JP2010205633A - Bipolar secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means of preventing peeling-off of an active material layer in a bipolar electrode. <P>SOLUTION: A bipolar secondary battery has a power generating element in which the bipolar electrode and an electrolyte layer are laminated. The bipolar electrode has a current collector including a resin layer which has a first resin as the base material, and has conductivity, a positive electrode active material layer formed on one face of the current collector, and a negative electrode active material layer formed on the other face of the current collector. The outer peripheral part of a single cell layer constituted of the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer is sealed by a sealing part having a second resin as the base material. Then, the maximum component of the first resin and the maximum part of the second resin are composed of the same polymer material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a bipolar secondary battery, and an assembled battery and a vehicle using the battery. In particular, the present invention relates to a bipolar secondary battery capable of preventing separation of an active material layer in a bipolar electrode, and an assembled battery and a vehicle using the battery.

  In recent years, hybrid vehicles (HEV), electric vehicles (EV), and fuel cell vehicles have been manufactured and sold from the viewpoint of environment and fuel consumption, and new developments are continuing. In these so-called electric vehicles, it is indispensable to use a power supply device capable of discharging and charging. As the power supply device, a secondary battery such as a lithium ion battery or a nickel metal hydride battery, an electric double layer capacitor, or the like is used. In particular, lithium ion secondary batteries are considered suitable for electric vehicles because of their high energy density and high durability against repeated charging and discharging, and various developments have been intensively advanced. However, in order to apply to the power sources for driving motors of various automobiles as described above, it is necessary to use a plurality of secondary batteries connected in series in order to ensure a large output.

  However, when a battery is connected via the connection portion, the output is reduced due to the electrical resistance of the connection portion. Further, the battery having the connection portion has a disadvantage in terms of space. That is, the connection portion causes a reduction in the output density and energy density of the battery.

  In order to solve this problem, bipolar secondary batteries such as bipolar lithium ion secondary batteries have been developed. A bipolar secondary battery has a plurality of bipolar electrodes in which a positive electrode active material layer is formed on one surface of a current collector and a negative electrode active material layer is formed on the other surface through an electrolyte layer and a separator. It has a power generation element. In other words, the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer form one single cell layer, and a plurality of the single cell layers are stacked with the current collector interposed therebetween.

  In a bipolar secondary battery having such a structure, when an electrolyte containing an electrolyte such as a liquid electrolyte or a polymer gel electrolyte is used, the electrolyte leaks out from the single battery layer, and the electrolyte of another single battery layer May come into contact with the liquid and cause a liquid junction. For this reason, normally, in a bipolar secondary battery, a seal part is disposed so as to surround the outer periphery of the single cell layer, and a liquid junction is prevented by sealing the single cell layer (for example, patents). Reference 1).

Japanese Patent Laid-Open No. 9-23003

  By the way, in the bipolar secondary battery, the current collector is preferably made of a lighter material from the viewpoint of improving the power density per unit mass of the battery. Therefore, in recent years, a current collector composed of a resin or a conductive polymer material to which a conductive filler is added has been proposed in place of the conventional metal foil.

  However, when the resin is used as the base material of the current collector in this way, heat is generated during charging and discharging of the bipolar secondary battery, but each member of the battery is thermally expanded by this heat. At this time, if the difference in thermal expansion between the current collector and the seal portion is large, stress is applied to the current collector. Since the current collector made of resin has a lower strength than the current collector made of metal foil, the stress causes strain in the current collector. In addition, there is a problem that displacement occurs in the laminated portion of the current collector surface and the active material layer surface, the active material layer formed on the current collector surface peels off, and the battery voltage decreases.

  This invention is made | formed in view of the said situation, and it aims at providing the means which prevents peeling of an active material layer in a bipolar electrode.

  The inventors of the present invention have studied a means for solving the above problem. As a result, a resin current collector is obtained by using a polymer material having the same maximum component of the resin used for the current collector and the resin used for the seal portion. It has been found that the stress applied to can be reduced. And it discovered that peeling of the electrolyte layer in a bipolar electrode could be prevented by this means, and completed this invention.

  That is, the bipolar secondary battery of the present invention has a power generation element in which a bipolar electrode and an electrolyte layer are laminated. The bipolar electrode includes a current collector including a conductive resin layer based on a first resin, a positive electrode active material layer formed on one surface of the current collector, and the other current collector. It has a negative electrode active material layer formed on the surface. The outer peripheral portion of the single battery layer composed of the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer is sealed with a seal portion using a second resin as a base material. The maximum component of the first resin and the maximum component of the second resin are the same polymer material.

  According to the present invention, since the difference in thermal expansion between the current collector and the seal portion is reduced, the stress applied to the current collector can be reduced. Thereby, the displacement in the lamination | stacking part of the electrical power collector surface and the active material layer surface is reduced, and peeling of the active material layer from the electrical power collector surface can be prevented.

1 is a schematic cross-sectional view schematically showing a bipolar secondary battery according to an embodiment of the present invention. FIG. 2A is a diagram schematically illustrating an embodiment of joining of a separator and a seal portion according to the present invention, FIG. 2A is a cross-sectional view of a power generation element, and FIG. 2B is a view when the power generation element is viewed from the stacking direction. It is a figure showing the junction part of a separator and a seal part. FIGS. 3A and 3B are diagrams schematically illustrating another embodiment of the bonding between the separator and the seal portion according to the present invention, in which FIG. 3A is a cross-sectional view of the power generation element, and FIG. It is a figure showing the junction part of the separator and seal part in the case. 4A and 4B are external views schematically showing an assembled battery according to an embodiment of the present invention, in which FIG. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. It is a side view. It is a conceptual diagram of the vehicle carrying the bipolar secondary battery or assembled battery of this invention.

  Hereinafter, preferred embodiments of the present invention will be described. The present embodiment relates to a bipolar secondary battery having a power generation element in which a bipolar electrode and an electrolyte layer are laminated. The bipolar electrode includes a current collector including a conductive resin layer based on a first resin, a positive electrode active material layer formed on one surface of the current collector, and the other current collector. It has a negative electrode active material layer formed on the surface. The outer peripheral portion of the single battery layer composed of the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer is sealed with a seal portion using a second resin as a base material. The maximum component of the first resin and the maximum component of the second resin are the same polymer material.

  Hereinafter, the present embodiment will be described with reference to the drawings. However, the technical scope of the present invention should be determined based on the description of the scope of claims, and is not limited to the following embodiments. 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.

<Bipolar type secondary battery>
FIG. 1 is a cross-sectional view schematically showing the overall structure of a bipolar secondary battery according to an embodiment of the present invention. The bipolar secondary battery 10 of this embodiment 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 laminate film 29 that is a battery exterior material. .

  As shown in FIG. 1, in the power generation element 21 of the bipolar secondary battery 10 of the present embodiment, a positive electrode active material layer 13 that is electrically coupled to one surface of the current collector 11 is formed. And a plurality of bipolar electrodes 23 having a negative electrode active material layer 15 electrically coupled to the opposite 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 secondary battery 10 has a configuration in which the single battery layers 19 are stacked. 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, a positive electrode current collector plate 25 is disposed so as to be adjacent to the outermost layer current collector 11a on the positive electrode side, and this is extended to form a laminate film 29 which is a battery exterior material. Derived. On the other hand, the negative electrode current collector plate 27 is disposed so as to be adjacent to the outermost layer current collector 11b on the negative electrode side, and similarly, this is extended and led out from the laminate film 29 which is an exterior of the battery.

  In the bipolar secondary battery 10 shown in FIG. 1, a seal portion 31 is provided around each unit cell layer 19. This seal portion 31 is short-circuited due to a liquid junction due to leakage of the electrolyte, contact between adjacent current collectors 11 in the battery, or slight irregularities at the end portions of the unit cell layer 19 in the power generation element 21. It is provided for the purpose of preventing the occurrence of By installing such a seal portion 31, long-term reliability and safety are ensured, and a high-quality bipolar 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 secondary battery 10, in order to prevent external impact and environmental degradation during use, the power generation element 21 is sealed under reduced pressure in a laminate film 29 that is a battery exterior material, and the positive electrode current collector plate 25 and the negative electrode current collector 25. A structure in which the electric plate 27 is taken out of the laminate film 29 is preferable. Hereinafter, main components of the bipolar secondary battery of this embodiment will be described.

[Bipolar electrode]
The bipolar electrode has a current collector and an active material layer formed on the surface of the current collector. More specifically, a positive electrode active material layer is formed on one surface of one current collector, and a negative electrode active material layer is formed on the other surface. The active material layer includes a positive electrode active material or a negative electrode active material, and further includes other additives as necessary.

(Current collector)
The current collector has a function of mediating transfer of electrons from one surface in contact with the positive electrode active material layer to the other surface in contact with the negative electrode active material layer. The current collector according to this embodiment essentially includes a conductive resin layer (hereinafter also simply referred to as “resin layer”), and may further include other layers as necessary.

  The resin layer can contribute to weight reduction of the current collector as well as a function as an electron transfer medium. The resin layer may include a base material made of the first resin and other members such as a conductive filler as necessary.

  The polymer material contained in the first resin is not particularly limited, and a conventionally known non-conductive polymer material or conductive polymer material can be used. However, in the bipolar battery of this embodiment, the maximum component of the first resin and the maximum component of the second resin are the same polymer material. In the present specification, the “maximum component” means a component having a maximum mass ratio with respect to the total mass of the resin. Since the second resin that is the base material of the seal portion needs to be insulative, the polymer material of the maximum component of the first resin needs to be a non-conductive polymer material. Conversely, as long as the first resin contains one kind of non-conductive polymer material, other non-conductive polymer materials and conductive polymer materials may be mixed as appropriate.

  Examples of preferable non-conductive polymer materials used as the base material include polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE)), polypropylene (PP), polyethylene terephthalate (PET), and polyether. Nitrile (PEN), polyimide (PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), Examples include polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), and polystyrene (PS). Such a non-conductive polymer material may have excellent potential resistance or solvent resistance. Examples of preferable conductive polymer materials include polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, and polyoxadiazole. Since such a conductive polymer material has sufficient conductivity even without adding a conductive filler, it is advantageous in terms of reducing the weight of the current collector. These non-conductive polymer materials or conductive polymer materials may be used alone or in a combination of two or more.

  In order to ensure the conductivity of the resin layer, a conductive filler may be added to the substrate as necessary. In particular, when the resin is composed only of a non-conductive polymer, a conductive filler is inevitably necessary to impart conductivity to the resin. The conductive filler can be used without particular limitation as long as it is a substance having conductivity. For example, metals, conductive carbon, etc. are mentioned as a material excellent in electroconductivity, electric potential resistance, or lithium ion barrier | blocking property.

  The metal is not particularly limited, but at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, Sb, and K, or these metals It is preferable to contain an alloy or metal oxide containing. These metals are resistant to the potential of the positive electrode or negative electrode formed on the current collector surface. For example, Al is resistant to the positive electrode potential, Ni and Cu are resistant to the negative electrode potential, and Ti and Pt are resistant to the potentials of both electrodes. Among these, an alloy containing at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, and Cr is more preferable.

  Specific examples of the alloy include stainless steel (SUS), Inconel (registered trademark), Hastelloy (registered trademark), and other Fe—Cr alloys, Ni—Cr alloys, and the like. By using these alloys, higher potential resistance can be obtained.

  The conductive carbon is not particularly limited, but is at least one selected from the group consisting of acetylene black, vulcan, black pearl, carbon nanofiber, ketjen black, carbon nanotube, carbon nanohorn, carbon nanoballoon, and fullerene. It is preferable to contain. These conductive carbons have a very wide potential window, are stable in a wide range with respect to both the positive electrode potential and the negative electrode potential, and have excellent conductivity. Among these, it is more preferable to include at least one selected from the group consisting of carbon nanotubes, carbon nanohorns, ketjen black, carbon nanoballoons, and fullerenes. Since these conductive carbons have a hollow structure, the surface area per mass is large, and the current collector can be further reduced in weight. In addition, electroconductive fillers, such as these metals and electroconductive carbon, can be used individually by 1 type or in combination of 2 or more types.

  The shape of the conductive filler is not particularly limited, and a known shape such as a granular shape, a fibrous shape, a plate shape, a lump shape, a cloth shape, and a mesh shape can be appropriately selected. For example, when it is desired to impart conductivity to a resin over a wide range, it is preferable to use a granular conductive filler. On the other hand, when it is desired to further improve the conductivity in a specific direction in the resin, it is preferable to use a conductive filler having a certain direction in the shape of a fiber or the like.

  The size of the conductive filler is not particularly limited, and fillers of various sizes can be used depending on the size and thickness of the resin layer or the shape of the conductive filler. As an example, the average particle diameter when the conductive filler is granular is preferably about 0.1 to 10 μm from the viewpoint of facilitating molding of the resin layer. In the present specification, “particle diameter” means the maximum distance L among the distances between any two points on the contour line of the conductive filler. As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted. The particle diameter and average particle diameter of an active material to be described later can be defined similarly.

  The content of the conductive filler contained in the resin layer is not particularly limited. In particular, when the resin includes a conductive polymer material and sufficient conductivity can be secured, it is not always necessary to add a conductive filler. However, when the resin is made of only a nonconductive polymer material, it is essential to add a conductive filler in order to impart conductivity. In this case, the content of the conductive filler is preferably 5 to 35% by mass, more preferably 5 to 25% by mass, and further preferably 5 to 5% by mass with respect to the total mass of the non-conductive polymer material. 15% by mass. By adding such an amount of conductive filler to the resin, sufficient conductivity can be imparted to the non-conductive polymer material while suppressing an increase in the mass of the resin layer.

  The form of dispersion of the conductive filler in the resin layer is not particularly limited, and may be a form that is uniformly dispersed in the resin that is the base material, or may be partially localized and dispersed. Of course. When it is desired to impart conductivity uniformly throughout the resin layer, the conductive filler is preferably dispersed uniformly throughout the resin.

  The thickness of one layer of the resin layer having conductivity is preferably 1 to 200 μm, more preferably 10 to 100 μm, and still more preferably 10 to 50 μm. When the thickness of the resin layer is in such a range, the resistance in the thickness direction can be suppressed sufficiently low. Therefore, it is possible to increase the output density of the battery by reducing the weight while securing the conductivity of the current collector. Furthermore, the life characteristics can be improved and the vibration resistance can be improved by reducing the liquid junction.

  The form of the current collector is not particularly limited as long as it includes a resin layer having conductivity, and can take various forms. For example, the shape of the current collector may be a laminate including other layers as needed in addition to the resin layer. Examples of other layers other than the resin layer include a metal layer and an adhesive layer, but are not limited thereto. For example, one type of conductive resin layer may form a current collector alone, or two or more types of conductive resin layers may be laminated. By laminating a plurality of resin layers in this manner, even if a minute crack occurs in each resin layer, the position of the crack does not match, so that a liquid junction can be prevented. In addition to the resin layer, a metal layer containing a metal such as aluminum, nickel, or copper, or an alloy thereof may be provided between the resin layers. By including such a metal layer, liquid junction between the positive electrode active material layer and the negative electrode active material layer in the bipolar electrode due to ion permeation in the resin layer can be prevented, and long-term reliability with improved lifetime characteristics Bipolar secondary batteries with excellent performance can be constructed. In addition, as a method of laminating the resin layer and the metal layer, a method of depositing metal on the resin layer, a method of fusing resin on the metal foil, and the like can be mentioned. In addition, when the current collector is formed by laminating two or more resin layers or metal layers, the two layers are from the viewpoint of reducing the contact resistance at the boundary surface of the layers or preventing peeling of the adhesive surface. It may be bonded via an adhesive layer. Examples of the material used for such an adhesive layer include metal oxide-based conductive pastes including zinc oxide, indium oxide, and titanium oxide; and carbon-based conductive pastes including carbon black, carbon nanotubes, and graphite. Preferably used.

  The thickness of the current collector is preferably thinner in order to increase the output density of the battery by reducing the weight. In a bipolar secondary battery, the current collector existing between the positive electrode active material layer and the negative electrode active material layer of the bipolar electrode may have a high electric resistance in the horizontal direction in the stacking direction. It is possible to reduce the thickness. Specifically, the thickness of the current collector is preferably 1 to 200 μm, more preferably 5 to 150 μm, and still more preferably 10 to 100 μm. By having such a thickness, it is possible to construct a battery having excellent output characteristics and excellent long-term reliability.

(Positive electrode active material layer)
The positive electrode active material layer includes a positive electrode active material. The positive electrode active material has a composition that occludes ions during discharging and releases ions during charging. A preferable example is a lithium-transition metal composite oxide that is a composite oxide of a transition metal and lithium. Specifically, Li · Co-based composite oxide such as LiCoO _2, Li · Ni-based composite oxide such as LiNiO _2, Li · Mn-based composite oxide such as spinel LiMn ₂ O _4, Li · such LiFeO ₂ Fe-based composite oxides and those obtained by replacing some of these transition metals with other elements can be used. These lithium-transition metal composite oxides are excellent in reactivity and cycle characteristics, and are low-cost materials. Therefore, it is possible to form a battery having excellent output characteristics by using these materials for electrodes. In addition, examples of the positive electrode active material include transition metal oxides such as LiFePO ₄ and lithium phosphate compounds and sulfate compounds; transition metal oxides such as V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , and MoO ₃ , and sulfides. A substance; PbO ₂ , AgO, NiOOH, or the like can also be used. The positive electrode active material may be used alone or in the form of a mixture of two or more.

  The average particle diameter of the positive electrode active material is not particularly limited, but is preferably 1 to 100 μm, more preferably 1 to 20 μm, from the viewpoint of increasing the capacity, reactivity, and cycle durability of the positive electrode active material. Within such a range, the secondary battery can suppress an increase in the internal resistance of the battery during charging and discharging under high output conditions, and can extract a sufficient current. In addition, when the positive electrode active material is secondary particles, it can be said that the average particle diameter of the primary particles constituting the secondary particles is preferably in the range of 10 nm to 1 μm. It is not limited to. However, it goes without saying that, depending on the manufacturing method, the positive electrode active material may not be a secondary particle formed by aggregation, agglomeration, or the like. As the particle diameter of the positive electrode active material and the particle diameter of the primary particles, a median diameter obtained using a laser diffraction method can be used. The shape of the positive electrode active material varies depending on the type and manufacturing method, and examples thereof include a spherical shape (powdered shape), a plate shape, a needle shape, a column shape, and a square shape, but are not limited thereto. Any shape can be used without any problems. Preferably, an optimal shape that can improve battery characteristics such as charge / discharge characteristics is appropriately selected.

(Negative electrode active material layer)
The negative electrode active material layer includes a negative electrode active material. The negative electrode active material has a composition capable of releasing ions during discharge and storing ions during charging. The negative electrode active material is not particularly limited as long as it can reversibly store and release lithium. Examples of the negative electrode active material include metals such as Si and Sn, TiO, Ti ₂ O ₃ , TiO ₂ , or Metal oxides such as SiO ₂ , SiO, SnO ₂ , complex oxides of lithium and transition metals such as Li _4/3 Ti _5/3 O ₄ or Li ₇ MnN, Li—Pb alloys, Li—Al alloys , Li, or carbon materials such as natural graphite, artificial graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, or hard carbon. Moreover, it is preferable that a negative electrode active material contains the element alloyed with lithium. By using an element that forms an alloy with lithium, it is possible to obtain a battery having a high capacity and an excellent output characteristic having a higher energy density than that of a conventional carbon-based material. The negative electrode active material may be used alone or in the form of a mixture of two or more.

  The element alloying with lithium is not limited to the following, but specifically, Si, Ge, Sn, Pb, Al, In, Zn, H, Ca, Sr, Ba, Ru, Rh, Ir, Pd, Pt, Ag, Au, Cd, Hg, Ga, Tl, C, N, Sb, Bi, O, S, Se, Te, Cl, and the like. Among these, from the viewpoint of configuring a battery having excellent capacity and energy density, at least one selected from the group consisting of carbon materials and / or Si, Ge, Sn, Pb, Al, In, and Zn. It is preferable to include an element, and it is particularly preferable to include an element of a carbon material, Si, or Sn. These may be used alone or in combination of two or more.

  The average particle size of the negative electrode active material is not particularly limited, but is preferably 1 to 100 μm, more preferably 1 to 20 μm from the viewpoint of increasing the capacity, reactivity, and cycle durability of the negative electrode active material. Within such a range, the secondary battery can suppress an increase in the internal resistance of the battery during charging and discharging under high output conditions, and can extract a sufficient current. In addition, when the negative electrode active material is secondary particles, it can be said that the average particle diameter of the primary particles constituting the secondary particles is preferably in the range of 10 nm to 1 μm. It is not limited to. However, it goes without saying that, depending on the manufacturing method, the negative electrode active material may not be a secondary particle formed by aggregation, lump or the like. As the particle diameter of the negative electrode active material and the particle diameter of the primary particles, a median diameter obtained by using a laser diffraction method can be used. The shape of the negative electrode active material varies depending on the type and manufacturing method, and examples thereof include a spherical shape (powdered shape), a plate shape, a needle shape, a column shape, and a square shape, but are not limited thereto. Any shape can be used without any problems. Preferably, an optimal shape that can improve battery characteristics such as charge / discharge characteristics is appropriately selected.

  The active material layer may contain other materials if necessary. For example, a conductive aid, a binder, and the like can 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 an active material layer. Examples of the conductive aid include carbon powders such as acetylene black, carbon black, ketjen black, and graphite, various carbon fibers such as vapor grown carbon fiber (VGCF; registered trademark), expanded graphite, and the like. However, it goes without saying that the conductive aid is not limited to these.

  Examples of the binder include polyvinylidene fluoride (PVdF), polyimide (PI), PTFE, SBR, and a synthetic rubber binder. However, it goes without saying that the binder is not limited to these. When the binder and the matrix polymer used as the gel electrolyte are the same, it is not necessary to use a binder.

  The compounding ratio of the components contained in the active material layer is not particularly limited. The blending ratio can be adjusted by appropriately referring to known knowledge about lithium ion secondary batteries. The thickness of the active material layer is not particularly limited, and conventionally known knowledge about the lithium ion secondary battery can be appropriately referred to. As an example, the thickness of the active material layer is preferably about 10 to 100 μm, and more preferably 20 to 50 μm. If the active material layer is about 10 μm or more, the battery capacity can be sufficiently secured. On the other hand, if the active material layer is about 100 μm or less, it is possible to suppress the occurrence of the problem of an increase in internal resistance due to the difficulty in diffusing lithium ions in the electrode deep part (current collector side).

  The method for forming the positive electrode active material layer (or the negative electrode active material layer) on the current collector surface is not particularly limited, and known methods can be used in the same manner. For example, as described above, a positive electrode active material (or a negative electrode active material) and, if necessary, an electrolyte salt for increasing ion conductivity, a conductive auxiliary agent for increasing electron conductivity, and a binder are appropriately used. A positive electrode active material slurry (or a negative electrode active material slurry) is prepared by dispersing and dissolving in a solvent. This is applied onto a current collector, dried to remove the solvent, and then pressed to form a positive electrode active material layer (or negative electrode active material layer) on the current collector. In this case, the solvent is not particularly limited, and N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylformamide, cyclohexane, hexane and the like can be used. When adopting polyvinylidene fluoride (PVdF) as a binder, NMP is preferably used as a solvent.

  In the above method, the positive electrode active material slurry (or the negative electrode active material slurry) is applied onto the current collector, dried, and then pressed. At this time, the porosity of the positive electrode active material layer (or the negative electrode active material layer) can be controlled by adjusting the pressing conditions.

  Specific means and press conditions for the press treatment are not particularly limited, and can be appropriately adjusted so that the porosity of the positive electrode active material layer (or the negative electrode active material layer) after the press treatment becomes a desired value. Specific examples of the press process include a hot press machine and a calendar roll press machine. Also, the pressing conditions (temperature, pressure, etc.) are not particularly limited, and conventionally known knowledge can be referred to as appropriate.

[Electrolyte layer]
The electrolyte layer has a function as a medium when lithium ions move between the electrodes. In the present embodiment, the electrolyte constituting the electrolyte layer is not particularly limited as long as it contains a supporting salt and a solvent as the electrolytic solution, and conventionally known liquid electrolytes and polymer gel electrolytes can be appropriately employed.

  The liquid electrolyte is obtained by dissolving a lithium salt as a supporting salt in a solvent. Examples of the solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propionate (MP), methyl acetate (MA), and methyl formate (MF). 4-methyldioxolane (4MeDOL), dioxolane (DOL), 2-methyltetrahydrofuran (2MeTHF), tetrahydrofuran (THF), dimethoxyethane (DME), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) , And γ-butyrolactone (GBL). These solvents may be used alone or as a mixture of two or more.

As the supporting salt (lithium salt) is not particularly _{limited, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiSbF 6, LiAlCl 4, Li 2 B 10 Cl 10, LiI, LiBr, LiCl Inorganic acid anion salts such as LiAlCl, LiHF ₂ and LiSCN, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiBOB (lithium bisoxide borate), LiBETI (lithium bis (perfluoroethylenesulfonylimide); And organic acid anion salts such as Li (C ₂ F ₅ SO ₂ ) ₂ N). These electrolyte salts may be used alone or in the form of a mixture of two or more.

  On the other hand, the polymer gel electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer having lithium ion conductivity. Examples of the matrix polymer having lithium ion conductivity include a polymer having polyethylene oxide in the main chain or side chain (PEO), a polymer having polypropylene oxide in the main chain or side chain (PPO), polyethylene glycol (PEG), poly Acrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), polyacrylonitrile (PAN), poly (methyl acrylate) (PMA), poly (Methyl methacrylate) (PMMA) etc. are mentioned. In addition, mixtures of the above-described polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, and the like can also be used. Among these, it is desirable to use PEO, PPO and their copolymers, PVdF, PVdF-HFP. In such a matrix polymer, an electrolyte salt such as a lithium salt can be well dissolved. In addition, the matrix polymer can exhibit excellent mechanical strength by forming a crosslinked structure.

[Separator]
In the bipolar secondary battery of this embodiment, since the electrolyte layer is composed of a liquid electrolyte or a polymer gel electrolyte, it is preferable to use a separator for the electrolyte layer for the purpose of holding the electrolytic solution. As the third resin used for the base material of the separator, the same material as the non-conductive polymer material used for the first resin described above can be used without limitation. Is omitted.

  There is no restriction | limiting in particular in the form of a separator, It can be a porous film | membrane which has many fine pores, a nonwoven fabric, or these laminated bodies. In addition, a composite resin film in which a polyolefin-based resin nonwoven fabric or a polyolefin-based resin porous film is used as a reinforcing material layer, and the reinforcing material layer is filled with a vinylidene fluoride resin compound may be used.

[Seal part]
The seal portion has a function of preventing a liquid junction due to leakage of the electrolyte, a contact between current collectors, and a short circuit at the end of the unit cell layer. The second resin used for the base material of the seal part is insulation, sealing performance against leakage of electrolyte, sealing performance against moisture permeation from outside (sealing performance), heat resistance under battery operating temperature, etc. As long as it has, there is no particular limitation. Therefore, as the second resin, the same non-conductive polymer material used in the first resin used as the base material of the current collector can be used. Among these, polyethylene and polypropylene are preferably used as the constituent material of the seal portion from the viewpoints of corrosion resistance, chemical resistance, ease of production (film forming property), economy, and the like.

  In the bipolar secondary battery of this embodiment, the maximum component of the first resin used as the base material of the resin layer and the maximum component of the second resin used as the base material of the seal portion are the same polymer. Material. By having such a configuration, the difference in thermal expansion due to heat during charging and discharging between the current collector and the seal portion is reduced, and the stress applied to the current collector can be reduced. Thereby, the displacement in the lamination | stacking part of the electrical power collector surface and an active material surface is reduced, and peeling of the active material layer from the electrical power collector surface can be prevented. Moreover, since the conformity of the first resin and the second resin is improved by this configuration, when the current collector surface and the seal portion surface are heat-sealed by a press process, the adhesion interface is reduced, Alternatively, the adhesion interface can be eliminated and the sealing reliability can be improved. Thereby, the leakage of the electrolyte solution from the unit cell layer can be effectively prevented.

  Furthermore, in each of the first resin and the second resin, the content ratio of the maximum component is preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass. preferable. That the content ratio of the maximum component is 100% by mass means that the first resin and the second resin are composed of only one type of polymer material. By increasing the content ratio of the maximum component contained in each resin, the difference in thermal expansion can be further reduced, and peeling of the active material layer from the current collector surface can be more effectively suppressed. Moreover, the interface at the time of fuse | melting the collector surface and the seal | sticker part surface can be reduced more, and the reliability of a seal | sticker improves more. In the present specification, when the current collector includes a plurality of resin layers, the base material of the resin layer constituting the current collector surface facing the seal portion is treated as the “first resin”.

  As the structure of the bipolar secondary battery of this embodiment, the difference between the total thickness of the members included in one single cell layer and the total thickness of the seal portion is ± 5 with respect to the total thickness of the seal portion. % Is preferable. The most preferable mode is a mode in which the total thickness of the members included in one single cell layer is equal to the total thickness of the seal portions. Here, the “member included in the unit cell layer” means a positive electrode active material layer and a negative electrode active material layer, and includes a separator when the electrolyte layer includes a separator. Furthermore, in addition to this, when a solid or gel-like member having a thickness in the stacking direction is included, the concept includes these members. The reason why such a form is preferable is as follows. When the sum of the thicknesses of the members included in the single battery layer is 5% or more larger than the sum of the thicknesses of the seal portions, the stress applied to the edge of the outer peripheral portion of the current collector can be increased. On the other hand, when the total thickness of the members included in the single cell layer is 5% or more smaller than the total thickness of the seal portion, the stress applied to the edge of the inner peripheral portion of the seal portion can be increased. Thus, if there is a difference between the total thickness of the members and the total thickness of the seal portion, stress is likely to occur in the direction in which the current collector is to be bent. Therefore, in order to reduce such stress, it is preferable that the difference between the total thickness of the members and the total thickness of the seal portions is within ± 5%.

  Further, as described above, since the bipolar secondary battery of this embodiment includes an electrolyte solution in the electrolyte layer, the electrolyte layer preferably includes a separator for holding the electrolyte solution. At this time, the separator is preferably joined to the seal portion from the viewpoint of further improving the seal reliability. That is, when at least a part of the peripheral edge portion of the separator is viewed from the stacking direction of the power generation elements, it is preferable that the separator is joined to the portion sealed with the seal portion. One embodiment of the joining of the separator and the seal portion is shown in FIG. In FIG. 2, the outer periphery of the separator 33 is larger than the outer periphery of the current collector 11, and the seal portion 31 is disposed so as to protrude from the peripheral edge of the current collector 11. The separator 33 is joined so as to protrude from the outer periphery of the seal portion 31. When this is viewed from the stacking direction of the power generation elements, the hatched portion is the joint surface between the separator 33 and the seal portion 31. Another embodiment of joining the separator and the seal portion is shown in FIG. According to FIG. 3, the outer periphery of the separator is smaller than the outer periphery of the current collector, and the seal portion is disposed so as to protrude from the peripheral portion of the current collector. The separator 33 is joined so as to be embedded in the seal portion 31. When this is viewed from the stacking direction of the power generation elements, the hatched portion represents the joint surface between the separator 33 and the seal portion 31. However, these forms of joining are merely examples, and various forms can be adopted as long as at least a part of the outer peripheral part of the separator is joined to the seal part.

  Thus, when the separator and the seal portion are joined, the maximum component of the first resin that is the base material of the current collector, the maximum component of the second resin that is the base material of the seal portion, It is preferable that the third resin which is the base material of the separator is the same polymer material. At this time, the content of the maximum component in each of the first resin, the second resin, and the third resin is preferably 80% by mass or more, more preferably 90% by mass or more, Most preferably, it is mass%. That the content ratio of the maximum component is 100% by mass means that the first resin, the second resin, and the third resin are composed of only one kind of polymer material. In the present specification, when the separator is a composite resin film containing a plurality of resins as described above, the resin base material constituting the separator surface facing the seal portion is treated as the “third resin”. .

  The reason why such a configuration is preferable in the present embodiment is as follows. Usually, the separator also causes thermal expansion due to heat during charging and discharging, like other members included in the battery. At this time, the expansion / contraction of the separator may generate a stress that causes the current collector to expand or contract via the seal portion. Therefore, by making the maximum component of the resin that is the base material of each member the same polymer material and setting the content of the maximum component in each resin to 90% by mass or more, the current collector, the seal portion, and the separator The difference in thermal expansion can be reduced. Thereby, the stress concerning a collector can be reduced and peeling of the active material layer from the collector surface can be prevented more effectively. In addition, by adopting such a configuration, the familiarity between the second resin and the third resin is improved, so that the adhesion interface is reduced when the separator surface and the seal portion surface are fused by pressing. Or, the adhesion interface is eliminated, and the durability of the seal portion is further improved.

  The polymer material which is the maximum component of the first resin, the second resin, or the third resin can be used without particular limitation as long as it is a non-conductive polymer material. The specific non-conductive polymer material is the same as the non-conductive polymer material used for the first resin serving as the base material of the current collector, and thus detailed description thereof is omitted here. Among such non-conductive polymer materials, it is preferable to use a thermoplastic polymer material, which is a material that is easily heat-sealed in order to improve seal reliability. Moreover, the workability in the process of laminating a bipolar electrode and a separator can be ensured by using a thermoplastic polymer material. That is, when a thermosetting resin is used, once the hot press treatment is performed, the resin is cured, so that there is a limitation that it becomes difficult to perform heat fusion again. However, when a thermoplastic resin is used, There is no limit. The melting point of the thermoplastic polymer material is preferably 100 to 200 ° C, more preferably 200 to 300 ° C, and further preferably 300 to 400 ° C. By having such a melting point, sealing reliability can be ensured even when the battery operating temperature is high. In addition, when mentioning melting | fusing point of a preferable nonelectroconductive polymer material, polyethylene (PE) is 110-130 degreeC, and polypropylene (PP) is 160-170 degreeC. Polyethernitrile (PEN) is 269 ° C, polyethylene terephthalate (PET) is 250-260 ° C, and thermoplastic polyimide (PI) is 380 ° C. By using these non-conductive polymer materials, excellent sealing performance can be maintained even at high temperature operation.

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

<Battery assembly>
An assembled battery can be obtained by electrically connecting a plurality of bipolar secondary batteries of this embodiment in series or in parallel. Thus, it becomes possible to adjust a capacity | capacitance and a voltage freely by parallelizing a some battery in series or in parallel.

  4 is an external view of a typical embodiment of the assembled battery according to the present invention, FIG. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. 4C is an assembled battery. FIG.

  As shown in FIG. 4, the assembled battery 300 according to this embodiment forms a small assembled battery 250 that can be attached and detached by connecting a plurality of bipolar secondary batteries of this embodiment in series or in parallel. A large capacity and 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 output density by connecting a plurality of these detachable small assembled batteries 250 in series or in parallel. It is also possible to form an assembled battery 300 having 4A is a plan view of the assembled battery, FIG. 4A is a front view, and FIG. 4C 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 secondary batteries are connected to produce the assembled battery 250, and how many assembled batteries 250 are laminated to produce the assembled battery 300 depends on the vehicle (electric vehicle) to be mounted. It may be determined according to the battery capacity and output.

<Vehicle>
The vehicle according to the present embodiment is characterized by mounting the lithium ion battery according to the present embodiment or a combination battery formed by combining a plurality of these. In this embodiment, since a battery having a long life and excellent long-term reliability and output characteristics can be configured, it is possible to configure a plug-in hybrid electric vehicle having a long EV travel distance and an electric vehicle having a long charge travel distance when such a battery is mounted. . In other words, the lithium ion battery of this embodiment or an assembled battery formed by combining a plurality of these can be used as a power source for driving a vehicle. The lithium ion battery of the present embodiment or a combination battery formed by combining a plurality of these is a vehicle, for example, a hybrid vehicle, a fuel cell vehicle, an electric vehicle (for automobiles, all four-wheel vehicles (passenger cars, trucks, buses and other commercial vehicles, This is because it can be used for motorcycles (including motorcycles) and tricycles (in addition to mini vehicles, etc.) to provide a long-life and highly reliable vehicle. 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. 5 is a conceptual diagram of a vehicle equipped with the assembled battery of this embodiment. As shown in FIG. 5, 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. A vehicle equipped with the assembled battery of this embodiment can be widely applied to a hybrid vehicle, a fuel cell vehicle and the like in addition to an electric vehicle as shown in FIG.

  The effect of this invention is demonstrated using a following example and a comparative example. However, the technical scope of the present invention is not limited only to the following examples. In the following, the polymer material used for the base material of the resin layer (first resin), the base material of the sealing material (second resin), and the base material of the separator (third resin) included in the current collector is changed. Thus, a bipolar secondary battery was produced and the cycle characteristics were evaluated.

<Production of bipolar electrode>
[Examples 1 to 3, Comparative Example 1]
A positive electrode active material slurry is prepared by mixing LiMn ₂ O ₄ as a positive electrode active material, acetylene black (AB) as a conductive additive, polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone (NMP) as a viscosity adjusting solvent. did. The compounding ratio of each component is LiMn ₂ O ₄ : AB: PVDF = 85: 5: 10 (mass ratio).

  Hard carbon as the negative electrode active material, acetylene black (AB) as the conductive additive, polyvinylidene fluoride (PVDF) as the binder, and N-methylpyrrolidone (NMP) as the viscosity adjusting solvent were mixed to prepare a negative electrode active material slurry. The compounding ratio of each component is hard carbon: AB: PVDF = 85: 5: 10 (mass ratio).

  A current collector (thickness: 100 μm) consisting only of a conductive resin layer containing 10% by mass of carbon black as a conductive filler was prepared. The current collector was prepared by mixing carbon black with a resin serving as a base material and forming a thin film by extrusion molding. The polymer materials constituting the resin that is the base material of the current collector in each example are as shown in Table 1 below.

  The prepared positive electrode active material slurry was applied to one surface of the current collector and dried to form a positive electrode active material layer having a thickness of 70 μm. Also, a negative electrode active material slurry was applied to the other surface of the current collector and dried to form a negative electrode active material layer having a thickness of 100 μm. Thus, the laminated body which formed the positive electrode active material layer in the one surface of the electrical power collector, and formed the negative electrode active material layer in the other surface was obtained.

  The obtained positive electrode active material layer / current collector / negative electrode active material layer laminate was cut to a size of 300 × 250 (mm) and formed on the outer periphery of 10 mm from the outer edge and the positive electrode active material layer and the negative electrode active material By peeling off the layer, the surface of the conductive resin layer as a current collector was exposed. As a result, a bipolar electrode was obtained in which each active material layer surface was 280 × 210 (mm) and a conductive resin layer having an outer peripheral portion of 10 mm from the outer edge was exposed.

(Production of bipolar secondary battery)
A sealing sheet having a width of 15 cm and a thickness of 70 μm was arranged on three sides of the exposed resin layer exposed portion (electrode uncoated portion) of the surface of the obtained bipolar electrode on which the positive electrode active material layer was formed. . The polymer materials constituting the resin that becomes the base material of the sealing sheet in each example are as shown in Table 1 below.

  Next, a separator of 290 × 240 (mm) and a thickness of 20 μm was disposed so as to cover all the bipolar electrodes on the side where the positive electrode active material layer was formed. The polymer materials constituting the resin serving as the base material of the separator in each example are as shown in Table 1 below. Then, the sheet | seat for sealing was arrange | positioned on the separator corresponding to an electrode non-application part, and the negative electrode surface of the bipolar electrode was piled up from it. Thus, bipolar electrode (negative electrode active material layer / current collector / positive electrode active material layer) / separator / bipolar electrode (negative electrode active material layer / current collector / positive electrode active material layer)... Separator / bipolar Four bipolar electrodes were laminated via a separator in the order of the type electrode (negative electrode active material layer / current collector / positive electrode active material layer). Then, the three sides on which the sealing sheets were arranged were pressed from above and below (0.2 MPa, 200 ° C., 5 seconds) to fuse the current collector, the seal portion, and the separator.

A solution in which LiPF ₆ as a lithium salt is dissolved at a concentration of 1.0 M in a PC-PE mixed solvent in which propylene carbonate (PC) and ethylene carbonate (EC) are mixed at 1: 1 (volume ratio) as an electrolytic solution. Prepared. And electrolyte solution was formed by inject | pouring electrolyte solution from remaining one side which is not sealed of said bipolar secondary battery structure, and making it hold | maintain to the separator distribute | arranged between bipolar electrodes. Then, a bipolar secondary battery structure in which three single battery layers are stacked is manufactured by placing a sealing sheet on the remaining unsealed side in the same manner as described above and pressing under the same conditions. did.

  After forming the electrolyte layer in this manner, a bipolar secondary battery was produced by sandwiching an aluminum tab for current extraction and vacuum-sealing using an aluminum laminate film as an exterior material. In addition, the lamination | stacking form of a collector, a separator, and a seal | sticker part is as showing in FIG.

  [Example 4] The thickness of the current collector is 100 μm, the thickness of the positive electrode active material layer is 70 μm, the thickness of the negative electrode active material layer is 100 μm, the thickness of the sealing sheet is 85 μm, and the thickness of the separator is 20 μm. Except having done, operation similar to the said Examples 1-3 and the comparative example 1 was performed. The polymer materials constituting the resin that is the base material of the current collector in each example are as shown in Table 1 below. Moreover, the lamination | stacking form of these members is as showing in FIG.

[Example 5]
Except for the following points, the same operations as in Examples 1 to 3 and Comparative Example 1 were performed.

  The laminate of the positive electrode active material layer / current collector / negative electrode active material layer is cut into a size of 300 × 250 (mm), and the positive electrode active material layer and the negative electrode active material layer formed on the outer peripheral portion of 10 mm from the outer edge are peeled off. I took it. Thus, a bipolar electrode was obtained in which each active material layer surface was 280 × 230 (mm), and the conductive resin layer on the outer peripheral portion 10 mm from the outer edge was exposed. A sealing sheet having a width of 15 cm was used. The separator used was 290 × 240 (mm). The polymer materials constituting the current collector, the sealing sheet, and the resin serving as the separator are as shown in Table 1 below. Moreover, the lamination | stacking form of these members is as showing in FIG.

(Evaluation of cycle characteristics)
Each bipolar secondary battery manufactured by the above method was charged to 4.2 V in a constant current method (CC, current: 0.5 C) in an atmosphere at 25 ° C., paused for 10 minutes, and then constant current ( (CC, current: 0.5 C), the battery was discharged to 2.5 V and rested for 10 minutes after the discharge. This charge / discharge process was defined as one cycle, and a 50-cycle charge / discharge test was conducted.

  A liquid junction does not occur even after 50 cycles of charge / discharge tests, and the battery voltage is maintained as “good”, and the liquid junction is confirmed by visual observation, or a significant decrease in battery voltage is observed. Rated as “bad”. The results are shown in Table 1.

  From the results shown in Table 1, the bipolar secondary batteries of Examples 1 to 5 maintained good battery characteristics even after 50 cycles of charge and discharge, and exhibited good cycle characteristics. This is because the difference in thermal expansion between the current collector and the seal due to heat during charging and discharging, or the difference in thermal expansion between the current collector, seal, and separator is small, reducing the stress on the current collector. It was thought that this was because peeling of the active material was prevented. Moreover, in Examples 1-5, the liquid junction by visual observation was not confirmed. This indicates that the adhesion between the current collector surface and the seal portion surface is good.

10 Bipolar secondary battery,
11 Current collector,
11a The outermost layer current collector on the positive electrode side,
11b The outermost layer current collector on the negative electrode side,
11c The outer circumference of the current collector,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 electrolyte layer,
19 cell layer,
21 power generation elements,
23 Bipolar electrode,
25 positive current collector,
27 negative current collector,
29 Laminated film,
31 seal part,
31c The outer periphery of the seal part,
31d inner circumference of the seal part,
33c The outer periphery of the separator,
250 small battery pack,
300 battery packs,
310 connection jig,
400 vehicles.

Claims (8)

A current collector including a resin layer having conductivity and having a first resin as a base material;
A bipolar electrode having a positive electrode active material layer formed on one surface of the current collector, and a negative electrode active material layer formed on the other surface of the current collector;
A bipolar secondary battery having a power generation element formed by laminating an electrolyte layer,
The outer peripheral portion of the single cell layer composed of the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer is sealed with a seal portion based on a second resin,
The bipolar secondary battery, wherein the maximum component of the first resin and the maximum component of the second resin are the same polymer material. The electrolyte layer has a separator based on a third resin,
At least a part of the peripheral edge of the separator is joined to the seal part,
The bipolar secondary battery, wherein the maximum component of the first resin, the maximum component of the second resin, and the maximum component of the third resin are the same polymer material.   The bipolar secondary battery according to claim 1, wherein the polymer material is a thermoplastic polymer material.   The bipolar secondary battery according to any one of claims 1 to 3, wherein the melting point of the polymer material is 100 to 400 ° C.   The bipolar secondary battery according to any one of claims 1 to 4, wherein the polymer material includes at least one selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polyether nitrile, and polyimide. .   The bipolar secondary battery according to any one of claims 1 to 5, which is a lithium ion secondary battery.   The assembled battery in which the bipolar secondary battery of any one of Claims 1-6 is electrically connected two or more.   A vehicle on which the bipolar secondary battery according to any one of claims 1 to 6 or the assembled battery according to claim 7 is mounted as a power source for driving a motor.

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