JP5359562B2 - Bipolar battery current collector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for preventing liquid junction between a positive electrode active material layer and a negative electrode active material layer in a bipolar electrode, and at the same time suppressing an increase in a resistance of the collector in a direction perpendicular to its surface, in a collector for a bipolar battery containing conductive resin. <P>SOLUTION: The collector for a bipolar battery includes a conductive resin layer and at least one layer of an ion blocking layer which is conductive and suppresses transmission of ions in the direction perpendicular to its surface. The resin layer and ion blocking layer are electrically joined so as to have higher conductivity of the joined layer in the direction perpendicular to its surface than that in its planar direction. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a current collector for a bipolar battery.

  In recent years, reduction of carbon dioxide emissions has been strongly desired for environmental protection. In the automobile industry, there is an expectation for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV), and the development of motor drive batteries that hold the key to their practical use has been carried out. ing. As batteries for automobiles, attention has been focused on lithium ion secondary batteries that can achieve high energy density and high output density. In particular, in the case of a bipolar battery, a current flows in the vertical direction (electrode stacking direction) through the current collector, so that the electron conduction path can be shortened and the output becomes high. Thereby, a battery with a high battery voltage can be constituted.

  The bipolar battery includes a current collector having a positive electrode active material layer and a negative electrode active material layer formed on each surface as a constituent member. A metal foil has been generally used as a current collector. However, for the purpose of reducing the weight of the current collector, Patent Document 1 proposes a current collector containing a conductive resin mixed with a carbon filler. Yes.

JP 2006-190649 A

  However, the current collector as described in Patent Document 1 has a lower electrolyte blocking property than the metal foil current collector. Therefore, when applied to a bipolar lithium ion secondary battery, ions are transmitted through the current collector of the bipolar electrode, and a liquid junction occurs between the positive electrode active material layer and the negative electrode active material layer in the bipolar electrode. I found out that there are cases where

  In order to solve this problem, a method is conceivable in which an ion blocking layer for suppressing the permeation of the electrolyte and lithium ions is laminated on the surface of the resin current collector. However, in such a method, since connection resistance is generated by stacking, resistance in the thickness direction (perpendicular direction) increases. As a result, the current collection efficiency of the current collector is lowered, and the battery performance can be lowered.

  Accordingly, the present invention provides a current collector for a bipolar battery containing a conductive resin, while preventing a liquid junction between the positive electrode active material layer and the negative electrode active material layer in the bipolar electrode, An object is to provide a means capable of reducing the resistance in the thickness direction (perpendicular direction).

  The inventors of the present invention have made extensive studies in view of the above problems. As a result, the resin layer and an ion blocking layer that suppresses permeation of ions in the direction perpendicular to the surface are included, and these layers are electrically joined so that the conductivity in the direction perpendicular to the plane is higher than the conductivity in the plane direction. It has been found that the above object can be achieved by using a current collector.

  According to the present invention, in a current collector including a resin layer and an ion blocking layer, by electrically connecting these layers, conduction in the direction perpendicular to the surface of the current collector is suppressed while suppressing lithium ion permeation. Sex can be secured. Therefore, in the bipolar battery current collector containing a resin having conductivity, while preventing the liquid junction between the positive electrode active material layer and the negative electrode active material layer in the bipolar electrode, the thickness direction of the current collector The resistance in the direction perpendicular to the surface can be reduced.

1 is a schematic cross-sectional view showing the structure of a bipolar lithium ion secondary battery. It is the cross-sectional schematic diagram which represented the electrical power collector of 1st Embodiment typically. It is the cross-sectional schematic which expanded and represented the electrical power collector of 1st Embodiment typically. It is the cross-sectional schematic which represented the electrical power collector of 2nd Embodiment typically. It is the cross-sectional schematic which represented the electrical power collector of 3rd Embodiment typically. It is the cross-sectional schematic which represented the electrical power collector of 4th Embodiment typically. It is the cross-sectional schematic which represented the electrical power collector of 5th Embodiment typically, (a) represents the electrical power collector which used the metal foil which has the particle | grains of a needle-like structure on the surface as an ion blocking layer, (B) represents the metal foil. It is the cross-sectional schematic which represented the electrical power collector of 6th Embodiment typically. It is a perspective view showing the appearance of a bipolar lithium ion secondary battery. It is an external view of an assembled battery. It is a conceptual diagram of the vehicle carrying an assembled battery. It is the photograph which image | photographed the cross section of the electroconductive film used in Example 1 with the scanning electron microscope (SEM). 4 is a graph showing contact resistance in a direction perpendicular to the current collectors obtained in Example 3 and Comparative Example 1. It is a graph showing the contact resistance of the current collector of the current collector obtained in Example 4 and Comparative Example 2. It is a graph showing the contact resistance of the surface normal direction of the electrical power collector obtained in Example 5 and Example 6. FIG.

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

  When distinguished by the structure and form of the bipolar 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 even when distinguished by the form of electrolyte of the bipolar battery. 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.

  Moreover, when it sees in the electrode material of a battery, or the metal ion which moves between electrodes, it does not restrict | limit in particular, It can apply to any well-known electrode material. Examples include lithium ion secondary batteries, sodium ion secondary batteries, potassium ion secondary batteries, nickel metal hydride secondary batteries, nickel cadmium secondary batteries, nickel metal hydride batteries, and the like, preferably lithium ion secondary batteries. . This is because in the lithium ion secondary battery, the voltage of the cell (single cell layer) is large, high energy density and high output density can be achieved, and it is excellent as a vehicle driving power source or an auxiliary power source.

  FIG. 1 is a schematic cross-sectional view schematically showing the entire structure of a bipolar lithium ion secondary battery 10. The bipolar lithium ion secondary battery 10 shown in FIG. 1 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.

  As shown in FIG. 1, the power generating element 21 of the bipolar lithium ion secondary battery 10 has a positive electrode active material layer 13 electrically coupled to one surface of the current collector 11, and is opposite to the current collector 11. It has a plurality of bipolar electrodes 23 formed with a negative electrode active material layer 15 electrically coupled to the side surface. Each bipolar electrode 23 is laminated via the electrolyte layer 17 to form the power generation element 21. The electrolyte layer 17 has a configuration in which an electrolyte is held at the center in the surface direction of a separator as a base material. At this time, the positive electrode active material layer 13 of one bipolar electrode 23 and the negative electrode active material layer 15 of another bipolar electrode 23 adjacent to the one bipolar electrode 23 face each other through the electrolyte layer 17. The bipolar electrodes 23 and the electrolyte layers 17 are alternately stacked. That is, the electrolyte layer 17 is interposed between the positive electrode active material layer 13 of one bipolar electrode 23 and the negative electrode active material layer 15 of another bipolar electrode 23 adjacent to the one bipolar electrode 23. ing.

  The adjacent positive electrode active material layer 13, electrolyte layer 17, and negative electrode active material layer 15 constitute one unit cell layer 19. Therefore, it can be said that the bipolar lithium ion secondary battery 10 has a configuration in which the single battery layers 19 are stacked. In addition, for the purpose of preventing liquid junction due to leakage of the electrolytic solution from the electrolyte layer 17, an insulating portion 31 is disposed on the outer peripheral portion of the unit cell layer 19. A positive electrode active material layer 13 is formed only on one side of the positive electrode outermost layer current collector 11 a located in the outermost layer of the power generation element 21. The negative electrode active material layer 15 is formed only on one surface of the outermost current collector 11b on the negative electrode side located in the outermost layer of the power generation element 21. However, the positive electrode active material layer 13 may be formed on both surfaces of the outermost layer current collector 11a on the positive electrode side. Similarly, the negative electrode active material layer 15 may be formed on both surfaces of the outermost layer current collector 11b on the negative electrode side.

  Further, in the bipolar secondary battery 10 shown in FIG. 1, the positive electrode current collector plate 25 is disposed so as to be adjacent to the outermost layer current collector 11 a on the positive electrode side, and this is extended and led out from the battery exterior material 29. . On the other hand, the negative electrode current collector plate 27 is disposed so as to be adjacent to the outermost layer current collector 11 b on the negative electrode side, and is similarly extended and led out from the battery exterior material 29.

  In the bipolar lithium ion secondary battery 10 shown in FIG. 1, an insulating part 31 is usually provided around each single battery layer 19. The insulating part 31 prevents the adjacent current collectors 11 in the battery from coming into contact with each other and a short circuit caused by a slight irregularity at the end of the unit cell layer 19 in the power generation element 21. Is provided. By installing such an insulating part 31, long-term reliability and safety can be ensured, and a high-quality bipolar lithium ion secondary battery 10 can be provided.

  Note that the number of stacks of the unit cell layers 19 is adjusted according to a desired voltage. Further, in the bipolar secondary battery 10, the number of stacking of the single battery layers 19 may be reduced if a sufficient output can be secured even if the thickness of the battery is made as thin as possible. Even in the bipolar lithium ion secondary battery 10, in order to prevent external impact and environmental degradation during use, the power generation element 21 is sealed in the battery exterior material 29 under reduced pressure, and the positive current collector plate 25 and the negative current collector plate It is preferable to adopt a structure in which 27 is taken out of the battery exterior material 29. Hereinafter, main components of the bipolar secondary battery of this embodiment will be described.

  FIG. 2 is a schematic cross-sectional view schematically showing the current collector 11 (first embodiment) of the bipolar lithium ion secondary battery 10. As shown in FIG. 2, the current collector 11 includes a resin layer 2 having conductivity and an ion blocking layer 3 (3a, 3b) having conductivity. Here, the resin layer 2 and the ion blocking layer 3 (3a, 3b) are electrically contacted and bonded so that the conductivity in the perpendicular direction of the current collector 11 is higher than the conductivity in the planar direction. Has been. With such a configuration, ions are blocked and conductivity in a perpendicular direction is ensured, so that the battery performance of the bipolar battery can be improved.

  The functions required of the current collector in the bipolar lithium ion secondary battery include a partition wall (barrier property) function, a function of conducting in the direction perpendicular to the plane, and a function of suppressing conduction in the in-plane direction.

  In the bipolar battery, since the electric charge generated on the negative electrode side is directly supplied to the positive electrode on the opposite side of the current collector, the current flows in the stacking direction, but the flow in the plane direction is not necessary. Therefore, in the current collector using resin, in order to improve the current collection efficiency of the current collector, it is effective to make the conductivity in the perpendicular direction higher than the conductivity in the plane direction.

  A current collector including a conductive resin layer has a large resistance in the planar direction. For this reason, when an internal short circuit occurs in a single battery constituting the bipolar battery, the current collector including the conductive resin layer suppresses the short circuit current, thereby preventing the bipolar battery from generating heat. In addition, since the current collector having high thermal conductivity has high heat dissipation, the heat distribution in the planar direction of the current collector including the conductive resin layer is made uniform, and the thermal expansion in the planar direction can be made uniform. As a result, deterioration of the bipolar battery can be further suppressed.

  However, in a bipolar secondary battery, when a current collector containing a conductive resin is used, the electrolytic solution and lithium ions may permeate and have a liquid junction. Therefore, it is necessary to stack an ion blocking layer such as a metal foil having a partition (barrier) function. However, when these are laminated, connection resistance is generated, and resistance in the direction perpendicular to the surface is increased. For example, when an insulating adhesive is used between the conductive resin and the metal foil, the contact resistance in the perpendicular direction can be increased by the insulating property of the adhesive. Further, if the metal and the resin are bonded only by thermocompression bonding, the bonding strength may be insufficient, and the resistance in the perpendicular direction may be further increased. On the other hand, even if the conductivity of the resin layer having conductivity is increased, the resistance in the planar direction of the current collector, including the conductivity in the planar direction of the ion blocking layer, is reduced, and the heat generation as described above is generated. It may be difficult to obtain the effect of preventing. Therefore, by electrically joining the conductive resin layer and the conductive ion blocking layer to produce a current collector having higher conductivity in the perpendicular direction than in the planar direction, an electrolytic solution is obtained. In addition, the current collection efficiency can be improved while suppressing the permeation of lithium ions. And the battery performance of a bipolar battery can be improved by using such a collector.

  The form in which the resin layer and the ion blocking layer are electrically bonded is not particularly limited. For example, a conductive material is introduced into the resin layer, and the conductive material is disposed so as to contact the ion blocking layer. Alternatively, a conductive adhesive layer containing a conductive material may be disposed between the resin layer and the ion blocking layer. Furthermore, the form which combined these can also be employ | adopted.

  FIG. 3 is a schematic cross-sectional view schematically showing the current collector of the first embodiment shown in FIG. 2 in an enlarged manner. In the current collector 11 of FIG. 3, the resin layer 2 includes a polymer material 5 and a conductive material 4. At least a part of the conductive material 4 is exposed at the interface 6 between the resin layer 2 and the ion blocking layer 3. By adopting such a form, the resin layer 2 and the ion blocking layer 3 are electrically connected, and the resistance in the perpendicular direction can be reduced. Preferably, at least a part of the conductive material 4 penetrates the resin layer 2. By the presence of the conductive material that penetrates the resin layer, the resistance in the direction perpendicular to the surface of the current collector can be further reduced.

  Hereinafter, the resin layer and the ion blocking layer constituting the current collector of the present embodiment will be described.

(Resin layer)
The resin layer is not particularly limited as long as it is a layer containing a polymer material and is a layer containing a conductive material that can be electrically joined to the ion blocking layer. Preferably, the resin layer has higher conductivity in the direction perpendicular to the planar direction.

  Specific forms of the resin layer include 1) a form in which the polymer material constituting the resin is a conductive polymer, and 2) a form in which the polymer material constituting the resin is a non-conductive polymer. When a non-conductive polymer is used, conductivity can be imparted to the resin layer by adding a conductive material.

  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 viewpoints of electron conductivity and stable use in the battery.

  Examples of non-conductive polymers include low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polybutylene and other olefin resins, ethylene-acetic acid Vinyl copolymer (EVA), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether nitrile (PEN), polyimide (PI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), silicone, epoxy resin, or a mixture thereof And the like. Since these materials have low ion conductivity, transmission of lithium ions can be suppressed.

  As described above, the resin layer preferably includes a conductive material in addition to the polymer material. The conductive material is not particularly limited as long as it has conductivity and can reduce the resistance in the perpendicular direction of the current collector by electrically connecting the ion blocking layer and the resin layer. Examples of the conductive material used include metals, alloys, diamond-like carbon, glassy carbon, carbon materials such as graphite, ceramics, metal carbide, metal nitride, and metal oxide. Alternatively, conductive beads or the like may be used. By using the above material, the conductivity in the direction perpendicular to the surface of the current collector can be further improved. These conductive materials may be used individually by 1 type, and may be used together 2 or more types.

  The form of the conductive material is not particularly limited, and may be a particulate form or a fiber form. The shape of the particles is not particularly limited, and a spherical shape, an oval shape, a cylindrical shape, or the like can be used. For example, when using a fiber-shaped material, if the average length is longer than the thickness of the resin layer, the probability that the conductive material will come into contact with the ion blocking layer is increased, and the conductivity of the current collector in the direction perpendicular to the surface is increased. It is preferable because it can contribute to improvement of the property. Further, when using a particulate conductive material as shown in the second embodiment to be described later, if a material having an average particle diameter larger than the thickness of the resin layer is used, there is a probability that the conductive material contacts the ion blocking layer. This is preferable because it increases and can contribute to the improvement of the conductivity in the direction perpendicular to the surface of the current collector.

  The average particle diameter or average length of the conductive material is not particularly limited, but is preferably about 0.01 to 60 μm. In the present specification, “particle diameter” or “length” means the maximum distance L among the distances between any two points on the contour line of the particulate or fiber material. As the value of “average particle diameter” or “average length”, using observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM), particles observed in several to several tens of fields are observed. A value calculated as an average value of the particle diameter or the fiber length is adopted. Particle diameters and average particle diameters of active material particles to be described later can be defined similarly.

  When the conductive material is in the form of a fiber as in this embodiment, it is preferable that the resin material is oriented in the direction perpendicular to the current collector surface as shown in FIG. By orienting the conductive material in the direction perpendicular to the plane, the conductivity in the direction perpendicular to the plane can be further improved, and conduction in the plane direction can be suppressed. Furthermore, in the case where one member of the conductive material penetrates the resin layer, if a conductive material in which only a portion in contact with the resin layer is coated with an insulating film (not shown) is used, It is preferable because conduction in the planar direction can be suppressed and battery performance can be improved.

  Further, as the resin layer, an anisotropic conductive film such as a commercially available nickel fiber alignment film may be used.

  In the case where one member of the conductive material penetrates the resin layer as in the present embodiment, only the portion of the conductive material that contacts the resin layer is coated with an insulating film (not shown). When used, conduction in the planar direction of the current collector can be suppressed, and battery performance can be improved.

  Although the usage-amount of the electroconductive material in a resin layer is not specifically limited, Preferably, it is preferable that it is 5 volume% or more with respect to a resin layer, More preferably, it is 5-90 volume%. If content of an electroconductive material is 5 volume% or more, the electroconductivity in a resin layer is fully securable.

  The resin layer may contain other additives in addition to the polymer material and the conductive material.

  The thickness of the conductive resin layer is not particularly limited, but is preferably 0.1 to 200 μm, and more preferably 0.1 to 100 μm. When the thickness of the resin layer is 0.1 μm or more, a current collector with high current collection efficiency can be obtained. If the thickness of the resin layer is 200 μm or less, a battery having a high battery capacity per unit volume can be obtained.

(Ion blocking layer)
The ion blocking layer has conductivity, prevents ion permeation in the current collector, and prevents a liquid junction between the positive electrode active material layer and the negative electrode active material layer in the bipolar electrode (partition (barrier) function) Have Therefore, by providing the ion blocking layer, electrode deterioration can be prevented and the durability of the battery can be improved.

  The ion blocking layer may be a single layer or two or more layers. The position where the ion blocking layer is disposed is not particularly limited, and may be provided between the resin layer and the positive electrode active material layer (positive electrode side ion blocking layer), for example, between the resin layer and the negative electrode active material layer. It may be provided (negative electrode side ion blocking layer). Furthermore, a resin layer composed of two layers may be formed, and an ion blocking layer may be disposed between them (an ion blocking layer provided inside the resin layer), or a combination of the above. Preferably, a positive electrode side ion blocking layer is provided on one surface of the resin layer, and a negative electrode side ion blocking layer is provided on the other surface. By setting it as such a structure, permeation | transmission of lithium ion and electrolyte solution can be suppressed more effectively.

  Examples of materials used for the positive electrode side ion blocking layer include aluminum, iron, chromium, nickel, titanium, vanadium, molybdenum, niobium, gold, silver, platinum, and alloys of these metals, metal carbides, metal nitrides, Preferable examples include at least one selected from the group consisting of metal oxides, diamond-like carbon, glassy carbon, and ceramics. Among these, aluminum is particularly preferable from the viewpoints of stability to the positive electrode potential, light weight, and low cost.

  Examples of the material used for the negative electrode side ion blocking layer include aluminum, copper, iron, chromium, nickel, titanium, vanadium, molybdenum, niobium, gold, silver, platinum, and alloys of these metals, metal carbides, Preferable examples include at least one selected from the group consisting of metal nitrides, metal oxides, diamond-like carbon, glassy carbon, and ceramics. Among these, copper and nickel are particularly preferable from the viewpoints of stability against the negative electrode potential, light weight, and low cost.

  Examples of the material used for the ion blocking layer provided inside the resin layer include at least one selected from the group consisting of a material used for the positive electrode side ion blocking layer and a material used for the negative electrode side ion blocking layer. Preferably mentioned.

  In addition, the material used for the positive electrode side ion blocking layer and the material used for the negative electrode side ion blocking layer may be the same or different. However, considering the corrosion resistance of the electrode, it is preferable that the material used for the positive electrode side ion blocking layer and the material used for the negative electrode side ion blocking layer are different.

  The thickness of the ion blocking layer is not particularly limited as long as it can function to prevent ion permeation in the current collector and prevent liquid junction between the positive electrode active material layer and the negative electrode active material layer in the bipolar electrode. Furthermore, it is preferable that it is the thickness which can express the effect which suppresses a short circuit current of the collector containing the resin layer which has electroconductivity. Specifically, the thickness of the ion blocking layer is preferably 0.001 to 50 μm. When there are a plurality of ion blocking layers, it is preferable that at least one thickness is in the above range, and it is more preferable that all the ion blocking layers have a thickness in the above range.

  Note that the current collector may contain other materials as necessary.

  Although the thickness of the whole electrical power collector is not specifically limited, In order to raise the output density of a battery, it is so preferable that it is thin. In a bipolar battery, the current collector present between the positive electrode active material layer and the negative electrode active material layer may have a high electrical resistance in the planar direction (the direction horizontal to the stacking direction), so the thickness of the current collector It is possible to reduce the thickness. Specifically, the thickness of the entire current collector is preferably 0.1 to 300 μm, and more preferably 0.1 to 200 μm.

Further, the resistance in the direction perpendicular to the current collector is preferably 5 mΩ / cm ² or less, more preferably 0.1 to 1 mΩ / cm ² . Further, the planar direction of the resistance of the current collector is in 10 m [Omega / cm ² or more, more preferably 100~2000mΩ / cm ^2.

  As a method of bonding the resin layer having conductivity and the ion blocking layer, it is possible to use an appropriate combination of existing resin thin film and metal thin film deposition techniques, lamination techniques, and lamination techniques.

  That is, a method of laminating a conductive resin layer and an ion blocking layer by thermocompression bonding, or a slurry containing a polymer material or a conductive polymer material in which a conductive material is added to the surface of the ion blocking layer. A method of applying and drying to form a resin layer may be used. Alternatively, the ion blocking layer may be formed by a technique in which a slurry containing a polymer material to which a conductive material is added, a conductive polymer material, or the like is applied to the surface of the ion blocking layer and dried, followed by thermocompression bonding. Further, a metal layer may be coated on the resin layer by vapor deposition, sputtering, or the like to form an ion blocking layer. A current collector in which an ion blocking layer and a resin layer are alternately laminated can be manufactured by repeating these methods for a current collector having a laminated structure of three or more layers. However, manufacturing methods other than these manufacturing methods may be used.

  The first embodiment described above has the following effects. In other words, by electrically joining the conductive resin layer and the conductive ion blocking layer using a conductive material that penetrates the resin layer, the conductivity in the perpendicular direction becomes the conductivity in the planar direction. Higher current collector can be obtained. As a result, the current collection efficiency can be improved while suppressing the permeation of the electrolyte and lithium ions. And the battery performance of a bipolar battery can be improved by using such a collector.

  FIG. 4 is a schematic cross-sectional view schematically showing an embodiment (second embodiment) of a current collector in which the conductive material contained in the resin layer is spherical. When a particulate conductive material is used, if the average particle diameter is larger than the thickness of the resin layer, the probability that the conductive material will come into contact with the ion blocking layer is increased, and the conductivity of the current collector in the direction perpendicular to the surface is increased. It is preferable because it can contribute to improvement of the property.

  FIG. 5 is a schematic cross-sectional view schematically showing the current collector 113 according to the third embodiment. The resin layer of the current collector 113 has a plurality of through holes 7, and the through holes 7 are filled with a conductive material 4 '. In such a form, a conductive path oriented in a direction perpendicular to the surface of the current collector can be formed. Therefore, the electrical conductivity in the planar direction of the current collector can be suppressed, and the electrical conductivity in the perpendicular direction can be increased. The conductive material filled in each through hole may be composed of one member or may include a plurality of members.

  The method for producing the current collector 113 of the third embodiment is not particularly limited. For example, the resin layer 2 having the through hole 7 in the film thickness direction is disposed on the ion blocking layer 3 b, and a binder solution containing the conductive material 4 ′ is poured into the through hole 7. Thereafter, the ion blocking layer 3b is overlaid on the resin layer 2, and the solvent of the binder solution is dried to obtain the current collector 113 having a conductive path in the through hole.

  As described above, at least a part of the conductive material is exposed at the interface between the resin layer and the ion blocking layer, so that the electrical conductivity in the perpendicular direction of the current collector is higher than the electrical conductivity in the planar direction. Embodiments are described which are joined together. In addition to this, a form in which a conductive adhesive layer containing a conductive material is present at least at a part of at least one interface between the resin layer and the ion blocking layer is also preferable.

  FIG. 6 is a schematic cross-sectional view schematically showing a current collector according to the fourth embodiment. According to the fourth embodiment shown in FIG. 6, the conductive adhesive layer 8 including the conductive material 9 exists on at least a part of at least one interface between the resin layer 2 and the ion blocking layer 3. By such a conductive adhesive layer 8, the resin layer 2 and the ion blocking layer 3 are electrically connected, and the resistance in the perpendicular direction can be reduced.

  Many adhesives used in the manufacture of ordinary battery electrodes have poor electrical conductivity, and the connection resistance increases when the resin layer is bonded to an ion blocking layer such as a metal foil. Even in the case of an adhesive containing an adhesive conductive material, when the conductive material is not electrically connected to the conductive polymer constituting the resin layer and the percolation path is not connected, the contact resistance at the interface increases. According to this embodiment, in order to reduce the connection resistance by joining the ion blocking layer and the conductive resin layer via the conductive adhesive layer containing a conductive material, the resistance in the direction perpendicular to the current collector is reduced. Can be reduced.

  Specifically, for example, as shown in FIG. 6, a conductive adhesive layer 8 including a particulate conductive material 9 and an adhesive 8 a is disposed between the resin layer 2 and the ion blocking layer 3. By disposing a conductive adhesive layer containing a conductive material at the interface between the resin layer and the ion blocking layer, it is possible to secure conductivity in the direction perpendicular to the current collector and improve current collection efficiency. Preferably, the conductive material is present dispersed in the conductive adhesive layer.

  Here, the average particle diameter of the conductive material contained in the conductive adhesive layer is preferably equal to or greater than the thickness of the conductive adhesive layer. When the average particle size of the conductive material contained in the conductive adhesive layer is equal to or greater than the thickness of the conductive adhesive layer, the conductive path between the conductive resin and the conductive adhesive layer becomes a point contact and the percolation path Since it can prevent becoming difficult to connect, the contact resistance of an interface can be reduced more. There is no problem even if the conductive material protrudes from the conductive adhesive layer, and the contact resistance can be reduced rather by increasing the area in contact with the ion blocking layer during lamination. However, when the particle diameter of the conductive material contained in the conductive adhesive layer is much larger than that of the conductive adhesive layer, the adhesive force becomes weak, and the metal layer is peeled off from the conductive resin due to vibration or the like. For this reason, the average particle diameter of the conductive particles contained in the conductive adhesive layer is preferably 0.5 to 1.5 times the thickness of the conductive adhesive layer, more preferably 0.8 to 1.2 times. If it is the said range, sufficient conductive path can be ensured and adhesive force is also maintained. Furthermore, it is preferable that the conductive material maintains its shape in the conductive adhesive layer. The thickness of the conductive adhesive layer is preferably 0.1 to 30 μm.

  Further preferably, the conductive material penetrates the ion blocking layer-conductive adhesive layer-resin layer. By setting it as such a form, the electroconductivity of the current collector in the direction perpendicular to the surface can be further improved.

  There are no particular restrictions on the material and shape of the conductive material contained in the conductive adhesive layer. Examples of the conductive material contained in the conductive adhesive layer include, but are not limited to, aluminum particles, SUS particles, carbon particles, silver particles, gold particles, copper particles, and titanium particles. Alloy particles may be used. As the conductive material, in addition to a particulate material, a carbon nanotube or the like that is put into practical use as a so-called filler-based conductive resin composition can be used.

  The content of the conductive material contained in the conductive adhesive layer is preferably 10 to 80% by mass, more preferably 20 to 80% by mass with respect to the total mass of the conductive adhesive layer. Preferably it is 40-80 mass%.

  Examples of the adhesive used for the conductive adhesive layer include, but are not limited to, rubber-based, silicone-based, olefin-based, and acrylic-based adhesives.

  As a method of laminating the conductive adhesive layer as shown in FIG. 6, for example, a slurry in which an adhesive and a conductive material are mixed is applied to the surface of the resin layer or the ion blocking layer to a desired thickness using an applicator or the like. Apply and dry. Thereafter, the resin layer or the ion blocking layer can be laminated and thermocompression bonded. Or, for example, prepare an ion blocking layer in which a fiber-shaped conductive material protrudes from the surface or a resin layer in which a fiber-shaped conductive material protrudes from the surface, and apply an adhesive to this surface to apply the resin layer or ion blocking layer. The layers may be bonded together.

  The conductive adhesive layer can be formed using a whisker-shaped conductive material as shown in FIG. 7 in addition to the case where the conductive adhesive layer is formed of an adhesive containing a conductive material as shown in FIG. Current collector of 5 embodiment).

  In FIG. 7, a metal foil having needle-shaped particles 9b (for example, whiskers) on the surface is prepared as the ion blocking layer 3 (FIG. 7 (b)). Then, the needle-like structured particles 9b are used as a conductive material and arranged at the interface between the resin layer 2 and the ion blocking layer 3 to electrically join them (FIG. 7A). Thereby, the contact resistance between the resin layer and the ion blocking layer can be reduced. Here, the height of the needle-like structure particles 9b is not particularly limited, but is, for example, 0.1 to 10 μm, and preferably 1 to 3 μm.

  Further, for example, as shown in FIG. 8, the contact resistance can be further reduced by using an ion blocking layer in which the conductive particles 9c are adhered on the needle-shaped particles 9b (in the sixth embodiment). Current collector). There are no particular restrictions on the material and shape of the conductive particles deposited on the needle-shaped particles, but it is preferable to use carbon particles from the viewpoint of ease of handling. At this time, the average particle diameter of the conductive particles deposited on the needle-like structure particles is not particularly limited, but is, for example, 30 nm to 5 μm. The density of the conductive particles is not particularly limited, and can be adjusted according to desired conductivity. For example, the conductive particles can be preferably attached to 10 to 90% by mass of the needle-shaped particles. A method for attaching the conductive particles on the needle-like structure particles is not particularly limited, and for example, a method of applying a substance such as a slurry containing a conductive substance and attaching it by heating can be used.

  The bipolar lithium ion battery described above is characterized by the structure of the current collector. Hereinafter, other main components will be described.

(Active material layer)
[Positive electrode (positive electrode active material layer) and negative electrode (negative electrode active material layer)]
The active material layer 13 or 15 contains an active material, and further contains other additives as necessary.

The positive electrode active material layer 13 includes a positive electrode 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.

The negative electrode active material layer 15 includes a negative electrode active material. Examples of the negative electrode active material include carbon materials such as 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. . 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 contained in each active material layer 13, 15 is not particularly limited, but is preferably 1 to 20 μm from the viewpoint of increasing the output.

  The positive electrode active material layer 13 and the negative electrode active material layer 15 include a binder.

  Although it does not specifically limit as a binder used for an active material layer, For example, the following materials are mentioned. Polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile (PEN), 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 hydrogenated product thereof, styrene / isoprene / styrene block copolymer and hydrogenated product thereof Thermoplastic polymers such as products, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FE) ), Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE) , Fluororesin such as polyvinyl fluoride (PVF), vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-) TFE fluorine rubber), vinylidene fluoride-pentafluoropropylene fluorine rubber (VDF-PFP fluorine rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene Fluoro rubber (VDF-PFP-TFE fluoro rubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluoro rubber (VDF-PFMVE-TFE fluoro rubber), vinylidene fluoride-chlorotrifluoroethylene fluoro rubber Examples thereof include vinylidene fluoride-based fluororubber such as (VDF-CTFE-based fluororubber), an epoxy resin, and the like. 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 alone or in combination of two.

  The amount of the binder contained in the active material layer is not particularly limited as long as it is an amount capable of binding the active material, but is preferably 0.5 to 15% by mass with respect to the active material layer. Yes, more preferably 1 to 10% by mass.

  Examples of other additives that can be included in the active material layer 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.

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.

  The compounding ratio of the components contained in the positive electrode active material layer and the negative electrode active material layer is not particularly limited. The mixing ratio can be adjusted by appropriately referring to known knowledge about the non-aqueous solvent secondary battery. The thickness of each active material layer is not particularly limited, and conventionally known knowledge about the battery can be appropriately referred to. For example, the thickness of each active material layer is about 2 to 100 μm.

(Electrolyte layer)
As the electrolyte constituting the electrolyte layer 13, a liquid electrolyte or a polymer electrolyte can be used.

  The liquid electrolyte has a form in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer. Examples of the organic solvent that can be used as the plasticizer include carbonates such as ethylene carbonate (EC) and propylene carbonate (PC). Further, as the supporting salt (lithium salt), a compound that can be added to the active material layer of the electrode, such as LiBETI, can be similarly employed.

  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 has a configuration in which the above liquid electrolyte is injected into a matrix polymer made of an ion conductive polymer. Examples of the ion conductive polymer used as the matrix polymer include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. In such polyalkylene oxide polymers, electrolyte salts such as lithium salts 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 polyolefin such as polyethylene or polypropylene.

  The intrinsic polymer 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 an intrinsic polymer electrolyte, there is no fear of liquid leakage from the battery, and the reliability of the battery can be improved.

  The matrix polymer of the gel electrolyte or the intrinsic polymer 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.

(Outermost layer current collector)
As the material of the outermost layer current collector, for example, a metal or a conductive polymer can be adopted. From the viewpoint of ease of taking out electricity, a metal material is preferably used. Specifically, metal materials, such as aluminum, nickel, iron, stainless steel, titanium, copper, are mentioned, for example. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil by which aluminum is coat | covered on the metal surface may be sufficient. Of these, aluminum and copper are preferable from the viewpoints of electron conductivity and battery operating potential.

(Tabs and leads)
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 material)
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 a power generation element (battery 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.

(Insulation part)
The insulating part 31 prevents a liquid junction due to leakage of the electrolytic solution from the electrolyte layer 17. In addition, the insulating part 31 prevents the adjacent current collectors in the battery from coming into contact with each other or the occurrence of a short circuit due to a slight irregularity at the end of the unit cell layer 19 in the power generation element 21. Is provided.

  As a material constituting the insulating portion 31, it should have insulating properties, sealing properties against falling off of the solid electrolyte, sealing properties against moisture permeation from the outside (sealing properties), heat resistance at the battery operating temperature, and the like. That's fine. For example, urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber and the like can be used. Among these, polyethylene resin and polypropylene resin are preferably used as the constituent material of the insulating portion 31 from the viewpoints of corrosion resistance, chemical resistance, ease of production (film forming property), economy, and the like.

  In addition, said bipolar battery can be manufactured by a conventionally well-known manufacturing method.

<Appearance structure of bipolar battery>
FIG. 9 is a perspective view showing the appearance of a laminated flat bipolar lithium ion secondary battery, which is a typical form of a bipolar battery.

  As shown in FIG. 9, the stacked 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 from both sides thereof. Has been pulled out. The power generation element (battery element) 57 is wrapped 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 (battery element) 57 includes a positive electrode tab 58 and a negative electrode tab 59. It is sealed in a state where it is pulled out to the outside. Here, the power generation element (battery element) 57 corresponds to the power generation element (battery element) 21 of the bipolar lithium ion secondary battery 10 shown in FIG. 1 described above, and is a positive electrode (positive electrode active material layer). ) 13, a plurality of single battery layers (single cells) 19 composed of the electrolyte layer 17 and the negative electrode (negative electrode active material layer) 15 are laminated.

  The lithium ion battery is not limited to a laminated flat shape, and a wound lithium ion battery may have a cylindrical shape, or such a cylindrical shape. There is no particular limitation such that the object may be deformed into a rectangular flat shape. 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 (battery element) is covered with an aluminum laminate film. With this configuration, weight reduction can be achieved.

  9 is not particularly limited, and the positive electrode tab 58 and the negative electrode tab 59 may be drawn from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be pulled out. However, the present invention is not limited to the one shown in FIG. 7, for example. 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 battery is suitable 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, a hybrid fuel cell vehicle, etc. Can be used.

<Battery assembly>
The assembled battery is configured by connecting a plurality of the bipolar batteries. Specifically, at least two or more are used, and are configured by serialization, parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series.

  FIG. 10 is an external view of a typical form of the assembled battery, FIG. 10A is a plan view of the assembled battery, FIG. 10B is a front view of the assembled battery, and FIG. 10C is a side view of the assembled battery. .

  As shown in FIG. 10, the assembled battery 300 includes a plurality of bipolar batteries connected in series or in parallel to form a small assembled battery 250 that can be attached / detached. Further, a battery pack 300 having a large capacity and a large output suitable for a vehicle driving power source and an auxiliary power source that require a high volume energy density and a high volume power density can also be formed by connecting a plurality, in series or in parallel. . 10A is a plan view of the assembled battery, FIG. 10B is a front view, and FIG. 10C is a side view. The small assembled battery 250 that can be attached / detached has an electrical connection means such as a bus bar. The assembled battery 250 is stacked in a plurality of stages using the connection jig 310. How many bipolar batteries are connected to produce the assembled battery 250 and how many assembled batteries 250 are laminated to produce the assembled battery 300 are determined by the battery capacity of the vehicle (electric vehicle) to be mounted. Depending on the output.

<Vehicle>
The bipolar battery can be mounted on a vehicle, for example, in the form of the assembled battery described above. Since a long-life battery excellent in long-term reliability and output characteristics can be configured, it is possible to configure a plug-in hybrid electric vehicle having a long EV mileage and an electric vehicle having a long charge mileage when such a battery is mounted. In other words, a bipolar battery or an assembled battery formed by combining a plurality of these batteries can be used as a power source for driving a vehicle. For example, if it is a car, a hybrid battery, a fuel cell car, an electric car (four-wheeled vehicles (passenger cars, commercial vehicles such as trucks, buses, light vehicles, etc.)) In addition, because it is used for motorcycles (including motorcycles) and tricycles, it becomes a long-life and reliable automobile. However, the application is not limited to automobiles. For example, it can be applied to various power sources for moving vehicles such as other vehicles, for example, trains, and power sources for mounting such as uninterruptible power supplies. It is also possible to use as.

  FIG. 11 is a conceptual diagram of a vehicle equipped with an assembled battery.

  As shown in FIG. 11, in order to mount the assembled battery 300 on a vehicle such as the electric vehicle 400, the battery pack 300 is mounted under the seat at the center of the vehicle body of the electric vehicle 400. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the assembled battery 300 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the assembled battery 300 as described above has high durability and can provide sufficient output even when used for a long period of time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance.

  Hereinafter, the present invention will be described through examples. However, the present invention is not limited to the following examples.

Example 1
As the resin layer, an anisotropic conductive film (TP-2 · ACF manufactured by Btech, USA, polymer material: polyamide, conductive material: nickel fiber, film thickness: 100 μm) was prepared. Using a batch-type hot press machine, the resin layer is sandwiched between a copper foil (thickness: 5 μm) as a negative electrode side ion blocking layer and an aluminum foil (thickness: 20 μm) as a positive electrode side ion blocking layer. Lamination was performed by thermocompression bonding at 0 ° C. and 0.4 MPa to obtain a current collector. The electric conductivity in the thickness direction of the anisotropic conductive film used was 150 μΩ or less (1.5 cm ² ), and the electric resistance in the plane direction was 20 MΩ or more.

  FIG. 12 shows an SEM photograph of a cross section of the anisotropic conductive film used. It can be seen that the nickel fibers are arranged in the direction perpendicular to the plane and contribute to high conductivity in the direction perpendicular to the plane.

(Example 2)
Example except that anisotropic conductive film (HM-2 · ACF, manufactured by Btech, USA, polymer material: polyamide, conductive material: carbon fiber, film thickness: 100 μm) was used as the resin layer In the same manner as in Example 1, a current collector was produced. The electric resistance in the thickness direction of the anisotropic conductive film was 15 mΩ or less (1.5 cm ² ).

(Example 3)
A conductive paint (Nippon Graphite Industries Co., Ltd. Bunny Height UCC, polymer material: rubber, conductive material: graphite (average particle size 15 μm), carbon black) was prepared as a resin layer. Using this conductive paint, a copper foil (thickness: 5 μm) as the negative electrode side ion blocking layer and an aluminum foil (thickness: 20 μm) as the positive electrode side ion blocking layer were bonded and laminated. Specifically, after applying a conductive adhesive onto a copper foil using an applicator having a gap equivalent to the average particle diameter of the conductive material particles, and drying at 100 ° C. for 10 minutes using a hot plate Then, thermocompression bonding was performed at 120 ° C. and 3 MPa using a batch-type hot press machine. The same operation was performed on the aluminum foil to obtain a current collector.

(Comparative Example 1)
Low density polyethylene and Ketjen black (Lion Corporation EC-600JD) were mixed and extruded with a biaxial extruder to prepare a resin layer. Using this resin layer, a copper foil (thickness: 5 μm) and an aluminum foil (thickness: 20 μm) were thermocompression bonded and laminated. Specifically, thermocompression bonding was performed at 120 ° C. and 3 MPa with a batch-type hot press.

(Contact resistance measurement)
The resistance in the thickness direction of the current collectors produced in Example 3 and Comparative Example 1 was measured by a four-terminal method using a resistance measuring device (TER-200SS manufactured by ULVAC-RIKO). The measurement pressure was 0.1 to 3.0 MPa, and the measurement temperature was room temperature. The results are shown in FIG. The result of the resistance measurement of the resin layer used in Comparative Example 1 is also shown. From FIG. 13, the resistance of the current collector manufactured in Comparative Example 1 was about 1500 mΩ · cm ² at 0.1 MPa. On the other hand, the resistance of the current collector produced in Example 3 was about 800 mΩ · cm ² under the same conditions. From the above results, it was found that when the resin layer and the ion blocking layer are bonded together, the resistance in the perpendicular direction is greatly reduced by electrically connecting them through the conductive adhesive layer.

  As described above, a current collector in a bipolar lithium ion secondary battery is required to have a partition wall (barrier property) function, a conductivity (conduction in the direction perpendicular to the surface) function, and a function to suppress conduction in the in-plane direction. The The current collectors produced in Examples 1 to 3 have a sufficient partition (barrier) function because a metal foil such as a copper foil or an aluminum foil is used as the ion blocking layer.

Further, regarding the resistance in the direction perpendicular to the surface of the current collector, as shown in FIG. 13, the resistance in the direction perpendicular to the surface of the current collector of Example 3 is about 800 mΩ · cm ² at 0.1 MPa, which can be used without any problem. It became clear that this was possible. Considering that a normal stacked lithium ion secondary battery conducts in the in-plane direction of the current collector, whereas a bipolar lithium ion secondary battery conducts in the direction perpendicular to the current collector Even when the volume resistivity of the current collector is high to some extent, it can be said that it can be used without any problem. As for the current collectors of Examples 1 and 2, since the metal portion of the conductive filler is exposed on the surface of the resin layer, the connection resistance when the resin layer and the ion blocking layer are laminated is negligible. small. Therefore, it is considered that the resistance in the direction perpendicular to the surface of the current collector is substantially equal to the resistance in the direction perpendicular to the surface of the resin layer.

  Further, in the current collectors of Examples 1 to 3, the thickness of the ion blocking layer using a metal material is reduced to about 20 μm, and in Examples 1 and 2, an anisotropic conductive material is used as the resin layer. By using it, it is considered that conduction in the in-plane direction of the current collector is sufficiently suppressed.

Example 4
Using an applicator with a gap of 15 μm on the surface of a copper foil (thickness: 5 μm), which is an ion blocking layer, conductive paint (Nippon Graphite Co., Ltd., Bunny Height UCC, polymer material: rubber, conductive material: graphite (average) Particle diameter 15 μm) and carbon black) were applied. Thereby, a conductive adhesive layer was formed. On this conductive adhesive layer, a conductive resin (olefin resin, thickness: 100 μm) as a resin layer was laminated and pasted. Then, after drying for 10 minutes at 100 degreeC using a hotplate, using a batch type hot press machine, it pressurized and thermocompression bonded at 120 degreeC and 3 MPa for 10 minutes, and obtained the electrical power collector.

(Comparative Example 2)
Example 4 except that the copper foil and the conductive resin were pressed at 120 ° C. and 3 MPa for 10 minutes and thermocompression bonded without forming the conductive adhesive layer using a batch-type hot press machine. A current collector was produced using the same method.

(Comparative Example 3)
A current collector was prepared in the same manner as in Example 4 except that an adhesive having no conductivity was used instead of the conductive adhesive in Example 4.

(Example 5)
An aluminum foil (Toyal Carbo (registered trademark), manufactured by Toyo Aluminum Co., Ltd.) having whiskers of aluminum carbide (Al ₄ C ₃ ) having a diameter of about 20 to 30 nm on the surface was prepared. A conductive adhesive layer was formed by applying and adhering a carbon-containing material containing carbon-containing particles to both surfaces. The composition of the carbon-containing material was prepared by dispersing carbon black having an average particle size of about 300 nm in a solvent (toluene and methyl ethyl ketone) to a solid content of 20%. A conductive resin (olefin resin, thickness: 100 μm), which is a resin layer, is laminated on this conductive adhesive layer, and thermocompression bonding is performed using a batch-type hot press machine at 120 ° C. and 3 MPa for 10 minutes. Thus, a current collector was obtained.

(Example 6)
A current collector was produced in the same manner as in Example 5 except that the solid content of the carbon-containing material was adjusted to 30% by mass.

(Contact resistance measurement)
The resistance in the thickness direction of the current collectors produced in Examples 4 to 6 and Comparative Example 2 was measured using a resistance measuring device (manufactured by ULVAC-RIKO). The measurement pressure was 0.1 to 3.0 MPa, and the measurement temperature was room temperature. The results are shown in FIG. 14 and FIG. The vertical axis | shaft of FIG. 14 and FIG. 15 is a relative value which set the resistance value in 0.1 Mpa of the used conductive resin to 1. In FIG. From the comparison between Example 4 and Comparative Example 1 in FIG. 14, when the resin layer and the ion blocking layer are bonded together, the resistance in the perpendicular direction is greatly reduced by electrically connecting them through the conductive adhesive layer. I found out that In the current collector of Example 4, since the size of the conductive material contained in the conductive adhesive layer is equal to the thickness of the conductive adhesive layer, the resin layer and the ion blocking layer are electrically directly joined. . In addition, when the adhesive agent which does not have electroconductivity like the comparative example 2 was used, reduction of contact resistance was not seen compared with the electrical power collector of the comparative example 2 (not shown). In addition, the volume resistivity in the plane direction was about 3.4 × 10 ⁻⁵ Ω · cm for all the current collectors.

  Furthermore, from the results of Examples 5 and 6 shown in FIG. 15, a layer formed by attaching conductive carbon particles to whiskers present on the surface of the metal as the ion blocking layer functions as a conductive adhesive layer. It was found that the contact resistance with the resin layer can be reduced. Further, from comparison between Examples 5 and 6, it was revealed that the interface resistance can be further reduced by increasing the amount of carbon particles attached to the whisker.

2 resin layer,
3, 3a, 3b ion blocking layer,
4, 4 'conductive material,
5 polymer materials,
6 Interface,
7 Through hole,
8 conductive adhesive layer,
8a adhesive,
9 conductive materials,
9b projecting structure,
9c conductive particles,
10, 50 Bipolar lithium ion secondary battery,
11, 111, 112, 113, 114, 115 current collector,
11a The outermost layer current collector on the positive electrode side,
11b The outermost layer current collector on the negative electrode side,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 electrolyte layer,
19 cell layer,
21, 57 power generation element,
23 Bipolar electrode,
25 positive current collector,
27 negative current collector,
29, 52 Battery exterior material,
31 insulation,
58 positive electrode tab,
59 Negative electrode tab,
250 small battery pack,
300 battery packs,
310 connection jig,
400 Electric car.

Claims (10)

A resin layer having electrical conductivity;
A bipolar battery current collector comprising: at least one ion blocking layer having conductivity and suppressing permeation of ions in a direction perpendicular to the plane;
The resin layer includes a polymer material and a conductive material, and at least a part of the conductive material is exposed at an interface between the resin layer and the ion blocking layer, and at least a part of the conductive material. Is a bipolar battery current collector that penetrates the resin layer . A resin layer having electrical conductivity;
A bipolar battery current collector comprising: at least one ion blocking layer having conductivity and suppressing permeation of ions in a direction perpendicular to the plane;
The resin layer includes a polymer material and a conductive material, at least a part of the conductive material is exposed at an interface between the resin layer and the ion blocking layer, and the resin layer is A bipolar battery current collector, comprising: the polymer material having a through hole in a direction; and the conductive material disposed in the through hole. The current collector for a bipolar battery according to claim 1 or 2 , wherein the conductive material has a fiber shape. The current collector for a bipolar battery according to any one of claims 1 to 3 , wherein the resin layer contains 5% by volume or more of the conductive material. A resin layer having electrical conductivity;
A bipolar battery current collector comprising: at least one ion blocking layer having conductivity and suppressing permeation of ions in a direction perpendicular to the plane;
The resin layer includes a polymer material and a conductive material, and at least one interface between the resin layer and the ion blocking layer is electrically bonded by a conductive adhesive layer, and the conductive adhesive layer Includes a particulate conductive material and an adhesive, and the particle size of the particulate conductive material contained in the conductive adhesive layer is equal to or greater than the thickness of the conductive adhesive layer. Electric body. A resin layer having electrical conductivity;
A bipolar battery current collector comprising: at least one ion blocking layer having conductivity and suppressing permeation of ions in a direction perpendicular to the plane;
The resin layer includes a polymer material and a conductive material, and at least one interface between the resin layer and the ion blocking layer is electrically bonded by a conductive adhesive layer, and the conductive adhesive layer Includes a particulate conductive material and an adhesive,
The bipolar battery current collector, wherein the particulate conductive material contained in the conductive adhesive layer is a particle having a whisker shape, and the conductive particle is further added to the particle having the whisker shape. . Wherein said ion blocking layer on both surfaces of the resin layer is disposed, the bipolar battery current collector according to any one of claims 1-6. The conductive material contained in the resin layer, a metal, an alloy, a carbon material, ceramics, metal carbides, metal nitrides, and one or more selected from the group consisting of metal oxides, according to claim 1 to 7 The current collector for a bipolar battery according to any one of the above. To any one of claims 1-8 including a bipolar battery current collector according bipolar electrode. A bipolar battery comprising the bipolar electrode according to claim 9 .