JP5768483B2 - Electrodes used in electrical devices - Google Patents

Description

  The present invention relates to an electrode used in an electric device.

  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. Generally, a lithium ion secondary battery has a configuration in which 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 are connected via an electrolyte layer and stored in a battery case. doing.

  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.

  Conventionally, as a process for producing such a positive electrode and a negative electrode, a slurry in which an active material or the like is mixed into a current collector (aluminum foil or the like for a positive electrode, and a copper foil or the like for a negative electrode is generally used) is used. There was a method of applying and drying. In the conventional manufacturing method that requires such a coating process, the shape of the current collector to be used is limited so that the liquid active material slurry does not drip. Mainly flat ones with no holes were common.

  On the other hand, in order to reduce the weight of the current collector that occupies a large proportion of the weight of the entire battery under the present circumstances where higher density is required, the current collector has a porous metal current collector having a plurality of through holes. A body has been proposed (for example, Patent Document 1).

JP-A-11-111272

  However, even when such a porous metal current collector is used, there is a restriction on the hole diameter of the through-hole formed in the current collector so that slurry mixed with an active material or the like does not hang from the through-hole. there were. As a result, there is a problem that the weight of the current collector cannot be reduced. Therefore, an object of the present invention is to provide means for reducing the weight of the current collector and reducing the weight of the electrode.

  Provided is an electrode having an active material layer formed on a current collector having a plurality of through-holes, which includes a non-conductive porous material and an active material held in the pores of the porous material. This solves the problem.

  The active material layer has a non-conductive porous body and has a structure in which the active material is held in the pores of the porous body. As described above, since the active material is held in the pores of the porous body, the slurry in which the active material or the like is mixed does not hang down from the through hole. There are no restrictions on the hole diameter. Therefore, the weight of the current collector can be reduced, and the electrode can be reduced in weight.

FIG. 1 is a schematic cross-sectional view showing a basic configuration of a flat (stacked) non-aqueous electrolyte lithium ion secondary battery, which is a typical embodiment of an electric device. FIG. 2 is an enlarged schematic cross-sectional view of the electrode of the first embodiment used in a stacked lithium ion secondary battery. FIG. 3 is a view showing a preferred embodiment of the electrode manufacturing method of the first embodiment. FIG. 4 is a diagram showing another preferred embodiment of the electrode manufacturing method of the first embodiment. FIG. 5 is an enlarged schematic cross-sectional view of the electrode of the second embodiment, which is used in a stacked lithium ion secondary battery that is not a bipolar type. FIG. 6 is an enlarged schematic cross-sectional view of the electrode of the third embodiment used in a stacked lithium ion secondary battery that is not a bipolar type. FIG. 7 is a perspective view showing the appearance of a flat lithium ion secondary battery which is a typical embodiment of the secondary battery.

  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 differ 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.

  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. With respect to the polymer gel electrolyte and the solid polymer electrolyte, these can be used alone, or the polymer gel electrolyte or the solid polymer electrolyte can be used by impregnating the separator.

  In the following description, a lithium ion battery that is not a bipolar type (internal parallel connection type) will be described with reference to the drawings, but it 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 positive electrode active material layers 13 disposed on both sides of a positive electrode current collector 11 having a plurality of through holes (hereinafter, “positive electrode current collector having a plurality of through holes” is also simply referred to as “positive electrode current collector”). Has a structure. In the negative electrode, negative electrode active material layers 15 are disposed on both sides of a negative electrode current collector 12 having a plurality of through holes (“negative electrode current collector having a plurality of through holes” is also simply referred to as “negative electrode current collector”). It has a structure. 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.

  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.

<Electrode of First Embodiment>
FIG. 2 is an enlarged schematic cross-sectional view of the electrode 35 (positive electrode and negative electrode) of the first embodiment used in the stacked lithium ion secondary battery 10.

  The electrode 35 of the present embodiment is an active material layer 33 (positive electrode active material layer, negative electrode active material layer) formed on a current collector 32 (positive electrode current collector, negative electrode current collector) having a plurality of through holes. Have The active material layer 33 includes a non-conductive porous body 31 and an active material 34 (positive electrode active material, negative electrode active material) held in the pores of the porous body 31. In this specification, the term “current collector” may refer to both a positive electrode current collector and a negative electrode current collector, or may refer to only one of them. Similarly, when describing as "active material layer", both a positive electrode active material layer and a negative electrode active material layer may be pointed out, and only one side may be pointed out. Similarly, when describing as "active material", both a positive electrode active material and a negative electrode active material may be pointed out, and only one side may be pointed out.

  Conventionally, even when a porous metal current collector is used, the diameter of the through hole formed in the current collector is restricted so that slurry mixed with an active material or the like does not drip from the through hole. As a result, the weight of the current collector cannot be reduced, and a battery including an electrode formed with such a current collector cannot be expected to reduce its weight. As a result, there was a problem that the capacity could not be improved and the density could not be increased.

  On the other hand, the active material layer used for the electrode of the present embodiment has a non-conductive porous body, and has a structure in which the active material is held in the pores of the porous body. As described above, since the active material is held in the pores of the porous body, the slurry in which the active material or the like is mixed does not hang down from the through hole. There are no restrictions on the hole diameter. As such, a battery having an electrode formed with such a current collector can significantly reduce its weight, and thus increase its capacity and increase its density. be able to.

  Further, the electrode of the present embodiment includes a current collector having a plurality of through holes as well as a specific active material layer. With such a configuration, the electron conductivity (lateral electron conductivity) toward the positive electrode current collector plate 25 and the negative electrode current collector plate 27 is significantly higher than in the case of using only such a specific active material layer as an electrode. improves. That is, the density of the battery and the lateral electron conductivity of the current collecting layer can be freely controlled.

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

[Current collector]
As the material of the current collector having a plurality of through holes of the present embodiment, for example, metal, carbon, conductive polymer, and the like can be used, and metal is preferably used. As the metal, aluminum, copper, platinum, nickel, tantalum, titanium, stainless steel, and other alloys are usually used.

  Examples of the shape of the through hole of the current collector having a plurality of through holes of the present embodiment include a quadrangle, a rhombus, a turtle shell shape, a hexagon, a round shape, a square shape, a star shape, and a cross shape. For example, there are so-called punching metal sheets in which a large number of holes having such a predetermined shape are formed by pressing, for example, in a staggered arrangement or a parallel arrangement. In addition, a so-called expanded metal sheet or the like in which a sheet having staggered cuts is stretched to form a large number of substantially diamond-shaped through holes can be used.

  The aperture ratio of the current collector having a plurality of through holes of the present embodiment is not particularly limited. As described above, the active material layer according to the present embodiment has a non-conductive porous body, and has a structure in which the active material is held in the pores of the porous body. As described above, since the active material is held in the pores of the porous body, the slurry in which the active material or the like is mixed does not hang down from the through hole. There is no restriction on the hole diameter. However, the lower limit of the aperture ratio of the current collector is preferably 10 area% or more, more preferably 30 area% or more, further preferably 50 area% or more, more preferably 70 area% or more, and further preferably 90 area. % Or more. Thus, in the electrode of this embodiment, a current collector having an aperture ratio of 90 area% or more can also be used. Moreover, as an upper limit, it is 99 area% or less, or 97 area% or less, for example. Thus, a battery with an electrode formed with a current collector having a significantly large aperture ratio can significantly reduce its weight, and thus increase its capacity, high density Can be made.

  Similarly, the opening diameter of the current collector having a plurality of through holes of the present embodiment is not particularly limited, but the lower limit is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 50 μm or more, particularly preferably. Is 150 μm or more. As an upper limit, it is 300 micrometers or less, for example, Preferably, it is about 200 micrometers or less. The opening diameter here is the diameter of the circumscribed circle of the opening. The diameter of the circumscribed circle is obtained by observing the surface of the current collector with a laser microscope or a tool microscope, fitting the circumscribed circle to the opening, and averaging the results.

Moreover, the thickness of the current collector having a plurality of through holes of the present embodiment is preferably 10 to 100 μm, more preferably 15 to 80 μm, and still more preferably 20 to 40 μm. As described above, conventionally, as a process for producing a positive electrode and a negative electrode, there has been a method in which a slurry mixed with an active material or the like is applied to a current collector and dried. When applying the slurry mixed with the active material or the like, it was necessary to pull the current collector with a certain amount of force (for example, about 500 N / mm ² ). For this reason, the current collector itself is required to have a tensile strength, and particularly for large batteries, it is necessary to apply a large area, and the value is large. As a result, the thickness of the current collector increased, resulting in an increase in battery weight and a decrease in capacity. On the other hand, when producing the electrode of this embodiment, it is not necessary to go through a conventional coating / drying process. Therefore, it is not necessary to have the tensile strength required in the coating / drying process, and accordingly, the thickness of the current collector can be reduced if necessary, and the design flexibility of the current collector can be reduced. Will improve.

[Active material layer (positive electrode active material layer, negative electrode active material layer)]
The active material layer used for the electrode of the present embodiment includes a non-conductive porous material and an active material retained in the pores of the porous material, and other additives as necessary. In addition.

(Non-conductive porous material)
As shown in FIG. 2, the active material layer 33 is formed by holding a granular active material 34 on a nonwoven fabric 31 that is a non-conductive porous body. The nonwoven fabric 31 holds the active material 34 while functioning as a three-dimensional skeleton of the active material layer 33. By encapsulating the active material 34 in the nonwoven fabric 31, the Young's modulus of the active material layer 33 is increased, battery performance deterioration due to expansion and contraction of the active material 34 during durability deterioration can be suppressed, and battery life can be extended. It becomes possible. The porosity of the nonwoven fabric 31 is not particularly limited, but is preferably 70% to 98%.

  The nonwoven fabric 31 is formed by overlapping fibers in different directions. For the non-woven fabric 31, a non-conductive material made of resin is used. For example, fibers such as polypropylene, polyethylene, polyethylene terephthalate, cellulose, and nylon can be applied. In addition, forms other than a nonwoven fabric may be applied as a porous body. As a form 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.

  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 fluorine rubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluorine rubber (VDF-PFMVE-TFE fluorine rubber), vinylidene fluoride-chlorotrifluoroethylene fluorine 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.

  Although there is no restriction | limiting in particular also about the thickness of each active material layer, From a viewpoint of suppressing electronic resistance, it is preferable that the thickness of each active material layer is about 1-120 micrometers.

[Electrode manufacturing method]
The electrode manufacturing method according to the present embodiment includes a step of disposing an active material layer on a current collector having a plurality of through holes, and the active material layer includes a non-conductive porous body and the porous material. Active material held in the pores of the material.

  As a preferred embodiment for producing the electrode of the present embodiment, as shown in FIGS. 3 and 4, first, an electrode slurry containing an electrode constituent material (for example, active material, conductive additive) and a solvent (for example, NMP). S is prepared in the impregnation tank 45. Next, the nonwoven fabric 31 is conveyed by the guide rolls 41, 42, and 43, is passed through the impregnation tank 45, and the nonwoven fabric 31 is impregnated with the electrode slurry S (step S11). Next, the electrode slurry S that has adhered excessively is scraped off by passing between the two rolls 44 with gaps adjusted (step S12). Then, it is dried in a drying furnace, the density is adjusted by rolling, and an active material layer (electrode layer) is formed (step S13). Then, the electrode of this embodiment can be manufactured by arrange | positioning this active material layer (electrode layer) on the electrical power collector which has several through-holes. In addition, it is also preferable to adjust the thickness of an electrode by crimping after arrangement.

  As described above, conventionally, even when a porous metal current collector is used, the diameter of the through hole formed in the current collector is prevented so that the slurry mixed with the active material does not hang from the through hole. There were restrictions. Furthermore, it is necessary to adjust the viscosity of the electrode slurry so that it does not hang from the through hole (that is, it is necessary to adjust the viscosity so that it does not hang from the through hole). It was restricted. On the other hand, when manufacturing the electrode of the first embodiment, it is not necessary to be particularly concerned about the viscosity of the electrode slurry S, and can be applied to a current collector having a plurality of through holes in a wide viscosity range. Here, the viscosity of the electrode slurry S in the present embodiment is preferably 500 to 10,000 mPa · s, more preferably 800 to 9000 mPa · s, and still more preferably 1000 to 8000 mPa · s.

  In addition, by passing the impregnating tank 45 and impregnating the nonwoven fabric 31 with the electrode slurry S in this way, it is possible to increase the production speed while suppressing the equipment cost, and to minimize the cost increase. A material layer (electrode layer) can be manufactured. Moreover, in this embodiment, since the electrode slurry S is dried in a state of being held on the nonwoven fabric 31, both sides can be dried and the drying time is shortened. Moreover, the cost of a porous body can be suppressed to the minimum by using the nonwoven fabric 31 as a porous body.

  As another embodiment, in order to impregnate the nonwoven fabric 31 with the electrode slurry S, it is also possible to apply the electrode slurry S from both sides of the nonwoven fabric 31 using, for example, a double-sided die coater. Thereby, a highly accurate active material layer can be created and battery performance can be improved. Further, since the electrode slurry S is dried while being held on the non-conductive nonwoven fabric 31, the electrode constituent material is adsorbed to the nonwoven fabric 31 having a large surface free energy, and uneven distribution of the electrode constituent material is suppressed even when high-temperature drying is performed. In addition, the drying time can be shortened without causing deterioration of the battery performance.

  As another embodiment, in order to impregnate the nonwoven fabric 31 with the electrode slurry S, for example, without impregnating the nonwoven fabric 31 with the guide rolls 41, 42, 43 and the like, There is also a method of impregnating the tank 45. With such a method, it is not necessary to prepare a separate apparatus, and the electrode constituent material can be held by a simple method.

  The electrode of the first embodiment described above has the following effects.

  The active material layer in the electrode of the first embodiment has a non-conductive porous body, and has a structure in which the active material is held in the pores of the porous body. As described above, since the active material is held in the pores of the porous body, the slurry in which the active material or the like is mixed does not hang down from the through hole. There are no restrictions on the hole diameter. Therefore, the weight of the current collector can be reduced, and the electrode can be reduced in weight. As a result, a battery including an electrode formed with such a current collector can significantly reduce its weight, and thus increase its capacity and increase its density. it can.

  Moreover, the electrode of this embodiment of the first embodiment includes not only a specific active material layer but also a current collector. With such a configuration, the electron conductivity in the lateral direction is significantly improved as compared with a mode in which only such a specific active material layer is used as an electrode. As a result, it is possible to freely control the density of the battery and the lateral electron conductivity of the current collecting layer.

<Electrode of Second Embodiment>
FIG. 5 is an enlarged schematic cross-sectional view of the electrode 65 (positive electrode and negative electrode) of the second embodiment used in the stacked lithium ion secondary battery 10. The electrode 65 of the second embodiment also has an active material layer 63 formed on a current collector 62 having a plurality of through holes, and the active material layer 63 includes a non-conductive porous body 61 and the above-described active material layer 63. It is the same as the electrode 35 of the first embodiment in that it includes the active material 64 held in the pores of the porous body. However, as shown in FIG. 5, the difference is that a conductive primer layer 66 is further formed between the current collector 62 and the active material layer 63. As described above, the configuration further including the conductive primer layer 66 has the following effects. That is, in addition to the effects described in the electrode of the first embodiment, electrons in a direction (longitudinal direction) in which one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto are opposed to each other with the electrolyte layer 17 interposed therebetween. The conductivity is significantly improved (see FIG. 1). In addition, since the conductive primer layer 66 also has a function as an adhesive that improves the adhesion between the current collector 62 and the active material layer 63, the contact between the current collector 62 and the active material layer 63 is improved. When the resistance decreases and the battery is configured, a high output can be expected.

(Conductive primer layer)
The conductive primer layer includes a resin layer having conductivity. Suitably, a conductive primer layer consists of a resin layer which has electroconductivity. In order for the conductive primer layer to have conductivity, specific modes include 1) a mode in which the polymer material constituting the resin is a conductive polymer, and 2) the resin layer is a resin and a conductive filler (conductive material). The form containing is mentioned.

  The conductive polymer is selected from materials that are conductive and have no conductivity with respect to ions used as charge transfer media. These conductive polymers are considered to be conductive because the conjugated polyene system forms an energy band. As a typical example, a polyene-based conductive polymer that has been put into practical use in an electrolytic capacitor or the like can be used. Specifically, polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, polyoxadiazole, or a mixture thereof is preferable. Polyaniline, polypyrrole, polythiophene, and polyacetylene are more preferable from the viewpoint of electronic conductivity and stable use in the battery.

  The conductive filler (conductive material) used in the form 2) is selected from materials having conductivity. Preferably, from the viewpoint of suppressing ion permeation in the resin layer having conductivity, it is desirable to use a material that does not have conductivity with respect to ions used as the charge transfer medium.

  Specific examples include, but are not limited to, aluminum materials, stainless steel (SUS) materials, carbon materials, silver materials, gold materials, copper materials, and titanium materials. These conductive fillers may be used alone or in combination of two or more. Moreover, these alloy materials may be used. Silver material, gold material, aluminum material, stainless steel material, carbon material is preferable, and carbon material is more preferable. Further, these conductive fillers (conductive materials) may be those obtained by coating a conductive material (the above-mentioned conductive material) around the particle ceramic material or resin material with plating or the like.

  Examples of the carbon material include 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. Can be mentioned. 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. When carbon materials are used as conductive particles, it is possible to reduce the compatibility of the electrolyte by applying a hydrophobic treatment to the surface of the carbon, making it difficult for the electrolyte to penetrate into the current collector holes. is there.

  The shape of the conductive filler (conductive 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. For example, when it is desired to impart conductivity to a resin over a wide range, it is preferable to use a particulate conductive material. On the other hand, when it is desired to further improve the conductivity in a specific direction in the resin, it is preferable to use a conductive material having a certain direction in the shape of a fiber or the like.

  Although the average particle diameter of a conductive filler is not specifically limited, It is desirable that it is about 0.01-10 micrometers. 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. Particle diameters and average particle diameters of active material particles to be described later can be defined similarly.

  In the case where the resin layer includes a conductive filler, the resin forming the resin layer may include a non-conductive polymer material that binds the conductive filler in addition to the conductive filler. Good. By using a non-conductive polymer material as the constituent material of the resin layer, the binding property of the conductive filler can be increased and the reliability of the battery can be increased. The polymer material is selected from materials that can withstand the applied positive electrode potential and negative electrode potential.

  Examples of polymer materials having no electrical conductivity are preferably polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyethernitrile (PEN), polyimide (PI), polyamide ( PA), polyamideimide (PAI), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC) ), Polyvinylidene fluoride (PVdF), polyvinylidene chloride (PVDC), or mixtures thereof. These materials have a very wide potential window and are stable to both positive and negative electrode potentials. Moreover, since it is lightweight, it becomes possible to increase the output density of the battery.

  The content of the conductive filler is not particularly limited. In particular, when the resin includes a conductive polymer material and sufficient conductivity can be secured, it is not always necessary to add a conductive filler. However, when the resin is made of only a nonconductive polymer material, it is essential to add a conductive filler in order to impart conductivity. The content of the conductive filler at this time is preferably 5 to 90% by mass, more preferably 30 to 85% by mass, and still more preferably 50 to 90% by mass with respect to the total mass of the nonconductive polymer material. 80% by mass. By adding such an amount of conductive filler to the resin, sufficient conductivity can be imparted to the non-conductive polymer material while suppressing an increase in the mass of the resin.

  The conductive primer layer may contain other additives in addition to the conductive filler and the resin, but preferably includes the conductive filler and the resin.

  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 polymer material is prepared, applied and cured. At the time of this coating, it may be prepared in a desired solvent (for example, NMP) to be in the form of a coating solution. Since the specific form of the polymer material used for the preparation of the slurry is as described above, the description thereof is omitted here. Examples of other components contained in the slurry include conductive fillers. Since specific examples of the conductive filler are also as described above, description thereof is omitted here. Alternatively, it can be obtained by mixing a polymer material, a conductive filler and other additives by a conventionally known mixing method, and molding the resulting mixture into a film. Alternatively, the conductive primer layer may be prepared as a separate layer and disposed on a desired one (for example, a current collector).

  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.

  The electrode manufacturing method according to the second embodiment is also applicable to the method described above, and further includes a step of further forming a conductive primer layer between the current collector and the active material layer. It can be manufactured by a manufacturing method. More specifically, there is a method in which a slurry containing a polymer material and a conductive filler is prepared, and this is applied to a current collector and cured. The method for producing such a conductive primer layer is also as described above, and is particularly preferably formed by applying a coating liquid containing a carbon material and a resin to a current collector and drying. Thus, by further forming a conductive primer layer, the current collector and the active material layer can be easily brought into close contact with each other, and productivity is improved.

  The electrode of the second embodiment described above has the following effects. That is, in addition to the effects described in the electrode of the first embodiment, the electron conductivity in the vertical direction is significantly improved. The conductive primer layer also has a function as an adhesive that improves the adhesion between the current collector and the active material layer. As a result, the contact resistance between the current collector and the active material layer is reduced, and high output can be expected when configured as a battery.

<Electrode of Third Embodiment>
FIG. 6 is an enlarged schematic cross-sectional view of the electrode 75 (positive electrode and negative electrode) of the third embodiment used in the stacked lithium ion secondary battery 10. The electrode 75 of the third embodiment also has an active material layer 73 formed on a current collector 72 having a plurality of through holes, and the active material layer 73 includes a non-conductive porous body 71 and the above-described active material layer 73. The electrode 35 is the same as the electrode 35 of the first embodiment in that it includes the active material 74 held in the pores of the porous body. However, a difference is that the surface of the current collector 72 in contact with the active material layer 73 is subjected to surface chemical treatment and surface roughening treatment in advance, and the surface treatment layer 76 exists. By performing such surface treatment, the contact resistance between the current collector 62 and the active material layer 63 is reduced. In addition, adhesion with the active material layer is also improved. As a result, when configured as a battery, high output can be expected. Further, from the viewpoint that it is not necessary to provide a separate member such as a conductive primer layer, the number of parts is reduced, leading to further weight reduction. As a result, when configured as a battery, it leads to higher density.

  Examples of the surface chemical treatment include acid treatment and chromate treatment. Examples of the surface roughening treatment include electrochemical etching treatment and etching treatment with acid or alkali.

  The electrode of the third embodiment described above has the following effects. That is, in addition to the effects described in the electrode of the first embodiment, the contact resistance between the current collector and the active material layer is reduced. In addition, adhesion with the active material layer is also improved. As a result, when configured as a battery, high output can be expected. In addition, the number of parts is reduced, further leading to weight reduction. As a result, when configured as a battery, it leads to higher density.

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

[Electrolyte layer]
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 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.

  In addition, when an electrolyte layer is comprised from a liquid electrolyte or a gel electrolyte, you may use a separator for an electrolyte layer. Specific examples of the separator include a microporous film made of a polyolefin such as polyethylene or polypropylene, a hydrocarbon such as polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), glass fiber, or the like.

  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.

[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. 7 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. 7, 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 is formed by laminating a plurality of single battery layers (single cells) 19 including a positive electrode (positive electrode active material layer) 13, an electrolyte layer 17, and a negative electrode (negative electrode active material layer) 15.

  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.

  Further, the removal of the tabs 58 and 59 shown in FIG. 9 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 addition, although the said embodiment illustrated the lithium ion battery as an electric device, it is not necessarily restricted to this, It can apply also to another type secondary battery, and also a primary battery. Moreover, it can be applied not only to batteries but also to capacitors.

  Although the said electrode is demonstrated still in detail using a following example and a comparative example, it is not necessarily limited only to a following example.

1. Preparation of Positive Electrode Slurry LiMn ₂ O ₄ (average particle diameter 20 μm) as a positive electrode active material, acetylene black as a conductive additive, and polyvinylidene fluoride (PVDF) as a binder in a mass ratio of 86: 6: 8 By mixing, a positive electrode slurry was obtained. In addition, when the positive electrode slurry was measured using a B-type viscometer, it was 7050 mPa · s (6 rpm).

2. Preparation of Negative Electrode Slurry By mixing graphite (average particle size 10 μm) as a negative electrode active material, acetylene black as a conductive additive, and PVDF as a binder at a mass ratio of 90: 4: 6, the negative electrode slurry is mixed. Obtained. The negative electrode slurry was 6200 Pa · s (6 rpm) as measured using a B-type viscometer.

3. Preparation of Precursor for Conductive Primer Layer A precursor of the conductive primer layer was obtained by mixing acetylene black (average particle size 50 nm) and PVDF at a mass ratio of 70:30.

  The solvents used in the above 1 to 3 were all NMP (N-methylpyrrolidone).

[Example 1]
(Preparation of positive electrode)
To the non-woven fabric (material: polyethylene) which is a non-conductive porous material, the above 1. The positive electrode slurry obtained in (1) was sufficiently impregnated, and then the thickness was controlled using a doctor blade. NMP was fully volatilized by putting it in a drying oven and drying at 100 ° C. By rolling it, a positive electrode active material layer formed in a sheet shape was obtained. The thickness of the positive electrode active material layer formed in this sheet shape was 100 μm.

  Subsequently, 3. on the one side of the positive electrode active material layer formed in this sheet shape. An Al mesh sheet (opening ratio 90%; thickness: 50 μm; opening diameter: 200 μm) was affixed by using the precursor of the conductive primer layer obtained in 1 above as a binder. At this time, the thickness of the conductive primer layer was 10 μm.

  NMP was fully volatilized by putting it in a drying oven and drying at 100 ° C. By rolling it, a positive electrode formed into a sheet shape was obtained. The total thickness of the positive electrode formed in this sheet shape was 105 μm.

(Preparation of negative electrode)
To the non-woven fabric (material: polyethylene) which is a non-conductive porous body, the above 2. The negative electrode slurry obtained in (1) was sufficiently impregnated, and then the thickness was controlled using a doctor blade. NMP was fully volatilized by putting it in a drying oven and drying at 100 ° C. The negative electrode active material layer formed in the sheet form was obtained by rolling it. The thickness of the negative electrode active material layer formed in this sheet shape was 100 μm.

  Subsequently, 3. on the one side of the negative electrode active material layer formed in the sheet shape. A Cu mesh sheet (opening ratio 90%; thickness: 30 μm; opening diameter: 200 μm) was affixed by using the precursor of the conductive primer layer obtained in 1 above as a binder. At this time, the thickness of the conductive primer layer was 10 μm.

  NMP was fully volatilized by putting it in a drying oven and drying at 100 ° C. The negative electrode formed in the sheet form was obtained by rolling it. The total thickness of the negative electrode formed in this sheet shape was 85 μm.

[Comparative Example 1]
Without using the precursor of the conductive primer layer as a binder to the Al mesh sheet used in Example 1, the above 1. When trying to apply the positive electrode slurry obtained in (1), the slurry dropped from the hole, and a sufficient positive electrode could not be obtained.

  In addition, in the Cu mesh sheet used in Example 1, the conductive primer layer precursor is not used as a binder, but the above 2. When an attempt was made to apply the negative electrode slurry obtained in 1), the slurry dropped from the hole, and a sufficient negative electrode could not be obtained.

[Example 2]
A polyethylene microporous membrane (thickness = 25 μm porosity: 55%) was prepared as a separator. Further, as the _{electrolyte, 1M LiPF 6 / (EC:} DEC) (EC: DEC = 1: 1 volume ratio) was prepared. A power generation element was produced by sandwiching the separator between the positive electrode produced in Example 1 and the negative electrode produced in Example 1.

  The obtained power generation element was placed in a bag made of an aluminum laminate sheet as an exterior, and the electrolytic solution prepared above was injected. Under vacuum conditions, the opening of the aluminum laminate sheet bag was sealed so that the current extraction tabs connected to both electrodes were led out to complete the test cell. The thickness of the obtained battery (test cell) was 215 μm.

10, 50 lithium ion secondary battery,
11 A positive electrode current collector (having a plurality of through holes),
12 A negative electrode current collector (having a plurality of through holes),
13 positive electrode active material layer,
15 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,
31, 61, 71 Non-conductive porous body,
41, 42, 43 guide rolls,
44 rolls,
45 impregnation tank,
58 positive electrode tab,
59 Negative electrode tab,
32, 62, 72 current collector (having a plurality of through holes),
33, 63, 73 active material layer,
34, 64, 74 active material,
35, 65, 75 electrodes,
76 Surface treatment layer.

Claims (8)

A current collector having a plurality of through holes;
An active material layer formed on the current collector,
The active material layer may include a non-conductive porous body having pores and an active material held in the porous body the pores in the said as the active material from falling from the holes After being held in the air holes, arranged on the current collector,
The active material is a positive electrode active material or a negative electrode active material,
The positive electrode active material is a lithium-transition metal composite oxide,
A lithium ion secondary battery electrode, wherein a conductive primer layer is further formed between the current collector and the active material layer.   The lithium ion secondary battery electrode according to claim 1, wherein the porous body is a resin woven or non-woven fabric.   The lithium ion secondary battery electrode according to claim 1 or 2, wherein a binder is further held in the pores of the porous body.   The lithium ion secondary battery containing the lithium ion secondary battery electrode of any one of Claims 1-3. Forming an active material layer in the non-conductive porous body having pores by holding the active material in the pores of the porous body so as not to fall from the pores ,
A step of disposing the active material layer on a current collector having a plurality of through holes ;
The active material is a positive electrode active material or a negative electrode active material,
The positive electrode active material is a lithium-transition metal composite oxide,
A method for producing a lithium ion secondary battery electrode, further comprising forming a conductive primer layer between the current collector and the active material layer. The active material layer prepares an electrode slurry containing the active material and a solvent in an impregnation tank,
The porous body of the non-conductive, and conveyed by the guide rolls, the passed through an impregnation bath, formed have a impregnating the electrode slurry into the non-conductive porous material, according to claim 5 The manufacturing method as described in. The active material layer is coated with an electrode slurry containing the active material and a solvent from both sides of the non-conductive porous body,
It has a drying in a state of being held to the electrode slurry in the porous body of the non-conductive, is formed by suppressing the uneven distribution of electrode constituent materials, production method of claim 5.   The manufacturing method of any one of Claims 5-7 in which the said electroconductive primer layer is formed by apply | coating the coating liquid containing a carbon material and resin.