JP2002359006A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery sufficiently exhibiting effects of large capacity due to the film thickening by preventing dispersion of separated active materials due to film thickening causing short-circuiting and capacitance drop and to provide a manufacturing method for the lithium secondary battery with higher productivity. SOLUTION: This secondary battery is provided with a positive electrode having a lithium compound as a positive electrode active material, a negative electrode using a compound capable of doping/de-doping lithium as a negative electrode active material, a spacer 5 insulating the positive electrode from the negative electrode, and nonaqueous electrolyte. This secondary battery is characterized in that the thickness of the positive electrode material layer 1 is 50 μm or more, and/or the thickness of the negative electrode material layer 3 is 60 μm or more, the spacer 5 has a bag shape, and the respective positive electrode and/or the negative electrode are contained in the bag-shaped spacer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery, a battery cell, and a method for manufacturing a battery.

[0002]

2. Description of the Related Art In recent years, various devices such as a camera-integrated VTR device, an audio device, a portable computer, and a cellular phone have been reduced in size and weight, and there has been a demand for higher performance of a battery as a power supply for these devices. Is growing. In particular, lithium secondary batteries capable of realizing high voltage and high energy density have been actively developed.

A lithium secondary battery comprises a positive electrode capable of inserting and extracting lithium ions, a negative electrode, and an electrolyte layer containing a non-aqueous electrolyte. Conventionally, a liquid composed of a non-aqueous organic substance has been used as the non-aqueous electrolyte. . However, a lithium secondary battery using such a non-aqueous electrolyte has a danger of liquid leakage and fire such as heat generation and fire resulting from an internal short circuit due to precipitation of lithium dendrite. Therefore, in recent years, in order to improve safety, development of a non-aqueous electrolyte, for example, a polymer electrolyte contained in a gel polymer and made non-fluidized has been performed.

[0004] Further, since the polymer electrolyte containing an electrolyte containing an electrolyte solution in a gel polymer as described above has a high ability to retain the electrolyte solution, the metal can used in a conventional lithium secondary battery is difficult. It can be used by being enclosed in a simple case. Such a polymer is lightweight and has shape flexibility as compared with a liquid system, so that it can be formed into a thin film such as a sheet, for example, and is advantageous in that a lightweight and space-saving battery can be manufactured. There is.

[0005] Further, with the advancement of functions of portable devices, batteries have been required to have higher capacities. As one of the countermeasures, thickening of the active material layer of the electrode has been studied. However, even if the film thickness was actually increased, it was difficult to achieve a high capacity up to a value close to the theoretical value.

[0006]

There has been a demand for a secondary battery capable of sufficiently exhibiting the effect of increasing the capacity by increasing the film thickness.
Further, there has been a demand for a method of manufacturing a secondary battery with higher productivity.

[0007]

The inventors of the present invention have studied the cause of the problem in order to solve the above-mentioned problems. As a result, when the film thickness is increased, the strength of the active material layer is not sufficient. When the active material layer is cut off, a part of the active material layer is detached, and the detached active material causes (1) short-circuiting in the battery, inducing a decrease in capacity and voltage, further swelling of the battery, heat generation, It was found that smoke was generated, and (2) the self-discharged lithium ion flow was inhibited, resulting in low capacity. Therefore, as a result of studying countermeasures, it has been found that such a problem can be prevented by placing the positive electrode and / or the negative electrode in a bag-shaped spacer. The use of a bag-shaped spacer is known in Japanese Patent Application Laid-Open No. 10-172565 and Japanese Patent Application Laid-Open No. 10-188938. It is not for the prevention of scattering. The present inventors have found application of a bag-shaped spacer in a secondary battery having a thick active material layer.

It has also been found that the use of a bag-shaped spacer can provide a secondary battery capable of sufficiently exhibiting the effect of increasing the capacity by increasing the thickness of the film, and that the secondary battery is manufactured with a high yield. The inventors have found that the present invention can be performed, and have completed the present invention. That is, the gist of the present invention is as follows (1) to (1).
0). (1) A positive electrode using a lithium compound as a positive electrode active material, a negative electrode using a compound capable of doping / dedoping lithium as a negative electrode active material, a spacer for insulating the positive electrode and the negative electrode, and a non-aqueous electrolyte In the secondary battery, the thickness of the positive electrode material layer is 50 μm or more and / or the thickness of the negative electrode material layer of the negative electrode is 60 μm, the spacer has a bag shape,
Alternatively, each of the negative electrodes is contained in a bag-shaped spacer.

(2) The secondary battery according to (1), wherein a plurality of positive electrodes and negative electrodes contained in the bag-shaped spacer are stacked. (3) The positive electrode and the negative electrode have a positive electrode material layer or a negative electrode material layer only on one side of the current collector, and two positive electrodes are stacked with the current collector side facing each other. The above (1) or (1), wherein the two stacked positive electrodes and / or the two stacked negative electrodes are stacked in a bag-like spacer in a state in which the two stacked positive electrodes and / or the two stacked negative electrodes are stacked with the conductors facing each other. The secondary battery of (2).

(4) The secondary battery according to any one of (1) to (3), wherein only the positive electrode or the negative electrode is contained in the bag-shaped spacer. (5) The above (1) to (1) to wherein the non-aqueous electrolyte is a non-fluid electrolyte.
The secondary battery according to any one of (4). (6) The secondary battery according to any one of (1) to (5), wherein the lithium compound is a lithium-cobalt composite oxide.

(7) The secondary battery according to any one of the above (1) to (6), wherein the compound capable of doping / dedoping lithium is a carbonaceous material. (8) A positive electrode, a negative electrode, a spacer, and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode material layer only on one side of the current collector, and the negative electrode has a negative electrode material layer only on one side of the current collector. , Positive electrode / spacer / negative electrode / negative electrode / spacer / positive electrode are stacked in this order. The two negative electrodes are stacked with the current collector side facing each other. The two spacers are heat-fused to form a bag. A battery cell comprising:

(9) A positive electrode having a positive electrode material layer only on one side of the current collector, a negative electrode having a negative electrode layer only on one side of the current collector, and a spacer are impregnated with an acrylic monomer containing a non-aqueous electrolyte. Next, a single cell is created by thermal polymerization,
A method for manufacturing a secondary battery, comprising: laminating two single cells with a negative electrode current collector facing each other; and thermally fusing two spacers into a bag shape.

(10) A positive electrode having a positive electrode material layer only on one side of the current collector, a negative electrode having a negative electrode layer only on one side of the current collector, and a spacer are impregnated with an acrylic monomer containing a non-aqueous electrolyte. Next, a single cell is formed by thermal polymerization, the two single cells are stacked with the negative electrode current collector facing the other, and two spacers are heat-fused to form a stacked cell to form a stacked cell. A method for manufacturing a secondary battery, comprising laminating a plurality of the batteries.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As the lithium compound in the present invention, a compound capable of inserting and extracting lithium ions is used. For example, oxides of transition metals such as Fe, Co, Ni, and Mn, and lithium and transition metals are used. Inorganic compounds such as composite oxides and transition metal sulfides are exemplified. Specifically, Mn
Transition metal oxide powders such as O, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ ; composite oxide powders of lithium and transition metal such as lithium such as lithium nickel oxide and lithium cobalt oxide;
Transition metal sulfide powders such as iS ₂ and FeS are mentioned.
A plurality of the above lithium compounds may be used as a mixture. Preferred lithium compounds in the present invention include composite oxides of lithium and transition metals, and specific examples include lithium nickelate, lithium cobaltate, and lithium manganate. More preferably, lithium cobaltate is used. When the lithium compound is granular, the particle size is usually 1 to 30 μm, preferably about 1 to 10 μm, in view of excellent battery characteristics such as rate characteristics and cycle characteristics.

In the present invention, the lithium compound is used as a positive electrode active material. In the present invention, the active material is a main material that causes an electromotive reaction of the battery, and means a material that can occlude and release Li ions.
Examples of the compound capable of doping / dedoping lithium in the present invention include graphite and coke in addition to the Li metal foil, and graphite is preferable. The particle size of the granular negative electrode active material is usually 1 to 1 in terms of excellent battery characteristics such as initial efficiency, rate characteristics, and cycle characteristics.
It is 50 μm, preferably about 5 to 30 μm.

The method for forming the positive electrode and the negative electrode of the secondary battery of the present invention is not particularly limited, and any method can be used.
For example, there is a method in which an electrolyte paint containing an active material and a monomer is mixed and kneaded to form a paste, which is then applied on a current collector and crosslinked with the monomer to form the paste. In the present invention, the active material and the binder are formed into a dispersion paint using a solvent capable of dissolving the binder, and the paint is applied on the current collector and dried to bind the active material to the current collector with the binder. It is preferable to form an electrode by performing the above. A commonly used dispersing machine can be used for dispersion coating, and a ball mill, a sand mill, a twin-screw kneader or the like can be used.

The coating may be performed on both sides or one side of the current collector, but in the present invention, the coating on one side of the current collector is preferable. There is no particular limitation on the coating apparatus for applying the paint on the current collector, and slide coating and extrusion type die coating, reverse roll, gravure, knife coater, kiss coater, microgravure, knife coater, rod coater, blade coater, etc. However, the extrusion method is most preferable in consideration of the viscosity of the paint and the thickness of the applied film.

In the present invention, a binder can be used to bind the active material on the current collector. As the binder, it is necessary to be stable to an electrolytic solution or the like, and various materials are used from the viewpoints of weather resistance, chemical resistance, heat resistance, flame retardancy and the like. Specifically, inorganic compounds such as silicate and glass, alkane polymers such as polyethylene, polypropylene and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polystyrene, polymethylstyrene, Polymers having a ring such as polyvinylpyridine, poly-N-vinylpyrrolidone; polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, poly Acrylic derivative polymers such as acrylamide; polyvinyl fluoride,
Fluorine-based 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; conductive polymers such as polyaniline can be used. Further, a mixture of the above-mentioned polymers, a modified product, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer, or the like can also be used. The weight molecular weight of these resins is usually 10
000-300000, preferably 100000-1
It is about 000000. If it is too low, the strength of the coating tends to decrease. On the other hand, if it is too high, the viscosity becomes high, and it may be difficult to form an electrode. Preferred examples of the binder resin include a fluorine-based resin and a CN group-containing polymer, and more preferably polyvinylidene fluoride.

The amount of the binder to be used per 100 parts by weight of the active material is usually at least 0.1 part by weight, preferably at least 1 part by weight, and is usually at most 30 parts by weight, preferably at most 20 parts by weight. If the amount of the binder is too small, the strength of the electrode tends to decrease, and if the amount of the binder is too large, the ion conductivity tends to decrease. In order to improve the conductivity and mechanical strength of the electrode, an electrode that exhibits various functions such as a conductive material and a reinforcing material, a powder, a filler, and the like may be contained in the electrode. The conductive material is not particularly limited as long as it is capable of imparting conductivity by mixing an appropriate amount with the above-mentioned active material, but usually, acetylene black, carbon black, carbon powder such as graphite, and various metal fibers, Foil and the like. The DBP oil absorption of the carbon powder conductive material is preferably 120 cc / 100 g or more,
In particular, 150 cc / 100 g or more is preferable because it holds the electrolytic solution. Additives include trifluoropropylene carbonate, 1,6-dioxaspiro [4,
4] Nonane-2,7-dione, 12-crown-4-ether, vinylene carbonate, catechol carbonate and the like can be used to increase the stability and life of the battery. Various inorganic and organic spheres as reinforcing materials,
A fibrous filler or the like can be used.

As the solvent used for coating, various organic and inorganic solvents can be used according to the active material and the binder used. Examples thereof include N-methylpyrrolidone and dimethylformamide. Methyl pyrrolidone. The solvent concentration in the paint is at least greater than 10% by weight, but is usually at least 20% by weight, preferably greater than 30% by weight, more preferably at least 35% by weight. The lower limit is usually 90% by weight or less, preferably 80% by weight or less. If the solvent concentration is too low, application may be difficult, and if it is too high, it may be difficult to increase the thickness of the applied film and the stability of the coating may be deteriorated.

In the present invention, the thickness of the positive electrode material layer is 50
μm or more, preferably 50 μm or more.
１００100 μm. If the thickness is too thin, high capacity cannot be achieved. The thickness of the negative electrode material layer is 60 μm in the present invention.
m or more, and preferably 60 to
110 μm. If the thickness is too thin, high capacity cannot be achieved.

The above-mentioned positive electrode material layer and negative electrode material layer each mean a layer containing an active material. As the current collector in the present invention, various types can be used which do not cause problems such as elution electrochemically and can function as a current collector of a battery, and usually, a metal or an alloy is used. For example, aluminum is generally used as the current collector of the positive electrode. Further, a copper foil is often used as the current collector of the negative electrode.

Preliminarily roughening the surface of these current collectors is a preferable method because the effect of binding to the electrode material layer can be improved. Examples of the surface roughening method include a method such as blasting and rolling with a rough roll, a polishing cloth paper to which abrasive particles are fixed, a grindstone, an emery buff, a wire brush provided with a steel wire, or the like. A mechanical polishing method for polishing the surface, an electrolytic polishing method, a chemical polishing method, and the like can be given.

Further, in order to reduce the weight of the secondary battery, that is, to improve the weight energy density, a perforated substrate such as an expanded metal or a punched metal can be used. In this case, the weight can be freely changed by changing the aperture ratio. When contact layers are formed on both surfaces of such a perforated type substrate, the peeling of the coating film tends to be less likely to occur due to the rivet effect of the coating film through this hole, but the aperture ratio becomes too high. In such a case, the contact area between the coating film and the base material becomes small, so that the adhesive strength may be rather lowered.

The thickness of the conductive electrode substrate is usually at least 1 μm, preferably at least 5 μm, and usually at most 100 μm, preferably at most 50. If it ’s too thick,
If the capacity of the entire battery is too low, on the contrary, if it is too thin, handling may be difficult. An undercoat primer layer may be formed on the current collector. The function of the primer layer is to improve the adhesiveness of the positive electrode or the negative electrode to the current collector.
The purpose of the present invention is to prevent a rapid decrease in capacity due to detachment of a coating film from a substrate in a charge / discharge cycle test process. The undercoat primer layer can be formed, for example, by applying an undercoat primer material paint containing a conductive material, a binder, and a solvent on a current collector and then drying the paint.

Examples of the conductive material used for the undercoat primer layer include carbon materials such as carbon black and graphite, metal powders, conductive organic conjugated resins, and the like. It is a substance such as carbon black and graphite that can also function as a substance. As the binder and the solvent used for the undercoat primer layer, those similar to the binder and the solvent used for the coating of the electrode material can be used. Also,
Since conductive resins such as polyaniline, polypyrrole, polyacene, disulfide-based compounds, and polysulfide-based compounds can have both functions of the conductive material and the binder, the conductive resin serves as both the conductive material and the binder. It can be used for an undercoat primer layer. Of course, the binder and the solvent used for the undercoat primer layer may be the same as or different from those used for the coating of the electrode material.

When a conductive material and a binder are used, the ratio of the binder to the conductive material is usually 1% by weight or more, preferably 5% by weight or more, and usually 300% by weight or less, preferably 100% by weight. % Or less. If the temperature is too low, peeling or the like is likely to occur in the process when using the battery. If the temperature is too high, the conductivity may decrease, and the battery characteristics may decrease.

The thickness of the undercoat primer layer is generally about 0.05 to 200 μm. Within this range, it is usually at least 0.05 μm, preferably at least 0.1 μm, and usually at most 10 μm, preferably at most 1 μm. If it is too thin, it is difficult to ensure uniformity, and if it is too thick, the volume capacity of the battery may be too low.

The electrolyte layer in the present invention comprises a gel polymer electrolyte in which an electrolyte is contained in a polymer to make it non-fluid, or a solid electrolyte comprising a polymer and a supporting electrolyte containing no electrolyte. Preferably, it is a gel polymer electrolyte. As the gel polymer electrolyte, a method using an electrolyte paint obtained by dissolving a polymer in an electrolyte solution from the beginning, or a method of preparing a monomer-containing electrolyte paint and then subjecting it to a cross-linking reaction to obtain a non-fluidized electrolyte were used as required. Materials and manufacturing methods can be adopted.

The electrolytic solution to be contained is preferably a non-aqueous electrolytic solution, which is generally obtained by dissolving a supporting electrolyte which is a lithium salt in a non-aqueous solvent. As the electrolytic solution, a non-aqueous substance that is stable as the electrolyte with respect to the positive electrode active material and the negative electrode active material, and that can perform a lithium ion to perform an electrochemical reaction with the positive electrode active material or the negative electrode active material. Some can be used.

As the lithium salt as a supporting electrolyte,
LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , L
iClO ₄ , LiI, LiBr, LiCl, LiAlC
1, LiHF ₂ , LiSCN, LiSO ₃ CF _{2 and the} like. Of these, LiPF ₆ and LiClO ₄ are particularly preferred. The content of these supporting electrolytes in the electrolyte is generally 0.5 to 2.5 mol / L.
It is.

The type of the solvent used for the electrolytic solution is not particularly limited, but a solvent having a relatively high dielectric constant is preferably used. Specifically, ethylene carbonate, propylene carbonate
Cyclic carbonates such as carbonate, dimethyl carbonate
Acyclic carbonates such as ethyl carbonate, diethyl carbonate and ethyl methyl carbonate; tetrahydrofuran;
Glymes such as methyltetrahydrofuran and dimethoxyethane; lactones such as γ-butyllactone; sulfur compounds such as sulfolane; and nitriles such as acetonitrile; Among them, 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. One or two selected from bones
A mixed solution of at least one kind is suitable, and particularly preferred is a mixed solution of one or more kinds selected from propylene carbonate, ethylene carbonate, dimethyl carbonate, and diethyl carbonate.

In a method of preparing a non-fluidized electrolyte by preparing a monomer-containing electrolyte coating and then performing a cross-linking reaction, a monomer that forms a polymer by performing a polymerization treatment such as ultraviolet curing or heat curing is added to the electrolytic solution. I do. Examples of the polymerizable monomer include those having an unsaturated double bond such as an acryloyl group, a methacryloyl group, a vinyl group and an allyl group. For example, 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 diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, diethylene glycol dimethacrylate,
Triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polyalkylene glycol diacrylate, polyalkylene glycol dimethacrylate, and the like can be used.Furthermore, trimethylolpropane alkoxylate triacrylate, pentaerythritol alkoxylate triacrylate, etc. Trifunctional monomers, tetrafunctional or higher functional monomers such as pentaerythritol alkoxylate tetraacrylate and ditrimethylolpropane alkoxylate tetraacrylate can also be used. Among these, those which are preferable in terms of reactivity, polarity, safety and the like may be used alone or in combination. Among them, polyethylene glycol diacrylate, trimethylolpropane alkoxylate triacrylate, and pentaerythritol alkoxylate tetraacrylate are particularly preferably used alone or in combination.

These monomers can be polymerized by heat, ultraviolet rays, electron beams or the like to make the electrolyte paint non-fluid. In this case, in order to make the reaction proceed effectively, a polymerization initiator may be added to the electrolytic solution. As the polymerization initiator, benzoin, benzyl, acetophenone,
Benzophenone, Michler's ketone, biacetyl, benzoyl peroxyzide, etc. can be used, and further, t-butyl peroxyneodenoate, α-cumylperoxyneodenoate, t-hexylperoxyneodecanate, 1-cyclohexyl Peroxyneodecanoates such as -1-methylethyl peroxyneodecanoate, t-amylperoxyneodecanoate, t-butylperoxyneoheptanoate, α-cumylperoxyneoheptanoate And peroxyneoheptanoates such as t-hexylperoxyneoheptanoate, 1-cyclohexyl-1-methylethylperoxyneoheptanoate and t-amylperoxyheptanoate. Preferably, t-butyl peroxy neodecanoate, α-cumyl peroxy neodecanoate, t-
Hexyl peroxy neodecanoate.

Further, a polymer which is produced by polycondensation of polyester, polyamide, polycarbonate, polyimide or the like, or a polymer which produces a polymer produced by polyaddition of polyurethane or polyurea may be used as the polymerizable monomer. it can. The content of the monomer is not particularly limited, but is preferably 1% or more in the electrolyte paint. When the content is low, the formation efficiency of the polymer is reduced, and the electrolyte is hardly non-fluidized.

In the method using an electrolyte paint containing a polymer from the beginning, a polymer which dissolves in an electrolyte at a high temperature and forms a gel electrolyte at a normal temperature can be preferably used.
Although it is a polymer having such properties, any material can be used as long as it is stable as a battery material.
For example, polymers having a ring such as polyvinylpyridine and poly-N-vinylpyrrolidone. Polymethyl methacrylate,
Acrylic derivative-based polymers such as polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, and polyacrylamide polyacrylamide. Fluorinated resins such as polyvinyl fluoride and polyvinylidene fluoride. CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide.
Polyvinyl alcohol polymers such as polyvinyl acetate and polyvinyl alcohol. Examples thereof include halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride. Preferred are fluorine-based resins such as polyvinyl fluoride and polyvinylidene fluoride. 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. Electrolyte used for lithium batteries as described below,
Since the electrolyte has polarity, it is preferable that the polymer also has a certain degree of polarity. The molecular weight of these polymers is preferably in the range from 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 electrolyte is desirably changed according to the molecular weight, and is preferably 0.1% to 30%. If the concentration is 0.1% or less, it is difficult to form a gel,
The retention of the electrolyte is reduced, causing problems of flow and liquid leakage. If the concentration is 30% 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 are deteriorated.

A solid electrolyte composed of a polymer and a supporting electrolyte containing no electrolyte can be formed by using a paint having a composition obtained by removing the solvent from the above-mentioned electrolyte paint. In this case, a formulation using a monomer is preferable in that the viscosity is low. A porous film is preferable as the spacer in the book. In addition, since the spacer is formed in a bag shape, it is preferable that the spacer be easily heat-sealed.
A spacer having a melting point of 90 to 150 ° C is preferred. As the porous film, a film made of a polymer or a thin film made of a powder and a binder can be preferably used, and a porous film of polyethylene, polypropylene or the like is more preferable.

The size of the spacer is required to be wider than the electrode. It is preferable that the electrolyte layer be used in combination with the spacer as a support, for example. Laminate the spacer on the electrode on which the active material is bound by the binder on the current collector, apply the above-mentioned electrolyte paint, which is made non-fluidized by a predetermined process, on the spacer, and fill in the voids in the porous film. After the impregnation, the non-fluidizing treatment is performed to de-fluidize the electrolyte, thereby forming an electrolyte layer.

These positive electrode, negative electrode and spacer are formed in a flat plate shape. The cutting to the required size, the formation into a flat plate shape, and the lamination of the positive electrode, the negative electrode, and the spacer can be performed at any place in the process. Although it is essential that the spacer of the present invention is in a bag shape, electrodes may be put in a bag shape.In the present invention, after laminating a sheet spacer and an electrode, the spacer is thermally fused. It is preferable to wear it into a bag.

In the present invention, it is essential that a positive electrode and / or a negative electrode be contained in a bag-shaped sparger.
It is sufficient that only one of the positive electrode and the negative electrode is contained in the bag-shaped spacer. As a specific example of the laminating method, a positive electrode having a positive electrode material layer only on one surface of a current collector and a negative electrode having a negative electrode material layer only on one surface of the current collector are used, and a positive electrode / spacer / anode / negative electrode / spacer / positive electrode is used. And the two negative electrodes are laminated with the current collector side facing the other side (the current collector side is back-to-back and laminated: see FIGS. 1 and 2). One battery cell can be formed by forming the two spacers into a bag shape by heat fusion. When the shape of the battery is quadrangular, heat fusion is usually performed on all four sides.
Only the sides may be used. Further, it is not always necessary to perform the heat-sealing so as to completely seal, but the heat-sealing may be performed in a broken line shape. In some cases, the battery element is wrapped by an exterior material and de-machined and sealed, and in this case, it is preferable that the battery is heat-sealed so as not to be completely sealed so that the gas in the bag-shaped spacer can also be degassed. .

In actual production of a battery cell, for example, a monomer containing a non-aqueous electrolyte is mixed with a positive electrode having a positive electrode material layer only on one side of a current collector, a negative electrode having a negative electrode layer only on one side of a current collector, And a spacer is impregnated and then thermally polymerized to form a single cell, the two single cells are laminated with the negative electrode current collector facing the other, and the two spacers are heat-sealed to form a bag. Can be As the monomer, an acrylic monomer is particularly preferred.

A thin battery can be manufactured by stacking a plurality of the battery cells (laminated cells) obtained as described above as necessary and closely storing them in a case made of a film having a variable shape. As a case made of a film having shape deformability, for example, made of a polymer film,
Light and thin laminated films can be used. As the laminate film, a film made of a laminate material of a metal foil and a polymer film can be suitably used. When storing, it is preferable to perform vacuum sealing. Of course, for convenience such as mounting the battery on the device, after the battery is sealed in the case, a plurality of cases can be stored in a rigid outer case if necessary.

[0043]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and may be appropriately modified and practiced without departing from the gist thereof. it can. Parts in the composition indicate parts by weight. Example 1 First, the following paints were prepared.

[Positive Electrode Paint] Composition Lithium cobaltate 90 parts Acetylene black 5 parts Polyvinylidene fluoride 5 parts N-methyl-2-hydroxylithone 80 parts All of the above raw materials were kneaded with a kneader for 2 hours to obtain a paste for a positive electrode. .

[Negative electrode paint] Composition Graphite (particle size: 15 μm) 90 parts Polyvinylidene fluoride 10 parts N-methyl-2-hydroxylidine 100 parts All the above-mentioned raw materials were kneaded for 2 hours by a kneader to prepare a negative electrode paste.

[Electrolyte paint] Composition Tetraethylene glycol diacrylate 14 parts Polyethylene oxide triacrylate 7 parts Lithium perchlorate 21 parts Polymerization initiator 1 part Additive (spirodilactone) 14 parts Electrolyte solution (propylene carbonate) 120 parts Electrolyte (ethylene carbonate) 120 parts All of the above compositions were mixed, stirred and dissolved to obtain an electrolyte paint.

Next, a positive electrode paint is applied on a 20 μm-thick aluminum current collector base material, and a negative electrode paint is applied on a 10 μm-thick copper current collector base material by extrusion die coating, followed by drying. A porous membrane bound on the current collector was created. Then, using a roll press (calender), an electrode sheet was produced by compacting while changing the linear pressure within the range of 100 to 400 kgf / cm. The thickness of the positive electrode material layer of this positive electrode was 80 μm, and the thickness of the negative electrode was 95 μm.

Electrolyte paint is applied to the positive electrode and the negative electrode, and a polymer porous film (made of polyethylene) having a larger area than the electrode separately immersed in the electrolyte paint is used. Spacer) / negative electrode / negative electrode /
Lamination was performed in the order of polymer porous film (spacer) / positive electrode (two negative electrodes were laminated with the current collector side facing each other). Next, the two spacers were heat-sealed using a heat-sealing machine to make the spacers into a bag shape (FIGS. 2 and 3). This is 9
The electrolyte was made non-fluid by heating at 0 ° C. for 30 minutes to form a flat battery cell (single cell) having a positive electrode, a negative electrode, and a non-fluidized electrolyte component.

Eight battery cells obtained as described above are superposed, a tab for extracting current is connected to the battery cells, and a vacuum case is formed in a bag-like case in which a laminate film composed of an aluminum film and a polymer film is formed opposite to each other. A flat battery was obtained by sealing and storing. Comparative Example 1 A flat battery was produced in the same manner as in Example 1 except that the two spacers were not heat-sealed (the two spacers were not formed into a bag). [Characteristics Evaluation] The above battery was charged at a constant current condition of 4.1 V at a current density of C / 2, and then left indoors for 5 days. With the capacity immediately after charging as 100%, the remaining capacity after 5 days was determined. Table 1 shows the results.

[0050]

[Table 1] From the above results, it is understood that the present invention sufficiently exerts the effect of increasing the capacity by increasing the film thickness. Also, from its structure,
Effects such as short-circuit prevention, mechanical strength UP, and safety UP such as heating and overcharging are also gasified. In addition, the method for manufacturing a secondary battery of the present invention does not require strict lamination for preventing short circuit, does not require a step of inserting an electrode into a bag-shaped spacer, and is a highly productive manufacturing method. I understand.

[0051]

According to the present invention, it is possible to provide a secondary battery capable of sufficiently exhibiting the effect of increasing the capacity by increasing the film thickness, and to provide a method of manufacturing a secondary battery with higher productivity. be able to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a stack of components of a battery cell before a spacer is thermally fused.

FIG. 2 is a cross-sectional view of the battery cell of the present invention.

FIG. 3 is a perspective view of a battery cell of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 positive electrode material layer 2 positive electrode current collector 3 negative electrode material layer 4 negative electrode current collector 5 spacer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 4/04 H01M 4/04 A 4/58 4/58 (72) Inventor Hiroyuki Oshima Shio, Kurashiki City, Okayama Prefecture F-term (reference) Mitsubishi Chemical Corporation Mizushima Office 5H021 AA02 BB11 CC08 CC18 EE04 HH03 5H029 AJ03 AJ05 AJ14 AK02 AK03 AK05 AL06 AL07 AL12 AM03 AM05 AM07 DJ04 HJ04 5H050 AA08 CA07 CA08 CA08 CA08 DA02 DA03 DA04 FA02 FA03 FA04 GA02 GA22 HA04

Claims (10)

[Claims] 1. A positive electrode comprising a lithium compound as a positive electrode active material, a negative electrode comprising a compound capable of doping / dedoping lithium as a negative electrode active material, a spacer for insulating the positive electrode and the negative electrode, and a non-aqueous electrolyte. The thickness of the positive electrode material layer is 50 μm or more and / or the thickness of the negative electrode material layer of the negative electrode is 60 μm, the spacer is a bag-like shape, and each of the positive electrode and / or the negative electrode is a bag-like spacer. A rechargeable battery characterized by being inside. 2. The secondary battery according to claim 1, wherein a plurality of positive and negative electrodes contained in the bag-shaped spacer are stacked. 3. The positive electrode and the negative electrode each have a positive electrode material layer or a negative electrode material layer only on one surface of the current collector, and two positive electrodes are laminated with the current collector side facing each other. Are laminated with their current collectors facing each other, and the laminated two positive electrodes and / or the laminated two negative electrodes are contained in a bag-like spacer in a state of being laminated respectively. Or the secondary battery according to 2. 4. The secondary battery according to claim 1, wherein only the positive electrode or the negative electrode is contained in the bag-shaped spacer. 5. The secondary battery according to claim 1, wherein the non-aqueous electrolyte is a non-fluid electrolyte. 6. The secondary battery according to claim 1, wherein the lithium compound is a lithium cobalt composite oxide. 7. The secondary battery according to claim 1, wherein the compound capable of doping / dedoping lithium is a carbonaceous material. 8. A positive electrode, a negative electrode, a spacer, and a non-aqueous electrolyte, wherein the positive electrode has a positive electrode material layer only on one side of the current collector, and the negative electrode has a negative electrode material layer only on one side of the current collector. And a positive electrode / spacer / negative electrode / negative electrode / spacer / positive electrode are stacked in this order. The two negative electrodes are stacked with their current collectors facing each other, and the two spacers are heat-sealed to form a bag. A battery cell characterized in that the battery cell is in a shape. 9. An acrylic monomer containing a non-aqueous electrolyte,
A positive electrode having a positive electrode material layer only on one side of the current collector, a negative electrode having a negative electrode layer only on one side of the current collector, and a spacer are impregnated, and then thermally polymerized to form a single cell. Are laminated with the negative electrode current collector facing each other, and 2
A method for manufacturing a secondary battery, wherein a plurality of spacers are thermally fused to form a bag. 10. An acrylic monomer containing a non-aqueous electrolyte is impregnated into a positive electrode having a positive electrode material layer only on one side of a current collector, a negative electrode having a negative electrode agent layer only on one side of a current collector, and a spacer, Create a single cell by thermal polymerization,
The two single cells are laminated with the negative electrode current collector facing each other, the two spacers are heat-fused to form a bag, and a plurality of the laminated cells are laminated. Manufacturing method of secondary battery.