JP2003068364A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery which is advantageous in thickness and cost with no process to provide an exterior material required. SOLUTION: The secondary battery includes a positive electrode having a lithium compound as an active material for the positive electrode, a negative electrode having a compound which can dope or remove doped lithium, as an active material for the negative electrode, a spacer insulating the positive and negative electrodes and an nonaqueous electrolyte, wherein either the positive electrode or the negative electrode (hereinafter called an 'Electrode A') has an electrode material layer on both faces of a current collector, and the other electrode (hereinafter called an 'Electrode B') has the electrode material layer on the face of the current collector, the Electrode B is folded back with the electrode material layer inside on a symmetrical center line, and an outer peripheral portion of the current collector for the Electrode B is sealed with the Electrode A and the spacer placed therebetween.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lithium secondary battery.

[0002]

2. Description of the Related Art In recent years, various devices such as a VTR device with a built-in camera, an audio device, a portable computer, and a mobile phone have been reduced in size and weight, and a demand for higher performance of a battery as a power source of these devices has been increased. Is increasing. Above all, the development of lithium secondary batteries capable of realizing high voltage and high energy density has become active.

A lithium secondary battery comprises a positive electrode capable of occluding and releasing lithium ions, a negative electrode, and an electrolyte layer containing a non-aqueous electrolyte. Conventionally, a liquid made 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 risk of leakage or ignition such as heat generation or ignition due to an internal short circuit due to deposition of lithium dendrite. Therefore, in recent years, in order to improve safety, development of a non-aqueous electrolytic solution, for example, a polymer electrolyte which is contained in a gel polymer and made non-fluidized has been carried out.

Further, since the polymer electrolyte including the electrolyte containing the electrolytic solution in the gel polymer as described above has a high electrolytic solution holding performance, the metal can used in the conventional lithium secondary battery can be used. It can be used by enclosing it in a simple case. Since such a polymer is lighter in weight and more flexible in shape than a liquid system, it is possible to form a thin film such as a sheet, which is advantageous in that a lightweight and space-saving battery can be produced. There is.

However, these secondary batteries need to be moisture-proofed, for example, sealed in a metallic outer package or sealed with an outer package having resin layers on both sides of the gas barrier layer. By providing the exterior material, the thickness is increased accordingly, and the merit of the small space is reduced, and an extra step of providing the exterior material is required in the first place.

[0006]

SUMMARY OF THE INVENTION There has been a demand for a secondary battery which does not require a step of providing an exterior material and is advantageous in terms of thickness and cost.

[0007]

The inventors of the present invention have studied the cause to solve the above-mentioned problems, and as a result, a step of separately providing an outer packaging material by making the current collector itself have a function as an outer packaging material is described. They have found that they can be omitted, and have completed the present invention. That is, the gist of the present invention is the following (1)-
It exists in (8).

(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 formed by
Either positive electrode or negative electrode (hereinafter referred to as "electrode A")
Has a pole material layer on both sides of the current collector, and the other (hereinafter referred to as “pole B”) has a pole material layer on one side of the current collector, and pole B is a pole material layer with a symmetrical center line. The secondary battery is characterized in that the current collector of the pole B is bent and the outer peripheral portion of the current collector of the pole B is sealed with the pole A and the spacer interposed.

(2) The pole A has a tab or lead for electrically connecting to the outside of the pole B, and the tab or lead penetrates the sealing portion of the pole B and is exposed to the outside of the pole B. The secondary battery according to (1) above. (3) The secondary battery according to (1) or (2), wherein the electrode A is contained in a bag-shaped spacer.

(4) The secondary battery according to any one of (1) to (3) above, wherein the pole A is a positive electrode and the pole B is a negative electrode. (5) The non-aqueous electrolyte is a non-fluidic electrolyte (1) to
The secondary battery according to any one of (4). (6) The secondary battery according to any of (1) to (5) above, wherein the lithium compound is a lithium cobalt composite oxide.

(7) The secondary battery as described in any one of (1) to (6) above, wherein the compound capable of doping / dedoping lithium is a carbonaceous material. (8) A battery pack in which a plurality of the secondary batteries according to any one of (1) to (7) above are stacked.

[0012]

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, and examples thereof include oxides of transition metals such as Fe, Co, Ni and Mn, and lithium and transition metals. Inorganic compounds such as complex oxides and transition metal sulfides can be mentioned. Specifically, Mn
O, V ₂ O ₅ , V ₆ O ₁₃ , transition metal oxide powder such as TiO ₂ , composite oxide powder of lithium and transition metal such as lithium nickel oxide and lithium cobalt oxide, T
Examples include transition metal sulfide powders such as iS ₂ and FeS.
You may mix and use the multiple types of said lithium compound. A preferable lithium compound in the present invention is a composite oxide of lithium and a transition metal, and specific examples thereof include lithium nickelate, lithium cobaltate, and lithium manganate. Lithium cobalt oxide is more preferable. When the lithium compound is granular, the particle size is usually about 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 addition, in the present invention, the active material is a main material that is a basis of an electromotive reaction of the battery, and means a material capable of inserting and extracting 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 generally 1 to 1 in terms of excellent battery characteristics such as initial efficiency, rate characteristics, and cycle characteristics.
The thickness is 50 μm, preferably about 5 to 30 μm.

The method of 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 may be mentioned a method in which an electrolytic coating material containing an active material and a monomer is mixed and kneaded to form a paste, which is then applied onto a current collector and the monomer is crosslinked. In the present invention, the active material and the binder are dispersed into a coating material using a solvent capable of dissolving the binder, and the coating material is applied to 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 doing so. A commonly used disperser can be used for forming a dispersion coating, and a ball mill, a sand mill, a biaxial 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, coating on one side of the current collector is preferable. The coating device for coating the current collector is not particularly limited, and slide coating, extrusion type die coating, reverse roll, gravure, knife coater, kiss coater, micro gravure, knife coater, rod coater, blade coater, etc. However, the extrusion method is the most preferable in consideration of the viscosity of the coating material and the coating film thickness.

In the present invention, a binder may be used to bind the active material on the current collector. As the binder, it is necessary to be stable with respect to the electrolytic solution, and various materials are used from the viewpoint 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 polyvinyl pyridine and poly-N-vinyl pyrrolidone; 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, polyvinylidene chloride, etc. Halogen-containing polymer; conductive polymers such as polyaniline can be used. Also, a mixture of the above polymers, a modified product, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer and the like can be used. The weight molecular weight of these resins is usually 10
000-3,000,000, preferably 100000-1
It is about 000000. If it is too low, the strength of the coating film tends to decrease. On the other hand, if it is too high, the viscosity becomes high and it may be difficult to form the electrode. Preferred binder resins include fluororesins and CN group-containing polymers, more preferably polyvinylidene fluoride.

The amount of the binder used is usually 0.1 part by weight or more, preferably 1 part by weight or more, and usually 30 parts by weight or less, preferably 20 parts by weight or less, based on 100 parts by weight of the active material. 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 ionic conductivity tends to decrease. In order to improve the conductivity and mechanical strength of the electrode, the electrode may contain additives such as a conductive material and a reinforcing material that exhibit various functions, powder, and a filler. The conductive material is not particularly limited as long as it can impart conductivity by mixing an appropriate amount with the active material, but is usually acetylene black, carbon black, carbon powder such as graphite, and fibers of various metals, Examples include foil. The DBP oil absorption of the carbon powder conductive material is preferably 120 cc / 100 g or more,
Particularly, 150 cc / 100 g or more is preferable because it holds the electrolytic solution. As additives, 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 improve the stability and life of the battery. As a reinforcing material, various inorganic and organic spheres,
Fibrous filler and the like can be used.

As the solvent used for coating, various organic and inorganic solvents can be used depending on the active material and binder to be used, and examples thereof include N-methylpyrrolidone and dimethylformamide, preferably N-. It is methylpyrrolidone. 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, and 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, the coating may be difficult, and if it is too high, it may be difficult to increase the coating film thickness and the stability of the coating may be deteriorated.

It is preferable that the positive electrode active material and the negative electrode active material have a large film thickness in terms of capacity and a thin film in terms of rate. The film thickness is usually 20 μm or more, preferably 30 μm or more, more preferably 50 μm or more, and most preferably 80 μm or more. The thickness of the positive electrode and the negative electrode is usually 200 μm or less, preferably 150 μm or less. The positive electrode material layer and the negative electrode material layer in the above mean layers containing an active material, respectively.

As the current collector in the present invention, various ones that do not electrochemically cause a problem such as elution and can function as a current collector of a battery can be used, and a metal or an alloy is usually used. For example, aluminum is generally used as the collector of the positive electrode. Further, a copper foil is often used as the current collector of the negative electrode. Roughening the surface of these current collectors in advance is a preferable method because the binding effect with the electrode material layer can be improved. As the surface roughening method, a method such as blasting or rolling with a rough surface roll, a polishing cloth paper to which abrasive particles are fixed, a grindstone, an emery buff, a wire brush equipped with a steel wire, or the like is a current collector. A mechanical polishing method for polishing the surface, an electrolytic polishing method, a chemical polishing method and the like can be mentioned.

The thickness of the conductive electrode substrate is usually 1 μm or more, preferably 5 μm or more, more preferably 1 μm or more, and usually 100 μm or less, preferably 50 μm or less, more preferably 30 μm or less. If it is too thick, the capacity of the whole battery will be too low, and if it is too thin, handling may be difficult. An undercoat primer layer can be formed on the current collector. The function of the primer layer is to improve the adhesion of the positive electrode or the negative electrode to the current collector. Compared to the case where the primer layer is not provided, the internal resistance of the battery is reduced by the improved adhesion, and the base material in the charge / discharge cycle test process is improved. It prevents a rapid decrease in capacity due to the detachment of the coating film from the. The undercoat primer layer can be formed by, for example, applying an undercoat primer material coating material containing a conductive material, a binder, and a solvent on a current collector, and then drying the applied material.

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. Preferably, the electrode active material is used. It is a substance such as carbon black or graphite that can also function as a substance. As the binder and solvent used for the undercoat primer layer, the same binder and solvent as those used for the coating material for the electrode material can be used. Also,
Since conductive resins such as polyaniline, polypyrrole, polyacene, disulfide compounds, and polysulfide compounds can have both functions of the conductive material and the binder, it can be used as both the conductive material and the binder. It can be used for the undercoat primer layer. Of course, the binder and solvent used for the undercoat primer layer may be the same as or different from those used for the paint 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 it is too low, peeling or the like tends to occur during the process of using the battery. If it is too high, the conductivity may decrease and the battery characteristics may deteriorate.

The thickness of the undercoat primer layer is generally about 0.05 to 200 μm. Within this range, it is usually 0.05 μm or more, preferably 0.1 μm or more, and usually 10 μm or less, preferably 1 μm or less. If it is too thin, it becomes difficult to ensure uniformity, and if it is too thick, the volumetric capacity of the battery may decrease too much.

The electrolyte layer in the present invention comprises a gel polymer electrolyte in which an electrolyte solution is contained in a polymer to make it non-fluidized, or a solid electrolyte composed of a supporting electrolyte and a polymer containing no electrolyte solution. A gel polymer electrolyte is preferred. As the gel polymer electrolyte, a method of using an electrolyte paint in which a polymer is dissolved in an electrolytic solution from the beginning, a method of preparing a monomer-containing electrolyte paint and then performing a crosslinking reaction to obtain a non-fluidized electrolyte, etc. Materials and manufacturing methods can be adopted.

The electrolytic solution to be contained is preferably a non-aqueous electrolytic solution, which is generally a non-aqueous solvent in which a supporting electrolyte which is a lithium salt is dissolved. The electrolytic solution is 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 lithium ions can move to cause an electrochemical reaction with the positive electrode active material or the negative electrode active material. One can be used.

As the lithium salt as the 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 preferable. The content of these supporting electrolytes in the electrolytic solution is generally 0.5 to 2.5 mol / L.
Is.

The type of solvent used in the electrolytic solution is not particularly limited, but a solvent having a relatively high dielectric constant is preferably used. Specifically, ethylene carbonate, propylene car
Cyclic carbonates such as carbon dioxide, dimethyl carbonate
, Diethyl carbonate, non-cyclic carbonates such as ethylmethyl carbonate, tetrahydrofuran, 2-
Examples include glymes such as methyltetrahydrofuran and dimethoxyethane, lactones such as γ-butyl lactone, sulfur compounds such as sulfolane, and nitriles such as acetonitrile, and one or a mixture of two or more thereof. Among these, especially cyclic carbonates such as ethylene carbonate and propylene carbonate, non-cyclic carbonates such as dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate. -One or two selected from bones
A mixed solution of one or more kinds is suitable, and a mixed solution of one or more kinds selected from propylene carbonate, ethylene carbonate, dimethyl carbonate and diethyl carbonate is particularly preferable.

In the method of preparing a monomer-containing electrolyte coating and then subjecting it to a cross-linking reaction to obtain a non-fluidized electrolyte, a monomer that forms a polymer by adding a polymerization treatment such as ultraviolet curing or heat curing is added to an electrolytic solution. To 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-vinylpyrrolidone, 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, etc. can be used, and further trimethylolpropane alkoxylate triacrylate, pentaerythritol alkoxylate triacrylate, etc. A trifunctional or higher functional monomer such as a trifunctional monomer, pentaerythritol alkoxylate tetraacrylate, or ditrimethylolpropane alkoxylate tetraacrylate can also be used. Of these, preferred ones in terms of reactivity, polarity, safety, etc. may be used alone or in combination. Of these, polyethylene glycol diacrylate, trimethylolpropane alkoxylate triacrylate, and pentaerythritol alkoxylate tetraacrylate are preferably used alone or in combination.

These electrolytes can be made non-fluid by polymerizing these monomers by heat, ultraviolet rays, electron beams or the like. In this case, in order to allow the reaction to proceed effectively, a polymerization initiator may be added to the electrolytic solution. As the polymerization initiator, benzoin, benzyl, acetophenone,
Benzophenone, Michler's ketone, biacetyl, benzoylperoxide, etc. can be used, and further t-butylperoxyneodecanoate, α-cumylperoxyneodecanoate, t-hexylperoxyneodecanoate, 1-cyclohexyl -1-Methylethyl peroxyneodecanoate, peroxyneodecanoate such as t-amylperoxyneodecanoate, t-butylperoxyneoheptanoate, α-cumylperoxyneoheptanoate , T-hexyl peroxy neoheptanoate, 1-cyclohexyl-1-methylethyl peroxy neo heptanoate, t-amyl peroxy heptanoate and the like, and the like can also be used. Preferably t-butyl peroxy neodecanoate, α-cumyl peroxy neodecanoate, t-
Hexyl peroxy neodecanoate.

Further, a monomer which produces a polymer produced by polycondensation of polyester, polyamide, polycarbonate, polyimide, etc., or a polymer produced by polyaddition of polyurethane, polyurea etc. may be used as the polymerizable monomer. it can. Although the content of the monomer is not particularly limited, it is preferably contained in the electrolytic coating in an amount of 1% or more. When the content is low, the efficiency of polymer formation decreases, and it becomes difficult to make the electrolyte non-fluidizable.

In the method of using an electrolyte paint containing a polymer from the beginning, a polymer which dissolves in an electrolytic solution at a high temperature and forms a gel electrolyte at a normal temperature can be preferably used.
Any polymer can be used as long as it is a polymer having such characteristics and is stable as a battery material.
Polymers having a ring such as polyvinyl pyridine and poly-N-vinyl pyrrolidone. Polymethylmethacrylate,
Acrylic derivative polymers such as poly (ethyl methacrylate), poly (butyl methacrylate), poly (methyl acrylate), poly (ethyl acrylate), poly (acrylic acid), poly (methacrylic acid) polyacrylamide. Fluorine-based resins such as polyvinyl fluoride and polyvinylidene fluoride. CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide.
Polyvinyl alcohol-based polymers such as polyvinyl acetate and polyvinyl alcohol. Examples thereof include halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride. Preferred are fluororesins such as polyvinyl fluoride and polyvinylidene fluoride. Further, a mixture of the above-mentioned polymers and the like, modified compounds, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers and the like can also be used. An electrolyte used in lithium batteries, as described below,
Since the electrolyte has a polarity, it is preferable that the electrolyte has a degree of polarity including a polymer. The molecular weight of these polymers is preferably in the range of 10,000 to 5,000,000. When the molecular weight is low, it becomes difficult to form a gel. If the molecular weight is high, the viscosity becomes too high, which makes the handling difficult.
The concentration of the polymer in the electrolytic solution is desirably changed according to the molecular weight, and is preferably 0.1% to 30%. When the concentration is 0.1% or less, it becomes difficult to form a gel,
Retention of the electrolytic solution is lowered, causing problems of flow and liquid leakage. When the concentration is 30% or more, the viscosity becomes too high, which causes difficulty in the process, and the ratio of the electrolytic solution decreases, the ionic conductivity decreases, and the battery characteristics such as rate characteristics deteriorate.

A solid electrolyte comprising a supporting electrolyte containing no electrolyte and a polymer 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 because of its low viscosity. The spacer in the present invention is preferably a porous film. The spacer is preferably bag-shaped from the viewpoint of preventing a short circuit due to displacement. From the viewpoint of forming a bag shape, a material that is easily heat-sealed is preferable, and a spacer having a melting point of 90 to 150 ° C. is preferable. 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 made of polyethylene, polypropylene or the like is more preferable.

It is essential that the size of the spacer is wider than that of the electrode. The electrolyte layer is preferably used in combination with the above spacer as a support. The spacer is laminated on the electrode on which the active material is bound by the binder on the current collector, and the above-mentioned electrolyte paint which is non-fluidized by a predetermined treatment is applied on the spacer to form a void in the porous film. After impregnation, a non-fluidizing treatment is performed to non-fluidize the electrolyte to form an electrolyte layer.

The positive electrode, the negative electrode, and the spacer are formed in a flat plate shape. Cutting into a required size, forming into a flat plate, and stacking of the positive electrode, the negative electrode, and the spacer can be performed at any place in the process. In the present invention, either one of the positive electrode or the negative electrode (electrode A) has an electrode material layer on both sides of the current collector,
The other (pole B) has a pole material layer on one side of the current collector, and the pole B is bent with the pole material layer on the inside at a symmetrical center line, and the pole A has spacers on both sides. It is essential that it is interposed between the pole material layers of the pole B.

Either one of the positive electrode or the negative electrode (electrode A) of the present invention has an electrode material layer on both sides of the current collector, but it may be coated on both sides of the current collector, or may be applied to the current collector. Even if it is laminated with the current collectors back to back applied on one side, the one side coated on the current collector is bent with the center line symmetrical to the inside with the current collector inside. May be. It should be noted that the bending with the current collector on the inner side at the center line which is symmetrical is as shown in FIG. In addition,
When the current collector has a tab, it may be bent with the current collector inside with respect to the center line which is symmetrical with the exception of the tab portion.

The other (pole B) has a pole material layer on one surface of the current collector with respect to the pole A, and the pole B is bent with the pole material layer on the inside at a symmetrical center line. If pole A is the positive pole, pole B is the negative pole, and if pole A is the negative pole, pole B
Is the positive electrode. Since it is generally preferable that the negative electrode has a larger area than the positive electrode in view of the diffusion of lithium, it is preferable that the pole A is the positive electrode and the pole B is the negative electrode. In addition, to bend with the pole material layer inside with a center line that is symmetric,
This is as shown in FIG. When the current collector has a tab, it may be bent with the pole material layer on the inner side at the center line which is symmetrical with the exception of the tab portion.

The pole A is interposed between the pole material layers of the pole B via spacers on both sides (FIG. 3). From the viewpoint of preventing the invasion of water, the pole B is sealed with the pole A and the spacer interposed. From the viewpoint of ease of manufacturing,
As shown in FIG. 4, it is preferable to seal the outer periphery of the current collector of the pole B. As a sealing method, ultrasonic fusion,
For example, seam fusion may be used, and the sealing material may be placed between the outer peripheral portions and heat-sealed. It is necessary that the pole A and the pole B are insulated from each other by the spacer, and the pole A is usually interposed on the both sides of the pole B by the spacer. In order to enhance the insulation between the pole A and the pole B, it is preferable that the spacer has a bag shape, and the pole A is preferably contained in the bag-shaped spacer.

Since the spacer and the pole A seal the outer periphery of the current collector of the pole B, the spacer B and the pole A are bent when the pole material layer is bent inside with the pole B being a symmetrical center line. It must be large enough to fit in. Further, in that case, the pole A needs to be provided with a tab or lead for electrically connecting to the outside of the pole B (FIG. 5), and the tab or lead penetrates the sealing portion of the pole B to the outside of the pole B. It is out (Fig. 6). At this time, the tab or the lead and the pole B need to be insulated, and the tab or the lead and the pole B need to have an insulator. The insulator is embodied in the form of a film, coating or the like. As the insulating material, a material having a sufficiently low electric conductivity, synthetic resin, paper, etc. is used, and as a filler, one to which glass fiber, mica, silica, titanium oxide, calcium carbonate, aluminum hydroxide, diatomaceous earth, etc. are added. Can be used. The synthetic resin is generally a thermoplastic resin or a thermosetting resin. The thermoplastic resin includes polyolefin resins such as polyethylene and polypropylene, ionomers, ethylene-vinyl acetate copolymers, polyamide resins, polyester resins and vinyl chloride resins, including modified products. The thermosetting resin includes acrylic resin, epoxy resin, polyurethane resin and the like. A film made of a synthetic resin is preferable, and a film of a polyolefin resin acid-modified product having a polar group is more preferable.

The secondary battery of the present invention also has an advantage that the electricity outlet of the pole B can be freely selected because the current collector of the pole B is its exterior part. Moreover, since all the poles B are electrically connected only by stacking the secondary batteries of the present invention, when stacking a plurality of the secondary batteries of the present invention to form an assembled battery, it is possible to compare with the conventional battery. , The process of connecting the pole B can be omitted, which is efficient.

When a plurality of secondary batteries of the present invention are connected to form a battery pack, as described above, the electrodes B can be easily electrically connected by stacking, and the secondary battery battery exterior part can be formed. A lead for connecting to the outside of the battery pack may be connected to any part of the above. For the pole A, the tab or lead of the pole A extending from the pole B may be arbitrarily connected.

[0042]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by the examples described below, and various modifications can be made without departing from the scope of the invention. it can. The parts in the composition are parts by weight. Example 1 First, the following paints were prepared.

[Positive electrode coating] Composition Lithium cobalt oxide 90 parts Acetylene black 5 parts Polyvinylidene fluoride 5 parts N-methyl-2-prolyldon 80 parts All of the above raw materials were kneaded with a kneading machine for 2 hours to prepare a positive electrode paste. .

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

[0045]   [Electrolyte paint] composition   Tetraethylene glycol diacrylate 14 parts   Polyethylene oxide triacrylate 7 parts   21 parts lithium perchlorate   Polymerization initiator 1 part   Additive (spirodilactone) 14 parts   Electrolyte (Propylene carbonate) 120 parts   Electrolyte (ethylene carbonate) 120 parts All of the above compositions were mixed and dissolved by stirring to obtain an electrolyte paint.

Next, the positive electrode coating material was applied onto a 20 μm thick aluminum current collector substrate, and the negative electrode coating material was applied onto a 10 μm thick copper current collector substrate by an extrusion type die coating and dried, and the active material was bound by a binder. A porous film bound on the current collector was prepared. Then, using a roll press (calendar), the electrode sheet as shown in FIG. 7 was produced by consolidating while changing the linear pressure in the range of 100 to 400 kgf / cm. The positive electrode material layer of this positive electrode had a thickness of 61 μm, and the negative electrode had a thickness of 52 μm.

After applying the electrolyte paint to the electrode material layer portions of the positive electrode and the negative electrode, as shown in FIG. 1, the positive electrode is bent with the current collectors inside at the symmetrical center lines, and as shown in FIG. Then, the negative electrode was bent with the pole material layer on the inner side at the center line which was symmetrical. Next, a polymer porous film (made of polyethylene) having a larger area than the electrode, which was separately immersed in the electrolyte paint, was used to interpose between the electrode material layers of the negative electrode via the separator on both sides of the positive electrode, as shown in FIG. . The electrolyte was made non-fluid by heating the negative electrode for 30 minutes at 90 ° C. with the electrode material layer inwardly bent at the center line which is symmetrical.

As shown in FIG. 6, an insulator on a film made of a polyolefin resin acid modified product (product name: MODIC AP-P513V manufactured by Mitsubishi Chemical) was placed between the tab and the negative electrode collector, and the tab The side outer peripheral portion was vacuum heat-sealed in the state where the above-mentioned insulator was arranged, and the other outer peripheral portion was sealed by seam fusion as shown in FIGS. 4 and 6. Test Example 1: Evaluation of battery characteristics Initial characteristics and negative electrode characteristics: The discharge capacity per hour of lithium cobalt oxide was 120 mAh / g, and the discharge rate was 1 from the ratio of this to the amount of the active material of the positive electrode of the lithium secondary battery for evaluation.
After obtaining the C and setting the rate, it is 4.2V at 0.5C
After being charged up to 3.2 V, the battery was charged up to 3.2 V at 1 C, and the initial capacities were obtained during charging and discharging. Also, the initial efficiency was obtained from these ratios. Then, after charging at 1C, 2
The battery was discharged at C, and the obtained discharge capacity was defined as a high rate capacity.
Further, the capacity retention rate was obtained from the ratio of the obtained high rate capacity and the discharge capacity at 1C in the previous period.

Initial charge capacity: 155 mAh / g Initial discharge capacity: 143mAh / g Initial efficiency: 92% High rate capacity: 110mAh / g Capacity maintenance rate: 77%

[0050]

According to the present invention, it is possible to provide a secondary battery which is advantageous in terms of thickness and cost without requiring a step of providing an exterior material.

[Brief description of drawings]

FIG. 1 is a diagram illustrating “bending with a current collector on an inner side at symmetrical centerlines” in the present invention.

FIG. 2 is a diagram illustrating “bending with the pole material layer on the inside at symmetrical centerlines” in the present invention.

FIG. 3 is a diagram illustrating that “electrode A is interposed between electrode material layers of electrode B via separators on both sides” in the present invention.

FIG. 4 is a diagram illustrating “sealing the outer peripheral portion of the current collector of the pole B” in the present invention.

FIG. 5 is a diagram illustrating “pole A or pole B provided with tabs or leads” in the present invention.

FIG. 6 is a sectional view of a secondary battery of the present invention.

FIG. 7 is a diagram of an electrode sheet according to the present invention.

[Explanation of symbols]

1 Current collector (A pole current collector) 2 pole material layer (A pole material layer) 3 Current collector (B pole current collector) 4 pole material layer (B pole material layer) 5 separator 6 tabs or leads 7 insulator

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 2/26 H01M 2/26 A 5H050 2/30 2/30 D 4/02 4/02 C D (72 ) Inventor Kiyoshi Hasegawa 4-6-1, Matsue, Kurashiki-shi, Okayama, Daiya Media Co., Ltd. (72) Inventor, Motonori Ueda, 3-10-10, Shiodotsu, Kurashiki, Okayama Mitsubishi Chemical Corporation F-term (reference) 5H011 AA09 BB04 CC06 DD06 EE04 FF02 FF04 GG09 5H021 AA06 BB04 CC00 CC18 EE04 5H022 AA09 BB02 BB03 CC03 5H029 AJ14 AK03 AL07 AL08 AM03 AM04 AM05 AM07 AM02 AM04 AM02 AM02 AM02 AM09 AM02 AM09 AM07 AM04 AM12 AM09 AM07 AM04 AM12 AM09 AM07 AM12 AA19 BA16 BA17 CA07 CA08 CA09 CB07 CB08 CB12 DA04 DA13 DA20 FA06 GA03 GA07 GA22

Claims (8)

[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. In the secondary battery formed as described above, either one of the positive electrode and the negative electrode (hereinafter referred to as “pole A”) has a pole material layer on both surfaces of the current collector, and the other (hereinafter referred to as “pole B”) is the current collector. It has a pole material layer on one side, and the pole B is bent with the pole material layer inside with a symmetrical center line.
A secondary battery, wherein the outer periphery of the current collector of the pole B is sealed with the pole A and a spacer interposed. 2. The pole A has tabs or leads for electrically connecting to the outside of the pole B, the tabs or leads being the poles B.
The secondary battery according to claim 1, wherein the secondary battery penetrates the sealed portion of the above and is exposed outside the electrode B. 3. The secondary battery according to claim 1, wherein the electrode A is contained in a bag-shaped spacer. 4. The secondary battery according to claim 1, wherein the pole A is a positive electrode and the pole B is a negative electrode. 5. The secondary battery according to claim 1, wherein the non-aqueous electrolyte is a non-fluidic 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 battery pack in which a plurality of secondary batteries according to claim 1 are stacked.