JP2007087758A - Electrode for battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means suppressing increase in internal resistance of a battery in charge/discharge in a high output condition and capable of taking out sufficient current in a lithium ion secondary battery. <P>SOLUTION: An electrode for a battery is formed by carrying an electrode material containing an active material in pores of a plate-like foamed metallic carrier, and the average particle size of the active material is 5 μm or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery electrode. In particular, the present invention relates to an improvement for improving the output characteristics of a battery.

  In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide has been strongly 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), and the development of secondary batteries for motor drive that holds the key to commercialization of these is thriving. Has been done.

  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 includes a positive electrode in which a positive electrode active material or the like is applied to both surfaces of a positive electrode current collector using a binder, and a negative electrode in which a negative electrode active material or the like is applied to both surfaces of a negative electrode current collector using a binder. However, it has the structure connected through an electrolyte layer and accommodated in a battery case.

  The lithium ion secondary battery used as a motor drive power source for automobiles as described above has extremely high output characteristics as compared with consumer lithium ion secondary batteries used in mobile phones, laptop computers, etc. The current situation is that research and development is underway to meet such demands.

Here, as a technique for improving the output characteristics of a lithium ion secondary battery in consideration of mounting in an automobile, for example, a positive electrode active material for a lithium secondary battery containing a Li—Mn—Ni composite oxide, A positive electrode for a lithium secondary battery, wherein an average diameter of primary particles of Li—Mn—Ni composite oxide is 2.0 μm or less and a BET specific surface area is 0.4 m ² / g or more. An active material is disclosed (see Patent Document 1).
JP 2003-68299 A

  According to the technique described in Patent Document 1, a lithium ion secondary battery having excellent discharge capacity characteristics and cycle durability can be provided. This is because, when the average diameter and specific surface area of the Li—Mn—Ni composite oxide, which is the positive electrode active material, are controlled to the above values, the surface area of the positive electrode active material that can come into contact with the electrolytic solution increases. This is probably because the reaction can proceed sufficiently.

  Thus, it is preferable from the viewpoint of increasing the output of the battery to further reduce the particle size of the active material contained in the active material layer of the electrode. However, if the particle size of the active material is reduced too much, there is a problem in that the internal resistance of the battery during charging / discharging under high output conditions increases, and the necessary current cannot be taken out sufficiently.

  Accordingly, an object of the present invention is to provide a means capable of suppressing an increase in internal resistance of a lithium ion secondary battery during charging / discharging under a high output condition and taking out a sufficient current.

  In view of the above problems, the present inventors have eagerly searched for the cause of the increase in internal resistance under high output conditions. As a result, it has been found that such an increase in internal resistance is due to the insufficient formation of a conductive network as the particle size of the active material decreases. Based on this knowledge, the present inventors have increased the content of the active material and conductive auxiliary agent, and increased the density of the active material layer by pressing the electrode in order to sufficiently form a conductive network between the active materials. I tried to make it. However, such a method has a problem that the internal resistance of the battery is increased although the conductive network is sufficiently secured. The present inventors have also eagerly searched for the cause of internal resistance accompanying such a decrease in porosity. As a result, such an increase in internal resistance does not sufficiently supply ions to the active material in the vicinity of the current collector that is farthest from the electrolyte layer because the channel in which ions should diffuse is too narrow in the electrode layer. It was found that this is caused by an increase in diffusion resistance.

  Based on these findings, the present inventors have moved away from the concept of using a current collector-active material layer laminate as a battery electrode to secure a conductive network in the active material layer with a conductive auxiliary agent, The inventors have arrived at a battery electrode having a novel configuration capable of sufficiently securing a channel.

  That is, the present invention is a battery electrode in which an electrode material containing an active material is supported in a void portion of a plate-like foamed metal carrier, and the average particle diameter of the active material is 5 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the increase in the internal resistance of the battery at the time of charging / discharging on high output conditions is suppressed, and the battery which can take out sufficient electric current can be provided.

  Embodiments of the present invention will be described below.

(First embodiment)
(Constitution)
A first aspect of the present invention is a battery electrode in which an electrode material containing an active material is supported in a void portion of a plate-like foamed metal carrier, and the average particle diameter of the active material is 5 μm or less.

  First, the structure of the battery electrode of the present invention will be described with reference to the drawings. In the present invention, the drawings are exaggerated for convenience of explanation, and the technical scope of the present invention is not limited to the forms shown in the drawings. Also, embodiments other than the drawings may be employed.

  FIG. 1 is a cross-sectional view showing an embodiment of a battery electrode of the present invention. The battery electrode 1 in the form shown in FIG. 1 is a bipolar electrode in which a positive electrode 13 is formed on one surface of a current collector 11 and a negative electrode 15 is formed on the other surface. And both the positive electrode 13 and the negative electrode 15 have the structure by which an active material (13c, 15c) is carry | supported by the space | gap part (13b, 15b) of a foam metal support | carrier (13a, 15a). As will be described later, the current collector 11 can be omitted in the battery electrode of the present invention. Further, in the embodiment shown in FIG. 1, only the active material is supported as the electrode material in the void portion of the foamed metal carrier. However, as will be described later, the electrode material may also include other materials.

  The bipolar electrode of the form shown in FIG. 1 can be employed in, for example, a bipolar lithium ion secondary battery (hereinafter also simply referred to as “bipolar battery”). Of course, it may be adopted for other batteries. In the form shown in FIG. 1, both the positive electrode and the negative electrode are battery electrodes of the present invention, but the technical scope of the present invention is not limited to such a form, and either the positive electrode or the negative electrode Embodiments in which only one is the electrode of the present invention can also be included.

  Hereinafter, the configuration of the battery electrode of the present invention will be described by taking as an example a case where it is employed in a lithium ion secondary battery. The battery electrode of this embodiment is characterized in that it has the predetermined structure described above. Therefore, there is no particular limitation on the selection of the foam metal carrier and the electrode material (active material, conductive additive, binder, etc.). Depending on the intended use, it may be selected by appropriately referring to conventionally known knowledge.

[Foamed metal carrier]
The foam metal carrier (13a, 15a) is a carrier composed of a plate-like foam metal. “Foamed metal” is a cork-like metal having a large number of pores inside, and is also referred to as a metal foam. In the battery electrode of the present invention, the foam metal carrier functions as a carrier for supporting the active material (13c, 15c). Further, since it is made of a metal material, it can have a function as a current collector. When the foam metal carrier has a function as a current collector, the conventionally used current collector 11 as shown in FIG. 1 can be omitted. However, in the case of using a bipolar electrode, it is preferable to have a portion corresponding to the current collector 11 because the electrolyte needs to be completely isolated between the positive electrode side and the negative electrode side.

  The material which comprises a foam metal support is not restrict | limited in particular, The metal material currently used as a constituent material of the conventional electrical power collector can be used similarly. Examples of the constituent material of the foam metal carrier include aluminum, nickel, copper, and stainless steel.

  The foaming property of the foamed metal carrier, in other words, the porosity is not particularly limited, and can be appropriately determined in consideration of the amount of the active material supported to obtain a desired battery capacity, desired electrode performance, and the like. However, since the ratio of the volume of the carrier to the electrode volume decreases as the porosity of the foam metal carrier increases, the volume for supporting the active material and the lithium ion diffusion path can be sufficiently secured. From such a viewpoint, the porosity of the foam metal carrier is preferably 90% or more, more preferably 92% or more, and further preferably 95% or more. However, the porosity of the metal foam support is not limited to the forms included in these ranges, and forms outside these ranges can also be adopted. The upper limit value of the porosity of the foam metal carrier is not particularly limited, but is preferably 98% or less in consideration of ease of manufacture and strength. Here, the value obtained from the ratio between the true volume calculated from the true density of the material and the apparent volume is adopted as the value of “the porosity of the foam metal carrier” in the present application.

  The thickness of the foam metal carrier (length “X” shown in FIG. 1) is not particularly limited, and is appropriately determined in consideration of the amount of active material and the like necessary for obtaining a desired battery capacity. sell. However, as the thickness of the foam metal carrier is thinner, the lithium ions contained in the electrode and the electrolyte layer must be diffused in the electrode, the distance is shortened, and the increase in internal resistance can be suppressed. From such a viewpoint, the thickness of the foam metal carrier is preferably 100 μm or less, more preferably 50 μm or less, and further preferably 30 μm or less. However, the thickness of the metal foam support is not limited to the forms included in these ranges, and forms outside these ranges can also be adopted. The lower limit of the thickness of the foam metal carrier is not particularly limited, but is preferably 5 μm or more in consideration of the amount of active material that can be supported, strength, and the like. Here, as the value of “thickness of the foam metal carrier” in the present application, a value measured by a micrometer is adopted.

  In the form shown in FIG. 1, the shape of the voids (13b, 15b) of the foam metal carrier is spherical. However, the shape is not limited to such a form, and the void portion may have any other shape as long as it is a continuous pore structure <a structure in which pores (cells) are connected>.

[Electrode material]
The electrode material contains, as an essential component, an active material that plays a central role in the charge / discharge reaction, and is carried in the void portion of the foam metal carrier described above, as shown in FIG.

  When the electrode of the present invention is used as a positive electrode, the electrode material includes a positive electrode active material. On the other hand, when the electrode of the present invention is used as a negative electrode, the electrode material includes a negative electrode active material.

As the positive electrode active material, for example, a lithium-transition metal composite oxide is preferable, and examples thereof include a Li—Mn composite oxide such as LiMn ₂ O ₄ and a Li—Ni composite oxide such as LiNiO ₂ . In some cases, two or more positive electrode active materials may be used in combination.

  As the negative electrode active material, the above lithium transition metal-composite oxide or carbon is preferable. Examples of carbon include graphite-based carbon materials such as natural graphite, artificial graphite, and expanded graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, and hard carbon. In some cases, two or more negative electrode active materials may be used in combination.

  In the battery electrode of the present invention, the average particle diameter of the active material described above is also defined. That is, the average particle diameter of the active material is 5 μm or less, more preferably 1 μm or less, and still more preferably 0.5 μm or less. When the average particle size of the active material is thus small, the effective surface area of the active material that can participate in the battery reaction (occlusion and release of lithium ions) increases, and the battery reaction can proceed efficiently. As a result, a sufficient current can be secured even under high output conditions, which is preferable. The lower limit of the average particle diameter of the active material is not particularly limited, but is preferably 0.05 μm or more considering that the active material tends to aggregate when it is too small. Here, as the value of “average particle diameter of active material” in the present application, a value measured by a technique called laser diffraction scattering method is adopted.

  The electrode material may contain other substances if necessary. For example, a conductive assistant and a binder are included, but when an electrode for an intrinsic polymer battery described later is prepared, a supporting salt (lithium salt), an ion conductive polymer, and the like can also be included. When an ion conductive polymer is included, a polymerization initiator for polymerizing the polymer may be included.

  A conductive support agent means the additive mix | blended in order to improve the electroconductivity of the electrode material contained in an electrode. Examples of the conductive assistant include carbon black such as acetylene black, ketjen black, and furnace black, carbon powder such as graphite, and various carbon fibers such as vapor grown carbon fiber (VGCF; registered trademark).

  Examples of the binder include polyvinylidene fluoride (PVdF) and a synthetic rubber binder.

Examples of the supporting 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. Here, the polymer may be the same as or different from the ion conductive polymer used in the electrolyte layer of the battery in which the electrode of the present invention is employed, but is preferably the same.

  The polymerization initiator is added to act on the crosslinkable group of the ion conductive polymer to advance the crosslinking reaction. Depending on the external factor for acting as an initiator, it is classified into a photopolymerization initiator, a thermal polymerization initiator and the like. Examples of the polymerization initiator include azobisisobutyronitrile (AIBN), which is a thermal polymerization initiator, and benzyl dimethyl ketal (BDK), which is a photopolymerization initiator.

  The compounding ratio of the components constituting the electrode material is not particularly limited. The blending ratio can be adjusted by appropriately referring to known knowledge about the battery.

[Current collector]
As shown in FIG. 1, the battery electrode of the present invention may have a structure laminated with a current collector. According to such a form, the movement of electrons from the negative electrode to the external load or from the external load to the positive electrode can be performed reliably. The specific form of the current collector used in such a form is not particularly limited, and conventionally known knowledge can be appropriately referred to for the battery current collector. As an example, the current collector is made of the same material as the above-described foam metal carrier, and the thickness thereof is about 1 to 30 μm. As described above, since the foam metal carrier itself is also made of a metal material and has conductivity, it goes without saying that electrons may be exchanged between the electrode and an external load without using a current collector. It is.

[Battery electrode]
The member described above constitutes the battery electrode of the present invention. When it repeats, the electrode for batteries of this invention has the structure by which the electrode material containing an active material is carry | supported by the space | gap part of a metal foam support.

  In a more preferred form, the porosity of the battery electrode itself can also be defined. In other words, the larger the porosity of the battery electrode in the completed state in which the electrode material is supported on the foam metal carrier, the more sufficient the diffusion path of lithium ions contained in the electrode and the electrolyte layer is secured, and the internal resistance of the battery increases. It can be effectively suppressed. From such a viewpoint, the porosity of the battery electrode of the present invention is preferably 50% or more, more preferably 55% or more, and further preferably 60% or more. However, the porosity of the battery electrode is not limited to the forms included in these ranges, and forms outside these ranges can also be adopted. The upper limit value of the porosity of the battery electrode is not particularly limited, but is preferably 80% or less because there is a possibility that the capacity per volume of the electrode may decrease if there are too many voids. Here, as the value of “the porosity of the battery electrode” in the present application, a value obtained by comparing the theoretical volume calculated from the density and mixing ratio of each member with the actual volume is adopted. .

(Production method)
Then, the manufacturing method of the battery electrode of this invention is demonstrated.

  The electrode of the present invention is prepared by, for example, preparing an active material slurry by adding an electrode material containing an active material to a solvent (active material slurry preparation step), and immersing the foam metal carrier in the active material slurry. It can be produced by impregnating the gap of the foam metal carrier with the electrode material (immersion process) and drying the foam metal carrier impregnated with the electrode material (dry process). When an ion conductive polymer is added to the electrode material (active material slurry) and a polymerization initiator is further added for the purpose of cross-linking the ion conductive polymer, it is simultaneously with the drying in the drying step or before the drying. Or you may give a polymerization process later (polymerization process).

  Hereinafter, although such a manufacturing method is demonstrated in detail in order of a process, it is not restrict | limited only to the following form.

[Active material slurry preparation process]
In this step, an electrode material, that is, a desired active material and, if necessary, other components (for example, a conductive additive, a binder, etc.) are mixed in a solvent to prepare an active material slurry. However, when an ion conductive polymer, a supporting salt (lithium salt), and a polymerization initiator are included, the solvent may not be used. Since the specific form of each component blended in the active material slurry is as described in the column of the configuration of the electrode of the present invention, detailed description is omitted here.

  The kind of solvent and the mixing means are not particularly limited, and conventionally known knowledge about electrode production can be appropriately referred to. As an example of the solvent, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylformamide and the like can be used. When adopting polyvinylidene fluoride (PVdF) as a binder, NMP is preferably used as a solvent.

  In this production method, it is also possible to control the porosity of the produced electrode by adjusting the mixing ratio of the solid content and the solvent in the active material slurry prepared in this active material slurry preparation step. Specifically, when it is desired to reduce the porosity of the obtained electrode, it is preferable to increase the blending amount of the solid content in the active material slurry. On the other hand, when it is desired to increase the porosity of the obtained electrode, it is preferable to reduce the amount of solid content in the active material slurry.

[Immersion process]
Subsequently, a foam metal carrier is prepared, and the prepared foam metal carrier is immersed in the active material slurry prepared above. Thus, the electrode material is impregnated in the void portion of the foam metal carrier. The impregnated electrode material remains in the void portion of the foam metal carrier even in the completed electrode, and participates in the battery reaction.

  Since the specific form of the foam metal carrier to be prepared is as described in the column of the configuration of the electrode of the present invention, the detailed description is omitted here.

  An immersion means for immersing the foam metal carrier in the active material slurry is not particularly limited. The conditions during the immersion are not particularly limited. For example, the immersion may be performed at room temperature (about 20 ° C.) to about 70 ° C. for about 10 seconds to 30 minutes under an atmospheric pressure or a vacuum atmosphere.

  Thereafter, the foam metal carrier impregnated with the electrode material is dried. Thereby, the solvent remaining in the foam metal carrier is removed.

  The drying means for drying the foam metal carrier is not particularly limited, and conventionally known knowledge about electrode production can be appropriately referred to. For example, heat treatment is exemplified. Drying conditions (drying time, drying temperature, etc.) can be appropriately set according to the amount of impregnation of the active material slurry and the volatilization rate of the solvent of the slurry.

  When the electrode material contains a polymerization initiator, the ion conductive polymer in the electrode material is cross-linked by a crosslinkable group by further performing a polymerization step.

  The polymerization treatment in the polymerization step is not particularly limited, and conventionally known knowledge may be referred to as appropriate. For example, when the electrode material contains a thermal polymerization initiator (AIBN or the like), the coating film is subjected to heat treatment. When the electrode material contains a photopolymerization initiator (BDK or the like), light such as ultraviolet light is irradiated. In addition, the heat processing for thermal polymerization may be performed simultaneously with said drying process, and may be performed before or after the said drying process.

  The battery electrode of the present invention is completed by the above method. In addition, you may press the obtained electrode to thickness direction as needed. Thereby, the thickness and porosity of the electrode can be controlled.

  Specific means and press conditions for the press treatment are not particularly limited, and can be appropriately adjusted so that the thickness and porosity of the electrode after the press treatment become a desired value. Specific examples of the press process include a hot press machine and a calendar roll press machine.

(Second Embodiment)
In 2nd Embodiment, a lithium ion secondary battery is comprised using said battery electrode of 1st Embodiment. That is, a second aspect of the present invention is a battery including at least one single cell layer in which a positive electrode, an electrolyte layer, and a negative electrode are laminated in this order, and at least one of the positive electrode and the negative electrode is for the battery of the present invention. It is a battery which is an electrode. The electrode of the present invention can be applied to any of a positive electrode, a negative electrode, and a bipolar electrode. A battery including the electrode of the present invention as at least one electrode belongs to the technical scope of the present invention. However, preferably, all of the electrodes constituting the battery are the electrodes of the present invention. By adopting such a configuration, the output characteristics of the battery can be effectively improved. As described above, according to the electrode of the present invention, the current collector can be omitted. Therefore, for example, when the electrode of the present invention is used as a bipolar electrode, in addition to the embodiment shown in FIG. 1, as shown in FIG. 2, the positive electrode which is the electrode of the present invention and the negative electrode which is the electrode of the present invention are used. They can be laminated as they are to form bipolar electrodes.

  The battery of the present invention may be a bipolar lithium ion secondary battery (hereinafter also referred to as “bipolar battery”). FIG. 3 is a cross-sectional view showing a battery of the present invention which is a bipolar battery. Hereinafter, the bipolar battery shown in FIG. 3 will be described in detail as an example, but the technical scope of the present invention is not limited to such a form.

  The bipolar battery 10 of this embodiment shown in FIG. 3 has a structure in which a substantially rectangular battery element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is an exterior.

  As shown in FIG. 3, the battery element 21 of the bipolar battery 10 of this embodiment includes a bipolar electrode in which a positive electrode 13 of the present invention and a negative electrode 15 of the present invention are formed on each surface of a current collector 11. There are a plurality of bipolar electrodes having the configuration shown in FIG. Each bipolar electrode is laminated via an electrolyte layer 17 to form a battery element 21. At this time, each bipolar electrode and the electrolyte layer 17 are arranged so that the positive electrode 13 of one bipolar electrode and the negative electrode 15 of another bipolar electrode adjacent to the one bipolar electrode face each other through the electrolyte layer 17. Are stacked. In FIG. 3, the illustration of voids present in the positive electrode 13 and the negative electrode 15 is omitted.

  The adjacent positive electrode 13, electrolyte layer 17, and negative electrode 15 constitute one unit cell layer 19. Therefore, it can be said that the bipolar battery 10 has a configuration in which the single battery layers 19 are stacked. In addition, an insulating layer 31 for insulating adjacent current collectors 11 is provided on the outer periphery of the unit cell layer 19. The current collector (outermost layer current collector) (11a, 11b) located in the outermost layer of the battery element 21 has a positive electrode active material layer 13 (positive electrode side outermost layer current collector 11a) or a negative electrode only on one side. One of the active material layers 15 (negative electrode side outermost layer current collector 11b) is formed.

  Furthermore, in the bipolar battery 10 shown in FIG. 3, the positive electrode side outermost layer current collector 11a is extended to form a positive electrode tab 25, which is led out from a laminate sheet 29 which is an exterior. On the other hand, the negative electrode side outermost layer current collector 11 b is extended to form a negative electrode tab 27, which is similarly derived from the laminate sheet 29.

  Hereinafter, members constituting the bipolar battery 10 of the present embodiment will be briefly described. However, since the components constituting the electrode are as described above, the description thereof is omitted here. Further, the technical scope of the present invention is not limited to the following forms, and conventionally known forms can be similarly adopted.

[Electrolyte layer]
A liquid electrolyte or a polymer electrolyte can be used as the electrolyte constituting the electrolyte layer 17. The liquid electrolyte has a form in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer. The type is not particularly limited, and various conventionally known electrolytic solutions can be appropriately used. For example, inorganic acid anion salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N or an organic acid anion salt selected from at least one lithium salt (electrolyte salt), cyclic carbonates such as propylene carbonate and ethylene carbonate; dimethyl carbonate; Chain carbonates such as methyl ethyl carbonate and diethyl carbonate; ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; γ-butyrolactone, etc. Lactones; Nitriles such as acetonitrile Esters such as methyl propionate; amides such as dimethylformamide; plasticizers such as aprotic solvents (organic solvents) mixed with at least one selected from methyl acetate and methyl formate ) Can be used. However, it is not necessarily limited to these.

  On the other hand, the polymer electrolyte is classified into a gel electrolyte containing an electrolytic solution and an intrinsic polymer electrolyte containing no electrolytic solution.

  The gel electrolyte is a solid polymer electrolyte having ion conductivity containing the above-mentioned electrolyte solution. Further, the same electrolyte solution was held in a polymer skeleton having no lithium ion conductivity. Also included.

  Examples of the solid polymer electrolyte having ion conductivity include known solid polymer electrolytes such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. These can be used in intrinsic (all solid) polymer electrolytes.

  Examples of the polymer having no lithium ion conductivity used for the polymer gel electrolyte include polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA). . However, it is not necessarily limited to these. PAN, PMMA, and the like, which are in a class with little ion conductivity, can be used as the above polymer having ion conductivity, but are used here as a polymer gel electrolyte. This is exemplified as a polymer having no lithium ion conductivity.

  In the case where the electrolyte layer 17 is composed of a liquid electrolyte or a gel electrolyte, a separator may be used for the electrolyte layer 17. Specific examples of the separator include a microporous film made of polyolefin such as polyethylene or polypropylene. Here, when the electrolyte layer 17 includes a separator, the thinner the separator, the better. This is because the distance of the electrolyte layer 17 to which lithium ions should move by diffusion is shortened, and an increase in the internal resistance of the battery can be effectively suppressed. From such a viewpoint, the thickness of the separator is preferably 20 μm or less, more preferably 15 μm or less, and further 10 μm or less. However, the thickness of the separator is not limited to a form included in these ranges, and a form outside these ranges can also be adopted. The lower limit value of the thickness of the separator is not particularly limited, but is preferably 1 μm or more in consideration of the strength of the electrolyte layer 17 and the like. Here, as the value of “separator thickness” in the present application, a value measured by a micrometer is adopted.

The intrinsic polymer electrolyte has a structure in which a supporting salt (lithium salt) is dissolved in the above solid polymer having ion conductivity, and does not include an organic solvent that is a plasticizer. Therefore, when the electrolyte layer is composed of an intrinsic polymer electrolyte, there is no fear of liquid leakage from the battery, and the battery reliability can be improved.
Here, even when the electrolyte layer is made of an intrinsic polymer electrolyte, the thickness of the electrolyte layer is preferably as small as possible. However, the electrolyte layer may be thicker than the case where the electrolyte layer includes a separator as described above. This is because when the electrolyte layer is made of an intrinsic polymer electrolyte, problems such as a decrease in lithium ion conductivity due to the presence of the separator are unlikely to occur. From such a viewpoint, the thickness of the electrolyte layer when the electrolyte layer 17 is made of an intrinsic polymer electrolyte is preferably 100 μm or less, more preferably 50 μm or less, and further preferably 30 μm or less. However, the thickness of the electrolyte layer made of the intrinsic polymer electrolyte is not limited only to the forms included in these ranges, and forms outside these ranges can also be adopted. The lower limit value of the thickness of the electrolyte layer in such a form is not particularly limited, but is preferably 1 μm or more in consideration of the strength of the electrolyte layer 17 and the like. Here, the value measured by a micrometer is adopted as the value of “the thickness of the electrolyte layer made of the intrinsic polymer electrolyte” in the present application.

[Insulation layer]
In the bipolar battery 10, an insulating layer 31 is usually provided around each single battery layer 19. The insulating layer 31 is provided for the purpose of preventing the adjacent current collectors 11 in the battery from contacting each other and short-circuiting due to a slight unevenness at the end of the battery cell layer 19 in the battery element 21. It is done. The installation of such an insulating layer 31 ensures long-term reliability and safety, and can provide a high-quality bipolar battery 10.

  The insulating layer 31 only needs to have insulating properties, sealing properties against falling off of the solid electrolyte, sealing properties against moisture permeation from the outside (sealing properties), heat resistance under battery operating temperature, etc. Urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber and the like can be used. Of these, urethane resins and epoxy resins are preferred from the viewpoints of corrosion resistance, chemical resistance, ease of production (film forming properties), economy, and the like.

[tab]
In the bipolar battery 10, the tabs (the positive electrode tab 25 and the negative electrode tab 27) electrically connected to the outermost current collector (11 a, 11 b) are taken out of the exterior for the purpose of taking out the current outside the battery. . Specifically, a positive electrode tab 25 electrically connected to the positive electrode outermost layer current collector 11a and a negative electrode tab 27 electrically connected to the negative electrode outermost layer current collector 11b are provided outside the exterior. It is taken out.

  The material of the tabs (the positive electrode tab 25 and the negative electrode tab 27) is not particularly limited, and a known material conventionally used as a tab for a bipolar battery can be used. Examples thereof include aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof. Note that the same material may be used for the positive electrode tab 25 and the negative electrode tab 27, or different materials may be used. As in this embodiment, the outermost layer current collectors (11a, 11b) may be extended to form tabs (25, 27), or a separately prepared tab may be connected to the outermost layer current collector.

  When the current collector is omitted and the electrode of the present invention also exhibits a current collecting function, a positive electrode tab 25 is connected to the positive electrode 13 located in the outermost layer, and a negative electrode tab is connected to the negative electrode 15 located in the outermost layer. 27 is connected.

[Exterior]
In the bipolar battery 10, the battery element 21 is preferably housed in an exterior such as a laminate sheet 29 in order to prevent external impact and environmental degradation during use. The exterior is not particularly limited, and a conventionally known exterior can be used. A polymer-metal composite laminate sheet or the like excellent in thermal conductivity can be preferably used in that heat can be efficiently transferred from a heat source of an automobile and the inside of the battery can be rapidly heated to the battery operating temperature.

(Third embodiment)
In the third embodiment, a plurality of bipolar batteries of the second embodiment are connected in parallel and / or in series to form an assembled battery.

  FIG. 4 is a perspective view showing the assembled battery of the present embodiment.

  As shown in FIG. 4, the assembled battery 40 is configured by connecting a plurality of bipolar batteries described in the second embodiment. Each bipolar battery 10 is connected by connecting the positive electrode tab 25 and the negative electrode tab 27 of each bipolar battery 10 using a bus bar. On one side surface of the assembled battery 40, electrode terminals (42, 43) are provided as electrodes of the entire assembled battery 40.

  A connection method in particular when connecting the some bipolar battery 10 which comprises the assembled battery 40 is not restrict | limited, A conventionally well-known method can be employ | adopted suitably. For example, a technique using welding such as ultrasonic welding or spot welding, or a technique of fixing using rivets, caulking, or the like can be employed. According to such a connection method, the long-term reliability of the assembled battery 40 can be improved.

  According to the assembled battery 40 of this embodiment, since each bipolar battery 10 constituting the assembled battery 40 is excellent in output characteristics, an assembled battery excellent in output characteristics can be provided.

  The bipolar batteries 10 constituting the assembled battery 40 may be connected in parallel to each other, or may be connected in series, or a combination of series connection and parallel connection. May be.

(Fourth embodiment)
In the fourth embodiment, the bipolar battery 10 of the second embodiment or the assembled battery 40 of the third embodiment is mounted as a motor driving power source to constitute a vehicle. As a vehicle using the bipolar battery 10 or the assembled battery 40 as a motor power source, for example, a complete electric vehicle not using gasoline, a hybrid vehicle such as a series hybrid vehicle or a parallel hybrid vehicle, and a fuel cell vehicle, a wheel motor is used. A car driven by

  For reference, FIG. 5 shows a schematic diagram of an automobile 50 on which the assembled battery 40 is mounted. The assembled battery 40 mounted on the automobile 50 has the characteristics as described above. For this reason, the automobile 50 equipped with the assembled battery 40 has excellent output characteristics, and can provide sufficient output even under high output conditions.

  As described above, some preferred embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and various modifications, omissions, and additions can be made by those skilled in the art. . For example, in the above-described second embodiment, a bipolar lithium ion secondary battery (bipolar battery) has been described as an example. However, the technical scope of the battery of the present invention is not limited to a bipolar battery. For example, it may be a lithium ion secondary battery that is not a bipolar type.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

<Example 1>
<Preparation of positive electrode>
Spinel-type lithium manganate (average particle size: 5 μm) (82 mass%) as a positive electrode active material, acetylene black (8 mass%) as a conductive additive, and polyvinylidene fluoride (PVdF) (10 mass%) as a binder An appropriate amount of N-methyl-2-pyrrolidone (NMP), which is a slurry viscosity adjusting solvent, was added to the solid content consisting of) to prepare a positive electrode active material slurry.

  On the other hand, foamed aluminum (porosity: 95%, thickness: 80 μm) was prepared as a foam metal carrier.

  The prepared foamed aluminum was immersed in the positive electrode active material slurry prepared above for 5 minutes, and the positive electrode active material slurry was sufficiently impregnated into the voids of the foamed aluminum.

  Thereafter, the foamed aluminum carrying the active material component was taken out and dried at 110 ° C. for 30 minutes to complete the positive electrode.

<Production of test cell>
The positive electrode produced above was punched to 15 mmφ using a punch, the positive electrode, the separator, and the counter electrode were laminated in this order, and an electrolyte was injected into the separator to produce a coin-type test cell. A lithium foil (thickness: 200 μm) was used as the counter electrode. As the separator, a polypropylene microporous film (thickness: 18 μm) was used. Furthermore, as an electrolytic solution, a solution in which LiPF ₆ as a lithium salt was dissolved at a concentration of 1M in an equal volume mixed solution of ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) was used.

<Example 2>
A positive electrode and a test cell were produced in the same manner as in Example 1 except that a positive electrode active material having an average particle diameter of 1 μm was used.

<Example 3>
A positive electrode and a test cell were prepared in the same manner as in Example 1 except that a positive electrode active material having an average particle diameter of 0.8 μm was used.

<Comparative Example 1>
A positive electrode and a test cell were prepared in the same manner as in Example 1 except that a positive electrode active material having an average particle diameter of 20 μm was used.

<Comparative example 2>
A positive electrode and a test cell were produced in the same manner as in Example 1 except that a positive electrode active material having an average particle diameter of 10 μm was used.

<Comparative Example 3>
The positive electrode active material slurry prepared in Example 1 was applied to the surface of an aluminum foil (thickness: 20 μm), which is a conventional current collector, and dried to form a coating film having a thickness of 100 μm. Thereafter, the obtained laminate was pressed to produce a positive electrode in which a positive electrode active material layer having a thickness of 80 μm was formed on the surface of the current collector.

  Using the positive electrode produced above, a test cell was produced in the same manner as in Example 1 above.

<Comparative example 4>
A positive electrode and a test cell were produced in the same manner as in Comparative Example 3 except that a positive electrode active material having an average particle diameter of 1 μm was used.

<Comparative Example 5>
A positive electrode and a test cell were produced in the same manner as in Comparative Example 3 except that a positive electrode active material having an average particle diameter of 0.8 μm was used.

<Evaluation of battery characteristics of test cell>
Using the test cells prepared in the above Examples and Comparative Examples, the output characteristics and charge / discharge cycle characteristics were evaluated by the following methods. The results are shown in Table 1 below.

<Evaluation of output characteristics>
First, the output characteristics of the test cells prepared in each of the above examples and comparative examples were evaluated. Specifically, after initial charge and discharge, a discharge test at 100 C was performed to calculate output characteristics. The conditions of the initial charge / discharge and discharge test are as follows.

[Initial charge / discharge conditions]
Charge: 50 mV vs Li ⁺ / Li at a constant current of 0.5 C for a total of 3 hours Discharge: Discharge to 2 V vs Li ⁺ / Li at a constant current of 0.5 C, cut off The cycle was repeated for initial charge / discharge.

[Discharge test conditions]
Charge: 50 mV vs Li ⁺ / Li for a total of 3 hours at a constant current of 0.5 C Discharge: Discharge to 2 V vs Li + / Li at a constant current of 100 C and cut off The percentage of capacity was calculated and used as output characteristics (%).

<Evaluation of charge / discharge cycle characteristics>
After the evaluation of the above output characteristics, charging / discharging was performed under the above-described initial charging / discharging conditions, and then a charging / discharging cycle test was performed to evaluate the charging / discharging cycle characteristics. The conditions of the cycle test are as follows.

[Charge / discharge cycle test conditions]
Charge: 50 mV vs Li ⁺ / Li at a constant current of 5 C for a total of 30 minutes Discharge: Discharge to 2 V vs Li ⁺ / Li at a constant current of 5 C, cut off After 500 cycles of the above charge and discharge Then, charging / discharging was performed under the above-described initial charging / discharging conditions, and the discharge capacities before and after the charging / discharging cycle were compared. As a result of comparison, the case where the capacity maintenance rate was 80% or more was determined as “no charge / discharge cycle deterioration”, and the case where the capacity maintenance rate was less than 80% was determined as “charge / discharge cycle deterioration”.

  From the results shown in Comparative Examples 1 and 2, if the particle size of the active material is too large, sufficient output characteristics cannot be obtained even if a foam metal is used as the active material carrier, and cycle deterioration may occur in some cases. Is shown. This is considered to be caused by the fact that the effective surface area that can participate in the reaction becomes small when the particle size of the active material is large, and the reaction on the surface of the active material becomes rate-determining particularly under a high output condition of 100C. .

  On the other hand, from the results shown in Comparative Examples 3 to 5, an electrode having the same configuration (current collector + active material layer) as in the past can still obtain sufficient output characteristics even if the particle diameter of the active material is reduced. This indicates that the durability against the charge / discharge cycle is insufficient. This is because, if the particle size of the active material is reduced in the electrode of the conventional configuration, the effective surface area that can participate in the reaction can be increased, but the conductive network between the active materials is not sufficiently formed, and the inside of the battery This is thought to be due to the increase in resistance.

  On the other hand, according to the electrode of the present invention, by setting the particle diameter of the active material to a predetermined value or less, an effective surface area that can participate in the reaction is sufficiently secured, and a foam metal is used as a carrier for the active material. By using it, a conductive network between active materials is sufficiently secured. As a result, the battery electrode of the present invention can provide a battery having excellent output characteristics even under high output conditions. In addition, according to the battery electrode of the present invention, a battery having excellent charge / discharge cycle durability can also be provided.

It is sectional drawing which shows one Embodiment of the battery electrode of this invention. It is sectional drawing which shows other embodiment of the battery electrode of this invention. It is sectional drawing which shows preferable one Embodiment of the bipolar battery of 2nd Embodiment. It is a perspective view which shows the assembled battery of 3rd Embodiment. It is the schematic of the motor vehicle of 4th Embodiment carrying the assembled battery of 3rd Embodiment.

Explanation of symbols

1 Bipolar electrode,
10 Bipolar battery,
11 Current collector,
13 positive electrode,
13a positive electrode side foam metal carrier,
13b The void portion of the positive electrode side foam metal carrier,
13c positive electrode active material,
15 negative electrode,
15a negative electrode side foam metal carrier,
15b The void portion of the negative electrode side metal foam support,
15c negative electrode active material,
17 electrolyte layer,
19 cell layer,
21 battery elements,
25 positive electrode tab,
27 negative electrode tab,
29 Laminate sheet,
31 insulating layer,
40 battery packs,
42, 43 electrode terminals,
50 cars.

Claims (11)

  An electrode for a battery, wherein an electrode material containing an active material is supported in a void portion of a plate-shaped foamed metal carrier, and an average particle diameter of the active material is 5 μm or less.   The battery electrode according to claim 1, wherein the electrode material further contains a binder or a conductive additive.   The battery electrode according to claim 1 or 2, wherein the porosity of the foam metal carrier is 90% or more.   The battery electrode according to any one of claims 1 to 3, wherein the thickness of the foam metal carrier is 100 µm or less.   The battery electrode according to any one of claims 1 to 4, wherein the porosity is 50% or more. A battery including at least one unit cell layer in which a positive electrode, an electrolyte layer, and a negative electrode are laminated in this order,
The battery in which at least one of the positive electrode or the negative electrode is the battery electrode according to any one of claims 1 to 5.   The battery according to claim 6, wherein when the electrolyte layer includes a separator, the thickness of the separator is 20 μm or less.   The battery according to claim 6, wherein when the electrolyte layer is made of an intrinsic polymer electrolyte, the thickness of the electrolyte layer is 100 μm or less.   The lithium ion secondary battery according to any one of claims 6 to 8, which is a bipolar lithium ion secondary battery.   The assembled battery using the lithium ion secondary battery of any one of Claims 6-9.   A vehicle in which the lithium ion secondary battery according to any one of claims 6 to 9 or the assembled battery according to claim 10 is mounted as a motor driving power source.

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