JP2008159570A - Bipolar battery and packed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bipolar battery and a packed battery suppressing dispersion of current density in a battery element. <P>SOLUTION: The bipolar battery has the battery element 30 with bipolar electrodes and electrolyte layers alternately stacked, and positive and negative terminals 51, 52 electrically connected to each end of the battery element to extract a current flowing in a surface direction. In the bipolar battery, the electrical resistance R3 of the current flowing in the surface direction of a region corresponding to the battery element in the positive and negative terminals is smaller than the total electrical resistance R1+R2 of the current flowing in a stacking direction between the positive and negative terminals. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bipolar battery and an assembled battery formed by electrically connecting a plurality of bipolar batteries.

  In recent years, reduction of carbon dioxide emissions has been strongly desired for environmental protection. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and we are eager to develop secondary batteries for motor drives that hold the key to their practical application. Has been done. As a secondary battery, attention is focused on a stacked bipolar battery that can achieve high energy density and high output density (see Patent Document 1).

A bipolar battery includes battery elements in which bipolar electrodes and electrolyte layers are alternately stacked and connected in series. In the bipolar electrode, a positive electrode is formed by providing a positive electrode active material layer on one surface of a current collector, and a negative electrode is formed by providing a negative electrode active material layer on the other surface. In a bipolar battery, current flows in the direction in which the bipolar electrodes are stacked in the battery element (hereinafter referred to as “stacking direction”), so the current path is short, the current loss is small, and the current collector is made ultrathin. You can also. Positive and negative terminals for taking out current flowing in the plane direction are electrically connected to the respective ends in the stacking direction of the battery elements.
JP 2001-236946 A (paragraphs 0019, 0021)

  In a bipolar battery, the battery has a correlation between the electrical resistance of the current flowing in the plane direction of the region corresponding to the battery element at the positive and negative terminals and the sum of the electrical resistance of the current flowing in the stacking direction between the positive and negative terminals. Variations in current density occur in the elements. Due to the variation in the current density, the deterioration of the battery element is promoted, and as a result, the durability may be reduced.

  The present invention has been made to solve the above-described problems associated with the prior art, and an object thereof is to provide a bipolar battery and an assembled battery that can suppress variations in current density among battery elements.

The present invention according to claim 1, which achieves the above object, is a battery element in which a bipolar electrode having a positive electrode formed on one surface of a current collector and a negative electrode formed on the other surface, and an electrolyte layer are alternately laminated. When,
Positive and negative terminals that are electrically connected to each of the ends of the battery element and extract a current flowing in the plane direction;
The bipolar battery has an electrical resistance of current flowing in a plane direction of a region corresponding to the battery element at the positive and negative terminals, which is smaller than a sum of electrical resistances of currents flowing in a stacking direction between the positive and negative terminals.

  The present invention according to claim 19 which achieves the above object is an assembled battery comprising a plurality of bipolar batteries electrically connected.

  According to the first aspect of the present invention, the electrical resistance of the current flowing in the plane direction of the region corresponding to the battery element in the positive and negative terminals is the electrical resistance of the current flowing in the stacking direction between the positive and negative terminals. Since the bipolar battery is smaller than the sum, it is possible to suppress the variation in current density in the battery element, and it is possible to suppress the deterioration of the battery element due to the variation in current density.

  According to the nineteenth aspect of the present invention, a bipolar battery is connected in series or in parallel to form an assembled battery, thereby suppressing deterioration of the battery element due to current density variation, and having a high capacity and high output. A battery can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. For easy understanding, each component is exaggerated in the drawings.

(First embodiment)
1A is a cross-sectional view showing the bipolar battery 10 according to the first embodiment of the present invention, and FIG. 1B is electrically connected to the current collector 21 at the terminal electrode of the battery element 30. FIG. 1C is a plan view showing the negative electrode terminal 52, and FIG. 1B is a modification of the negative electrode terminal 52 shown in FIG. FIG. 2A is a cross-sectional view showing the bipolar electrode 20, and FIG. 2B is a cross-sectional view for explaining the single cell layer 32.

  Referring to FIGS. 1 and 2, a bipolar battery 10 is configured by alternately laminating bipolar electrodes 20 and electrolyte layers 31 and housing battery elements 30 in which these are connected in series in an outer case 40. . In the bipolar electrode 20, a positive electrode active material layer 22 is provided on one surface of a current collector 21 to form a positive electrode 23, and a negative electrode active material layer 24 is provided on the other surface to form a negative electrode 25 (FIG. 2). (See (A)). In the battery element 30 in which the bipolar electrode 20 is laminated, a single battery layer 32 is constituted by the positive electrode active material layer 22, the electrolyte layer 31, and the negative electrode active material layer 24 sandwiched between adjacent current collectors 21 and 21. (See FIG. 2B). In the positive electrode terminal electrode 33 of the battery element 30, only the positive electrode active material layer 22 is provided on one surface of the end current collector 21e, and the electrolyte layer 31 is formed on the uppermost bipolar electrode 20 in FIG. Laminated. In the negative electrode terminal electrode 34 of the battery element 30, only the negative electrode active material layer 24 is provided on one surface of the end current collector 21e, and the electrolyte layer 31 is provided under the lowest bipolar electrode 20 in FIG. Laminated. As shown in FIG. 1A, the electrolyte layer 31 includes a layer in which a polymer gel electrolyte is infiltrated into a porous separator 31a that separates the positive electrode and the negative electrode, and the separator 31a and the positive electrode active material. A polymer gel electrolyte layer 31 b that conducts ions between the layer 22 and the negative electrode active material layer 24 is provided. The material of the separator 31a which is a part of the electrolyte layer 31 is PE (polyethylene) having porosity (breathability), but is not particularly limited. For example, other polyolefins such as PP (polypropylene), laminates having a three-layer structure of PP / PE / PP, polyamide, polyimide, aramid, and non-woven fabric can be used. Nonwoven fabrics are, for example, cotton, rayon, acetate, nylon, and polyester. The separator 31a is an insulator that separates the positive electrode and the negative electrode, but ions and current flow when the electrolyte permeates into the porous portion of the separator 31a.

  Positive and negative terminals 51 and 52 for taking out current flowing in the surface direction are electrically connected to the respective ends in the stacking direction of the battery element 30. Specifically, the positive electrode terminal 51 is electrically connected to the end current collector 21 e of the positive electrode end electrode 33, and the negative electrode terminal 52 is electrically connected to the end current collector 21 e of the negative electrode end electrode 34. ing. The positive electrode terminal 51 has a size larger than at least the projected area of the positive electrode active material layer 22 of the positive electrode terminal electrode 33, and is superimposed on the end current collector 21e so as to cover the projected surface of the positive electrode active material layer 22. Has been placed. Similarly, the negative electrode terminal 52 has a size larger than at least the projected area of the negative electrode active material layer 24 of the negative electrode terminal electrode 34, and is on the end current collector 21e so as to cover the projected surface of the negative electrode active material layer 24. Is placed on top of each other. The terminals 51 and 52 and the end current collector 21e are electrically evenly joined over the entire projection surface of the active material layers 22 and 24. For this reason, the terminals 51 and 52 receive current uniformly from the entire surface of the end current collector 21e where the current substantially flows, and can suppress variations in current density.

  In the bipolar battery 10, the electrical resistance of the current flowing in the plane direction of the region corresponding to the battery element 30 at the positive and negative terminals 51 and 52 and the electrical resistance of the current flowing in the stacking direction between the positive and negative terminals 51 and 52. Due to the correlation with the sum, the battery element 30 has a variation in current density. Due to this variation in current density, the deterioration of the battery element 30 is promoted. That is, when a variation in current density occurs, the current value flowing in the stacking direction becomes excessive with respect to a predetermined location with respect to the plane direction, the amount of heat generated at that location increases, and expands in the stacking direction. It is considered that the resistance value is further reduced and the current value becomes excessive and the deterioration is promoted.

  Therefore, in the bipolar battery of the present invention, the electrical resistance of the current flowing in the surface direction of the region corresponding to the battery element 30 in the positive and negative terminals 51 and 52 is the stacking direction between the positive and negative terminals 51 and 52. It is set to be smaller than the sum of the electric resistances of the currents flowing through the current. By maintaining such a correlation, variation in current density in the battery element 30 can be suppressed, and deterioration of the battery element 30 due to variation in current density can be suppressed.

  In particular, by setting the ratio of the electric resistance of the current flowing in the plane direction to the sum of the electric resistance of the current flowing in the stacking direction, preferably 0.57 or less, variation in current density in the battery element 30 is suitably suppressed. be able to. More preferably, by setting the ratio to 0.01 or less, the variation in current density in the battery element 30 can be made small enough to be ignored, and the deterioration of the battery element 30 due to the variation in current density is eliminated. be able to.

  FIG. 3 is a conceptual diagram for explaining the electric resistance of the current in the bipolar battery 11.

  The battery element 30 of the bipolar battery 11 is formed by laminating a plurality of laminated bodies 30a (two in the illustrated example) in which the bipolar electrodes 20 and the electrolyte layers 31 are alternately laminated in a unit number. ing. By adopting a form in which an arbitrary number of stacked bodies 30a as a unit are stacked, a high-voltage battery according to requirements can be easily provided. Moreover, it becomes easy also on manufacture by defining the laminated body 30a used as a unit.

  As shown in FIG. 3, the electric resistance of the current flowing in the stacking direction is the battery resistance R1 of the battery element 30, the contact resistance r2a between the terminal of the battery element 30 and each of the positive and negative terminals 51 and 52, and The contact resistance r2b between the laminated bodies 30a is included. Battery resistance R1 is the sum of battery resistance r1 in each laminated body 30a. The sum of the contact resistances r2a and r2b is represented by the contact resistance R2. The electric resistance R3 of the current flowing in the surface direction at the positive and negative terminals 51 and 52 is in the surface direction of the region corresponding to the battery element 30 at each terminal 51 and 52 (toward the positive and negative electrode lead portions 51a and 52a side). It is the sum of the electric resistance r3 of the flowing current.

  Specifically, the currents flowing in the plane direction are regions corresponding to the positive electrode side end current collector 21e and the negative electrode side end current collector 21e shown in FIG. Current flowing through the positive electrode terminal 51 and the negative electrode terminal 52.

  In the bipolar battery 10 shown in FIG. 1A, since the battery element 30 includes only one laminated body 30a, the battery resistance R1 of the battery element 30 and the terminal of the battery element 30 are positive and negative. The contact resistance r2a between each of the terminals 51 and 52 is included. Since the contact resistance r2b does not exist, the contact resistance R2 is the sum of the contact resistance r2a.

  The battery resistance R1 of the battery element 30 can be evaluated by a method in which a constant current is passed through the bipolar battery and a voltage drop is calculated from the voltage after 5 seconds and the voltage before discharging. The contact resistance is measured by the same method. These values can be easily measured by measuring the voltage measurement position at a predetermined position. The electric resistance R3 of the current flowing in the surface direction at the positive and negative terminals 51 and 52 is determined by the type, thickness, and length of the material used. The length is the distance between the part where the terminals 51 and 52 correspond to the electrode part, that is, the part overlapping the electrode reaction part. Specifically, with respect to the volume resistivity ρ (Ω · cm) inherent to the material of the positive and negative terminals 51 and 52 shown in FIG. 3, the plane (aa cross section) cut by a plane orthogonal to the plane of the terminals 51 and 52. When the cross-sectional area is A (cm 2) and the length of the surface (electrode reaction surface) corresponding to the battery element region of the terminals 51 and 52 is L (cm), the resistance r 3 (Ω) is r 3 = (ρ × L ) / A. 1B shows the negative electrode terminal 52 and the negative electrode lead portion 52a of FIG. 1A, but instead of this, the lead portion is also provided on the surface facing the negative electrode lead as shown in FIG. 1C. 52b may be added, or a lead portion 52C indicated by a dotted line may be added to the center portion of the terminal 52, or may be protruded from the exterior case 40. Thereby, the length L of the surface corresponding to the region of the battery element is substantially halved, and it is possible to set the resistance value low. 1B and 1C show the shape of the negative electrode terminal side, the positive electrode side has the same shape.

  The configuration of the bipolar battery 40 may be a known material used for a general lithium ion secondary battery, and is not particularly limited. Hereinafter, the terminals 51 and 52, the outer case 40, the current collector 21, the positive electrode 23 (positive electrode active material layer 22), the negative electrode 25 (negative electrode active material layer 24), and the electrolyte layer 31 in the bipolar battery 10 will be further described.

[Positive electrode terminal 51, negative electrode terminal 52]
The terminals 51 and 52 arranged on the end current collector 21e have a function as terminals for taking out current. As the material of the terminals 51 and 52, a material used in a lithium ion battery can be used. For example, aluminum, copper, titanium, and other highly conductive materials are preferable. However, even if the material has low conductivity, if the thickness direction is increased, the resistance can be reduced to an acceptable level, and a sufficient flow of electricity in the plane direction can be ensured. Therefore, stainless steel (SUS) or the like having lower conductivity than aluminum or the like can be used. Aluminum is preferably used from the viewpoints of corrosion resistance, ease of production, economy, and the like. The material of the positive electrode terminal 51 and the negative electrode terminal 52 may be the same material or different materials.

  By processing the end portions of the terminals 51 and 52 into a lead shape, the positive electrode lead portion 51 a and the negative electrode lead portion 52 a are formed integrally with the terminals 51 and 52. The positive electrode lead portion 51a and the negative electrode lead portion 52a taken out from the outer case 40 are preferably covered with a heat-shrinkable heat-shrinkable tube or the like. This is to prevent the lead parts 51a and 52a from coming into contact with the heat source when the distance between the lead parts 51a and 52a and the heat source is small, and causing adverse effects on components (particularly electronic devices) due to electric leakage.

  In the first embodiment, the case where the ends of the terminals 51 and 52 are formed in a lead shape is illustrated. However, in the bipolar battery of the present invention, the terminals 51 and 52 themselves extend outward from the outer case 40. You don't have to. The bipolar battery includes, for example, a rectangular terminal that is in planar contact with the end current collector 21e and is accommodated in the outer case 40, and leads that are attached to the terminal by welding and extend outward from the outer case 40. May be. As this lead, a known lead used in a lithium ion battery or the like can be used.

[Exterior case 40]
In the bipolar battery 10, the battery element 30 and the terminals 51, 52 are accommodated in the outer case 40 in order to mitigate impact from the outside during use and prevent environmental degradation. The outer case 40 is formed of a flexible sheet-like material, and seals the battery element 30, the positive terminal 51, and the negative terminal 52. Furthermore, the internal pressure of the outer case 40 is a pressure lower than the atmospheric pressure Pa. The terminals 51 and 52 are merely placed on the end current collector 21e, and mechanical fastening is not performed between them. Conductivity between the terminals 51 and 52 and the end current collector 21e is ensured by metal contact due to pressure acting when sealed by the outer case 40. An adhesive or non-adhesive coating agent excellent in conductivity may be interposed between the terminals 51 and 52 and the end current collector 21e. This is because the metal contact between the two becomes dense and the conductivity is more reliable.

  The sheet-like material may be a flexible material that can be easily deformed without being broken by a pressure difference between the inside and the outside of the outer case 40. The battery element 30 is pressurized from above and below in the figure via the terminals 51 and 52 by hydrostatic pressure using the atmospheric pressure Pa.

  If the connection between the terminals 51 and 52 and the end current collector 21e is electrically non-uniform over the entire surface, the current density varies, which may promote deterioration. In the present embodiment, the relationship between the pressure inside the outer case 40 <the pressure outside the outer case 40 (= atmospheric pressure Pa) is satisfied by the hydrostatic pressure using the atmospheric pressure Pa. And the end current collector 21e are electrically uniform over the entire surface. Therefore, the variation in current density distribution is suppressed, and the promotion of deterioration due to the variation in current density is suppressed. In addition, the output of the battery can be reliably increased by reducing the resistance of the terminals 51 and 52.

  Further, the sheet-like material preferably exhibits electrical insulation without allowing electrolyte or gas to permeate and is chemically stable with respect to the material such as the electrolyte, and examples thereof include synthetic resins such as polyethylene, polypropylene, and polycarbonate. The

  As the sheet material, a laminate film 41 including a metal foil and a synthetic resin film can also be suitably applied. This is because it is preferable for reducing the heat sealing property of the outer case 40 and the possibility of air contact of the electrolyte and further reducing the weight. The laminate film 41 has a three-layer structure in which a metal foil 42 made of a metal (including an alloy) such as aluminum, stainless steel, nickel, or copper is covered with insulating synthetic resin films 43 and 44 such as a polypropylene film. In addition to the polymer-metal composite laminate film 41, an aluminum laminate pack can be used similarly.

The polymer-metal composite laminate film 41, the aluminum laminate pack and the like are preferably excellent in thermal conductivity. This is because when mounted on an automobile, heat can be efficiently transmitted from the automobile heat source to the bipolar battery 10 and the battery element 30 can be quickly heated to the battery operating temperature.

  When the laminate film 41 is used for the exterior case 40, the battery element 30 and the terminals 51 and 52 are housed and sealed by joining part or all of the periphery of the laminate film 41 by heat fusion. To do. The lead parts 51a and 52a are sandwiched between the heat-sealed parts and exposed to the outside of the laminate film 41.

  If the outer case 40 is applied to the laminate film 41 as in the present embodiment, the outer case 40 is easily deformed, and the hydrostatic pressure using the atmospheric pressure Pa can be applied to the battery element 30. Furthermore, since the layer of the metal foil 42 is present, the gas permeability is lowered, and the pressure difference between the inside and the outside can be maintained over a long period of time. As a result, the terminals 51 and 52 and the end current collector 21e Stable electrical contact can be maintained over a long period of time.

  The case where the terminals 51 and 52 are brought into close contact with the end current collector 21e by hydrostatic pressure using the atmospheric pressure Pa is exemplified. However, in the bipolar battery of the present invention, the pressure inside the outer case 40 <the outer case 40 exterior. As long as the pressure relationship is satisfied, the medium generating the hydrostatic pressure is not limited. For example, the terminals 51 and 52 may be brought into close contact with the end current collector 21e by hydrostatic pressure using at least one medium of gas, liquid, or solid powder, or a medium obtained by mixing them.

[Current collector 21]
The current collector 21 of the present embodiment is made of stainless steel (SUS). Since stainless steel is stable with respect to both the positive electrode active material and the negative electrode active material, the active material layers 22 and 24 can be formed on both the front and back surfaces of the stainless steel single layer.

  In the terminal electrodes 33 and 34, the positive electrode active material layer 22 or the negative electrode active material layer 24 is formed only on one surface of the end current collector 21e.

  The thickness of the current collector 21 is not particularly limited, but is about 1 μm to 100 μm.

[Positive electrode 23 (positive electrode active material layer 22)]
The positive electrode 23 includes a positive electrode active material. In addition to this, a conductive aid, a binder, and the like may be included. The gel electrolyte is sufficiently infiltrated into the positive electrode 23 and the negative electrode 25 by chemical crosslinking or physical crosslinking.

As the positive electrode active material, a composite oxide of transition metal and lithium, which is also used in a solution-type lithium ion battery, can be used. 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 Examples thereof include Fe-based composite oxides. In addition, transition metal and lithium phosphate compounds and sulfuric acid compounds such as LiFePO ₄ ; transition metal oxides and sulfides such as V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , and MoO ₃ ; PbO ₂ , AgO, NiOOH etc. are mentioned.

  The particle diameter of the positive electrode active material is not limited as long as it can be formed into a paste by spraying the positive electrode material and spray coating or the like in order to reduce the electrode resistance of the bipolar battery 10. What is smaller than the generally used particle size used in the type of lithium ion battery may be used. Specifically, the average particle diameter of the positive electrode active material is preferably 0.1 μm to 10 μm.

  The polymer gel electrolyte is a solid polymer electrolyte having ion conductivity containing an electrolyte solution usually used in a lithium ion battery. Further, in the polymer skeleton having no lithium ion conductivity, In addition, those holding the same electrolytic solution are also included.

Here, the electrolyte solution (electrolyte salt and plasticizer) contained in the polymer gel electrolyte may be any electrolyte solution that is normally used in lithium ion batteries. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF. ₆ , inorganic acid anion salts such as LiAlCl ₄ and Li ₂ B ₁₀ Cl ₁₀ , organic acid anions such as LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, and Li (C ₂ F ₅ SO ₂ ) ₂ N Including at least one lithium salt (electrolyte salt) selected from ionic salts, cyclic carbonates such as propylene carbonate and ethylene carbonate; chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane Ethers such as 1,2-dimethoxyethane and 1,2-dibutoxyethane; Lactones such as γ-butyrolactone; Nitriles such as acetonitrile; Esters such as methyl propionate; Amides such as dimethylformamide; Methyl acetate Further, those using an organic solvent (plasticizer) such as an aprotic solvent in which at least one selected from methyl formate or a mixture of two or more thereof can be used. However, it is not necessarily limited to these.

  Examples of the polymer having ion conductivity include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

  For example, polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), etc. are used as the polymer having no lithium ion conductivity used for the polymer gel electrolyte. it can. However, it is not necessarily limited to these. Note that PAN, PMMA, etc. are in a class that has almost no ionic conductivity. Therefore, the PAN, PMMA, and the like can be used as a polymer having the ionic conductivity described above, but are used here as a polymer gel electrolyte. This is exemplified as a polymer having no lithium ion conductivity.

As the lithium salt, for _{example, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 and the like inorganic acid anion _{salts, Li (CF 3 SO 2)} 2 N, An organic acid anion salt such as Li (C ₂ F ₅ SO ₂ ) ₂ N or a mixture thereof can be used. However, it is not necessarily limited to these.

  Examples of the conductive assistant include acetylene black, carbon black, and graphite. However, it is not necessarily limited to these.

  In the present embodiment, the electrolyte solution, lithium salt, and polymer (polymer) are mixed to prepare a pregel solution, and the positive electrode 23 and the negative electrode 25 are impregnated.

  The blending amount of the positive electrode active material, the conductive assistant and the binder in the positive electrode 23 should be determined in consideration of the intended use of the battery (emphasis on output, emphasis on energy, etc.) and ion conductivity. For example, if the amount of the electrolyte in the positive electrode 23, particularly the solid polymer electrolyte, is too small, the ionic conduction resistance and the ionic diffusion resistance in the active material layer will increase, and the battery performance will deteriorate. On the other hand, if the amount of the electrolyte in the positive electrode 23, particularly the solid polymer electrolyte, is too large, the energy density of the battery is lowered. Therefore, in consideration of these factors, the solid polymer electrolytic mass meeting the purpose is determined.

The thickness of the positive electrode 23 is not particularly limited, and should be determined in consideration of the intended use of the battery (emphasis on output, emphasis on energy, etc.) and ion conductivity, as described for the blending amount. The thickness of the general positive electrode active material layer 22 is about 10 to 500 μm.

[Negative Electrode 25 (Negative Electrode Active Material Layer 24)]
The negative electrode 25 includes a negative electrode active material. In addition to this, a conductive aid, a binder, and the like may be included. Except for the type of the negative electrode active material, the contents are basically the same as those described in the section of “Positive electrode 23”, and thus the description thereof is omitted here.

  As the negative electrode active material, a negative electrode active material that is also used in a solution-type lithium ion battery can be used. For example, metal oxide, lithium-metal composite oxide metal, carbon and the like are preferable. More preferred are carbon, transition metal oxide, and lithium-transition metal composite oxide. More preferred are titanium oxide, lithium-titanium composite oxide, and carbon. These may be used alone or in combination of two or more.

  In the present embodiment, the positive electrode active material layer 22 uses a lithium-transition metal composite oxide as the positive electrode active material, and the negative electrode active material layer 24 uses carbon or a lithium-transition metal composite as the negative electrode active material. An oxide is used. This is because a battery having excellent capacity and output characteristics can be configured.

[Electrolyte layer 31]
The electrolyte layer 31 is a layer composed of a polymer having ion conductivity, and the material is not limited as long as it exhibits ion conductivity.

  The electrolyte of this embodiment is a polymer gel electrolyte. As described above, after impregnating a pregel solution into a separator as a substrate, the electrolyte is used as a polymer gel electrolyte by chemical crosslinking or physical crosslinking.

  Such a polymer gel electrolyte is an all-solid polymer electrolyte having ion conductivity such as polyethylene oxide (PEO) containing an electrolytic solution usually used in a lithium ion battery. A polymer gel electrolyte that contains a similar electrolyte solution in a polymer skeleton having no lithium ion conductivity such as vinylidene (PVDF) is also included. Since these are the same as the polymer gel electrolyte described as a kind of electrolyte contained in the positive electrode 23, description thereof is omitted here. The ratio of the polymer and the electrolyte constituting the polymer gel electrolyte is wide. When 100% of the polymer is an all-solid polymer electrolyte and 100% of the electrolyte is a liquid electrolyte, all of the intermediates correspond to the polymer gel electrolyte. The term “polymer electrolyte” includes both a polymer gel electrolyte and an all solid polymer electrolyte.

  The polymer gel electrolyte can be included in the positive electrode 23 and / or the negative electrode 25 as described above, in addition to the polymer electrolyte constituting the battery. However, the polymer gel electrolyte is different depending on the polymer electrolyte constituting the battery, the positive electrode 23, and the negative electrode 25. Molecular electrolytes may be used, the same polymer electrolyte may be used, or different polymer electrolytes may be used depending on the layer.

  The thickness of the electrolyte constituting the battery is not particularly limited. However, in order to obtain a compact bipolar battery 10, it is preferable to make it as thin as possible within a range that can ensure the function as an electrolyte. The thickness of the general solid polymer electrolyte layer 31 is about 10 to 100 μm. However, the shape of the electrolyte can be easily formed so as to cover the upper surface of the electrode (positive electrode 23 or negative electrode 25) as well as the outer peripheral portion of the side by taking advantage of the manufacturing method. It is not always necessary to have a substantially constant thickness.

In the bipolar battery 10, when the electrolyte solution contained in the electrolyte layer 31 oozes out, the layers are electrically connected to each other and do not function as a battery. This is called a liquid junction.

  When a liquid or semi-solid gel substance is used for the electrolyte layer 31, it is necessary to provide a seal between the current collector 21 and the separator 31a so that the electrolyte does not leak. Therefore, as shown in FIGS. 1 and 2B, a seal member 36 is provided between the current collector 21 and the separator 31 a so as to surround the unit cell layer 32. The seal member 36 is, for example, a double-sided tape in which an adhesive material is applied to both surfaces of a base material. The base material is formed of an insulating resin such as polypropylene (PP), polyethylene (PE), or polyamide synthetic fiber. The pressure-sensitive adhesive is formed of a solvent-resistant material such as synthetic rubber, butyl rubber, synthetic resin, or acrylic. The sealing member 36 prevents liquid leakage from the single cell layer 32 and prevents a short circuit due to contact between the current collectors 21.

  The electrolyte layer 31 can also use a solid electrolyte. This is because by using a solid as the electrolyte, it is possible to prevent liquid leakage, preventing a liquid junction that is a problem peculiar to bipolar batteries, and providing a highly reliable bipolar battery. In addition, since a configuration for preventing leakage is not required, the configuration of the bipolar battery can be simplified.

Examples of the solid electrolyte include known solid polymer electrolytes such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. The solid polymer electrolyte layer contains a supporting salt (lithium salt) in order to ensure ionic conductivity. As the supporting salt, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or a mixture thereof can be used. However, it is not necessarily limited to these. Polyalkylene oxide polymers such as PEO and PPO can dissolve lithium salts such as LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F ₅ ) ₂ well. Moreover, excellent mechanical strength is exhibited by forming a crosslinked structure.

(Second Embodiment)
4 is a perspective view showing the bipolar battery 12 according to the second embodiment, FIG. 5 is a sectional view taken along line 5-5 of FIG. 4, and FIG. 6 is a perspective view showing the bipolar battery 12 in an exploded state. 7 is a perspective view showing a state in which the pressurizing unit 70 is arranged on the upper portion of the negative electrode terminal 52, FIG. 8 is an exploded perspective view showing the pressurizing unit 70, and FIG. 9 is a line 9-9 in FIG. It is sectional drawing which follows. Members common to those in the first embodiment are denoted by the same reference numerals, and description thereof is partially omitted. In the following description, for simplification, the electric resistance R3 of the current flowing in the surface direction corresponding to the region of the battery element in the positive and negative terminals 51 and 52 is abbreviated as “electric resistance R3 in the surface direction”, A sum R1 + R2 of electric resistances of currents flowing in the stacking direction between the positive and negative terminals 51 and 52 is abbreviated as “electric resistance R1 + R2 in the stacking direction”.

  The bipolar battery 12 of the second embodiment is different from the first embodiment in that it further includes a pressurizing unit 70 (corresponding to a pressurizing unit) that pressurizes the battery element 30 in the stacking direction. . The pressurizing unit 70 is configured to be able to bias applied pressures having different strengths at each of a plurality of positions with respect to the surface direction of the battery element 30. By energizing pressures having different strengths at each of a plurality of positions, the contact state of each member constituting the unit cell layer 32, each of the end of the battery element 30, and each of the positive and negative terminals 51, 52 The contact state between each other and the contact state between the stacked bodies 30a can be changed at each of the plurality of positions. If the applied pressure is increased, the contact state becomes “dense” and the battery resistance R1 and the contact resistance R2 can be reduced. On the contrary, if the applied pressure is reduced, the contact state becomes “rough”, and the battery resistance R1 and the contact resistance R2 can be increased. The electrical resistance R3 in the surface direction does not change even if the applied pressure is changed. Therefore, the correlation between the electrical resistance R3 in the surface direction and the electrical resistance R1 + R2 in the stacking direction can be changed at each of the plurality of positions.

The pressurizing unit 70 is preferably capable of energizing pressures having different strengths for each of the divided sections with respect to the surface direction of the battery element 30. This is because it is easy to change the contact state between the various members described above by energizing pressures having different strengths for each section having a certain size.

  Each of the compartments is preferably divided equally into a rectangular shape. By dividing the sections evenly, the amount of change in the contact state with respect to the amount of change in the applied pressure becomes uniform for each section. Therefore, the correlation between the electrical resistance R3 in the plane direction and the electrical resistance R1 + R2 in the stacking direction can be accurately and easily changed to a desired correlation for each section.

  The pressurizing unit 70 is configured to energize pressures having different strengths at each of a plurality of positions so that the electrical resistance R3 in the plane direction is smaller than the electrical resistance R1 + R2 in the stacking direction. ing. This is because by maintaining such a correlation, variations in current density in the battery element 30 can be suppressed, and deterioration of the battery element 30 due to variations in current density can be suppressed.

  Here, by making the pressing force urged by the pressurizing unit 70 larger than the reference pressing force, the electrical resistance R1 + R2 in the stacking direction becomes smaller than the electrical resistance R1 + R2 in the stacking direction at the reference pressing force. it can. Therefore, the ratio (= R3 / (R1 + R2)) can be increased. On the contrary, by making the pressure applied by the pressure unit 70 smaller than the reference pressure, the electric resistance R1 + R2 in the stacking direction becomes the electric resistance R1 + R2 in the stacking direction at the reference pressure. Can be bigger. Therefore, the ratio (= R3 / (R1 + R2)) can be reduced.

  The electric resistance R3 in the surface direction corresponding to the region of the battery element has little temperature dependency, but the battery resistance R1 and the contact resistance R2 have temperature dependency. That is, when the ambient temperature in which the bipolar battery 12 is placed increases, the amount of change in the electrical resistance R3 in the surface direction is small, but the battery resistance R1 and the contact resistance R2 are small. Therefore, the ratio (= R3 / (R1 + R2)) increases.

  Therefore, in order to change the correlation between the electrical resistance R3 in the surface direction corresponding to the region of the battery element and the electrical resistance R1 + R2 in the stacking direction according to the temperature, the pressurizing unit 70 changes the temperature of the battery element 30. It is preferable that the detection part 71 to detect and the action | operation part 72 which produces | generates the pressurization force according to the detected temperature are included.

  When the detected temperature is higher than the reference operating temperature, the operating unit 72 generates a pressurizing force that is smaller than the reference operating temperature, and when the detected temperature is lower than the reference operating temperature, A pressurizing force larger than the pressurizing force at the operating temperature is generated. When the atmospheric temperature is higher than the operating temperature, the applied pressure is reduced, so that the ratio (= R3 / (R1 + R2)) can be reduced as described above. On the contrary, when the atmospheric temperature becomes lower than the operating temperature, the applied pressure increases, so that the ratio (= R3 / (R1 + R2)) can be increased.

  The effect that the applied pressure increases when the detected temperature is lower than the reference operating temperature also has the following advantages. That is, when the bipolar battery 12 is mounted on a device that generates vibration at the time of starting (for example, an automobile equipped with an internal combustion engine), the battery element 30 generally operates as a reference before starting the device. The temperature is lower than the temperature. At this time, a pressurizing force larger than the pressurizing force at the reference operating temperature is applied to the battery element 30. Therefore, even if the vibration accompanying the start of the device is applied to the bipolar battery 12, the battery element 30 can sufficiently resist the vibration, and it is possible to prevent the battery element 30 from being caused by the vibration.

  4 to 9, the bipolar battery 12 has an exterior case 73 that houses the battery element 30 while leading out some of the positive and negative terminals 51 and 52 to the outside. The detection unit 71 and the operation unit 72 include a block body 74 formed of a shape memory alloy that contracts when the temperature of the battery element 30 becomes higher than a reference operation temperature, at least one of the positive and negative terminals 51 and 52. And the exterior case 73 are arranged by arranging the shrinking direction along the stacking direction.

  Since the battery resistance R1 tends to decrease when the temperature of the battery element 30 becomes, for example, 40 ° C. or higher, the alloy composition of the shape memory alloy is determined so that the reference operating temperature becomes 40 ° C. Note that the reference operating temperature is merely an example, and is not limited to this temperature, and a desired temperature such as 50 ° C. can be selected. As a material of the shape memory alloy, a known Ni—Ti alloy (Nitinol) can be used, and the block body 74 is formed from a bidirectional repetitive operation type element.

  8 × 6 block bodies 74 are arranged (see FIGS. 6 and 7), and the correlation between the electrical resistance R3 in the plane direction and the electrical resistance R1 + R2 in the stacking direction can be changed every 48 sections. . Needless to say, the number of the block bodies 74 and the sections is not limited to this case, and an appropriate number of divisions can be selected. Each block body 74 is set on the frame 76 while disposing the partition walls 75 (see FIG. 8). FIG. 5 shows a state in which a part of the block body 74 is contracted. The vertical direction in FIG. 5 corresponds to the direction in which the block body 74 contracts and the direction in which the battery elements 30 are stacked.

  In the section where the block body 74 is shrunk due to a temperature higher than the reference operating temperature, an action of increasing the ratio (= R3 / (R1 + R2)) works as the temperature rises. = R3 / (R1 + R2)) is reduced at the same time. As a result, the ratio (= R3 / (R1 + R2)) is maintained almost constant. Therefore, even if temperature changes, the variation in the current density in the battery element 30 can be suppressed, and the deterioration of the battery element 30 due to the variation in the current density can be suppressed.

  In the second embodiment, a shape memory alloy is used to apply pressures having different strengths at each of a plurality of positions. However, the present invention is not limited to this case. For example, pressures having different strengths may be applied to each of a plurality of positions by using the spring force of a spring or using fluid pressure such as air pressure or hydraulic pressure. In the former case, a structure in which the amount of compression of the spring is variable (for example, a structure that can adjust the distance between the terminal and the spring retainer) may be provided in each of the plurality of positions. In the latter case, What is necessary is just to provide the valve member which adjusts the pressure of the fluid supplied to each of several positions.

(Third embodiment)
FIG. 10 is a perspective view showing an assembled battery 60 according to the third embodiment.

  The assembled battery 60 is configured by electrically connecting a plurality of the above-described bipolar batteries in parallel and / or in series. By paralleling and / or serializing, the capacity and voltage can be freely adjusted.

  The illustrated assembled battery 60 is obtained by connecting a plurality of bipolar batteries 10 of the first embodiment connected in series and further connected in parallel. As electrodes of the assembled battery 60, electrode terminals 61 and 62 are provided on one side surface of the assembled battery 60.

In the assembled battery 60, as a method of connecting the bipolar batteries 10 to each other, ultrasonic welding,
Thermal welding, laser welding, rivets, caulking, electron beam, or the like can be used. By adopting such a connection method, the assembled battery 60 having long-term reliability can be manufactured.

  According to the third embodiment, since the bipolar battery 10 is connected in series or in parallel to form the assembled battery 60, a high-capacity, high-power battery can be obtained. In addition, each bipolar battery 10 is highly reliable because it suppresses deterioration of the battery elements due to variations in current density, and can improve the long-term reliability of the assembled battery 60.

  Depending on the required capacity and voltage, an assembled battery in which all of the plurality of bipolar batteries 10 are connected in parallel or an assembled battery in which all are connected in series can be used.

(Fourth embodiment)
FIG. 11 is a schematic configuration diagram showing an automobile 100 as a vehicle according to the fourth embodiment.

  It is desirable that the above-described bipolar batteries 10 and 12 or the assembled battery 60 be mounted on a vehicle and used as a power source for an electric device such as a motor. This is because the bipolar batteries 10 and 12 and the assembled battery 60 have the above-described characteristics, and thus a vehicle on which these are mounted becomes a long-life and highly reliable vehicle.

  The illustrated automobile 100 is equipped with an assembled battery 60 and is used as a power source for a motor. Examples of the automobile using the assembled battery 60 as a motor power source include an electric car, a hybrid car, and a car in which each wheel is driven by a motor.

  The vehicle is not limited to the automobile 100, and the same effects can be obtained even if the bipolar batteries 10, 12 and the assembled battery 60 are mounted on a train.

(Example)
Examples of bipolar batteries will be described below. The produced bipolar batteries are of two types, those having a normal type battery element and those having a high output type battery element. Each is as follows.

1. Creation of normal type battery elements <Formation of electrodes>
Positive electrode 23:
LiMn ₂ O ₄ (85 wt%, average particle size 15 μm) as a positive electrode active material, acetylene black (5 wt%) as a conductive additive, polyvinylidene fluoride (PVDF) (10 wt%) as a binder, slurry viscosity adjusting solvent N-methyl-2-pyrrolidone (NMP) (appropriate amount) was added and mixed to prepare a positive electrode slurry. A positive electrode slurry was applied to one side of a stainless steel foil (thickness: 5 μm), which was a current collecting holiday, and dried to form a positive electrode.

Negative electrode 25:
Hard carbon (90% by weight, average particle size 20 μm) as a negative electrode active material, PVDF (10% by weight) as a binder, NMP (suitable amount) as a slurry viscosity adjusting solvent were mixed, and these were mixed to prepare a negative electrode slurry. . A negative electrode slurry was applied to the opposite surface of the stainless steel foil coated with the positive electrode and dried to form a negative electrode.

  A heated roll press was applied to the bipolar electrode to press the electrode. The electrode after pressing had a positive electrode of 50 μm and a negative electrode of 50 μm.

  Then, these were cut | disconnected to 320 mm x 220 mm, and the peripheral part 10 mm of an electrode produced what has the part which has not apply | coated the electrode previously.

  As a result, a bipolar electrode having a 300 mm × 200 mm electrode portion and a 10 mm seal margin in the peripheral portion was prepared.

<Formation of gel electrolyte>
Polypropylene nonwoven fabric 50 μm, 5% by weight of monomer solution (copolymer of polyethylene oxide and polypropylene oxide) having an average molecular weight of 7500 to 9000 which is a precursor of an ion conductive polymer matrix, EC + PC (1: 1) as an electrolyte solution A pregel solution consisting of 95% by weight, 1.0M LiBF ₄ and a polymerization initiator (BDK) was immersed, sandwiched between quartz glass substrates and irradiated with ultraviolet rays for 15 minutes to crosslink the precursor, thereby obtaining a polymer electrolyte layer. . The size of the gel electrolyte layer was 310 mm × 210 mm.

<Lamination>
An electrolyte-holding nonwoven fabric was placed on the positive electrode of the bipolar electrode, and a hot melt having a three-layer structure was placed around the sealing margin to form a sealing material.

  These were laminated in a predetermined number of layers (see Table 1 described later), and the seal portion was fused by applying heat and pressure from above and below to seal each layer.

  A normal type battery element was prepared by the above steps.

2. Creation of high output type battery element <Formation of electrode>
Positive electrode 23:
LiNiO ₂ (85% by weight, average particle size 6 μm) as a positive electrode active material, acetylene black (5% by weight) as a conductive additive, polyvinylidene fluoride (PVDF) (10% by weight) as a binder, N as a slurry viscosity adjusting solvent -Methyl-2-pyrrolidone (NMP) (appropriate amount) was added and mixed to prepare a positive electrode slurry. A positive electrode slurry was applied to one side of a stainless steel foil (thickness: 5 μm), which was a current collecting holiday, and dried to form a positive electrode.

Negative electrode 25:
Hard carbon (90 wt%, average particle size 8 μm) as a negative electrode active material, PVDF (10 wt%) as a binder, NMP (appropriate amount) as a slurry viscosity adjusting solvent were mixed, and these were mixed to prepare a negative electrode slurry. . A negative electrode slurry was applied to the opposite surface of the stainless steel foil coated with the positive electrode and dried to form a negative electrode.

  A heated roll press was applied to the bipolar electrode to press the electrode. The pressed electrode was 15 μm for the positive electrode and 20 μm for the negative electrode.

  Then, these were cut | disconnected to 320 mm x 220 mm, and the peripheral part 10 mm of an electrode produced what has the part which has not apply | coated the electrode previously.

  As a result, a bipolar electrode having a 300 mm × 200 mm electrode portion and a 10 mm seal margin in the peripheral portion was prepared.

<Formation of gel electrolyte>
Polypropylene nonwoven fabric 50 μm, 5% by weight of monomer solution (copolymer of polyethylene oxide and polypropylene oxide) having an average molecular weight of 7500 to 9000 which is a precursor of an ion conductive polymer matrix, EC + PC (1: 1) as an electrolyte solution A pregel solution composed of 95% by weight, 1.0M LiPF ₆ and a polymerization initiator (BDK) was immersed, sandwiched between quartz glass substrates and irradiated with ultraviolet rays for 15 minutes to crosslink the precursor, thereby obtaining a polymer electrolyte layer. . The size of the gel electrolyte layer was 310 mm × 210 mm.

<Lamination>
An electrolyte-holding nonwoven fabric was placed on the positive electrode of the bipolar electrode, and a hot melt having a three-layer structure was placed around the sealing margin to form a sealing material.

  These were laminated in a predetermined number of layers (see Table 1), and the seal portion was fused by applying heat and pressure from above and below, and each layer was sealed.

  The high output type battery element was created by the above process.

  A predetermined number of these battery elements were laminated (see Table 1), positive and negative terminals for taking out a predetermined current were sandwiched from above and below, and vacuum-sealed in an aluminum laminate to complete a bipolar battery.

  The resistance value per single layer of each battery element was 0.0328Ω for the normal type and 0.0100Ω for the high output type. The high output type battery element was used in Example 6 and Comparative Examples 1 and 2.

<Simulation>
FIG. 12 is a circuit diagram used for a simulation for verifying variation in current density.

  In the simulation, a two-dimensional cross-sectional direction was used as shown in FIG. The area was divided into 8 areas, and the applied current was 10A. The current value per area, that is, per unit area is 1.25 A (= 10/8).

  As a variation in current flowing in the vertical direction at this time, “(maximum current value of current flowing in the vertical direction−minimum current value) / current value per unit area (for example, 1.25 A above)” It was defined as the variation in current density.

  By incorporating the measured values of the resistance values R1, R2, and R3 into this simulation, the current density variation in the battery was simply calculated. The results are shown in Table 2.

<Long-term evaluation of large current charge / discharge>
First, the prototype battery was discharged at a constant current of 100 mA, and the discharge capacity was measured.

  Thereafter, these batteries were charged at a constant current (CC) with a current of 20 A, then discharged at a constant current of 20 A (CC), and this was taken as one cycle, and the charge / discharge test was repeated continuously for one month (charge 10 seconds). 10 seconds, 100,000 cycles). Further, the charge / discharge test was continuously repeated for 3 months (charging 10 seconds, 10 seconds, 300000 cycles).

  Finally, the battery was discharged at a constant current of 100 mA, and the discharge capacity was measured.

  Table 3 below shows the results of the discharge capacity after the cycle when the initial discharge capacity is 100%.

  From the result of the simulation and the result of the large current long-term reliability test, first, as in Comparative Examples 1 and 2, the surface direction electric resistance R3 corresponding to the battery element region of the current extraction terminal is the stacking direction in the battery. When the electric resistance is larger than R1 + R2, the simulation results show that the current density varies extremely (60% and 58%), and as a result, the deterioration (42% and 41%) is significant after large current discharge. .

  On the other hand, when the electrical resistance R3 in the surface direction corresponding to the battery element region of the current extraction terminal is smaller than the electrical resistance R1 + R2 in the stacking direction in the battery as in Examples 1 to 15, the simulation in Table 2 is performed. As a result, it was found that the variation in current density can be suppressed to 10% or less, and as a result, the capacity retention rate can be maintained at 46% or more after 3 months of large current charge / discharge. This three-month large-current charge / discharge is a severe durability test. If 40% can be maintained even in this test, the battery life in normal use is sufficient.

  As a result, the electrical resistance R3 in the surface direction corresponding to the battery element region of the current extraction terminal is smaller than the electrical resistance R1 + R2 in the stacking direction in the battery, so that it can be used as a product even after high current charge / discharge at a high load. It was found that it was possible to keep within the possible degradation.

  Further, the electric resistance R3 in the surface direction corresponding to the battery element region of the current extraction terminal is set to 0.57 or less with respect to the electric resistance R1 + R2 in the stacking direction in the battery, thereby causing a variation in current density of 9.9. % And 10% or less.

  More preferably, by setting the ratio to 0.01 or less, the variation in current density was 0.1% or less (substantially 0 in the simulation), and it was found that the variation in current density could be made small enough to be ignored. As a result, a capacity maintenance rate of 90% or more can be secured in the 1 month large current charge / discharge, and even in the 3 month large current charge / discharge, which is a severe durability test, even in Example 10 with the lowest capacity maintenance rate, 89% In both cases, it can be said that about 90% or more of the capacity can be maintained. In Example 4, when the ratio is 0.0113, the capacity maintenance rate is 85% after 1 month of the cycle and the capacity maintenance rate is 51% after 3 months of the cycle. In view of the measurement error, it was found that the ratio 0.01 was set as a critical value, and the capacity retention rate rapidly improved and converged below that, as will be described later.

    FIG. 1C shows the results of long-term reliability shown in Table 3, where the horizontal axis is the ratio (= R3 / (R1 + R2)), and the vertical axis is the capacity retention rate (%) after the 1 month cycle and after the 3 month cycle. The results are graphed. From this graph, it was found that when the ratio (= R3 / (R1 + R2)) is smaller than 1, the capacity retention rate is drastically improved and the battery quality is secured. More preferably, the capacity retention rate suddenly improves at 0.01 or less, reaches approximately 90% or more of the upper limit, and is no longer caused by current variation, but is caused by repeated charge / discharge cycles. It is thought that it was caused only by this. As described above, the experiment shows that the capacity retention rate is rapidly improved when the ratio (= R3 / (R1 + R2)) is smaller than 1 and when the ratio is 0.01 or less. We found a new critical value that is extremely important for suppressing the current density variation and ensuring quality performance.

  Accordingly, the electric resistance R3 in the surface direction corresponding to the battery element region of the current extraction terminal is preferably 1 or less, more preferably 0.01 or less, with respect to the electric resistance R1 + R2 in the stacking direction in the battery. The current density variation can be almost completely eliminated, the deterioration of the battery elements due to the current density variation can be eliminated, and a bipolar battery excellent in large current charge / discharge can be provided. .

Sectional drawing which shows the bipolar battery which concerns on the 1st Embodiment of this invention It is a top view which shows the negative electrode terminal electrically connected to the electrical power collector of the terminal pole of a battery element. It is a top view which shows the modification of the negative electrode terminal of FIG. It is a graph which shows the long-term reliability result of Table 3. FIG. 2A is a cross-sectional view showing a bipolar electrode, and FIG. 2B is a cross-sectional view for explaining a single cell layer. It is a conceptual diagram with which it uses for description of the electrical resistance of the electric current in a bipolar battery. It is a perspective view which shows the bipolar battery which concerns on 2nd Embodiment. It is sectional drawing which follows the 5-5 line of FIG. It is a perspective view which decomposes | disassembles and shows a bipolar battery. It is a perspective view which shows a mode that a pressurization unit is arrange | positioned at the upper part of a negative electrode terminal. It is a disassembled perspective view which shows a pressurization unit. It is sectional drawing which follows the 9-9 line of FIG. It is a perspective view which shows the assembled battery which concerns on 3rd Embodiment. It is a schematic block diagram which shows a motor vehicle as a vehicle which concerns on 4th Embodiment. It is the circuit diagram used for the simulation which verifies the variation in current density.

Explanation of symbols

10, 12 Bipolar battery,
20 bipolar electrodes,
21 current collector,
21e end collector,
22 positive electrode active material layer,
23 positive electrode,
24 negative electrode active material layer,
25 negative electrode,
30 battery elements,
30a laminate,
31 electrolyte layer,
32 cell layer,
33 Positive electrode terminal electrode,
34 Negative terminal pole,
36 sealing member,
40 exterior case,
41 Laminate film (sheet-like material),
42 metal foil,
43, 44 Synthetic resin film 51 Positive terminal (positive terminal),
51a positive electrode lead part,
52 negative terminal (negative terminal),
52a negative electrode lead part,
60 battery packs,
70 Pressurizing unit (pressurizing part),
71 detector,
72 actuators,
73 exterior case,
74 Block body (detection unit, operation unit) formed of shape memory alloy,
100 automobile (vehicle),
Pa atmospheric pressure,
R1 battery resistance of the battery element,
R2 contact resistance,
R1 + R2 Sum of electrical resistances of currents flowing in the stacking direction between the positive and negative terminals,
R3, the electrical resistance of the current flowing in the plane direction of the region corresponding to the battery element at the positive and negative terminals,
contact resistance between each of the ends of the r2a battery element and each of the positive and negative terminals,
r2b Contact resistance between laminates.

Claims (20)

A battery element in which a positive electrode is formed on one surface of a current collector and a negative electrode is formed on the other surface, and an electrolyte layer, and a battery element,
A positive and negative terminal that is electrically connected to each of the ends of the battery element and extracts a current flowing in the surface direction;
A bipolar battery in which an electric resistance of a current flowing in a plane direction of a region corresponding to the battery element in the positive and negative terminals is smaller than a sum of electric resistances of currents flowing in a stacking direction between the positive and negative terminals.   The ratio of the electric resistance of the current flowing in the surface direction of the region corresponding to the battery element to the total electric resistance of the current flowing in the stacking direction is preferably 0.57 or less, more preferably 0.01 or less. The bipolar battery according to claim 1.   The electrical resistance of the current flowing in the stacking direction includes a battery resistance of the battery element and a contact resistance between each terminal of the battery element and each of the positive and negative terminals. 2. The bipolar battery according to 2.   3. The battery element according to claim 1, wherein the battery element is formed by stacking a plurality of stacked bodies in which the bipolar electrodes and the electrolyte layers are alternately stacked in a unit number along the stacking direction. Bipolar battery.   The electric resistance of the current flowing in the stacking direction is the battery resistance of the battery element, the contact resistance between each of the terminal of the battery element and each of the positive and negative terminals, and the contact resistance between the stacked bodies, The bipolar battery according to claim 4, comprising: A pressure unit that pressurizes the battery element in the stacking direction;
The said pressurization part is comprised so that the applied pressure from which intensity | strength differs in each of several position with respect to the surface direction of the area | region corresponding to the said battery element in the said battery element can be urged | biased. The bipolar battery described in 1.   7. The pressurizing unit is capable of energizing pressures having different strengths for each of a plurality of divided sections with respect to a surface direction of a region corresponding to the battery element in the battery element. The bipolar battery described.   The bipolar battery according to claim 7, wherein each of the sections is equally divided into a rectangular shape.   Each of the plurality of positions is such that the pressurizing unit maintains a relationship in which the electrical resistance of the current flowing in the plane direction of the region corresponding to the battery element is smaller than the sum of the electrical resistances of the current flowing in the stacking direction The bipolar battery according to any one of claims 6 to 8, wherein pressures having different strengths are applied. By making the applied pressure urged by the pressurizing unit larger than the reference applied pressure, the sum of the electric resistances of the currents flowing in the stacking direction is the current flowing in the stacking direction at the reference applied pressure. Less than the total electrical resistance of
By making the applied pressure urged by the pressurizing unit smaller than the reference applied pressure, the sum of the electric resistances of the currents flowing in the stacking direction is the current flowing in the stacking direction at the reference applied pressure. The bipolar battery according to any one of claims 6 to 9, wherein the bipolar battery is made larger than a total sum of electrical resistances. The pressurization unit includes a detection unit that detects a temperature of the battery element, and an operation unit that generates a pressurizing force according to the detected temperature.
When the detected temperature is higher than the reference operating temperature, the operating unit generates a pressurizing force that is smaller than the reference operating temperature, and when the detected temperature is lower than the reference operating temperature. The bipolar battery according to any one of claims 6 to 10, wherein a pressurizing force larger than the pressurizing force at the reference operating temperature is generated. An outer case that houses the battery element while leading a part of the positive and negative terminals to the outside;
The detection unit and the operation unit include a block body formed of a shape memory alloy that contracts when the temperature of the battery element becomes higher than the reference operation temperature, and at least one of the positive and negative terminals and the exterior The bipolar battery according to claim 11, wherein the bipolar battery is configured such that the shrinking direction is arranged along the stacking direction between the case and the case. An outer case that houses the battery element while leading a part of the positive and negative terminals to the outside;
2. The bipolar bipolar battery according to claim 1, wherein the outer case is formed of a flexible sheet-like material, and the inner pressure of the case is lower than atmospheric pressure.   The bipolar battery according to claim 13, wherein the sheet material is a laminate film including a metal foil and a synthetic resin film.   The bipolar battery according to claim 1, wherein an aluminum plate is used for each of the positive and negative terminals.   The bipolar battery according to claim 1, wherein the electrolyte layer uses a solid electrolyte. Lithium-transition metal composite oxide is used as the positive electrode active material,
The bipolar battery according to claim 1, wherein carbon or a lithium-transition metal composite oxide is used as the negative electrode active material.   The bipolar battery according to claim 1, which is mounted as a power source for driving a vehicle.   An assembled battery formed by electrically connecting a plurality of the bipolar batteries according to claim 1.   The assembled battery according to claim 19, which is mounted as a power source for driving a vehicle.

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