JP2013065471A - Electrode and electric device using the same - Google Patents

Abstract

The present invention provides means capable of reducing misalignment in a battery manufacturing process.
SOLUTION: A non-conductive porous material is used as a base material, a positive electrode active material is held in a pore in a surface layer portion on one side of the porous material, and a pore in a surface layer portion on the other side An electrode in which a negative electrode active material is held.
[Selection] Figure 2

Description

  The present invention relates to an electrode and an electric device using the same.

  In recent years, in order to cope with global warming, reduction of the amount of carbon dioxide is eagerly desired. In the automobile industry, there is a great expectation for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV). Electric devices such as secondary batteries for motor drive that hold the key to their practical application. Is being actively developed.

  As a secondary battery for driving a motor, a lithium ion secondary battery having the highest theoretical energy among all the batteries is attracting attention, and is currently being developed rapidly. Lithium ion secondary batteries generally have a positive electrode and a negative electrode having an active material layer in which an active material or the like is applied to a current collector together with a binder, connected via an electrolyte layer in which an electrolyte is held in a separator. (For example, patent document 1).

  The non-aqueous electrolyte secondary battery used as a motor drive power source for automobiles and the like as described above has extremely high output characteristics compared to consumer non-aqueous electrolyte secondary batteries used in mobile phones, notebook computers, etc. It is required to have. At present, research and development is underway to meet such demands.

International Publication No. 2000/59063 Pamphlet

  The manufacturing process of a battery having a configuration as described in Patent Document 1 usually includes a process of sequentially stacking a positive electrode, an electrolyte layer, and a negative electrode. In a general lithium ion secondary battery, since a plurality of single battery layers composed of a positive electrode, an electrolyte layer, and a negative electrode are stacked, stacking deviation may occur in the process of repeatedly stacking these layers. When such a stacking shift occurs, it is difficult to stably manufacture a high-performance battery, and thus an additional measure such as a positioning mechanism is required to avoid the stacking shift.

  Accordingly, an object of the present invention is to provide means capable of reducing stacking deviation in a battery manufacturing process.

  In view of the above problems, the present inventors have made extensive studies. As a result, the center part in the thickness direction of the non-conductive porous body is used as a separator, and by using the electrodes in which the positive electrode active material and the negative electrode active material are respectively held in the pores of the surface layer parts on both sides, the above I found that the problem was solved.

  That is, the present invention has a non-conductive porous material as a base material, the positive electrode active material is held in the pores of the surface layer portion on one side of the porous material, and the surface layer portion on the other side is vacant. An electrode in which a negative electrode active material is held in a hole.

  According to the present invention, the positive electrode active material layer, the separator, and the negative electrode active material layer can be manufactured as an integral structure. As a result, it is possible to avoid stacking deviations that occur when the layers are stacked.

1 is a schematic cross-sectional view showing a basic configuration of a flat (stacked) non-bipolar non-aqueous electrolyte lithium ion secondary battery that is an embodiment of an electric device. It is a section schematic diagram showing the electrode of this embodiment. It is a schematic diagram showing the active material layer in the electrode of this embodiment. It is a cross-sectional schematic diagram showing the nonelectroconductive porous body used for manufacture of the electrode of this embodiment. It is the schematic which shows the manufacturing process of the electrode of this embodiment. It is a section schematic diagram showing the electrode of this embodiment. It is a section schematic diagram showing the electrode of this embodiment. It is a perspective view showing the appearance of a flat lithium ion secondary battery which is one embodiment of an electric device.

  First, a nonaqueous electrolyte lithium ion secondary battery will be described as a preferred embodiment of the electric device, but is not limited to the following embodiment. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  When distinguished by the structure and form of the lithium ion secondary battery, it is not particularly limited, such as a stacked (flat) battery or a wound (cylindrical) battery, and can be applied to any conventionally known structure.

  Moreover, when viewed in terms of electrical connection form (electrode structure) in a lithium ion battery, it can be applied to both non-bipolar (internal parallel connection type) batteries and bipolar (internal series connection type) batteries. is there.

  Similarly, there is no particular limitation when distinguished by the form of electrolyte. For example, the present invention can be applied to any of a liquid electrolyte type battery in which a separator is impregnated with a nonaqueous electrolytic solution, a polymer gel electrolyte type battery also called a polymer battery, and a solid polymer electrolyte (all solid electrolyte) type battery. The polymer gel electrolyte and the solid polymer electrolyte can be used by impregnating them in a separator.

  In the following description, a non-bipolar type (internal parallel connection type) lithium ion battery will be described with reference to the drawings. However, the present invention should not be limited to these.

  FIG. 1 is a schematic diagram showing the basic configuration of an embodiment of a flat (stacked) nonaqueous electrolyte lithium ion secondary battery (hereinafter also simply referred to as “stacked battery”). As shown in FIG. 1, the stacked battery 10 of the present embodiment has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a battery exterior material 29 that is an exterior body. Have. Here, the power generation element 21 has a configuration in which a positive electrode, an electrolyte layer 17, and a negative electrode are stacked. The positive electrode has a structure in which the positive electrode active material layer 13 is disposed on both surfaces of the positive electrode current collector 11. The negative electrode has a structure in which the negative electrode active material layers 15 are disposed on both surfaces of the negative electrode current collector 12. Specifically, the negative electrode, the electrolyte layer, and the positive electrode are laminated in this order so that one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto face each other with the electrolyte layer 17 therebetween. . Thereby, the adjacent positive electrode, electrolyte layer, and negative electrode constitute one unit cell layer 19. Therefore, it can be said that the stacked battery 10 of the present embodiment has a configuration in which a plurality of the single battery layers 19 are stacked and electrically connected in parallel. The number of times the single battery layer 19 is stacked can be adjusted according to a desired voltage.

  In addition, although the positive electrode active material layer 13 is arrange | positioned only at one side in the outermost layer positive electrode collector located in both outermost layers of the electric power generation element 21, an active material layer may be provided in both surfaces. That is, instead of using a current collector dedicated to the outermost layer provided with an active material layer only on one side, a current collector having an active material layer on both sides may be used as it is as an outermost current collector. In addition, the arrangement of the positive electrode and the negative electrode is reversed from that in FIG. 1, so that the outermost layer negative electrode current collector is positioned on both outermost layers of the power generation element 21, and the outermost layer negative electrode current collector is disposed on one or both surfaces. A negative electrode active material layer may be disposed.

  The positive electrode current collector 11 and the negative electrode current collector 12 are respectively attached with a positive electrode current collector plate 25 and a negative electrode current collector plate 27 that are electrically connected to the respective electrodes (positive electrode and negative electrode), and are sandwiched between end portions of the battery exterior material 29. Thus, it has a structure led out of the battery exterior material 29. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 are ultrasonically welded to the positive electrode current collector 11 and the negative electrode current collector 12 of each electrode, respectively, via a positive electrode lead and a negative electrode lead (not shown) as necessary. Or resistance welding or the like.

  Hereinafter, the electrode of this embodiment will be described in more detail.

  FIG. 2 is an enlarged schematic cross-sectional view of the electrode 30 of the present embodiment used in the lithium ion secondary battery 10 shown in FIG.

  The electrode 30 of the present embodiment is configured using a non-conductive porous body 31 as a base material. The positive electrode active material 32a is held in the pores of the surface layer portion on one side of the porous body 31, and the positive electrode active material layer 33 is formed. Further, the negative electrode active material 32b is held in the pores of the surface layer portion on the other side of the porous body 31, and the negative electrode active material layer 35 is formed. And between the positive electrode active material layer 33 and the negative electrode active material layer 35, it has the separator 37 which is a layer which does not contain an active material.

  As shown in FIG. 3, the positive electrode active material layer 33 and the negative electrode active material layer 35 in the electrode 30 of the present embodiment are formed on, for example, a non-woven fabric that is a non-conductive porous body 31 and a particulate active material 32 (32 a , 32b). As shown in FIG. 2, the non-conductive porous body 31 functions as a three-dimensional skeleton of the active material layers 33 and 35 in the upper and lower surface layer portions excluding the central portion in the thickness direction. The upper active material 32 (32a, 32b) is held.

  Further, the non-conductive porous body 31 functions as a separator 37 at the center in the thickness direction, and an electrolyte layer can be formed by holding the electrolyte therein.

  The manufacturing process of a general lithium ion secondary battery is to prepare separately a positive electrode coated with a positive electrode active material layer, an electrolyte layer formed by holding an electrolyte in a separator, and a negative electrode coated with a negative electrode active material layer. The process of laminating in order is included. However, in such a battery manufacturing process, it is difficult to avoid misalignment when the positive electrode, the electrolyte layer, and the negative electrode are stacked. When stacking shift occurs, it becomes difficult to stably manufacture a high-performance and highly reliable battery. Such stacking shift is particularly caused when a large flat plate type battery such as a lithium ion secondary battery for an electric vehicle is manufactured, or when the number of stacked single battery layers composed of a positive electrode, an electrolyte layer, and a negative electrode is increased. When there are many, the influence is great. Therefore, it has been necessary to suppress misalignment using a positioning mechanism or the like.

  On the other hand, according to the electrode 30 of the present embodiment, as shown in FIG. 2, the positive electrode active material layer 33, the separator 37, and the negative electrode active material layer 35 are formed using the non-conductive porous body 31 as a base material. It is formed as a unitary structure. With such an integrated structure, stacking deviation can be significantly reduced as compared to the case where the positive electrode, the electrolyte layer, and the negative electrode are each formed and then stacked. In particular, it is possible to completely avoid the stacking deviation that may occur in the single cell layer. Therefore, a high-performance and highly reliable battery can be obtained stably.

  As shown in FIG. 4A, the non-conductive porous body 31 used in the electrode 30 of the present embodiment has a uniform material, porosity, and average pore diameter in the thickness direction. There may be. Further, as shown in FIG. 4B, a porous body having a different material in the thickness direction, a porosity, and an average diameter of the pores (for example, a porous body 31 ′ having a laminated structure) may be used. Good. In this case, it is preferable to form an active material layer by holding the active material in the surface layer portion 311 of the porous body 31 ′ having a laminated structure, and to form a separator using the central portion 312. Furthermore, the porous body 31 ′ having a laminated structure preferably has a form in which the porosity of the central portion 312 in the thickness direction is smaller than the porosity of the surface layer portion 311. By adopting such a configuration, the active material is less likely to penetrate into the central portion 312 having a relatively low porosity, and thus a more reliable function as a separator can be obtained. Moreover, the film thicknesses of the positive electrode active material layer and the negative electrode active material layer can be made uniform. For this reason, the current density distribution in the planar direction of the electrode becomes uniform, and a battery that is not easily deteriorated can be obtained.

  Preferably, in the porous body 31 ′ having a laminated structure, the average diameter of the pores existing in the central portion 312 in the thickness direction is smaller than the average diameter of the pores existing in the surface layer portion 311. By adopting such a configuration, a solution containing an active material is less likely to penetrate into the central portion 312 having a relatively low porosity, and thus a more reliable function as a separator can be obtained. Moreover, the film thicknesses of the positive electrode active material layer and the negative electrode active material layer can be made uniform. For this reason, the current density distribution in the planar direction of the electrode becomes uniform, and a battery that is not easily deteriorated can be obtained.

  In the porous body 31 ′ having a laminated structure, the central portion 312 and the surface layer portion 311 in the thickness direction may be made of materials having different hydrophobicity / hydrophilicity. As will be described later, the electrode of the present embodiment is manufactured, for example, by impregnating and applying a slurry containing an active material to the surface layer portion of a porous body. At this time, when applying a slurry using water or a water-soluble solvent, the central portion 312 in the thickness direction is made of a hydrophobic material, and the surface layer portion 311 is made of a hydrophilic material. Is preferred. By doing so, the active material is held in the surface layer portion 311, but the solution containing the active material does not easily penetrate into the central portion 312 in the thickness direction. For this reason, a more reliable function as a separator can be obtained. At this time, the porosity or the average diameter of the holes in the central portion 312 in the thickness direction is more preferably smaller than the porosity or the average diameter of the holes in the surface layer portion 311.

(Non-conductive porous material)
The non-conductive porous body 31 can be formed using, for example, a nonwoven fabric. By using a nonwoven fabric, it becomes easy to produce an electrode and the porosity can be easily adjusted by pressing. The nonwoven fabric is formed by overlapping fibers in different directions. Non-conductive materials made of resin are used for the nonwoven fabric. For example, polyolefin resins such as polypropylene and polyethylene, ester resins such as polyethylene terephthalate and polyethylene naphthalate, cellulose resins such as cellulose and triacetyl cellulose, nylon, etc. Of fibers can be applied. Among these, polyolefin-based resins and cellulose-based resins are preferable because they have high resistance to battery operating environments and can improve the long-term reliability of the battery. The non-conductive porous body 31 may be formed using a material other than the nonwoven fabric. As a material other than the nonwoven fabric, a woven fabric made of a resin (for example, polypropylene, polyethylene, polyethylene terephthalate) or the like can be considered. Thus, the structure as described above can be achieved by using a resin woven or non-woven fabric that is malleable and ductile, relatively light and strong.

  Further, a porous body (nonwoven fabric) 31 ′ having a laminated structure as shown in FIG. The method for producing the nonwoven fabric 31 ′ having a laminated structure is not particularly limited, and the nonwoven fabric constituting the surface layer portion 311 and the center portion 312 can be laminated by, for example, heat fusion treatment, heat embossing, hydroentanglement treatment, or the like. .

  In addition, the nonwoven fabric which can be used for this embodiment may be one in which a functional group such as a sulfonic acid group, an alkylene group or a carbonate group is introduced on the fiber surface. Since such a functional group has a coordination property with respect to a cation, it has a function of accelerating the movement of the cation of the electrolyte when used as a separator. In particular, it is preferable to introduce a nonwoven fabric in which these functional groups are introduced on the fiber surface as the nonwoven fabric constituting the central portion of the laminated nonwoven fabric. The method for introducing a functional group onto the fiber surface is not particularly limited. For example, a sulfonic acid group can be introduced by immersing a non-woven fabric in a bath of concentrated sulfuric acid and carrying out sulfonation treatment.

  In addition, although there is no restriction | limiting in particular about the thickness of each active material layer 33 and 35 and the separator 37, From a viewpoint of suppressing electronic resistance, the thickness of each active material layer 33 and 35 is about 1-120 micrometers. It is more preferable that it is about 50-100 micrometers. Further, the thickness of the separator 37 at the center is preferably 5 to 100 μm, and more preferably 10 to 50 μm. If the thickness of the separator 37 is 5 μm or more, the electrolyte retainability is good, and if it is 100 μm or less, the resistance is hardly increased excessively.

  The size of the electrode is determined according to the intended use of the battery. For example, if it is used for a large battery that requires a high energy density, an electrode having a large area is used. The lithium ion secondary battery according to the present embodiment is preferably a large flat stacked battery, and the size of the electrode is, for example, a long side of 100 mm or more, preferably 100 mm × 100 mm or more, more preferably. Is 200 mm × 200 mm or more.

  In the present specification, components (including not only active materials but also binders and conductive assistants) that can be held in the pores of the porous body may be collectively referred to as “electrode constituent materials”.

(Active material)
A conventionally well-known thing can be used as an active material.

As the positive electrode active material, for example, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Co—Mn) O _2, and lithium-such as those in which a part of these transition metals are substituted with other elements Examples include transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds. In some cases, two or more positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material from the viewpoint of capacity and output characteristics. Of course, positive electrode active materials other than those described above may be used.

Examples of the negative electrode active material include carbon materials such as graphite (graphite), soft carbon, and hard carbon, lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ), metal materials, lithium alloy negative electrode materials, and the like. Is mentioned. In some cases, two or more negative electrode active materials may be used in combination. Preferably, from the viewpoint of capacity and output characteristics, a carbon material or a lithium-transition metal composite oxide is used as the negative electrode active material. Of course, negative electrode active materials other than those described above may be used.

  The average particle diameter of each active material is not particularly limited, but is preferably 1 to 25 μm from the viewpoint of high output.

  The amount of the positive electrode active material and the negative electrode active material is not particularly limited, but is preferably in the range of 50 to 99% by mass, more preferably 70 to 97%, and still more preferably 80 to 95% based on the total amount of the electrode constituent materials. It is.

(Other additives)
The active material is not only retained in the pores of the porous material in the active material layer used in the electrode of the present embodiment, but other additives (for example, a binder (binder), a conductive aid, It is also preferred that electrolyte salt (lithium salt, ion conductive polymer, etc.) is retained.

  Although it does not specifically limit as a binder, For example, the following materials are mentioned. Polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), isoprene Rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and its hydrogenated product, styrene / isoprene / styrene block copolymer and its hydrogenated product, etc. Thermoplastic polymer, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Tet Fluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyfluorinated Fluorine resin such as vinyl (PVF), vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-TFE-based fluorine) Rubber), vinylidene fluoride-pentafluoropropylene-based fluoro rubber (VDF-PFP-based fluoro rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluoro rubber (VDF-PFP-TFE fluoro rubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluoro rubber (VDF-PFMVE-TFE fluoro rubber), vinylidene fluoride-chlorotrifluoroethylene fluoro rubber (VDF) Vinylidene fluoride fluororubbers such as (-CTFE fluororubber) and epoxy resins. Among these, polyvinylidene fluoride, polyimide, styrene / butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable. These suitable binders are excellent in heat resistance, have a very wide potential window, are stable at both the positive electrode potential and the negative electrode potential, and can be used for the active material layer. These binders may be used independently and may use 2 or more types together.

  The amount of the binder is not particularly limited as long as it can bind the active material or the like, but is preferably 0.5 to 15% by mass, more preferably based on the total amount of the electrode constituent materials. Is 1-10 mass%.

  In addition, as described above, examples of the additive include a conductive additive, an electrolyte salt (lithium salt), and an ion conductive polymer.

  The conductive assistant refers to an additive that is blended in order to improve the conductivity of the positive electrode active material layer or the negative electrode active material layer. Examples of the conductive assistant include carbon materials such as carbon black such as acetylene black, graphite, and vapor grown carbon fiber. When the active material layer contains a conductive additive, an electronic network inside the active material layer is effectively formed, which can contribute to improvement of the output characteristics of the battery. The content of the conductive auxiliary is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and further preferably 4 to 10% by mass with respect to the total amount of the electrode constituent material.

Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like.

  Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers.

[Electrode manufacturing method]
The electrode manufacturing method of the present embodiment includes a step of preparing a non-conductive porous body, a step of impregnating and applying a positive electrode active material to a surface layer portion of one surface of the porous body, and the porous body A step of impregnating and applying a negative electrode active material to the surface layer part of the other surface, leaving an uncoated part at the center in the thickness direction, and the porous body impregnated and coated with the positive electrode active material and the negative electrode active material Pressing. By using such a process, the electrode of this embodiment can be efficiently manufactured.

As a preferred embodiment for producing the electrode of this embodiment, as shown in FIG. 5, first, a non-conductive porous body is prepared. The material of the non-conductive porous body is as described above. Preferably, the nonwoven fabric which is a non-conductive porous body has a basis weight of 5 to 30 g / m ² , more preferably 5 to 15 g / m ² . Moreover, the porosity of the nonwoven fabric is preferably 90% or more, and more preferably 95% or more. When the basis weight and the porosity of the nonwoven fabric are in the above ranges, the active material can be efficiently impregnated and an active material layer having a uniform thickness can be formed. Moreover, the basis weight of an uncoated part increases after pressing, and a basis weight that can suitably function as a separator can be obtained. The thickness of the nonwoven fabric is not particularly limited, but is preferably 300 to 600 μm, more preferably 300 to 500 μm. If it is the said range, the active material layer and separator of appropriate thickness can be formed.

When a non-woven fabric having a laminated structure is used as the non-conductive porous body, the basis weight of the surface layer portion is preferably 5 to 30 g / m ² , more preferably 5 to 15 g / m ² . Further, the porosity of the surface layer portion is preferably 90% or more, and more preferably 95% or more. The basis weight of the central part is preferably 30 to 100 g / m ² , more preferably 30 to 50 g / m ² . The porosity of the central part is preferably 40 to 70%, more preferably 40 to 50%. When the weight per unit area and the porosity are within the above ranges, the slurry containing the active material in the central part is less likely to be impregnated, and a more reliable function as a separator can be obtained.

  When using the nonwoven fabric of laminated structure, the thickness of a surface layer part becomes like this. Preferably it is 50-150 micrometers, and the thickness of a center part becomes like this. Preferably it is 100-300 micrometers.

  Next, an electrode slurry (a slurry containing a positive electrode active material and a slurry containing a negative electrode active material) containing an electrode constituent material (for example, an active material and a conductive additive) and a solvent is prepared. The kind of solvent and the mixing means are not particularly limited, and conventionally known knowledge can be referred to as appropriate. As an example of the solvent, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylformamide, water and the like can be used. When an aqueous solvent such as water is used, for example, carboxymethyl cellulose (CMC) may be added.

And the slurry containing a negative electrode active material is apply | coated to the other surface to one side of the slurry nonwoven fabric containing a positive electrode active material, and it is made to dry. The basis weight when applying the slurry containing the active material is not particularly limited, but is preferably ² to ²⁰ g / m ² . The coating method is not particularly limited as long as a coating thickness of about 100 μm can be obtained. For example, knife coater method, gravure coater method, screen printing method, Mayer bar method, die coater method, reverse roll coater method, inkjet Method, spray method, roll coater method and the like.

  The coating thickness of the slurry containing the active material is not particularly limited, but is preferably 50 to 150 μm, particularly preferably about 100 μm. At this time, the thickness of the uncoated portion is preferably controlled to 100 to 300 μm, particularly preferably about 200 μm. However, when the porous body 31 ′ having a laminated structure as shown in FIG. 4B is used, the coating thickness of the slurry is controlled to be equal to or less than the thickness of the surface layer portion 311. By using a porous body having a porosity of the surface layer portion larger than that of the central portion, the thickness of the active material layer and the separator portion can be more accurately controlled, and the possibility of a short circuit can be avoided. . At this time, the slurry is prepared using a water-soluble solvent such as water or NMP, and the porous body 31 ′ having a laminated structure is composed of a hydrophilic nonwoven fabric in the surface layer portion and a hydrophobic nonwoven fabric in the central portion. Is more preferable.

  Next, the applied slurry is dried to remove the solvent. The drying method and conditions are not particularly limited. The drying temperature is, for example, 20 to 80 ° C., and the drying time is, for example, 2 seconds to 50 hours.

  Thereafter, pressing is performed to obtain an electrode in which the positive electrode active material layer, the separator, and the negative electrode active material layer are integrated. The pressing means is not particularly limited, and conventionally known means can be appropriately employed. If an example of a press means is given, a calendar roll, a flat plate press, etc. will be mentioned.

  In the electrode thus obtained, the thickness of the positive electrode active material layer and the negative electrode active material layer is preferably 1 to 120 μm, and preferably 50 to 100 μm. Moreover, the thickness of the part of a separator becomes like this. Preferably it is 5-100 micrometers, More preferably, it is 10-50 micrometers.

  FIG. 6 is a schematic cross-sectional view of an electrode 40 used in the lithium ion secondary battery 10 according to another embodiment. In the electrode 40 according to the present embodiment, as shown in FIG. 6, current collectors (a positive electrode current collector 34 a and a negative electrode current collector 34 b) are stacked on the surfaces of the positive electrode active material layer 33 and the active material negative electrode layer 35. be able to.

  The thickness of the current collectors 34a and 34b is not particularly limited.

  The current collectors 34a and 34b can be formed using a normal metal foil or the like, or can be formed using a vacuum process. Specifically, it can be formed by any method such as sputtering, vapor deposition, ion plating and thermal spraying. Examples of the sputtering method include an electron cyclotron resonance sputtering method, a radio frequency (RF) sputtering method, a magnetron sputtering method, a counter target sputtering method, a mirrortron sputtering method, and an ion beam sputtering method, but are not limited thereto. . Examples of the vapor deposition method include CVD (chemical vapor deposition method) and PVD (physical vapor deposition method). Examples of CVD include, but are not limited to, thermal CVD, plasma CVD, photo CVD, epitaxial CVD, and atomic layer CVD. Examples of PVD include, but are not limited to, sputtering, pulsed laser deposition, vacuum deposition, ion plating, molecular beam epitaxy, electron beam deposition, and thermal spraying. In the electrode 40 of this embodiment, at least one of the positive electrode current collector 34a and the negative electrode current collector 34b is preferably formed by a method such as sputtering, vapor deposition, ion plating, or thermal spraying, and more preferably by vapor deposition. By forming a metal film using a method such as sputtering, vapor deposition, ion plating, and thermal spraying, the current collector function can be provided, and the current collector, active material layer, and separator are integrated. Can do. Therefore, the effect of preventing the stacking deviation can be improved. When the current collector is formed by vapor-depositing a metal, the thickness of the vapor-deposited metal film is preferably 1 μm or less.

  Specifically, examples of the metal include aluminum, nickel, iron, stainless steel, titanium, copper, and other alloys. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil by which aluminum is coat | covered on the metal surface may be sufficient. Among these, aluminum, stainless steel, and copper are preferable from the viewpoints of electronic conductivity and battery operating potential.

  FIG. 7 is a schematic cross-sectional view of an electrode 60 used in the lithium ion secondary battery 10 according to another embodiment. As shown in FIG. 7, the electrode 60 according to the present embodiment has a conductive property between the positive electrode current collector 34 a and the positive electrode active material layer 33 or between the negative electrode current collector 34 b and the negative electrode active material layer 35. A primer layer 38 is further formed. The conductive prime layer 38 may be formed on either the positive electrode side or the negative electrode side, or may be formed on both the positive electrode side and the negative electrode side as shown in FIG. As described above, the configuration further including the conductive primer layer 38 can significantly improve the electron conductivity in the direction perpendicular to the surface of the electrode. Further, since the conductive primer layer 38 also has a function as an adhesive that improves the adhesion between the current collectors 34a and 34b and the active material layers 33 and 35, the current collectors 34a and 34b and the active material The contact resistance between the layers 33 and 35 decreases, and a high output can be expected when configured as a battery.

(Conductive primer layer)
The conductive primer layer 38 is preferably a resin layer containing a resin, a conductive material, and a dispersion material. Preferably, the conductive primer layer comprises a chlorine containing polymer. Specific examples of the chlorine-containing polymer include, for example, polyvinyl chloride (PVC), polyvinylidene chloride (PVdC), chlorinated polyethylene, vinyl chloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride. -Propylene copolymer, vinyl chloride-styrene copolymer, vinyl chloride-isobutylene copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-styrene-maleic anhydride terpolymer, vinyl chloride-styrene- Acrylonitrile terpolymer, vinyl chloride-butadiene copolymer, vinyl chloride-isoprene copolymer, vinyl chloride-chlorinated propylene copolymer, vinyl chloride-vinylidene chloride-vinyl acetate terpolymer, vinyl chloride- Maleic acid ester copolymer, vinyl chloride-methacrylic acid ester copolymer, vinyl chloride Acrylonitrile copolymer, vinyl chloride - like various vinyl ether copolymers. Further, blends of these chlorine-containing polymers with each other, or synthetic resins not containing these chlorine-containing polymers and chlorine, such as acrylonitrile-styrene copolymer, acrylonitrile-styrene-butadiene terpolymer, ethylene-vinyl acetate. Examples thereof include a copolymer, an ethylene-ethyl (meth) acrylate copolymer, a blended product with polyester, and the like. These chlorine-containing polymers may be used as they are, or in the form of a solution or latex.

  From the viewpoint of adhesion between the current collector and the active material layer, the chlorine-containing polymer is preferably a polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene, or a copolymer containing polyvinylidene chloride (polyvinylidene chloride copolymer). More preferably, it is a polyvinylidene chloride or a copolymer containing vinylidene chloride. More preferred is a copolymer containing vinylidene chloride. In particular, it is preferable to use a latex of a copolymer containing vinylidene chloride.

  Furthermore, the conductive primer layer includes a conductive material and a dispersing material for dispersing the conductive material.

  Examples of the conductive material include, for example, at least one selected from the group consisting of acetylene black, vulcan, black pearl, carbon nanofiber, ketjen black, carbon nanotube, carbon nanohorn, carbon nanoballoon, hard carbon, and fullerene. A seed carbon material is preferred. These carbon materials have a very wide potential window, are stable in a wide range with respect to both the positive electrode potential and the negative electrode potential, and are excellent in conductivity. Also, since the carbon material is very lightweight, the increase in mass is minimized. Furthermore, since carbon materials are often used as conductive aids for electrodes, even if they come into contact with these conductive aids, the contact resistance is very low because of the same material.

  The shape of the carbon material is not particularly limited, and a known shape such as a particle shape, a powder shape, a fiber shape, a plate shape, a lump shape, a cloth shape, or a mesh shape can be appropriately selected.

  The average particle diameter of the carbon material is not particularly limited, but is desirably about 0.01 to 10 μm. In the present specification, “particle diameter” means the maximum distance L among the distances between any two points on the contour line of the conductive filler. As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted. The particle diameters and average particle diameters of the active material particles described above can be defined similarly.

  Specific examples of the dispersing material include, for example, carboxymethyl cellulose; polycarboxylic acids such as fumaric acid, itaconic acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid; a reaction of an isocyanate monomer or an isocyanate prepolymer with a polyester polyol. An acrylic urethane resin obtained by further reacting the product obtained by reacting a (meth) acrylate having a hydroxy group such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate with the product obtained. Carboxymethyl cellulose is preferred.

  The content of the chlorine-containing polymer contained in the conductive primer layer is preferably 30 to 98.9% by mass, more preferably 33 to 97% by mass, where the total of the chlorine-containing polymer, the conductive material, and the dispersing material is 100% by mass. %. The content of the conductive material contained in the conductive primer layer is preferably 1 to 50% by mass, more preferably 2 to 48% by mass, where the total of the chlorine-containing polymer, the conductive material, and the dispersing material is 100% by mass. It is. Furthermore, the content of the dispersing material contained in the conductive primer layer is preferably 0.1 to 20% by mass, more preferably 1 to 19%, where the total of the chlorine-containing polymer, the conductive material and the dispersing material is 100% by mass. % By mass. If it is the above ranges, the effect as a conductive primer layer will be acquired efficiently.

The conductive primer layer may contain other additives in addition to the chlorine-containing polymer, the conductive material, and the dispersion material.

  The conductive primer layer can be manufactured by a conventionally known method. For example, it can be manufactured by using a spray method or a coating method. Specifically, there is a technique in which a slurry containing a chlorine-containing polymer is prepared, and applied and cured. At the time of this coating, it may be prepared with a desired solvent (for example, water, N-methyl-2-pyrrolidone (NMP), etc.) to form a coating solution. Since the specific form of the chlorine-containing polymer used for the preparation of the slurry is as described above, the description thereof is omitted here. Examples of the other components contained in the slurry include a conductive material and a dispersion material, and since specific examples thereof are also as described above, description thereof is omitted here. Alternatively, a mixture obtained by mixing a chlorine-containing polymer and a conductive material, a dispersion material, and other additives by a conventionally known mixing method is formed into a film shape, and then the film is laminated on a current collector. A conductive primer layer is formed.

  Although there is no restriction | limiting in particular also in the thickness of a conductive primer layer, For example, Preferably it is 1-10 micrometers, More preferably, it is 2-9 micrometers.

(Electrolyte layer)
The electrode according to the present embodiment can form a single cell layer in the battery 10 shown in FIG. 1 by forming an electrolyte layer by holding the electrolyte in the separator portion. There is no restriction | limiting in particular in the electrolyte which comprises an electrolyte layer, Polymer electrolytes, such as a liquid electrolyte and a polymer gel electrolyte and a polymer solid electrolyte, can be used suitably. The means for holding the electrolyte in the separator portion is not particularly limited, and for example, means such as impregnation, coating, and spraying can be applied.

The liquid electrolyte is obtained by dissolving a lithium salt as a supporting salt in a solvent. Examples of the solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propionate (MP), methyl acetate (MA), and methyl formate (MF). 4-methyldioxolane (4MeDOL), dioxolane (DOL), 2-methyltetrahydrofuran (2MeTHF), tetrahydrofuran (THF), dimethoxyethane (DME), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) , And γ-butyrolactone (GBL). These solvents may be used alone or as a mixture of two or more. As the supporting salt (lithium salt) is not particularly _{limited, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiSbF 6, LiAlCl 4, Li 2 B 10 Cl 10, LiI, LiBr, LiCl Inorganic acid anion salts such as LiAlCl, LiHF ₂ , LiSCN, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiBOB (lithium bisoxide borate), LiBETI (lithium bis (perfluoroethylenesulfonylimide); And organic acid anion salts such as Li (C ₂ F ₅ SO ₂ ) ₂ N). These electrolyte salts may be used alone or in the form of a mixture of two or more.

On the other hand, the polymer electrolyte is classified into a gel electrolyte containing an electrolytic solution and a polymer solid electrolyte containing no electrolytic solution. The gel electrolyte has a configuration in which the liquid electrolyte is injected into a matrix polymer having Li ⁺ conductivity. As the matrix polymer having Li ⁺ conductivity, for example, a polymer having polyethylene oxide in the main chain or side chain (PEO), a polymer having polypropylene oxide in the main chain or side chain (PPO), polyethylene glycol (PEG), poly Acrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), polyacrylonitrile (PAN), poly (methyl acrylate) (PMA), poly (Methyl methacrylate) (PMMA) etc. are mentioned. In addition, mixtures of the above-described polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, and the like can also be used. Among these, it is desirable to use PEO, PPO and their copolymers, PVdF, PVdF-HFP. In such a matrix polymer, an electrolyte salt such as a lithium salt can be well dissolved.

  The polymer solid electrolyte has a structure in which a supporting salt (lithium salt) is dissolved in the matrix polymer, and does not include an organic solvent that is a plasticizer. Therefore, when the electrolyte layer is composed of a polymer solid electrolyte, there is no fear of liquid leakage from the battery, and the battery reliability can be improved.

  A matrix polymer of a polymer gel electrolyte or a polymer solid electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. are performed on a polymerizable polymer (for example, PEO or PPO) for forming a polymer electrolyte, using an appropriate polymerization initiator. A polymerization treatment may be performed. In addition, the said electrolyte may be contained in the active material layer of an electrode.

  The lithium ion secondary battery described above is characterized by an electrode. Hereinafter, other main components will be described.

[Tab and Lead]
A tab may be used for the purpose of taking out the current outside the battery. The tab is electrically connected to the outermost layer current collector or current collector plate, and is taken out of the laminate sheet which is a battery exterior material.

  The material which comprises a tab in particular is not restrict | limited, The well-known highly electroconductive material conventionally used as a tab for lithium ion secondary batteries can be used. As a constituent material of the tab, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable, and aluminum, copper, and the like are more preferable from the viewpoint of light weight, corrosion resistance, and high conductivity. Is preferred. Note that the same material may be used for the positive electrode tab and the negative electrode tab, or different materials may be used.

  The positive terminal lead and the negative terminal lead are also used as necessary. As the material of the positive terminal lead and the negative terminal lead, a terminal lead used in a known lithium ion secondary battery can be used. It should be noted that the part taken out from the battery outer packaging material 29 has a heat insulating property so as not to affect the product (for example, automobile parts, particularly electronic devices) by contacting with peripheral devices or wiring and causing leakage. It is preferable to coat with a heat shrinkable tube or the like.

[Battery exterior materials]
As the battery exterior material 29, a known metal can case can be used, and a bag-like case using a laminate film containing aluminum that can cover the power generation element can be used. For example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used as the laminate film, but the laminate film is not limited thereto. A laminate film is desirable from the viewpoint that it is excellent in high output and cooling performance, and can be suitably used for a battery for large equipment for EV and HEV.

In addition, said lithium ion secondary battery can be manufactured with a conventionally well-known manufacturing method.

[Appearance structure of lithium ion secondary battery]
FIG. 8 is a perspective view showing the appearance of a flat lithium ion secondary battery which is a typical embodiment of the secondary battery.

As shown in FIG. 8, the flat lithium ion secondary battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for taking out electric power are drawn out from both sides thereof. Yes. The power generation element 57 is encased by the battery outer packaging material 52 of the lithium ion secondary battery 50, and the periphery thereof is heat-sealed. The power generation element 57 is sealed with the positive electrode tab 58 and the negative electrode tab 59 pulled out to the outside. Has been. Here, the power generation element 57 corresponds to the power generation element 21 of the lithium ion secondary battery 10 shown in FIG. 1 described above.
The power generation element 57 includes a positive electrode (positive electrode active material layer) 13, an electrolyte layer 17, and a negative electrode (negative electrode active material layer).
A plurality of single battery layers (single cells) 19 composed of 15 are stacked.

  The lithium ion secondary battery is not limited to a stacked flat shape. The wound lithium ion secondary battery may have a cylindrical shape, or may have a shape that is a flattened rectangular shape by deforming such a cylindrical shape. There is no particular limitation. In the said cylindrical shape thing, a laminate film may be used for the exterior material, and the conventional cylindrical can (metal can) may be used, for example, It does not restrict | limit. Preferably, the power generation element is covered with an aluminum laminate film. With this configuration, weight reduction can be achieved.

  Also, the removal of the tabs 58 and 59 shown in FIG. 8 is not particularly limited. The positive electrode tab 58 and the negative electrode tab 59 may be pulled out from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be divided into a plurality of parts and taken out from each side, as shown in FIG. It is not limited to. Further, in a wound type lithium ion battery, instead of a tab, for example, a terminal may be formed using a cylindrical can (metal can).

  The lithium ion secondary battery is used as a power source for driving a vehicle or an auxiliary power source that requires a high volume energy density and a high volume output density as a large capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, and a hybrid fuel cell vehicle. It can be suitably used.

  In the above embodiment, the lithium ion secondary battery is exemplified as the electric device. However, the present invention is not limited to this, and can be applied to other types of secondary batteries and further to primary batteries. Moreover, it can be applied not only to batteries but also to capacitors.

10, 50 lithium ion secondary battery,
11, 34a positive electrode current collector,
12, 34b negative electrode current collector,
13, 33 positive electrode active material layer,
15, 35 negative electrode active material layer,
17 electrolyte layer,
19 cell layer,
21, 57 power generation element,
25 positive current collector,
27 negative current collector,
29, 52 Battery exterior material,
30, 40, 60 electrodes,
31 Non-conductive porous body,
31 ′ non-conductive porous body having a laminated structure,
32 active material,
32a positive electrode active material,
32b negative electrode active material,
37 separator,
38 conductive primer layer,
58 positive electrode tab,
59 Negative electrode tab,
311 surface layer,
312 Central part.

Claims (9)

  It has a non-conductive porous material as a base material, the positive electrode active material is held in the pores of the surface layer portion on one side of the porous material, and the negative electrode active material is stored in the pores of the surface layer portion on the other side. An electrode that holds a substance.   2. The electrode according to claim 1, wherein the porous body is formed using a nonwoven fabric in which a porosity in a central portion in a thickness direction is smaller than a porosity in a surface layer portion.   The electrode according to claim 2, wherein the porous body has a hydrophobic central portion in the thickness direction and a hydrophilic surface layer portion.   The electrode according to any one of claims 1 to 3, wherein an electrolyte is held at a central portion in a thickness direction of the porous body.   The electrode according to any one of claims 1 to 4, wherein a metal film is deposited as a current collector on the surface on which the positive electrode active material or the negative electrode active material is held.   The electrode according to claim 5, further comprising a conductive primer layer between the metal film and the surface on the side where the positive electrode active material or the negative electrode active material is held.   An electrical device comprising the electrode according to claim 1. Providing a non-conductive porous body;
Impregnating and applying a positive electrode active material to a surface layer portion of one surface of the porous body;
A step of impregnating and applying a negative electrode active material to the surface layer part of the other surface, leaving an uncoated part at the center in the thickness direction of the porous body;
Pressing the porous body impregnated and coated with the positive electrode active material and the negative electrode active material;
A method for producing an electrode, comprising:   The said porous body is a manufacturing method of Claim 8 which is a nonwoven fabric with the porosity of the center part of the thickness direction smaller than the porosity of a surface layer part.

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