The present invention relates to a battery including a battery element that is stacked in a plurality of directions and that has tabs of each metal foil for a positive electrode and tabs of a metal foil for a negative electrode joined to each other to form a terminal portion. More specifically, the present invention relates to a battery in which the metal foils for the positive electrode and the negative electrode are bonded with high bonding strength without generating a defective portion such as a short circuit.

[0002]

2. Description of the Related Art As a thin battery, there is known a thin battery in which a laminated battery element formed by laminating a plurality of flat membrane unit battery elements having a positive electrode and a negative electrode in a thickness direction is covered with a laminate film. This battery element is formed by laminating a positive electrode formed by forming a positive electrode material layer on a positive electrode metal foil and a negative electrode formed by forming a negative electrode material layer on a negative electrode metal foil via an electrolyte layer. A plurality of such unit battery elements are stacked in the thickness direction, and the tabs of the metal foil for the positive electrode and the tabs of the metal foil for the negative electrode of each unit battery element are respectively bundled and joined to form a positive electrode terminal portion and a negative electrode terminal portion. It was done. The positive electrode lead and the negative electrode lead joined to the positive electrode terminal and the negative electrode terminal, respectively, are drawn out of a laminate film as an exterior material.

Conventionally, in such a thin battery, a plurality of metal foils for a positive electrode and a metal foil for a negative electrode have been joined by ultrasonic welding. Ultrasonic welding is a method of applying physical vibration by applying ultrasonic waves to the parts to be joined and joining mainly by plastic deformation of the metal foil, and usually a horn that generates ultrasonic waves is attached to the parts to be joined. The horns are brought into contact with each other, and the ultrasonic waves generated by the horn are used for bonding.

[0004]

However, in the case of ultrasonic welding, there is a problem that metal powder is easily generated from the metal foil because physical vibration is applied to the metal foil. The generation of metal powder is not preferable because it causes a short circuit between the positive electrode and the negative electrode.

In recent years, the number of stacked unit battery elements has been increased in order to increase the capacity and voltage of batteries. In the case where the number of stacked unit battery elements in the form of a thin film is increased (for example, 7 or more) as described above, in ultrasonic welding,
In particular, the joining of the tabs apart from the horn tends to be insufficient. As a result, there is a possibility that separation occurs between the tabs or between the tab and the lead during the subsequent battery assembling step or during use of the battery, or a large electric resistance is generated due to a poor connection.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and is a battery in which seven or more unit battery elements are assembled into a battery element, and the unit battery elements are connected to each other to form a terminal portion. An object of the present invention is to provide a battery in which tabs of a metal foil for a positive electrode and a negative electrode are joined with high joining strength without generating a defective portion such as a short circuit.

[0007]

Means for Solving the Problems The present inventors have found that the above object can be achieved by substantially integrating the joined portions by resistance welding or the like, and completed the present invention.

The gist of the present invention resides in the following.

(1) A battery in which seven or more unit battery elements are assembled into a battery element, and the unit battery elements are connected to each other to form a terminal, and the unit battery element is joined at the terminal. A battery wherein the parts are substantially integrated with the material constituting the terminal part. (2) A thin-film unit battery element obtained by laminating a positive electrode having a metal for a positive electrode and a negative electrode having a metal for a negative electrode via an electrolyte layer, wherein the metal foil for a positive electrode and the metal foil for a negative electrode are each Seven or more unit battery elements extending from the lamination surface and having tabs formed thereon are stacked in a thickness direction of seven or more, and the tabs of the metal foils for each positive electrode and the tabs of the metal foils for each negative electrode are joined to each other. A battery comprising a battery element serving as a terminal portion, wherein a joint portion of the unit battery element in the terminal portion is substantially integrated with a material constituting the terminal portion. (3) The battery according to (1) or (2), wherein the joining portion is formed by melting and resolidifying the metal foil. (4) The battery according to (1) to (3), wherein the joining portion is formed by resistance welding. (5) The battery according to (2) to (4), wherein the metal foil for a positive electrode contains aluminum. (6) The battery according to (2) to (5), wherein the negative electrode metal foil contains copper. (7) The battery according to any one of (1) to (6), wherein the unit cell element has a non-fluid electrolyte. (8) The battery according to any one of (1) to (7), wherein the battery element is covered with an exterior material formed of a laminate film having a resin layer formed on both surfaces of a metal layer. (9) The battery according to any one of (1) to (8), wherein the other end of a lead having one end extending outside the exterior material is joined to the joint portion.

In the present invention, "substantially integrating metal foils" refers to a state in which the metal foils are not physically distinguished and the bonding interface does not substantially exist. For example, a material formed by once melting a metal foil and then re-solidifying the metal foil corresponds to the “metal foils are substantially integrated”. As such a joining process, resistance welding is particularly suitable.

In resistance welding, a joint portion is sandwiched between two welding electrodes having high electric resistance, and a metal at the joint portion is melted by Joule heat generated when a large current flows between the electrodes, and the metal is then reheated. Joining is performed by solidification. A metal powder is not generated at a joint where the metal foils are substantially integrated by such resistance welding or the like. High adhesive strength. Therefore, the electrical resistance of the joint is small. Even if the number of stacked unit battery elements is large, they can be firmly joined. Since the joining portion is flat, encapsulation and sealing with a laminate film are easy. Thus, a high-performance, high-quality battery is provided.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A battery according to an embodiment will be described below with reference to the drawings.

Hereinafter, as an embodiment of the present invention, a configuration in the case of a lithium secondary battery will be described with reference to FIGS.

FIG. 1 shows a preferred example of a unit battery element of the lithium secondary battery element. The unit battery element includes a positive electrode in which a positive electrode active material layer (positive electrode material layer) 23 is provided on a positive electrode metal foil (positive electrode current collector) 22, a spacer (electrolyte layer) 24, and a negative electrode metal foil (negative electrode). Current collector) 26
It is obtained by laminating a negative electrode on which a negative electrode active material layer (negative electrode material layer) 25 is provided.

[0015] Seven or more unit battery elements are stacked (assembled).
To make a battery element.
Alternately, a unit battery element in a forward posture (FIG. 1) with the positive electrode on the upper side and a negative electrode on the lower side, and a unit battery element in a reverse posture (not shown) with the positive electrode on the lower side and the negative electrode on the upper side. To be laminated. That is, the unit battery elements adjacent in the stacking direction are stacked such that the same electrodes face each other (that is, the positive electrodes and the negative electrodes face each other).

A positive electrode tab 4a extends from the positive metal foil 22 of the unit battery element, and a negative electrode tab 4b extends from the negative metal foil 26.

As shown in FIG. 1, instead of a unit battery element in which a positive electrode active material layer 23, a spacer 24 and a negative electrode active material layer 25 are laminated between a positive electrode metal foil 22 and a negative electrode metal foil 26,
As shown in FIG. 2, a positive electrode active material layer (a positive electrode material layer) 11a or a negative electrode active material layer (a negative electrode material layer) 12a is laminated on both surfaces of a positive electrode metal foil 15a or a negative electrode metal foil 15b as a core material. A positive electrode 11 and a negative electrode 12 were prepared.
3 and a spacer (electrolyte layer) 13 as shown in FIG.
May be alternately stacked to form a unit battery element. In this case, a combination of a pair of the positive electrode 11 and the negative electrode 12 (strictly, from the center in the thickness direction of the metal foil 15a of the positive electrode 11 to the center in the thickness direction of the metal foil 15b of the negative electrode 12) corresponds to a unit battery element. I do.

The planar shape of the electrode is arbitrary, and may be a square, a triangle, a polygon, or the like.

As shown in FIGS. 1 and 3, metal foils 22, 26 or 1
Tabs 4a, 4b for lead connection are extended from 5a, 15b from the lamination surface. When the electrode is square,
Normally, as shown in FIG. 4 which is a perspective view of a battery element 1 which is a laminate of such unit battery elements, a tab 4a projecting from the positive electrode metal foil 22 is formed near one side of one side of the electrode. The tab 4b of the metal foil for the negative electrode is formed near the other side. Then, of the tabs 4a and 4b drawn out from each unit cell element, the tabs 4a from the positive electrode are bundled in the stacking direction (that is, overlapped with each other), and the positive electrode lead is joined as described later, The tabs 4b from the negative electrode are also bundled together, and the negative electrode leads are joined to form terminal portions. Such stacking of a plurality of unit battery elements in parallel is effective in increasing the capacity of the battery.

The tabs 4a and 4b are connected to flaky metal leads as described later. As a result, the lead and the positive and negative electrodes of the battery element are electrically coupled.

In the present invention, the joining between the tabs 4a and 4b and more preferably the joining between the tabs 4a and 4b and the lead are substantially performed by melting and re-solidifying the metal foil by resistance welding or the like. It is performed by a method of integrating.

Hereinafter, resistance welding suitable as a joining method in the present invention will be described with reference to FIG. FIG.
FIG. 5A is a schematic perspective view illustrating a method of joining tabs and leads, and FIG. 5B is an enlarged cross-sectional view of a joining portion. In FIG. 5A, the positive electrode and the negative electrode active material layers are not shown.

As shown in FIG. 5A, the positive electrode metal foil 22
7 or more tabs 4a extending from the lamination surface of the positive electrode metal foil 26, and seven or more tabs 4b extending from the lamination surface of the positive electrode metal foil 26 are laminated.
Are laminated. Then, as shown in FIG. 5B, these tabs 4a or 4b and the lead 21 are sandwiched in the laminating direction by a pair of welding electrodes 30A and 30B having a high electric resistance made of molybdenum or the like. A large current flows between 30B and the tab 4a or 4b at the joint is generated by the generated Joule heat.
Then, the metal of the lead 21 is melted and then solidified to join (in FIG. 5A, a portion surrounded by a broken line indicates a welded portion).

[0024] The joining portion by this resistance welding (FIG. 5A)
(A portion surrounded by a broken line) tends to have a low bonding strength, while if too large, the bonding portion may be damaged. Therefore, this joint has a diameter of 0.1
５5 mm, preferably 0.5 to 2 mm.

In the resistance welding, the speed of the rise of the welding current is important, and it is desirable to design the welding apparatus so that the rise of the current is as fast as possible.

In the present invention, the number of tabs joined by such resistance welding or the like, that is, the number of stacked unit battery elements is 7 or more, preferably 10 or more, and particularly preferably 1 or more.
5 or more. The effect of the present invention is particularly remarkably exhibited in a battery having a large number of stacked unit battery elements.
However, if the number of stacked unit battery elements is excessively large, joining may be difficult.
Hereinafter, it is particularly preferable that it is 40 or less.

The constituent materials of each part of the unit battery element will be described below.

As the metal foils 15a and 22 for the positive electrode, metal foils such as aluminum, stainless steel and nickel can be used.
Particularly, aluminum is preferable, and the metal foil 15b for the negative electrode is used.
As 26, a metal foil such as copper, stainless steel, nickel or the like can be used, and copper is particularly preferable. The thickness of these metal foils (tabs) is usually 1 to 30 μm, preferably 1 to 20 μm.
m. If it is too thick, the battery capacity may be reduced, and if it is too thin, handling may be difficult. Further, the size of the tab extending from the lamination surface of the metal foil for the positive electrode metal foil and the metal foil for the negative electrode is too small to make resistance welding difficult, and excessively large is disadvantageous for downsizing the battery. Therefore, the width of the portion extending from the tab is 1 to 10 mm, preferably 3 to 10 mm.
It is preferably about 8 mm.

As the positive electrode active material (positive electrode material), an inorganic compound or an organic compound can be used as long as it can occlude and release lithium ions. As the inorganic compound, a transition metal oxide, a composite oxide of lithium and a transition metal, a transition metal sulfide, specifically, a transition metal oxide such as MnO, V ₂ O ₅ , TiO ₂ , lithium nickelate, cobalt Examples thereof include composite oxides of lithium and a transition metal such as lithium oxide and lithium manganate, and transition metal sulfides such as TiS ₂ , FeS and MoS ₂ . 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. The positive electrode active material may be used by mixing these inorganic compounds and organic compounds. Particularly preferred is a composite oxide of lithium and at least one transition metal selected from the group consisting of cobalt, nickel and manganese.

The particle size of the positive electrode active material may be appropriately selected in accordance with the other components of the battery.
0 μm, especially 1 to 10 μm is preferable because battery characteristics such as initial efficiency and cycle characteristics are improved.

As the negative electrode active material (negative electrode material), usually,
Examples include carbon-based substances such as graphite and coke.
This carbon-based material may be used as a mixture with a metal, a metal salt, an oxide, or the like, or in the form of a coating. Examples of the negative electrode active material include oxides and sulfates of silicon, tin, zinc, manganese, iron, nickel and the like, metallic lithium, Li-Al, Li-
A lithium alloy such as Bi-Cd and Li-Sn-Cd, a lithium transition metal nitride, 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 from the viewpoint of improving battery characteristics such as initial efficiency, late characteristics, and cycle characteristics.
m, preferably 10 μm or less. If the particle size is too large, the electron conductivity deteriorates. In addition, it is usually 0.
It is at least 5 μm, preferably at least 7 μm.

In order to bind the positive electrode active material and the negative electrode active material onto the metal foil for the positive electrode and the metal foil for the negative electrode, 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. As resin,
For example, polyethylene, polypropylene, poly-1,1
-Alkane polymers such as dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polymers having a ring such as polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone; polymethyl methacrylate, polymethacrylic acid Ethyl, polybutyl methacrylate, polymethyl acrylate,
Acrylic polymers such as polyethyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide;
Fluorinated resins such as polyvinyl fluoride, 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 poly Halogen-containing polymers such as vinylidene chloride; conductive polymers such as polyaniline 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 amount of the binder relative to 100 parts by weight of the active material is preferably 0.1 to 30 parts by weight, and more preferably 1 to 15 parts by weight. If the amount of the resin is too small, the strength of the electrode may decrease. If the amount of the resin is too small, the capacity may decrease, or the late characteristics may decrease.

The positive electrode active material and the negative electrode active material may contain additives, such as conductive materials and reinforcing materials, exhibiting various functions, powders, fillers, and the like, if necessary.

The conductive material is not particularly limited as long as it can impart conductivity by mixing an appropriate amount with the above-mentioned active material. Usually, carbon powder such as acetylene black, carbon black and graphite, and various kinds of metals are used. Fibers, foils and the like can be mentioned. Additives include trifluoropropylene carbonate, vinylene carbonate, 1,6-Di
oxaspiro [4,4] nonane-2,7-d
ion, 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 and organic spherical and fibrous fillers can be used.

As a method of forming an electrode (active material layer) on the metal foil for the positive electrode and the metal foil for the negative electrode, for example, a powdery active material is mixed with a binder together with a solvent, and a ball mill,
A method in which a material dispersed in a coating material using a sand mill, a twin-screw kneader, or the like is applied to a metal foil and dried is suitably performed. In this case, the kind of the solvent used is not particularly limited as long as it is inert to the electrode 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 electrode material layer can be formed by a method of pressing or spraying on a metal foil in a state where the active material is mixed with a binder and heated and softened. Furthermore, it can also be formed by firing the active material alone on a metal foil.

An ion mobile phase is usually formed in the positive and negative electrodes. The proportion of the ion mobile phase in the electrode is
The higher the value, the easier the ion migration becomes. The preferable is the rate characteristic, while the lower the value, the higher the capacitance. Preferably 1
0 to 50% by volume. As materials 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 active material layer and the negative electrode active material layer be thicker in terms of capacity and thinner on the rate. The layer thickness is usually at least 20 μm, preferably at least 30 μm, more preferably at least 50 μm, most preferably at least 80 μm. The thickness of the positive and negative electrode active material layers is usually 200 μm
Or less, preferably 150 μm or less.

The spacers (electrolyte layers) 13 and 24 usually contain various kinds of electrolytes such as an electrolyte having fluidity and a non-flowable electrolyte such as a gel electrolyte and a completely solid electrolyte.
An electrolyte or a gel electrolyte is preferable in terms of battery characteristics, and a non-fluid electrolyte is preferable in terms of safety. In particular, when a non-fluid electrolyte is used, liquid leakage can be more effectively prevented with respect to a battery using a conventional electrolytic solution, so that the advantage of using a case having a shape changeability such as a laminated film described later is advantageous. You can make the most of it.

The electrolyte used for the electrolyte layer is usually a solution obtained by dissolving a supporting electrolyte in a non-aqueous solvent.

As the supporting electrolyte, a non-aqueous substance which is stable as an electrolyte with respect to the positive electrode active material and the negative electrode active material and which can undergo lithium ion to perform an electrochemical reaction with the positive electrode active material or the negative electrode active material. Any one can be used. Specifically, LiPF
_{6, LiAsF 6, LiSbF 6,} LiBF 4, LiC
10 ₄ , LiI, LiBr, LiCl, LiAlCl,
Lithium salts such as LiHF ₂ , LiSCN, and LiSO ₃ CF ₂ are mentioned. Of these, LiPF ₆ ,
LiClO ₄ is preferred.

When these supporting electrolytes are used in the state of being dissolved in a non-aqueous solvent, the concentration is 0.5 to 2.5 mol / L.
Is preferred. 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, acyclic carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; glymes such as tetrahydrofuran, 2-methyltetrahydrofuran, and dimethoxyethane;
One or more of lactones such as -butyllactone, sulfur compounds such as sulfolane, and nitriles such as acetonitrile are exemplified.

Among these, one or more solvents selected from cyclic carbonates such as ethylene carbonate and propylene carbonate, and non-cyclic carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are particularly suitable. is there. Further, additives and the like may be added to these solvents. Examples of the additive include trifluoropropylene carbonate, vinylene carbonate, 1,6-dioxaspi
ro [4,4] nonane-2,7-dione, 1
2-crown-4-ether and the like can be used for the purpose of increasing the stability and life of the battery.

The gel electrolyte that can be used for the electrolyte layer is usually obtained by holding the above-mentioned electrolyte solution with a polymer. That is,
The gel electrolyte is one in which the electrolyte is generally held in a polymer network, and the fluidity as a whole is significantly reduced. Such a gel electrolyte exhibits properties such as ionic conductivity that are close to those of a normal electrolyte solution, but fluidity, volatility and the like are significantly suppressed, and safety is enhanced. The ratio of the polymer in the gel electrolyte is preferably 1 to 50% by weight. 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 tends to decrease and battery characteristics tend to deteriorate.

As the polymer used for the gel electrolyte,
There is no particular limitation as long as it is a polymer that can form a gel together with the electrolyte, and polyester, polyamide, polycarbonate, those produced by polycondensation such as polyimide,
Polyurethane, polyurea, etc. produced by polyaddition, acrylic derivative polymers such as polymethyl methacrylate, and polyadditions produced by polyvinyl polymerization such as polyvinyl acetate, polyvinyl chloride, polyvinylidene fluoride, etc. and so on. Preferred polymers include polyacrylonitrile and polyvinylidene fluoride. Here, the polyvinylidene fluoride includes not only a homopolymer of vinylidene fluoride but also a copolymer with another monomer component such as hexafluoropropylene. Also, acrylic acid, methyl acrylate,
Ethyl acrylate, ethoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxyethyl acrylate, polyethylene glycol monoacrylate,
Ethoxyethyl methacrylate, methoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, polyethylene glycol monomethacrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl acrylate, glycidyl acrylate, allyl acrylate, acrylonitrile, N-vinyl pyrrolidone, diethylene glycol di Acrylic obtained by polymerizing acrylic monomers such as acrylate, triethylene glycol diacrylate, tetraethylene glycol acrylate, polyethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate. Can be used polymers are also preferred.

The weight average molecular weight of the above polymer is usually 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 with respect to the electrolytic solution may be appropriately selected according to the molecular weight, but is preferably 0.1 to 30% by weight. If the concentration is too low, 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 too high, the viscosity becomes too high, which causes difficulties in the process, and the proportion of the electrolytic solution is reduced, the ionic conductivity is reduced, and the battery characteristics such as late characteristics may be deteriorated.

A completely solid electrolyte layer may be used as the electrolyte layer. As such a solid electrolyte, various solid electrolytes known so far 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 electrolyte layer, a material obtained by impregnating a porous sheet such as a porous membrane with the above electrolyte may be used.

The thickness of the electrolyte layer is usually 1 to 200 μm,
Preferably, it is 5 to 100 μm.

As the porous sheet, specifically, the thickness is usually 1 μm or more, preferably 5 μm or more, and usually 200 μm or more.
μm or less, preferably 100 μm or less is used. The porosity is usually 10 to 95%, preferably 30 to 8%.
It is about 5%. As a material of the porous sheet, a polyolefin or a polyolefin in which part or all of hydrogen atoms have been substituted with fluorine can be used. Specifically, a microporous film, a nonwoven fabric, a woven fabric, or the like formed using a synthetic resin such as polyolefin can be used.

Next, the battery element formed by laminating the above-described unit battery elements and joining the tabs of the metal foil for the positive electrode and the metal foil for the negative electrode with the leads, respectively, was covered with an outer package. A preferred battery embodiment will be described with reference to FIGS.

FIG. 6 is an exploded perspective view of the battery according to the embodiment, FIG. 7 is a sectional view of a main part of the battery, and FIG. 8 is a perspective view of the battery.

This battery has a battery element 1 as shown in FIG.
Is housed in the concave portion (housing portion) 3b of the exterior material 3, the exterior material 2 is put on the exterior material 3, and the peripheral edges 2a and 3a of the exterior materials 2 and 3 are joined by vacuum sealing.

As shown in FIG. 6, the exterior material 2 is flat. The exterior material 3 is a shallow, open box-like shape having a housing portion 3b formed of a rectangular box-shaped recess and a peripheral portion 3a projecting outward in a flange shape from four peripheral edges of the housing portion 3b.

The battery element 1 is accommodated in the accommodating portion 3b of the exterior material 3, and the exterior material 2 is covered.

A pair of leads 21 extending from the battery element 1
Are peripheral portions 2a, 3a of one side of the exterior materials 2, 3, respectively.
It is drawn out through the mating surface of each other. afterwards,
Under a reduced pressure (preferably vacuum) atmosphere, the four peripheral edges 2a and 3a of the outer packaging materials 2 and 3 are hermetically joined to each other by a method such as thermocompression bonding or ultrasonic welding.
3 is enclosed.

The joining pieces 4A, 4F and 4G are formed by joining the peripheral edges 2a and 3a to each other. The joining pieces 4A, 4F, 4G project outward from the enclosing part 4B enclosing the battery element 1. Therefore, of the joining pieces 4A, 4F, 4G, 4A, 4G are
Bent along B, adhesive or adhesive tape (not shown)
It is fastened to the side surface of the enclosing part 4B by the method described above.

In FIG. 6, the insulating material is separately supplied to the positive terminal portion and the negative terminal portion. However, in the present invention, in order to further improve the effect of preventing short-circuit, the positive terminal portion and the negative terminal portion are separated. It is preferable to cover the entire side surface of the battery element over the part.

In FIG. 6, the exterior materials 2 and 3 are separate bodies. However, in the present invention, the exterior materials 2 and 3 may be integrally formed as shown in FIG. In FIG. 9, one side of the exterior material 3 and one side of the exterior material 2 are connected, and the exterior material 2 has a lid shape that is connected to the exterior material 3 so as to be bent. A concave portion of the housing portion 3b is formed from one side where the exterior materials 2 and 3 are continuous,
This one side has the same configuration as the joining piece except that no joining piece is formed.

FIGS. 6 and 9 show the exterior material 3 having the accommodation portion 3b and the flat exterior material 2, but in the present invention, as shown in FIG. , 7b
And a peripheral portion 6 projecting from four peripheral edges of the housing portions 6b and 7b.
The battery element 1 may be encapsulated by the exterior materials 6 and 7 having the components a and 7a. In FIG. 10, the exterior materials 6 and 7 are integrated in a series, but they may be separate bodies as in FIG. 6.

In the present invention, as shown in FIG. 11, one flat sheet-like exterior material 8 is folded in two along the center side 8a to form two pieces of a first piece 8A and a second piece 8B. Forming
The battery element 1 is interposed between the first piece 8A and the second piece 8B, and as shown in FIG. 12, the peripheral parts 8b of the first piece 8A and the second piece 8B are joined to encapsulate the battery element 1. You may.

In this embodiment, since the bent joint piece is fixed along with the encapsulating portion with an adhesive or an adhesive tape, the strength and rigidity of the side surface of the battery are high. . Of course, the bent joint piece is also prevented from separating from the envelope. Further, since the strength and rigidity of the side surface of the battery are high, even when the side surface receives an impact, the active material is prevented from peeling off.

As the lead 21, it is preferable to use an annealed metal for at least one of the positive electrode lead and the negative electrode lead 21 and preferably for both of the leads.
As a result, a battery having excellent bending durability as well as strength can be obtained.

As the kind of metal used for the lead, aluminum, copper, nickel, SUS or the like can be generally used. The preferred material for the positive electrode lead is aluminum. A preferable material for the lead of the negative electrode is copper.

The thickness of the lead 21 is usually 1 μm or more, preferably 10 μm or more, more preferably 20 μm or more.
Most preferably, it is 40 μm or more. If the thickness is too small, the mechanical strength of the lead such as tensile strength tends to be insufficient. The thickness of the lead is usually 1000 μm or less, preferably 500 μm or less, and more preferably 100 μm or less. If the thickness is too large, the bending durability tends to deteriorate, and the case tends to be difficult to seal the battery element. The advantage of using the later-described annealed metal for the lead is more remarkable as the thickness of the lead is larger.

The width of the lead is usually from 1 mm to 20 mm, particularly from about 1 mm to 10 mm, and the length of the lead exposed to the outside is usually from about 1 mm to 50 mm. The lamination width (W in FIG. 5B) of the lead with the tab 4a or 4b is preferably about 0.5 to 10 mm.

The tab 4 shown in FIGS. 5A and 5B
The direction of superposition of the leads 21a and 4b and the lead 21 is opposite to the direction of superposition of the tabs 4a and 4b and the lead 21 shown in FIG. 7, but the direction of superposition is not particularly limited.

It is preferable that the exterior members 2, 3, 6, 7, and 8 have shape variability. As a result, it is possible to easily change the shape of the battery in various ways. Further, after the interior of the exterior material is evacuated, by sealing the peripheral portion of the exterior material, a pressing force can be applied to the battery element 1, and as a result, battery characteristics such as cycle characteristics are improved. be able to.

As the material of the exterior material, a metal such as aluminum or nickel-plated iron or copper, a synthetic resin, or the like can be used. Preferably, a laminated composite material in which a metal and a synthetic resin are laminated is used. Can be By using this laminated composite material, the thickness and weight of the case member can be reduced, and the capacity of the battery as a whole can be improved.

FIG. 13 shows a laminate composite material.
As shown in (A), a laminate in which a metal layer 40 and a synthetic resin layer 41 are laminated can be used. This metal layer 40
Is for preventing infiltration of water or maintaining shape retention, and may be a simple metal such as aluminum, iron, copper, nickel, titanium, molybdenum, gold, or an alloy such as stainless steel, Hastelloy, or a metal oxide such as aluminum oxide. . Particularly, aluminum having excellent workability is preferable.

The formation of the metal layer 40 can be performed using a metal foil, a metal deposition film, a metal sputter, or the like.

The synthetic resin layer 41 is used to protect the case member, prevent invasion by the electrolyte, prevent contact between the metal layer and the battery element, or protect the metal layer. In the present invention, the elastic modulus and the tensile elongation of the synthetic resin are not limited. Therefore, the synthetic resin in the present invention includes what is generally called an elastomer.

As the synthetic resin, thermoplastics, thermoplastic elastomers, thermosetting resins and plastic alloys are used. These resins include those in which a filler such as a filler is mixed.

The laminated composite material is shown in FIG.
As shown in (B), a synthetic resin layer 41 for functioning as an outer protective layer is provided on the outer surface of the metal layer 40, and corrosion on the inner surface and contact between the metal layer and the battery element are prevented on the inner surface. A three-layer structure in which the synthetic resin layers 42 functioning as inner protective layers for protecting the layers can be formed.

In this case, the resin used for the outer protective layer is
Preferably, resins excellent in chemical resistance and mechanical strength, such as polyethylene, polypropylene, modified polyolefin, ionomer, amorphous polyolefin, polyethylene terephthalate, and polyamide are desirable.

As the inner protective layer, a synthetic resin having chemical resistance is used, and for example, polyethylene, polypropylene, modified polyolefin, ionomer, ethylene-vinyl acetate copolymer and the like can be used.

Further, as shown in FIG. 14, the composite material may be provided with an adhesive layer 43 between the metal layer 40, the synthetic resin layer 41 for forming the protective layer, and the synthetic resin layer 42 for forming the corrosion-resistant layer. Furthermore, in order to adhere the case members to each other,
An adhesive layer made of a resin such as polyethylene or polypropylene that can be welded can be provided on the innermost surface of the composite material. A case is formed using these metals, synthetic resins or composite materials. The case may be formed by fusing the periphery of the film-like body, or the sheet-like body may be drawn by vacuum forming, pressure forming, press forming or the like. Also,
It can also be molded by injection molding a synthetic resin. When injection molding is used, the metal layer is usually formed by sputtering or the like.

In order to provide a housing portion formed of a concave portion in the exterior material, drawing can be performed.

The data of the confirmation experiment will be shown below.

Twenty-one copper foils each having a thickness of 20 μm are laminated, and resistance welding (electrode material: molybdenum, current value: 1.8) is performed.
mA) to integrate the joints. The diameter of the welded portion was 1 mm. Joining was performed without any problem, and the tensile strength at that time was 8.6 N. On the other hand, when the same joining was performed by ultrasonic welding, the tensile strength was 2.3N.

The above results show that when the number of laminations is large, resistance welding has higher joining strength than ultrasonic welding.

[0083]

As described above in detail, according to the present invention, it is possible to provide a battery in which unit cell elements are joined with high joining strength without generating a defective portion.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a unit battery element according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a positive electrode or a negative electrode according to the embodiment of the present invention.

FIG. 3 is a schematic sectional view of a battery element according to an embodiment of the present invention.

FIG. 4 is a perspective view showing a battery element according to the embodiment of the present invention.

FIG. 5A is a schematic perspective view illustrating a method of joining tabs and leads according to an embodiment of the present invention, and FIG. 5B is an enlarged cross-sectional view of a joining portion. .

FIG. 6 is an exploded perspective view of the battery according to the embodiment.

FIG. 7 is a cross-sectional view of a main part of the battery according to the embodiment.

FIG. 8 is a perspective view of the battery according to the embodiment.

FIG. 9 is a perspective view of a battery according to another embodiment in the process of being manufactured.

FIG. 10 is a perspective view of a battery according to still another embodiment in the process of being manufactured.

FIG. 11 is a perspective view of a battery according to still another embodiment in the process of being manufactured.

FIG. 12 is a plan view of the battery of FIG. 11 in the process of being manufactured.

FIGS. 13A and 13B are longitudinal cross-sectional views each showing an example of a composite material constituting an exterior material.

FIG. 14 is a longitudinal sectional view showing another example of the composite material constituting the exterior material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery element 2, 3, 6, 7, 8 Exterior material 4a, 4b Tab 4A, 4F Joint piece part 4B, 4G Enclosure piece part 11 Positive electrode 11a Positive electrode active material 12 Negative electrode 12b Negative electrode active material 13 Non-fluid electrolyte layer 15a Metal foil for positive electrode 15b Metal foil for negative electrode 21 Lead 22 Metal foil for positive electrode 23 Positive electrode active material layer 24 Spacer (electrolyte layer) 25 Negative electrode active material layer 26 Negative metal foil 40 Metal layer 41, 42 Synthetic resin layer 43 Adhesive layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H01M 4/66 H01M 4/66 A 10/40 10/40 Z (72) Inventor Koji Yamaguchi Kurashiki, Okayama Prefecture 4-6-1 Matsue F-term in DIA MEDIA CORPORATION (Reference) 5H011 AA01 AA09 CC02 CC06 CC10 DD13 EE04 FF02 GG09 HH02 KK00 5H017 AA03 AS01 AS10 CC01 EE01 EE05 HH00 HH05 5H022 AA09 AA19 BB16 CC12 CC13 CC13 CC23 CC24 CC30 EE01 EE03 EE04 5H029 AJ11 AJ14 AK02 AK03 AK05 AK16 AK18 AL01 AL02 AL04 AL06 AL07 AL11 AL12 AL18 AM02 AM03 AM04 AM05 AM07 AM16 BJ04 BJ12 CJ05 CJ06 DJ02 DJ05 DJ07 EJ01 EJ12 HJ00 HJ

Claims (9)

[Claims] 1. A battery comprising a group of seven or more unit battery elements to form a battery element, and connecting the unit battery elements to each other to form a terminal portion, wherein a junction portion of the unit battery element at the terminal portion is provided. Wherein the material constituting the terminal portion is substantially integrated. 2. A thin-film unit battery element obtained by laminating a positive electrode having a metal for a positive electrode and a negative electrode having a metal for a negative electrode via an electrolyte layer, wherein the metal foil for a positive electrode and the metal foil for a negative electrode are Seven or more unit battery elements each having tabs extending from the lamination surface are stacked in the thickness direction, and tabs of each positive electrode metal foil and tabs of each negative electrode metal foil are mutually connected. A battery comprising a battery element which is joined to form a terminal, wherein a joining portion of the unit battery element in the terminal is substantially integrated with a material constituting the terminal. 3. The battery according to claim 1, wherein the joint is formed by melting and resolidifying a metal foil. 4. The battery according to claim 1, wherein the joining portion is formed by resistance welding. 5. The battery according to claim 2, wherein the positive electrode metal foil contains aluminum. 6. The battery according to claim 2, wherein the negative electrode metal foil contains copper. 7. The battery according to claim 1, wherein the unit cell element has a non-fluid electrolyte. 8. The battery according to claim 1, wherein the battery element is covered with an exterior material made of a laminate film having a resin layer formed on both surfaces of a metal layer. Battery. 9. The battery according to claim 1, wherein one end of a lead extending to the outside of the exterior material is joined to the joining portion.