CN1237650C - Lithium-ion secondary battery and its manufacturing method - Google Patents

Abstract

The purpose of the present invention is to produce a lithium ion secondary battery which can maintain electrical connection between electrodes without using a strong outer container, has high energy density, can be made thin, and has excellent charge and discharge characteristics. The battery of the present invention has a multilayer electrode laminate (8) in which a positive electrode (3) having a positive electrode active material layer (7) and a positive electrode current collector (6), a negative electrode (5) having a negative electrode active material layer (9) and a negative electrode current collector (10), and a separator (4) having an electrolyte containing lithium ions disposed between the two electrodes are adhered to each other by bonding the positive electrode active material layer (7), the negative electrode active material layer (9), and the separator (4) to each other through a porous adhesive resin layer (11), and the electrolyte is held in a through-hole (12) formed in the adhesive resin layer (11) and communicating the positive electrode active material layer (7), the negative electrode active material layer (9), and the separator (4).

Description

Lithium-ion secondary battery and its manufacturing method

technical field

The present invention relates to a lithium-ion secondary battery in which a positive electrode and a negative electrode intermediary a separator for maintaining an electrolyte are opposed to each other. More specifically, the present invention relates to a lithium ion secondary battery in which the electrical connection between the positive electrode and the negative electrode (electrode) and the separator is improved, and has a thin shape, etc. Shaped battery structures and fabrication methods for forming the structures.

Background technique

There is a great need to reduce the size and weight of portable electronic devices, and to achieve this goal, the performance of batteries must be improved. For this reason, various batteries have been developed and improved in order to improve battery performance in recent years. Improvements in the characteristics required for batteries include higher voltage, higher energy density, higher load resistance, arbitrary shape, and assurance of safety. Among them, the lithium-ion battery is the secondary battery that can achieve high voltage, high energy density, and high load resistance among the existing batteries, and its improvement is still actively carried out so far.

The main constituent parts of such a lithium ion secondary battery are a positive electrode, a negative electrode, and an ion conductive layer sandwiched between the two electrodes. In the practical lithium-ion secondary battery, the positive electrode is mixed with active material powder such as lithium-cobalt composite oxide, conductive powder and binder resin, coated on the aluminum collector, and made into a plate shape. For the electrode, the negative electrode uses carbonaceous active material powder mixed with binder resin, coated on the copper current collector, and made into a plate-shaped electrode. On the other hand, the ion conductive layer is made of a porous film such as polyethylene or polypropylene filled with a non-aqueous solvent containing lithium ions.

For example, FIG. 9 is a schematic cross-sectional view showing the structure of a conventional cylindrical lithium ion secondary battery disclosed in JP-A-8-83608. In FIG. 9 , 1 is an outer cylinder made of stainless steel which doubles as a negative electrode terminal, and 2 is an electrode body arranged in the outer cylinder 1. The electrode body 2 is a positive electrode 3, and a separator 4 and a negative electrode 5 are wound in a spiral structure. . In order to maintain electrical connection with the positive electrode 3 , the separator 4 and the negative electrode 5 , the electrode body 2 needs to apply pressure to the electrode surface from the outside. Therefore, the electrode body 2 is arranged in a solid metal container to ensure all face-to-face internal contact. In the case of a prismatic battery, a method in which a rectangular electrode body is bundled and placed in a prismatic metal container and pressed from the outside can be performed.

In the aforementioned commercially available lithium ion secondary batteries, the method of bonding the positive electrode and the negative electrode is to use a strong outer container made of metal or the like. If there is no external container, the electrodes will be separated, and it will be difficult to maintain the electrical connection between the electrodes through the ion conductive layer (separator layer), and the characteristics of the battery will deteriorate. On the other hand, since such an outer container accounts for a large weight and volume of the battery as a whole, not only the energy density of the battery itself is reduced, but also the shape of the battery is limited by the rigidity of the outer container itself, making it difficult to make any shape.

Against such a background, lithium-ion secondary batteries that do not require an external container are being developed with the aim of reducing weight and thickness. The key to developing a battery that does not require an external container is how to maintain the electrical connection between the positive and negative electrodes and the ion-conducting layer (separator) sandwiched between them without applying force from the outside. As one joining means that does not require such an external force, a method of sticking electrodes and separators with resin or the like has been proposed.

For example, Japanese Patent Application Laid-Open No. 5-159802 describes a production method of integrating an ion-conductive solid electrolyte layer with a positive electrode and a negative electrode by heating using a thermoplastic resin binder. In this case, the electrodes and the electrolyte layer are integrated so that the electrodes are in close contact with each other. Therefore, even if no force is applied from the outside, the electrical connection between the electrodes can be maintained and the battery can be operated.

Since the existing lithium-ion secondary battery has the above-mentioned structure, in order to ensure the adhesion between the electrodes and the separator and the electrical connection between the electrodes, a strong outer container is used, and the outer shell other than the power generation part The proportion of the container to the volume and weight of the entire battery increases, which is disadvantageous when manufacturing a battery with high energy density. Although it is conceivable to attach the electrode and the ion conductor with an adhesive resin, for example, if only the adhesive resin is used to attach the electrolyte and the electrode, there will be problems due to the high resistance of the adhesive resin layer. The ion conduction resistance inside the battery case increases and battery characteristics deteriorate.

In the example of Japanese Patent Laid-Open No. 5-159802, the electrode and the solid electrolyte are bonded by a binder, but since the interface between the electrode and the electrolyte is covered by the binder, the conductivity of ions is lower than that of, for example, a liquid electrolyte. Not good. Even if an ion-conductive binder is used, no material having an ion-conductivity equal to or higher than that of a liquid electrolyte has been found, and it is difficult to obtain battery performance equivalent to that of a battery using a liquid electrolyte.

Contents of the invention

In order to solve the above problems, the inventors of the present invention have diligently studied the optimal bonding method of the separator and the electrodes, and its purpose is to provide a device that does not increase the ion conduction resistance between the electrodes without using a strong outer container. A lithium-ion secondary battery having a high energy density, a thinner shape, an arbitrary shape, and an excellent charge-discharge performance is provided, and a method for manufacturing the same.

The first lithium ion secondary battery of the present invention has a multilayer electrode laminate, and the electrode laminate is configured with a positive electrode with a positive electrode active material layer and a positive electrode current collector, and a negative electrode active material layer with a negative electrode current collector. Negative electrode, a separator for holding an electrolyte solution containing lithium ions arranged between the above-mentioned positive electrode and the negative electrode, and holding the above-mentioned electrolyte solution while bonding between the above-mentioned positive electrode active material layer and the above-mentioned negative electrode active material layer and the above-mentioned separator layer , and a porous adhesive resin layer that connects the positive electrode, the separator layer, and the negative electrode to each other through ion conduction. According to this, the electrode and the separator can be bonded by using the adhesive resin layer, and by maintaining the liquid electrolyte in the through hole of the adhesive resin layer connecting the electrode and the separator, the electrode-electrolyte connection can be ensured. Good ionic conductivity of the interface, so that a lithium-ion secondary battery with high energy density, thinner, arbitrary shape, and excellent charge-discharge characteristics can be manufactured. It is also possible to obtain a battery capacity proportional to the number of layers of the electrode laminate.

In the second to fourth lithium ion secondary batteries of the present invention, in the first lithium ion secondary battery, the plurality of layers of the electrode stack is formed by alternately arranging positive electrodes and negative electrodes between a plurality of cut separator layers. Between, or between wound insulation layers, or between folded insulation layers. Accordingly, it is possible to obtain a thin, light-weight battery with excellent charge-discharge characteristics and a battery capacity proportional to the number of stacked electrode stacks with a simple structure.

In the fifth lithium ion secondary battery of the present invention, in the above first lithium ion secondary battery, the porosity of the porous adhesive resin layer is equal to or higher than that of the separator layer.

In a sixth lithium ion secondary battery of the present invention, in the fifth lithium ion secondary battery, the porous adhesive resin layer has a porosity of 35% or more.

By making the porosity of the porous adhesive resin layer equal to or higher than that of the separator, for example, 35% or more, the ion conductivity resistivity of the adhesive resin layer holding the electrolyte can be given an appropriate value. .

In the seventh lithium ion secondary battery of the present invention, in the above first lithium ion secondary battery, the ion conduction resistivity of the adhesive resin layer holding the electrolyte and the ion conduction resistance of the separator holding the electrolyte same rate or less. Accordingly, excellent charge and discharge characteristics are maintained without deteriorating the charge and discharge characteristics.

In the eighth lithium ion secondary battery of the present invention, in the above first lithium ion secondary battery, the bonding strength between the positive electrode active material layer and the separator is equal to the bonding strength between the positive electrode active material layer and the positive electrode current collector Or on it, and the bonding strength between the negative electrode active material layer and the above-mentioned separator is equal to or above the bonding strength between the above-mentioned negative electrode active material layer and the negative electrode current collector. Accordingly, the destruction of the electrode occurs preferentially over the peeling between the electrode and the separator. The electrodes and the separator can be firmly bonded through the adhesive resin layer. And can fully maintain the electrical connection between the electrodes.

A ninth lithium-ion secondary battery of the present invention is the above-mentioned first lithium-ion secondary battery, wherein the adhesive resin layer uses a single fluorine-based resin or a mixture mainly composed of a fluorine-based resin.

A tenth lithium ion secondary battery of the present invention is the ninth lithium ion secondary battery described above, wherein polyvinylidene fluoride is used as the fluorine-based resin.

In an eleventh lithium ion secondary battery of the present invention, in the above first lithium ion secondary battery, polyvinyl alcohol or a mixture containing polyvinyl alcohol as a main component is used for the adhesive resin layer.

The adhesive resin layer adopts fluorine-based resin or a mixture mainly composed of fluorine-based resin, polyvinyl alcohol or a mixture mainly composed of polyvinyl alcohol, and a lithium-ion secondary battery having the above-mentioned excellent characteristics can be obtained.

The manufacturing method of the first lithium ion secondary battery of the present invention comprises the process of forming a positive electrode active material layer on a positive electrode current collector to prepare a positive electrode, and forming a negative electrode active material layer on a negative electrode current collector to prepare a negative electrode. The process of coating the surface of at least one of the above-mentioned positive electrode active material layer and the separator layer opposite to it, and the surface of at least one of the above-mentioned negative electrode active material layer and the separator layer opposite to it, the above-mentioned The process of bonding the positive electrode active material layer and the above negative electrode active material layer alternately between the separator layers, pressurizing the above-mentioned bonded product while heating, evaporating the solvent in the above-mentioned adhesive resin solution to form an adhesive resin layer, and bonding A step of forming a plurality of layers of an electrode laminate with the positive electrode active material layer, the negative electrode active material layer, and the separator layer. By this method, a lithium-ion secondary battery having a high energy density, a thinner shape, an arbitrary shape, and excellent charge-discharge characteristics can be produced simply and efficiently.

Description of drawings

Fig. 1, Fig. 2 and Fig. 3 are schematic cross-sectional views showing a battery structure and an electrode laminate of a lithium ion secondary battery according to an embodiment of the present invention, and Fig. 4 is a schematic view showing electrodes shown in Fig. 1 , Fig. 2 and Fig. 3 A schematic cross-sectional view of the structure of a laminate, FIG. 5 is an explanatory diagram showing a method of applying an adhesive resin solution using a bar coating method according to an embodiment of the present invention, and FIG. Fig. 7 is an explanatory diagram showing a method of applying an adhesive resin solution by a dipping method according to an embodiment of the present invention. Fig. 8 It is a characteristic diagram showing the relationship between the amount of the adhesive resin in the adhesive resin solution and the internal resistance when forming the adhesive resin layer according to one embodiment of the present invention. FIG. 9 shows a conventional lithium ion A schematic cross-sectional view of an example of a secondary battery.

Detailed ways

Fig. 1, Fig. 2 and Fig. 3 are schematic cross-sectional views showing the battery structure of a lithium ion secondary battery according to an embodiment of the present invention, and Fig. 4 shows the structure of the electrode stack shown in Fig. 1, Fig. 2 and Fig. 3 Sectional schematic. In the figure, 8 is an electrode laminated body, and this electrode laminated body 8 is made by joining the positive electrode 3 on the positive electrode current collector 6 with the positive electrode active material layer 7, and the negative electrode active material layer 9 is bonded on the negative electrode current collector 10. Negative electrode 5, the separator layer 4 that holds the electrolyte solution containing lithium ions disposed between the positive electrode 3 and the negative electrode 5, the porous adhesive resin that joins the positive electrode active material layer 7 and the negative electrode active material layer 9 and the separator layer 4 The adhesive resin layer 11 has a plurality of through holes 12 connecting the positive electrode active material layer 7 and the negative electrode active material layer 9 with the separator layer 4, and the electrolyte solution is held in the through holes.

The electrode layer (i.e., the active material layers 7, 9) and the separator layer 4 as the electrolyte layer are bonded to each other with a porous adhesive resin layer 11, so that the bonding strength between the electrode and the separator can be ensured, and the The peeling between electrodes and separators that is difficult to suppress in existing batteries. By retaining the electrolytic solution inside, that is, in the through hole 12 connected to the interface between the electrode and the separator formed on the adhesive resin layer 11, good ionic conductivity at the electrode-electrolyte interface can be ensured while reducing the gap between the electrodes. ionic conduction resistance. The amount of ions generated in the active material inside the electrode and the speed and amount of movement of the ions to the opposite electrode can reach the level of a conventional lithium ion battery having an outer casing. The electrical connection between the electrodes can be maintained without applying external force. Therefore, there is no need for a strong outer container that maintains the battery structure, and the battery can be made lightweight, thin, and of any shape, while achieving excellent charge-discharge characteristics and battery performance comparable to batteries using an electrolyte solution.

By making the ion conductivity resistivity of the adhesive resin layer 11 holding the electrolytic solution equal to or lower than the ion conductivity resistivity of the separator layer 4 holding the electrolytic solution, the use of such an adhesive resin layer 11 will not make the Deterioration of charge and discharge characteristics can maintain the charge and discharge characteristics of the battery at the level of existing batteries.

The ion conductivity resistivity of the adhesive resin layer 11 can be adjusted mainly by changing its porosity and thickness. The porosity can be adjusted, for example, by the amount of the adhesive resin relative to N-methylpyrrolidone in the adhesive resin solution forming the adhesive resin layer. Preferably, the porosity is equal to or higher than that of the spacer layer 4 used, for example, 35% or higher.

And make the bonding strength of the positive electrode active material layer and the separator equal to or higher than the bonding strength of the above-mentioned positive electrode active material layer and the positive electrode collector, and make the bonding strength of the negative electrode active material layer and the above-mentioned separator layer and the above-mentioned negative electrode The bonding strength between the active material layer and the negative electrode current collector is equal to or greater than that, that is, the bonding strength is preferably equal to or higher than the strength for bonding and integrating the active material layer and the current collector inside the electrode. When the peeling test was carried out after the battery was produced, it was confirmed that when the bonding strength between the electrode and the separator was sufficiently large, the destruction of the electrode (the active material layer and the current collector) occurred more preferentially than the peeling between the electrode and the separator. stripping). The bonding strength can be adjusted by selecting, for example, the thickness of the adhesive resin layer and selecting the adhesive resin.

The adhesive resin used to join the active material layer and the separator can be a material that forms a porous film that is insoluble in the electrolyte and does not react chemically inside the battery, for example, a fluorine-based resin or a fluorine-based resin as a main component. A mixture of polyvinyl alcohol or a mixture with polyvinyl alcohol as the main component. Specifically, polymers or copolymers with fluorine atoms in the molecular structure such as vinylidene fluoride and 4-ethylene fluoride, polymers or copolymers with vinyl alcohol in the molecular skeleton, or polymethacrylic acid can be used. Mixtures of methyl ester, polystyrene, polyethylene, polypropylene, polyvinylidene chloride, polyvinyl chloride, polyacrylonitrile, polyethylene oxide, etc. Particularly suitable is polyvinylidene fluoride which is a fluorine-based resin.

The lithium ion secondary battery with above-mentioned structure is through on the surface of at least one of the positive electrode active material layer 7 and the spacer layer 4 opposite to it, and at least one of the negative electrode active material layer 9 and the spacer layer 4 opposite to it. The adhesive resin solution is coated on the surface, the positive electrode active material layer 7 and the negative electrode active material layer 9 are laminated alternately between the separators 4, the laminated product is pressurized and heated at the same time, and the adhesive resin solution is evaporated. Porous adhesive resin layer 11 is formed from a solvent, and positive electrode active material layer 7 , negative electrode active material layer 9 and separator 4 are bonded together.

As the active material adopted in the present invention, the positive electrode adopts composite oxides of transition metals such as lithium and cobalt, nickel or manganese, chalcogen compounds, or materials containing these composite compounds and various additive elements, and the negative electrode preferably adopts graphitizable carbon, non-graphitizable carbon, carbon-based compounds such as polyacene and polyacetylene, and aromatic carbohydrates containing pyrene and other acene structures, as long as they can absorb and release lithium ions that are the main body of battery operation can be used. These active substances can be in granular form, and the particle size can be 0.3-20 microns, particularly preferably 0.3-5 microns.

As the binder resin for forming the active material into an electrode plate, a resin that is insoluble in an electrolytic solution and does not undergo an electrochemical reaction inside the electrode laminate can be used. Specifically, monomers or copolymers such as vinylidene fluoride, vinyl fluoride, acrylonitrile, and ethylene oxide, ethylene propylene diamine rubber, and the like can be used.

Metals that are stable in the battery can be used for the current collector, and it is preferable to use aluminum for the positive electrode and copper for the negative electrode. The shape of the current collector can be foil, mesh, or expanded mesh, and the mesh and expanded mesh are preferable in terms of large void areas and easy retention of the electrolyte after bonding.

The adhesive resin used to bond the current collector and the active material layer is the same as the adhesive resin used to bond the active material layer and the separator layer, and can be used to form an insoluble electrolyte that does not generate electricity inside the battery. Resin of the porous membrane that chemically reacts. Specifically, polymers with fluorine molecules in the molecular structure such as vinylidene fluoride and 4-ethylene fluoride can be used, or a mixture with polymethyl methacrylate, polystyrene, polyethylene, polypropylene, etc., in the molecular structure Polymers or copolymers with vinyl alcohol in the backbone, or can be used with polymethyl methacrylate, polystyrene, polyethylene, polypropylene, polyvinylidene chloride, polyvinyl chloride, polyacrylonitrile, polyethylene oxide, etc. mixture. Particularly suitable are polyvinylidene fluoride or polyvinyl alcohol.

A porous film, net, non-woven fabric, etc. can be used for the isolation layer, and any material can be used as long as it has sufficient strength. The material thereof is not particularly limited, and may be polyethylene or polypropylene from the viewpoint of adhesiveness and safety.

As the solvent and electrolyte salt supplied to the electrolytic solution used as a lithium ion conductor, non-aqueous solvents and lithium-containing electrolyte salts currently used in batteries can be used. Specifically, ether-based solvents such as dimethoxyethane, diethoxyethane, diethyl ether, and dimethyl ether, and ester-based solvents such as propylene carbonate, ethylene carbonate, diethyl carbonate, and dimethyl carbonate can be used. A single liquid of a solvent, and a mixture of two types of the same solvent or different solvents. The electrolyte salt provided to the electrolyte can be LiPF ₆ , LiASF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiC(CF ₃ SO ₂ ) ₃ etc.

As a method of applying the adhesive resin, a method using a bar coater, a method using a spray gun, and a dipping method can be used.

For example, in the method of using a bar coater, as shown in the explanatory diagram of FIG. 5, the adhesive resin is dripped in a line shape on the moving separator material 13, and the dripped resin is rolled with a coating bar 15, thereby bonding the material. The adhesive resin is evenly coated on one side of the isolation layer material, then, the isolation layer material is twisted 180 degrees, and the adhesive resin is coated in the same way on the uncoated cloth surface. According to this, a large amount of adhesive resin is uniformly coated on the separation layer in a short time. 14 is an adhesive resin dropping port, 16 is a support roller, and 17 is a separation layer reel.

As shown in the explanatory diagram of FIG. 6, the method of using a spray gun is to spray the adhesive resin solution or liquid adhesive resin on the spacer after the adhesive resin solution or liquid adhesive resin is charged into the spray gun 18. On the layer material 13, an adhesive resin is attached to the spacer layer material 13. At least one or more spray guns 18 are arranged on both faces of the release layer material 13, and the adhesive resin solution is continuously sprayed while moving the release layer material 13, so that the two faces of the release layer can be continuously coated. covered with adhesive resin. Like a bar coater, it is possible to coat a large amount of adhesive resin on a separator in a short time.

The dipping method is a coating method of coating the adhesive resin on both surfaces of the isolation layer by dipping the isolation layer in an emulsified solution of the adhesive resin and lifting it up. That is, as shown in FIG. 7, after all the separator material 13 is immersed in an emulsified solution of an adhesive resin (hereinafter referred to as an emulsion adhesive resin) 21, it is sandwiched with a residual liquid removal roller 24 to remove the remaining material. The emulsion-like adhesive resin 21 is pulled up at the same time, thereby coating the entire surface of the release layer with the adhesive resin. 22 is a support roller. By adopting the dipping method, the coating process can be simplified and a large amount of adhesive resin can be coated in a short time.

The following examples are given to illustrate the present invention, but of course the present invention is not limited thereto.

Example 1

(Preparation of positive electrode)

The cathode active material paste made by dispersing 87 parts by weight of LiCoO ₂ , 8 parts by weight of graphite powder, and 5 parts by weight of polyvinylidene fluoride in N-methylpyrrolidone was coated with a thickness of 300 microns by the doctor blade method, and the active substance film. A 30-micron-thick aluminum mesh forming a positive electrode current collector was added on top of it, and the prepared positive-electrode active material paste was coated with a thickness of 300 microns by a doctor blade method. Arrange it in a dryer at 60°C for 60 minutes until it reaches a semi-dry state. The prepared laminate was lightly rolled with a rotary roller whose gap between the rollers was adjusted to 550 μm, and the laminate was bonded to form a positive electrode.

After immersing the positive electrode in the electrolytic solution, the peel strength between the positive electrode active material layer and the positive electrode current collector was measured and found to be 20 to 25 gf/cm.

(Preparation of Negative Electrode)

The negative electrode active material paste that 95 parts by weight of Mesofe-zumi クロビ-ズカ-bon (trade name; manufactured by Osaka Gas) and 5 parts by weight of polyvinylidene fluoride are dispersed in N-methylpyrrolidone (abbreviated as NMP) is used The doctor blade method was applied at a thickness of 300 micrometers to make a thin film of the active material. A 20-micrometer-thick copper mesh forming a negative electrode current collector was added thereon, and the prepared negative electrode active material paste was coated with a thickness of 300 micrometers by a doctor blade method. This was placed in a dryer at 60° C. for 60 minutes to be in a semi-dry state. The prepared laminate was lightly rolled with a rotary roller whose gap was adjusted to 550 μm, and the laminate was bonded to form a negative electrode.

After the negative electrode was immersed in the electrolytic solution, the peel strength between the negative electrode active material layer and the negative electrode current collector was measured, and it was 10 to 15 gf/cm.

(Disposition of adhesive resin solution)

First, 5 parts by weight of polyvinylidene fluoride and 95 parts by weight of N-methylpyrrolidone (hereinafter abbreviated as NMP) were mixed in proportion, and stirred sufficiently to form a uniform solution to prepare a viscous adhesive resin solution.

(production of batteries)

The adhesive resin solution prepared as described above was coated on one side of each of the two release layers.

Coating of the adhesive resin solution was performed by the bar coater method shown in FIG. 5 . Take out the separation layer material 13 that is bundled into roll shape, width is 12 centimeters, thickness 25 micrometers by the porous polypropylene sheet (made by ヘキスト, セルガ-ド#2400) constitutes, on its one face and the separation layer The adhesive resin solution was dripped on a line perpendicular to the direction in which the material was taken out. By rotating the coating rod 15 made of finely winding a wire with a diameter of 0.5 mm on a tube with a diameter of 1 cm while moving the spacer material 13, the adhesive resin solution dripped on the wire Evenly coated on the entire isolation layer material 13. The coating amount of the adhesive resin was adjusted by changing the dripping amount of the adhesive resin solution. Afterwards, before the adhesive dries, two separation layers are used to sandwich the above-prepared strip-shaped positive electrode (or negative electrode) with their respective coated surfaces for bonding and lamination, and are dried at 60°C.

Punch out the two spacers 4 between which the positive electrode 3 (or negative pole) is bonded to a specified size, coat one side of the punched spacer layer with the above-mentioned adhesive resin solution, and punch it together to a specified size. Negative pole 5 (or positive pole) of the negative electrode 5 (or positive pole), then, be coated with above-mentioned adhesive resin solution on one side of the other spacer that punches out into specified size, the coated surface of this another spacer is pasted on the negative pole that is bonded in advance 5 (or positive) side. This process was repeated to form a battery body having a multilayer electrode laminate, and the electrode body was dried while being pressurized to obtain a battery body having a flat laminated structure as shown in FIG. 1 . The NMP was evaporated from the adhesive resin layer by drying to form a porous adhesive resin layer having through holes connecting the positive electrode, the negative electrode, and the separator.

The battery body of the above-mentioned flat laminated structure is formed by spot welding the collector sheets connected to the respective ends of the positive electrode and the negative electrode current collector of the battery body of the flat laminated structure according to the positive electrodes and the negative electrodes. electrically connected in parallel.

The electrode body with the plate-like laminated structure is immersed in a mixed solvent of ethylene carbonate and dimethyl carbonate (molar ratio: 1:1) to dissolve lithium hexafluorophosphate at a concentration of 1.0mol/ ^dm3 . After soaking in the liquid, it was melted by heat and sealed in a pouch made of aluminum laminated film to produce a battery having a flat plate-shaped laminated battery body.

In the stage of immersing and injecting in the electrolytic solution, the peel strengths of the positive electrode active material layer and the separator layer, and the negative electrode active material layer and the separator layer were measured, and the strengths were 25 to 30 gf/cm and 15 to 20 gf/cm, respectively.

As described above, in this lithium ion secondary battery, while the positive electrode 3 and the separator 4 and the negative electrode 5 and the separator 4 are bonded together by the adhesive resin layer 11, a plurality of Connect the through hole 12 between the positive electrodes 3, 5 and the separator 4, and ensure good ion conductivity by keeping the electrolyte in the through hole 12, thereby making it unnecessary to apply pressure from the outside, that is, not requiring a strong exterior Containerized, thin, lightweight batteries with excellent charge and discharge characteristics. And a battery capacity proportional to the number of layers of the electrode laminate 8 is obtained.

8 is a characteristic diagram showing the internal resistance of the battery when the adhesive resin layer is prepared when the amount of the adhesive resin in the adhesive resin solution is 5 parts by weight, 7 parts by weight, and 10 parts by weight among NMP. . It can be seen that the resistance increases sharply between 5 parts by weight and 7 parts by weight. Since the thickness of the adhesive resin layer 11 is proportional to the amount of adhesive resin in the adhesive resin solution, it can be considered that due to the retention rate of the electrolyte solution and the distribution state of the electrolyte solution in the adhesive resin layer 11, in this area Rapidly changing resistance rises sharply. The resistance value at 5 parts by weight is substantially the same as the resistance value measured by applying sufficient pressure between the electrodes 3 , 5 and the separator 4 without the adhesive resin layer 11 .

Example 2

Only the adhesive resin solution shown in Example 1 was changed, and the other was the same as in Example 1, and a battery having an electrode body having a flat laminated structure as shown in FIG. 1 was produced.

(Preparation of Adhesive Resin Solution)

Polytetrafluoroethylene, copolymer of vinylidene fluoride and acrylonitrile, mixture of polyvinylidene fluoride and acrylonitrile, mixture of polyvinylidene fluoride and polyethylene oxide, polyvinylidene fluoride and polyethylene terephthalate Mixtures, mixtures of polyvinylidene fluoride and polymethyl methacrylate, mixtures of polyvinylidene fluoride and polystyrene, mixtures of polyvinylidene fluoride and polypropylene, mixtures of polyvinylidene fluoride and polyethylene, respectively with the same composition The ratio is mixed with N-methylpyrrolidone to prepare an adhesive resin solution with a certain viscosity.

Using this adhesive resin solution, a battery having an electrode body having a flat laminated structure was produced in the same manner as in Example 1.

In the stage of injecting the electrolyte solution into the battery body with a flat laminated structure, the peel strengths of the positive electrode active material layer and the separator layer, the negative electrode active material layer and the separator layer were measured, and the strengths were 25-70gf/cm, 15-70gf/cm, respectively. 70gf/cm range.

Example 3

Only the adhesive resin solution shown in Example 1 was changed, and the others were the same as in Example 1 to prepare a battery having an electrode body with a flat laminated structure as shown in FIG. 1 .

(Preparation of Adhesive Resin Solution)

Polyvinyl alcohol, a mixture of polyvinyl alcohol and polyvinylidene fluoride, a mixture of polyvinyl alcohol and polyacrylonitrile, and a mixture of polyvinyl alcohol and polyethylene oxide are respectively dissolved in NMP or mixed to form an adhesive solution with a certain viscosity.

Using these adhesive resin solutions, a battery having a battery body having a flat-shaped wound laminate structure was produced in the same manner as in Example 1 above.

At the stage of injecting the electrolytic solution into the battery body with a flat laminated structure, the peel strengths of the positive electrode active material layer and the separator layer, and the negative electrode active material layer and the separator layer were measured and found to be 20 gf/cm or more.

Example 4.

In this example, using the positive electrode and negative electrode shown in Example 1, the adhesive resin solution shown in Examples 1 to 3 was used to prepare an electrode with a flat-shaped winding laminated structure as shown in Figure 2 body battery.

(Preparation of battery)

Coat the adhesive resin solution on each side of two tape-shaped spacers made of porous polypropylene sheets (manufactured by ヘキスト, セヘキスト, Seluga-do #2400) bundled into a roll shape, Sandwich the strip-shaped negative electrode (or positive electrode) between them to make them stick together. After bonding, place them in a warm air dryer at 60°C for 2 hours to evaporate NMP.

Coating of the adhesive resin solution was carried out by the bar coater method shown in FIG. 5 .

Next, an adhesive resin solution is applied on one side of the belt-shaped separator 4 bonded with the negative electrode 5 (or positive electrode) therebetween, and one end of the separator is bent by a certain amount, and the positive electrode 3 (or positive electrode) is clamped in the crease. Negative electrode), for overlapping, through the lamination device. Next, apply an adhesive resin solution on the other side of the strip-shaped separator, and attach another positive electrode 3 (or negative electrode) at a position opposite to the positive electrode 3 (or negative electrode) clamped in the crease in advance. , the separator is rolled into an elliptical shape, and the process of laminating another positive electrode 3 (or negative electrode) and winding the separator is repeated to form a battery body with a multilayer electrode laminate, and the battery body is pressurized while Drying was carried out to produce a battery body with a flat-shaped winding type laminated structure as shown in FIG. 2 .

The battery body of the above-mentioned flat laminated structure is bonded by spot welding the current collector sheets connected to the respective ends of the positive electrode and the negative electrode current collector of the battery body of the flat laminated structure according to the positive electrodes and the negative electrodes. electrically connected in parallel.

The electrode body of this flat laminated structure is immersed in a mixed solvent of ethylene carbonate and dimethyl carbonate (molar ratio: 1:1), which is produced by dissolving lithium hexafluorophosphate at a concentration of 1.0 mol/ ^dm3. After being immersed in the electrolyte, it is sealed in a pouch made of aluminum laminated film by heat fusion to make a battery.

At the stage of injecting the electrolyte solution into the battery body with a flat laminated structure, the peel strengths of the positive electrode active material layer and the separator layer, the negative electrode active material layer and the separator layer were measured, and the strengths were 25-30gf/cm, 15-20gf /cm.

Example 5.

In this example, using the positive electrode and negative electrode shown in Example 1, the adhesive resin solution shown in Examples 1 to 3 was used to prepare an electrode with a flat-shaped winding laminated structure as shown in Figure 3 body battery. The difference from Example 4 is that the positive electrode, the negative electrode and the separator are wound at the same time.

(production of batteries)

Pull out two strip-shaped separators 4 made of porous polypropylene sheets (manufactured by ヘキスト, セルガ-ド#2400) that are bundled into a roll, and arrange the strip-shaped negative electrodes 5 (or positive electrodes) on the two separated sheets. Between the layers 4, the strip-shaped positive electrode 3 (or negative electrode) is arranged to protrude to the outside of one separator layer 4 by a certain amount.

Next, apply an adhesive resin solution on the inner surface of each separator 4 and the outer surface of the separator that configures the positive electrode 3 (or negative electrode), and overlap the positive electrode 3 (or negative electrode) and two separators 4 and the negative electrode. 5 (or positive pole), through a laminating device, and then coat an adhesive resin solution on the outer surface of another separator 4, and bend the protruding positive pole 3 (or negative pole) to the coated surface for lamination, and use The separator laminated so as to wrap the curved positive electrode 3 (or negative electrode) inwardly is rolled into an ellipse to form a battery body having a multilayer electrode laminate, and the battery body is placed under pressure at 60°C. The NMP was evaporated in a warm air dryer for 2 hours, and a battery body with a flat roll-type laminated structure was made.

Coating of the adhesive resin solution was carried out by the bar coater method shown in FIG. 5 .

By spot-welding the current collector sheets connected to the respective ends of the positive electrode and the negative electrode current collector of the battery body of the flat laminated structure according to the positive electrodes and the negative electrodes, the battery of the above-mentioned flat laminated structure electrically connected in parallel.

After immersing the electrode body of this flat laminated structure in a mixed solvent of ethylene carbonate and dimethyl carbonate (1:1 molar ratio) in an electrolyte solution in which lithium hexafluorophosphate was dissolved at a concentration of 1.0 mol/ ^dm3 , Sealed in a bag made of aluminum oxide laminated film by hot melting to make a battery.

Example 6.

In the above-mentioned Examples 4 and 5, the example in which the battery body with a flat laminated structure has a strip-shaped separator wound up is shown, and it may be a product in which a strip-shaped positive electrode (or negative electrode) is joined between the strip-shaped separators. The structure of folding and pasting the negative electrode (or positive electrode).

The above-mentioned examples illustrate the case where the adhesive resin solution is applied by the bar coater method, but the adhesive resin solution may also be applied by a spray gun.

As shown in Figure 6, the separation layer material 13 made of a porous polypropylene sheet (made by ヘキスト, セルガ-ド#2400) that is bundled into a roll shape with a width of 12 cm and a thickness of 25 microns is taken out, and packed in a The adhesive resin solution spray gun 18 sprays the adhesive resin solution onto the release layer. The adhesive resin solution can be evenly coated on both surfaces of the spacer material 13 by spraying. The application amount of the adhesive resin solution can be adjusted by changing the spray amount.

The above embodiments illustrate the case where the positive electrode 3 and the negative electrode 5 are electrodes made by bonding the active material layer on the current collector, and electrodes in which the active material layer itself is the current collector can also be used.

Possibility of industrial use

It can be used as a secondary battery for portable electronic devices such as laptop computers and mobile phones, and can achieve small size, light weight, and arbitrary shape while improving battery performance.

Claims (10)

1. A lithium ion secondary battery is characterized in that there is a multilayer electrode laminate, which is equipped with a positive electrode with a positive electrode active material layer and a positive electrode current collector, and a negative electrode with a negative electrode active material layer and a negative electrode current collector , a separator for maintaining an electrolyte solution containing lithium ions disposed between the positive electrode and the negative electrode, and maintaining the electrolyte solution while bonding between the positive electrode active material layer and the negative electrode active material layer and the separator layer, and a porous adhesive resin layer in which the positive electrode, the separator layer, and the negative electrode are connected to each other through ion conduction, wherein The adhesive resin layer uses a fluorine-based resin or a mixture mainly composed of a fluorine-based resin, or uses polyvinyl alcohol or a mixture mainly composed of polyvinyl alcohol. 2. The lithium ion secondary battery according to claim 1, wherein the plurality of layers of the battery laminate is formed by alternately arranging positive electrodes and negative electrodes between a plurality of cut separators. 3. The lithium ion secondary battery according to claim 1, wherein the plurality of layers of the battery laminate is formed by alternately arranging positive electrodes and negative electrodes between wound separators. 4. The lithium ion secondary battery according to claim 1, wherein the plurality of layers of the battery laminate is formed by alternately arranging positive electrodes and negative electrodes between a plurality of folded separator layers. 5. The lithium ion secondary battery according to claim 1, wherein the porosity of the porous adhesive resin layer is equal to or higher than that of the separator layer. 6. The lithium ion secondary battery according to claim 5, wherein the porous adhesive resin layer has a porosity of 35% or more. 7. The lithium ion secondary battery according to claim 1, wherein the ion conductivity resistivity of the adhesive resin layer holding the electrolyte solution is equal to or lower than the ion conductivity resistivity of the separator layer holding the electrolyte solution. 8. The lithium ion secondary battery according to claim 1, characterized in that the joint strength of the positive electrode active material layer and the separator is equal to or higher than the joint strength of the above-mentioned positive electrode active material layer and the positive electrode current collector, and The bonding strength between the negative electrode active material layer and the separator layer is equal to or higher than the bonding strength between the negative electrode active material layer and the negative electrode current collector. 9. The lithium ion secondary battery according to claim 8, wherein polyvinylidene fluoride is used as the fluorine-based resin. 10. The preparation method of lithium ion secondary battery is characterized in that comprising the operation of forming positive electrode active material layer on positive electrode current collector and preparing positive electrode, forming negative electrode active material layer and the operation of preparing negative electrode on negative electrode current collector, in The process of coating the surface of at least one of the above-mentioned positive electrode active material layer and the separator layer opposite to it, and the surface of at least one of the above-mentioned negative electrode active material layer and the separator layer opposite to it, the above-mentioned The process of laminating the positive electrode active material layer and the above negative electrode active material layer alternately between the separator layers, pressurizing the above lamination product while heating, evaporating the solvent in the above adhesive resin solution to form a porous adhesive resin layer, The process of bonding the above-mentioned positive electrode active material layer and the above-mentioned negative electrode active material layer and the separator layer to form a plurality of layers of the electrode laminate, wherein The adhesive resin layer uses a fluorine-based resin or a mixture mainly composed of a fluorine-based resin, or uses polyvinyl alcohol or a mixture mainly composed of polyvinyl alcohol.

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