JP4297472B2 - Secondary battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lithium secondary battery.
[0002]
[Prior art]
In recent years, various devices such as a camera-integrated VTR device, an audio device, a portable computer, a mobile phone, and the like have been reduced in size and weight, and a demand for higher performance of a battery as a power source of these devices is increasing. In particular, lithium secondary batteries capable of realizing high voltage and high energy density are actively developed.
[0003]
A lithium secondary battery includes a positive electrode and a negative electrode capable of occluding and releasing lithium ions, and an electrolyte layer containing a non-aqueous electrolyte. Conventionally, a liquid made of a non-aqueous organic material has been used as the non-aqueous electrolyte. However, a lithium secondary battery using such a non-aqueous electrolyte has a risk of leakage and ignition such as heat generation and ignition due to an internal short circuit due to deposition of lithium dendrite. Therefore, in recent years, in order to improve safety, a polymer electrolyte that has been contained in a non-aqueous electrolyte, for example, a gel polymer, and has been made non-fluid has been developed.
[0004]
Furthermore, since the polymer electrolyte including the electrolyte containing the electrolyte solution in the gel polymer as described above has a high retention performance of the electrolyte solution, it is changed to a metal can used in a conventional lithium secondary battery, It can be used in a simple case. Since such a polymer is lighter and more flexible than a liquid system, it can be made into a thin film like a sheet, for example, and it is possible to produce a lightweight and space-saving battery. There is.
[0005]
However, these secondary batteries have been required to be moisture-proof, for example, sealed with a metal exterior material or sealed with an exterior material provided with resin layers on both sides of the gas barrier layer. By providing the exterior material, the thickness is increased accordingly, and the merit of a small space is reduced. In the first place, an extra process for providing the exterior material is necessary.
[0006]
[Problems to be solved by the invention]
There has been a demand for a secondary battery that does not require a step of providing an exterior material and is advantageous in terms of thickness and cost.
[0007]
[Means for Solving the Problems]
  Therefore, as a result of examining the cause to solve the above problems, the present inventors have found that the step of separately providing an exterior material can be omitted by providing the current collector with a function as the exterior material, and the present invention has been completed. It came to do. That is, the gist of the present invention is the following (1) to(9)Exist.
[0008]
(1) Insulating a positive electrode using a lithium compound as a positive electrode active material, a negative electrode using a compound capable of doping and dedoping lithium as a negative electrode active material, and the positive electrode and the negative electrodeWider than the positive and negative electrodesIn a secondary battery comprising a spacer and a non-aqueous electrolyte,The non-aqueous electrolyte is a non-fluid electrolyte,Either the positive electrode or the negative electrode (hereinafter referred to as “Pole A”) has an electrode material layer on both sides of the current collector.Here, “having an electrode material layer on both sides” means that the electrode material on one side of the current collector is laminated with the current collectors back to back, or the current collector One of the poles on one side is folded with the current collector inside, eitherThe other (hereinafter referred to as “Pole B”) has a pole material layer on one side of the current collector, and the pole B is bent with a symmetrical center line with the pole material layer on the inside. And the pole A has a size that can be accommodated while 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 therebetween. battery.
[0009]
(2)A non-fluid electrolyte is formed by a method in which a monomer-containing electrolyte coating is prepared and then applied onto the positive electrode, negative electrode, spacer, and then subjected to a crosslinking reaction.The secondary battery as described in (1) above.
(3)The secondary battery according to (1) or (2) above, wherein the spacer is a polymer porous film.
[0010]
(4) Pole A, Having a tab or lead for electrical connection to the outside of the pole B, the tab or lead passing through the sealing portion of the pole B and coming out of the pole BThe secondary battery according to any one of (1) to (3).
(5)The pole A is in the bag-shaped spacerThe secondary battery according to any one of (1) to (4) above.
(6)The pole A is the positive electrode and the pole B is the negative electrodeThe secondary battery according to any one of (1) to (5) above.
[0011]
(7) LithiumThe compound is a lithium cobalt composite oxideThe secondary battery according to any one of (1) to (6).
(8)The secondary battery according to claim 1, wherein the compound capable of doping and dedoping lithium is a carbonaceous material.
(9) A battery pack in which a plurality of the secondary batteries according to any one of (1) to (8) are stacked.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
As the lithium compound in the present invention, a compound capable of occluding and releasing lithium ions is used. For example, oxides of transition metals such as Fe, Co, Ni, Mn, composite oxides of lithium and transition metals, transition metal sulfides Inorganic compounds such as products. Specifically, MnO, V₂O_Five, V₆O₁₃TiO₂ Transition metal oxide powder such as lithium nickel oxide, lithium oxide such as lithium cobalt oxide, and complex oxide powder of lithium and transition metal such as lithium cobalt oxide, TiS₂And transition metal sulfide powders such as FeS. You may mix and use multiple types of said lithium compound. 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, it is lithium cobaltate. When the lithium compound is granular, the particle size is usually about 1 to 30 μm, preferably about 1 to 10 μm, from the viewpoint of excellent battery characteristics such as rate characteristics and cycle characteristics.
[0013]
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 the electromotive reaction of the battery, and means a material that can occlude and release Li ions.
Examples of the compound capable of doping and dedoping lithium in the present invention include graphite and coke in addition to the Li metal foil, preferably graphite. The particle size of the granular negative electrode active material is usually about 1 to 50 μm, preferably about 5 to 30 μm, from the viewpoint of excellent battery characteristics such as initial efficiency, rate characteristics, and cycle characteristics.
[0014]
The formation method in particular of the positive electrode and negative electrode of the secondary battery of this invention is not restrict | limited, Arbitrary methods can be used. For example, there is a method in which an electrolyte coating containing an active material and a monomer is mixed and kneaded to obtain a paste, which is then applied onto a current collector and crosslinked by crosslinking the monomer. In the present invention, the active material and the binder are dispersed into a paint using a solvent capable of dissolving the binder, and the paint is applied onto the current collector and dried to bind the active material onto the current collector with the binder. It is preferable to form an electrode by doing so. For dispersion coating, a commonly used disperser can be used, and a ball mill, a sand mill, a twin-screw kneader, or the like can be used.
[0015]
In addition, regarding application | coating, although the both sides of a collector may be sufficient as one side, what was apply | coated to the single side | surface of a collector is preferable in this invention.
There are no particular restrictions on the coating device for applying the paint on the current collector, 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 most preferable in consideration of the viscosity of the paint and the coating film thickness.
[0016]
In the present invention, a binder can be used to bind the active material onto the current collector. As a binder, it is necessary to be stable with respect to electrolyte solution etc., and various materials are used from a 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 rings 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; Fluorine resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; Polyvinyl alcohol polymers such as polyvinyl alcohol; polyvinyl chloride, halogen-containing polymers such as polyvinylidene chloride; and conductive polymers such as polyaniline can be used. Further, a mixture such as the above-mentioned polymer, 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 about 10,000 to 3000000, preferably about 100,000 to 1000000. 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 increases and it may be difficult to form an electrode. Preferable binder resins include fluorine resins and CN group-containing polymers, and more preferably polyvinylidene fluoride.
[0017]
The amount of the binder used relative to 100 parts by weight of the active material is usually 0.1 parts 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. 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 electroconductivity and mechanical strength of an electrode, you may contain the additive, powder, filler, etc. which express various functions, such as an electroconductive material and a reinforcing material. The conductive material is not particularly limited as long as it can provide conductivity by mixing an appropriate amount of the above active material. Usually, carbon powder such as acetylene black, carbon black, graphite, various metal fibers, Examples include foil. The DBP oil absorption amount of the carbon powder conductive material is preferably 120 cc / 100 g or more, and particularly preferably 150 cc / 100 g or more because the electrolyte solution is retained. Additives include trifluoropropylene carbonate, 1,6-dioxaspiro [4,4] nonane-2,7-dione, 12-crown-4-ether, vinylene carbonate, catechol carbonate, etc. Can be used to enhance. As the reinforcing material, various inorganic, organic spherical and fibrous fillers can be used.
[0018]
As the solvent used for coating, various organic and inorganic materials can be used according to the active material and binder to be used. For example, N-methylpyrrolidone and dimethylformamide can be used, and preferably N-methylpyrrolidone. is there. The solvent concentration in the paint is at least 10% by weight, but is usually 20% by weight or more, preferably more than 30% by weight, more preferably 35% by weight or more. Moreover, as a minimum, it is 90 weight% or less normally, Preferably it is 80 weight% or less. If the solvent concentration is too low, coating may be difficult. If the solvent concentration is too high, it may be difficult to increase the coating film thickness and the stability of the coating may be deteriorated.
[0019]
The positive electrode active material and the negative electrode active material are preferably thicker in terms of capacity but thinner 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 film thickness of the positive electrode and the negative electrode is usually 200 μm or less, preferably 150 μm or less.
In addition, the positive electrode material layer and the negative electrode material layer in the above mean layers each containing an active material.
[0020]
As the current collector in the present invention, various materials that can function as a current collector of a battery without causing problems such as electrochemical dissolution can be used, and usually a metal or an alloy is used. For example, aluminum is generally used as the positive electrode current collector. In addition, a copper foil is often used as the negative electrode current collector.
Roughening the surfaces of these current collectors in advance is a preferable method because the binding effect with the electrode material layer can be improved. Current roughening methods include a method of rolling with a blasting process or a rough roll, a polishing cloth with a fixed abrasive particle, a grinding wheel, emery buff, a wire brush with a steel wire, etc. Examples thereof include a mechanical polishing method for polishing the surface, an electrolytic polishing method, and a chemical polishing method.
[0021]
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 entire battery will be too low. Conversely, if it is too thin, handling may be difficult.
An undercoat primer layer can also be formed on the current collector. The function of the primer layer is to improve the adhesion of the positive electrode or negative electrode to the current collector. Compared to the case where no primer layer is provided, the battery internal resistance is reduced by the improved adhesion, and the base material in the charge / discharge cycle test process This prevents a rapid decrease in capacity due to coating film detachment from. 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 it.
[0022]
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. Carbon black, graphite and other substances that can function.
As the binder and solvent used for the undercoat primer layer, the same binders and solvents used for the coating material of the electrode material can be used. In addition, conductive resins such as polyaniline, polypyrrole, polyacene, disulfide compounds, polysulfide compounds and the like can have both functions of the conductive material and the binder. It can also 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 coating material of the electrode material.
[0023]
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. is there. If it is too low, peeling during the process tends to occur when using the battery. If it is too high, the conductivity may decrease and the battery characteristics may deteriorate.
[0024]
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 will be difficult to ensure uniformity, and if it is too thick, the volume capacity of the battery may be too low.
[0025]
The electrolyte layer in the present invention is composed of a gel polymer electrolyte containing an electrolyte solution in a polymer and non-fluidized, or a solid electrolyte composed of a supporting electrolyte and a polymer not containing an electrolyte solution. A gel polymer electrolyte is preferable.
As gel polymer electrolyte, as required, a method using an electrolyte coating in which a polymer is first dissolved in an electrolytic solution, a method of preparing a non-fluidized electrolyte by cross-linking reaction after preparing a monomer-containing electrolyte coating, etc. Materials and manufacturing methods can be adopted.
[0026]
The electrolyte solution to be contained is preferably a non-aqueous electrolyte solution, which is generally a solution obtained by dissolving a supporting electrolyte that is a lithium salt in a non-aqueous solvent. The electrolyte is a non-aqueous material that is stable as an electrolyte with respect to the positive electrode active material and the negative electrode active material and that can perform migration for lithium ions to electrochemically react with the positive electrode active material or the negative electrode active material. Some can be used.
[0027]
As a lithium salt as a supporting electrolyte, LiPF₆, LiAsF₆, LiSbF₆, LiBF_FourLiClO_Four, LiI, LiBr, LiCl, LiAlCl, LiHF₂, LiSCN, LiSO_ThreeCF₂ Etc. Of these, LiPF in particular₆And LiClO_FourIs preferred. The content of these supporting electrolytes in the electrolytic solution is generally 0.5 to 2.5 mol / L.
[0028]
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, cyclic carbonates such as ethylene carbonate and propylene carbonate, acyclic carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. -Glymes such as Toto, tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxyethane, lactones such as γ-butyllactone, sulfur compounds such as sulfolane, nitriles such as acetonitrile, etc. Can do. Of these, cyclic carbonates such as ethylene carbonate and propylene carbonate, acyclic carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferred. -1 type, or 2 or more types of mixed solutions chosen from bonates are suitable, Especially preferably, they are 1 type, or 2 or more types of mixed solutions chosen from propylene carbonate, ethylene carbonate, dimethyl carbonate, and diethyl carbonate. is there.
[0029]
In the method of preparing a non-fluidized electrolyte by preparing a monomer-containing electrolyte coating and then cross-linking it, a monomer that forms a polymer by applying a polymerization treatment such as ultraviolet curing or heat curing is added to the electrolyte.
Examples of the polymerizable monomer include those having an unsaturated double bond such as acryloyl group, methacryloyl group, vinyl group, and 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 dimethyl ester Chlorate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polyalkylene glycol diacrylate, polyalkylene glycol dimethacrylate, etc. can be used, and trimethylolpropane alkoxylate triacrylate, pentaerythritol alkoxylate triacrylate A tetrafunctional or higher functional monomer such as pentaerythritol alkoxylate tetraacrylate, ditrimethylolpropane alkoxylate tetraacrylate, or the like can also be used. Of these, those preferable from the viewpoint 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.
[0030]
These monomers can be polymerized by heat, ultraviolet rays, electron beams or the like to make the electrolyte paint non-flowable. In this case, in order to make the reaction proceed effectively, a polymerization initiator can be added to the electrolytic solution. As the polymerization initiator, benzoin, benzyl, acetophenone, benzophenone, Michler's ketone, biacetyl, benzoyl peroxide and the like can be used, and t-butylperoxyneodecanoate, α-cumylperoxyneodecanoate, t Peroxyneodecanoates such as hexylperoxyneodecanoate, 1-cyclohexyl luo 1-methylethylperoxyneodecanoate, t-amylperoxyneodecanoate, t-butylperoxyneohepta Peroxy such as noate, α-cumylperoxyneoheptanoate, t-hexylperoxyneoheptanoate, 1-cyclohexyl lu 1-methylethylperoxyneoheptanoate, t-amylperoxyheptanoate Neoheptanoates can also be used. T-Butylperoxyneodecanoate, α-cumylperoxyneodecanoate, and t-hexylperoxyneodecanoate are preferable.
[0031]
Moreover, the monomer which produces | generates the polymer | macromolecule produced | generated by polyaddition, such as a polymer, such as a polyester, polyamide, a polycarbonate, a polyimide, polycondensation, a polyurethane, a polyurea, can also be used as a polymerizable monomer.
The content of the monomer is not particularly limited, but preferably 1% or more in the electrolyte coating. When the content is low, the formation efficiency of the polymer is lowered, and it is difficult to make the electrolyte non-fluid.
[0032]
In the method using an electrolyte coating containing a polymer from the beginning, a polymer that 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. For example, a polymer having a ring such as polyvinyl pyridine and poly-N-vinyl pyrrolidone. Acrylic derivative polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid and polyacrylamide polyacrylamide. Fluorine 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. And halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride. Preferred are fluorine-based resins such as polyvinyl fluoride and polyvinylidene fluoride. Moreover, it can be used even if it is a mixture, such as said polymer, a modified body, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer, etc. As will be described later, since the electrolyte and electrolyte used in the lithium battery have polarity, it is preferable that the polymer has a certain degree of polarity. 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 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 solution 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, and the 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, resulting in difficulty in the process, and the ratio of the electrolytic solution is lowered, the ionic conductivity is lowered, and the battery characteristics such as the rate characteristics are lowered.
[0033]
A solid electrolyte composed of a supporting electrolyte and a polymer not containing an electrolytic solution can be formed by using a paint having a composition obtained by removing the solvent from the above-described electrolyte paint. In this case, the prescription using a monomer is preferable from the viewpoint of low viscosity.
As the spacer in the present invention, a porous film is preferable. In addition, from the viewpoint of preventing a short circuit due to misalignment, the spacer is preferably bag-shaped. From the viewpoint of forming a bag, those that are easily heat-sealed are preferred, and spacers having a melting point of 90 to 150 ° C. are 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 such as polyethylene or polypropylene is more preferable.
[0034]
It is essential that the size of the spacer is wider than that of the electrode.
The electrolyte layer preferably uses, for example, the 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-described electrolyte coating that is made non-fluidized by a predetermined treatment is applied on the spacer to form voids in the porous film. After impregnation, the electrolyte can be made non-fluidized by performing a non-fluidization treatment to form an electrolyte layer.
[0035]
  These positive, negative,Wider than positive and negative electrodesThe spacer is formed in a flat plate shape. Cutting to a required size, forming into a flat plate shape, and laminating a positive electrode, a negative electrode, and a spacer can be performed at any place in the process. In the present invention, either the positive electrode or the negative electrode (electrode A) has an electrode material layer on both sides of the current collector, and the other (electrode B) has an electrode material layer on one surface of the current collector. Is folded with the pole material layer inside on a symmetrical center line,At that time, the spacer and the pole A are sized so as to fit between the bent portions of the pole B, and the outer periphery of the current collector of the pole B is sealed with the pole A and the spacer interposed therebetween.It is essential that
[0036]
  Either the positive electrode or the negative electrode (electrode A) of the present invention has electrode material layers on both sides of the current collector,Here, “having an electrode material layer on both sides” means that the electrode material on one side of the current collector is laminated with the current collectors back to back, or one surface of the current collector It is either the one with the pole material in the bent with the current collector inside,
  In addition,A current collector coated on one side and bent with a symmetrical centerline with the current collector insideIs as shown in FIG. Note that when the current collector has a tab, the current collector may be bent with the center line being left-right symmetrical except for the tab portion.
[0037]
With respect to the pole A, the other (pole B) has a pole material layer on one side of the current collector, and the pole B is bent with a pole material layer on the inside at a symmetrical center line. When the pole A is a positive electrode, the pole B is a negative electrode, and when the pole A is a negative electrode, the pole B is a positive electrode. Since the negative electrode usually has a larger area than the positive electrode because of lithium diffusion, it is preferable that the pole A is the positive electrode and the pole B is the negative electrode. In addition, as shown in FIG. 2, it bend | folds with the pole material layer inside by the centerline used as left-right symmetry. When the current collector has a tab, it may be bent with the pole material layer on the inner side at a symmetrical center line except for the tab portion.
[0038]
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 moisture from entering, the pole B is sealed with the pole A and a spacer interposed therebetween. From the viewpoint of ease of manufacture, it is preferable to seal the outer peripheral portion of the current collector of the pole B as shown in FIG. Examples of the sealing method include ultrasonic fusion and seam fusion, and a sealing material may be put between the outer peripheral portions and thermally fused. In addition, the pole A and the pole B need to be insulated by the spacer, and the pole A is usually interposed in the pole B via the spacer on both sides. In order to improve the insulation between the pole A and the pole B, the spacer is preferably in a bag shape, and the pole A is preferably contained in the bag-like spacer.
[0039]
Since the outer periphery of the current collector of the pole B is sealed, the spacer and the pole A are folded between the pole B and the pole B when the pole B is folded at the center line which is symmetric. It must be large enough to fit.
In this case, the pole A needs to be provided with a tab or lead for electrical connection with the outside of the pole B (FIG. 5). The tab or lead penetrates the seal portion of the pole B and goes outside the pole B. It has come out (Fig. 6). At this time, the tab or lead and the pole B need to be insulated, and an insulator is required between the tab or lead and the pole B. The insulator is implemented in the form of a film, coating or the like. Insulating materials include materials with sufficiently low electrical conductivity, synthetic resins, paper, etc., and those with glass fiber, mica, silica, titanium oxide, calcium carbonate, aluminum hydroxide, diatomaceous earth, etc. added as fillers Can be used. The synthetic resin is generally a thermoplastic resin or a thermosetting resin. Examples of the thermoplastic resin include polyolefin resins such as polyethylene and polypropylene, ionomers, ethylene-vinyl acetate copolymers, polyamide resins, polyester resins, and vinyl chloride resins, including modified products. Thermosetting resins include acrylic resins, epoxy resins, polyurethane resins, and the like. A film made of a synthetic resin is preferable, and a polyolefin resin acid-modified film having a polar group is more preferable.
[0040]
The secondary battery of the present invention also has an advantage that the electrical outlet of the pole B can be freely selected because the current collector of the pole B serves as the exterior portion. In addition, since all the poles B are electrically connected only by stacking the secondary batteries of the present invention, when a plurality of secondary batteries of the present invention are stacked to form an assembled battery, compared to conventional batteries. This eliminates the labor (process) of connecting the pole B and is efficient.
[0041]
When a plurality of the secondary batteries of the present invention are connected to form a battery pack, as described above, the electrical connection of the pole B can be easily performed by stacking, and any secondary battery battery exterior part can be connected. What is necessary is just to connect the lead connected with the exterior of a battery pack to a location. For the pole A, the tab or lead of the pole A coming out from the pole B may be arbitrarily connected.
[0042]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited at all by the following Example, In the range which does not change the summary, it can change suitably and can implement. In addition, the part in a composition shows a weight part.
Example 1
First, the following paints were prepared.
[0043]
[Positive electrode paint]
composition
90 parts of lithium cobaltate
5 parts of acetylene black
Polyvinylidene fluoride 5 parts
80 parts of N-methyl-2-pyrrolidone
All the above raw materials were kneaded for 2 hours with a kneader to obtain a positive electrode paste.
[0044]
[Negative electrode paint]
composition
Graphite (particle size 15μm) 90 parts
Polyvinylidene fluoride 10 parts
N-methyl-2-pyrrolidone 100 parts
All the above raw materials were kneaded with a kneader for 2 hours to obtain a negative electrode paste.
[0045]
[Electrolyte paint]
composition
14 parts of tetraethylene glycol diacrylate
Polyethylene oxide triacrylate 7 parts
Lithium perchlorate 21 parts
Polymerization initiator 1 part
Additive (spirodilactone) 14 parts
Electrolyte (propylene carbonate) 120 parts
Electrolyte (ethylene carbonate) 120 parts
All the above compositions were mixed, dissolved and stirred to obtain an electrolyte paint.
[0046]
Next, the positive electrode paint is applied to a 20 μm thick aluminum current collector base material, and the negative electrode paint is applied to a 10 μm thick copper current collector base material by extrusion type die coating and dried. A porous membrane bound on top was created. Next, an electrode sheet as shown in FIG. 7 was produced by using a roll press (calendar) and compacting while changing the linear pressure in the range of 100 to 400 kgf / cm. The thickness of the positive electrode material layer of this positive electrode was 61 μm, and the thickness of the negative electrode was 52 μm.
[0047]
After applying the electrolyte coating to the positive electrode layer portion of the positive electrode and the negative electrode, as shown in FIG. 1, the positive electrode is bent with a symmetrical center line with the current collector inside, and as shown in FIG. Was folded with the pole material layer inside on a symmetrical center line. Next, a polymer porous film (made of polyethylene) having a larger area than the electrode, which was separately immersed in an electrolyte paint, was interposed between the positive electrode layers of the negative electrode via separators on both sides of the positive electrode as shown in FIG. . The electrolyte was made non-fluidized by heating it at 90 ° C. for 30 minutes in a state where the negative electrode was completely bent with the electrode material layer inside with a symmetrical center line.
[0048]
As shown in FIG. 6, an insulator on film using a polyolefin resin acid modified product (product name: Modic AP-P513V manufactured by Mitsubishi Chemical Corporation) as a raw material is arranged between the tab and the negative electrode current collector, and the outer peripheral portion on the tab side Was vacuum heat-sealed with the above insulator disposed, and the other outer periphery was sealed by seam sealing as shown in FIGS.
Test Example 1: Battery characteristics evaluation
Initial characteristics and negative electrode characteristics: The discharge capacity per hour of lithium cobaltate was set to 120 mAh / g, and the rate was determined by determining the discharge rate 1C from the ratio of this to the amount of active material of the positive electrode of the lithium secondary battery for evaluation. Above, after charging to 4.2V at 0.5C, it discharged to 3.2V at 1C, and the initial capacity was determined at the time of charging and at the time of discharging, respectively. Moreover, the initial efficiency was calculated | required from these ratios. Next, after charging at 1 C, discharging was performed at 2 C, and the obtained discharge capacity was set as a high rate capacity. Furthermore, the capacity retention rate was determined from the ratio between the obtained high rate capacity and the discharge capacity in the previous 1C.
[0049]
Initial charge capacity: 155 mAh / g
Initial discharge capacity: 143 mAh / g
Initial efficiency: 92%
High rate capacity: 110 mAh / g
Capacity maintenance rate: 77%
[0050]
【The invention's effect】
According to the present invention, a secondary battery that is advantageous in terms of thickness and cost can be provided without requiring a step of providing an exterior material.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating “folding a current collector inside with a symmetrical center line” according to the present invention;
FIG. 2 is a diagram illustrating “folding with the pole material layer inside on a symmetrical center line” according to the present invention.
FIG. 3 is a diagram illustrating that “the pole A is interposed between the pole material layers of the pole B via the separators on both sides” in the present invention.
FIG. 4 is a diagram illustrating “sealing the outer periphery of the current collector of the pole B” according to the present invention.
FIG. 5 is a diagram illustrating “Pole A or B with a tab or lead” according to the present invention.
FIG. 6 is a cross-sectional view of the 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 pole material layer)
3 Current collector (B pole current collector)
4 pole material layer (B pole pole material layer)
5 Separator
6 Tab or lead
7 Insulator

Claims (9)

  A positive electrode using a lithium compound as a positive electrode active material, a negative electrode using a compound capable of doping and dedoping lithium as a negative electrode active material, a spacer that insulates the positive electrode from the negative electrode, a spacer wider than the positive electrode and the negative electrode, and a nonaqueous electrolyte In the secondary battery provided, the non-aqueous electrolyte is a non-fluid electrolyte, and either the positive electrode or the negative electrode (hereinafter referred to as “electrode A”) has electrode material layers on both sides of the current collector. Here, “having an electrode material layer on both sides” means that the electrode material on one side of the current collector is laminated with the current collectors back to back, or the current collector One having a pole material on one side is folded with the current collector inside, and the other (hereinafter referred to as “pole B”) has a pole material layer on one side of the current collector. B is a symmetrical center line and is bent with the pole material layer inside, The spacer and the pole A have a size that can be accommodated while the pole B is bent, and the outer periphery of the current collector of the pole B is sealed with the pole A and the spacer interposed therebetween. A secondary battery which is a secondary battery. The secondary battery according to claim 1, wherein the non-fluid electrolyte is formed by a method in which a monomer-containing electrolyte coating is prepared and then applied onto the positive electrode, the negative electrode, and the spacer and then subjected to a crosslinking reaction.   The secondary battery according to claim 1, wherein the spacer is a polymer porous film.    The pole A has a tab or lead for electrical connection with the outside of the pole B, and the tab or lead passes through the sealing portion of the pole B and comes out of the pole B. A secondary battery according to any one of the above.    The secondary battery according to claim 1, wherein the pole A is contained in a bag-shaped spacer.    The secondary battery according to claim 1, wherein the pole A is a positive electrode and the pole B is a negative electrode.  The secondary battery according to claim 1, wherein the lithium compound is a lithium cobalt composite oxide.    The secondary battery according to claim 1, wherein the compound capable of doping and dedoping lithium is a carbonaceous material.    A battery pack in which a plurality of the secondary batteries according to claim 1 are stacked.

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