JP4552570B2 - Bipolar battery - Google Patents

Description

  The present invention relates to a bipolar battery. Specifically, the present invention relates to an improvement in means for suppressing deterioration of a bipolar battery.

  In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide has been strongly desired. In the automobile industry, there is a great expectation for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV), and motor drive power sources that hold the key to commercialization are actively developed. It has been broken.

  As a power source for driving a motor, a lithium ion secondary battery having a high theoretical energy is attracting attention, and is currently being developed rapidly. Among these, a bipolar lithium ion secondary battery (so-called bipolar battery) is known as one that can be discharged at a high output (see, for example, Patent Document 1).

  The bipolar battery has a configuration in which a plurality of bipolar electrodes each having a positive electrode active material layer formed on one surface and a negative electrode active material layer formed on the other surface are stacked via an electrolyte layer. Then, a positive electrode tab and a negative electrode tab are respectively joined to a current collector (outermost layer current collector) located on the outermost layer on both sides to form a battery element, and this battery element is tabbed using an exterior such as a laminate sheet. The bipolar battery is completed by sealing so as to be drawn out.

  In the bipolar battery, a current flows in the power generation element in a direction perpendicular to the surface of the current collector. Further, the internal resistance at the interface between adjacent unit cells (cells) is so small that it can be ignored. With such a configuration, the bipolar battery can be discharged at a high output density.

Therefore, the bipolar battery is particularly useful when mounted as a power source for driving a motor of an automobile or the like that requires a particularly high output density.
Japanese Patent Laid-Open No. 11-204136 (page 3, FIG. 8)

  Here, when the conventional bipolar battery is charged and discharged under a high output condition, the current flowing through the outermost layer current collector is concentrated around the joint portion of the tab. Also, in the battery element, there are a part where a large amount of current flows and a part where the current flows depending on the position of the joint portion of the tab. For example, in the bipolar battery described in Patent Document 1, a relatively large amount of current flows on both sides in the longitudinal direction of the battery element on which the tab is installed, and a relatively small amount of current flows on the center of the battery element away from the tab. .

  When such a non-uniform distribution of current density occurs in the battery element, deterioration progresses preferentially due to exhaustion of the active material, generation of heat, or the like in a portion where a large amount of current flows. The life characteristics of a battery are greatly affected by the deteriorated part. Therefore, if the deterioration of some battery elements progresses, the life characteristic of the battery will decrease even if there is a part that has hardly deteriorated. End up. Since this problem becomes more prominent as the current flowing through the battery element increases, the present situation is that there is a strong demand for the development of means for solving the above-mentioned problems while improving the output density.

  Therefore, an object of the present invention is to provide means capable of improving the life characteristics of the battery element of the bipolar battery.

In the bipolar battery of the present invention, a single battery in which a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer are laminated in this order is further laminated via a current collector, and the outermost layer current collector and the tab are separated. The battery element is joined, and the outermost layer current collector has at least one portion having an electrical resistance in a planar direction higher than that of the joined portion .

  According to the bipolar battery of the present invention, the non-uniform density distribution of the current flowing inside the battery element, which occurs when charging / discharging under high output conditions, can be relaxed. For this reason, it can contribute to the improvement of the lifetime characteristic of a bipolar battery.

  Hereinafter, embodiments of the present invention 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.

(First embodiment)
In the first aspect of the present invention, a unit cell in which a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer are laminated in this order is further laminated through a current collector, and a tab is joined to the outermost current collector. A bipolar battery having a battery element, wherein a planar direction of the outermost layer current collector is moved away from a junction between the outermost layer current collector and the tab in a planar direction of the outermost layer current collector. The bipolar battery is characterized in that the electrical resistance of the battery increases.

  FIG. 1 is a cross-sectional view showing a bipolar battery of the present embodiment (first embodiment).

  The bipolar battery 10 of this embodiment shown in FIG. 1 has a structure in which a battery element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is an exterior. Here, the planar shapes of the laminate sheet 29 and the battery element 21 are substantially rectangular.

  As shown in FIG. 1, the bipolar battery 10 of this embodiment includes a plurality of bipolar electrodes in which a positive electrode active material layer 13 is formed on one surface of a current collector 11 and a negative electrode active material layer 15 is formed on the other surface. Have Each bipolar electrode is laminated via an electrolyte layer 17 to form a battery element 21. At this time, each bipolar electrode and electrolyte layer are arranged such that the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode face each other through the electrolyte layer 17. 17 are stacked.

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

  Further, in the bipolar battery 10 shown in FIG. 1, a positive electrode tab 25 is joined to the positive electrode side outermost layer current collector 11a, and the positive electrode tab 25 is led out from a laminate sheet 29 which is an exterior. On the other hand, a negative electrode tab 27 is bonded to the negative electrode side outermost layer current collector 11 b, and the negative electrode tab 27 is similarly derived from the laminate sheet 29.

  In the present embodiment, the joint 25 ′ between the positive electrode tab 25 and the positive electrode outermost layer current collector 11 a is formed on one side of the substantially rectangular positive electrode outermost layer current collector 11 a (the paper surface located on the right side in FIG. 1). (Side along the direction perpendicular to). On the other hand, the joint 27 ′ between the negative electrode tab 27 and the negative electrode side outermost layer current collector 11 b is formed on one side of the substantially rectangular negative electrode side outermost layer current collector 11 b (located on the left side in FIG. 1 and perpendicular to the paper surface). (Side along the right direction).

  Hereinafter, the outermost layer current collector (11a, 11b) which is one of the characteristic configurations of the present embodiment will be described in detail. In the present embodiment, the negative electrode side outermost layer current collector 11b will be described as an example, but the positive electrode side outermost layer current collector 11a has the same configuration. The same applies to other forms described later.

  In the bipolar battery 10 of the present embodiment, the thickness of the negative electrode side outermost layer current collector 11b monotonously decreases as the distance from the junction 27 ′ with the negative electrode tab 27 increases in the plane direction of the outermost layer current collector. Characterized by points. Specifically, as shown in FIG. 1, the thickness of the outermost layer current collector decreases from one side where the joint with the tab is located toward the side facing the one side. . That is, the thickness of the negative electrode side outermost layer current collector 11b is determined from one side (side along the direction perpendicular to the paper surface on the left side in FIG. 1) where the joint portion 27 ′ with the negative electrode tab 27 is located. , And decreases toward the side opposite to the one side (the side along the direction perpendicular to the paper surface located on the right side of FIG. 1). In the form shown in FIG. 1, the thickness of the negative electrode side outermost layer current collector 27 decreases linearly as the distance from the junction 27 ′ with the negative electrode tab increases. However, it is not limited only to such a form, and in some cases, it may be reduced curvilinearly (for example, exponential or logarithmic).

  In the present application, “the thickness monotonously decreases as the distance in the plane direction” means that there is at least one portion where the thickness decreases as the distance in the plane direction increases, and the thickness decreases as the distance in the plane direction increases. Means that it will not increase. When the thickness of the outermost layer current collector is decreased, the decrease may be continuous as shown in FIG. 1 or may be stepwise.

  The outermost layer current collector (11a, 11b) is made of a homogeneous material, but the configuration of the outermost layer current collector is the same as in the case of a general bipolar battery, so its description Will be described later.

(Production method)
Then, the manufacturing method of the bipolar battery 10 of this embodiment is demonstrated.

  When manufacturing the bipolar battery 10 of this embodiment, first, the positive electrode active material layer 13 is formed on one surface of the current collector 11, and the negative electrode active material layer 15 is formed on the other surface. Is made. As for the outermost layer current collector, only the positive electrode active material layer 13 is formed on one surface of the positive electrode side outermost current collector 11a, and only the negative electrode active material layer 15 is formed on one surface of the negative electrode side outermost current collector 11b. Form. As the outermost layer current collectors (11a, 11b), those having a substantially rectangular shape whose thickness decreases linearly in the longitudinal direction are used.

  Next, in the direction in which the positive electrode active material layer 13 formed on the bipolar electrode faces the negative electrode active material layer 15 formed on another bipolar electrode through the electrolyte layer 17, Are stacked. At this time, the outermost layer current collector (11a, 11b) is laminated on the uppermost surface and the lowermost surface of the laminate so that the surface on which the active material is not formed is exposed. Further, the outermost layer current collectors (11a, 11b) are arranged such that the thickness decreasing direction is reversed between the positive electrode side outermost layer current collector 11a and the negative electrode side outermost layer current collector 11b.

  Further, during the lamination, the insulating layer 31 is sandwiched between the adjacent current collectors 11 so as to surround the single battery layer 19 including the positive electrode active material layer 13, the electrolyte layer 17, and the negative electrode active material layer 15. After lamination, the edge of the laminated body is hot-pressed to thermally bond the insulating layer 31 to the current collector 11, thereby completing the battery element 21 of the laminated bipolar battery.

  Thereafter, the positive electrode tab 25 and the negative electrode tab 27 are joined to the outermost layer current collector (11a, 11b), and the battery element 21 is sealed with a laminate sheet 29 so that the positive electrode tab 25 and the negative electrode tab 27 are led out. When the tabs (25, 27) are joined, the positive electrode tab 25 is joined to the edge of the side on the thick side of the substantially rectangular positive electrode side outermost layer current collector 11a. The negative electrode tab 27 is joined to the edge of the thicker side of the current collector 11b. The method for joining the outermost layer current collector and the tab is not particularly limited, and a conventionally known welding method or the like can be used. Examples of the welding method include ultrasonic welding and spot welding. Of these, ultrasonic welding is preferably used because joining at low temperatures is possible.

  The laminate sheet 29 can be sealed, for example, by heat sealing by heat sealing, impulse sealing, ultrasonic welding, high frequency welding, or the like.

  Through the above steps, the bipolar battery 10 of this embodiment having a plurality of single battery layers 19 is completed. In addition, when it is necessary to inject | pour electrolyte solution into the electrolyte layer 17, injection | pouring of electrolyte solution may be performed before the hot press of the insulating layer 31, and may be performed after a hot press. Further, the polymer precursor (monomer) contained in the electrolytic solution may be crosslinked by heating the battery element 21 before or after hot pressing the insulating layer 31.

(Function)
Next, the operation of the bipolar battery of this embodiment will be described.

  Since the operation of the bipolar battery of this embodiment is the same as that of a general bipolar battery, the description thereof is omitted here. Below, the effect | action based on the structure of outermost layer electrical power collectors (11a, 11b) is mainly demonstrated. Specifically, for the current flowing in the stacking direction of the battery element 21 through the interface between the outermost layer current collector (11a, 11b) and the adjacent active material layer (13, 15), the negative electrode side outermost layer current collector 11b. As an example, description will be made in comparison with a conventional bipolar battery.

  First, the case of a conventional bipolar battery will be described.

  FIG. 2 is a conceptual diagram for explaining how current flows in the negative electrode side outermost layer current collector 11b of a conventional bipolar battery.

  Here, as shown in FIG. 2, the branch point of the flow of the current flowing from the negative electrode tab 27 along the direction (X direction shown in FIG. 2) in which the distance from the joint portion 27 ′ to the negative electrode tab 27 increases. Nine locations are assumed at equal intervals (see points A to I in FIG. 2). At each branch point, the current branches in the direction away from the joint portion 27 ′ with the negative electrode tab 27 (X direction shown in FIG. 2) and the stacking direction of the battery elements 21 (Y direction shown in FIG. 2). Furthermore, it is assumed that the negative electrode active material layer 15 can flow only at these branch points. In FIG. 2, for the sake of convenience of explanation, branch points are assumed throughout the outermost layer current collector 11b. However, in the following description, the outermost current collector 11b is reduced by reducing the interval between the branch points. This is true for only a part.

  In general, the electrical resistance R is represented by the following formula 1.

(In the formula, ρ represents electric resistivity (Ω · m), L represents length (m), and A represents cross-sectional area (m ² ).)
In Equation 1, the electrical resistivity ρ is a value inherent to the substance, and is a constant value for members made of a homogeneous material.

  Here, when the length in the X direction at each branch point is fixed to a small constant value ΔL, it can be seen from Equation 1 that the electrical resistance in the X direction at each branch point is inversely proportional to the cross-sectional area A in the X direction. Therefore, in the outermost layer current collector 11b of the conventional bipolar battery in which the cross-sectional area in the X direction is always constant, the electrical resistance in the planar direction (X direction) of the current collector 11b is the junction 27 ′ with the negative electrode tab 27. Regardless of the distance from, it is always a constant value.

  On the other hand, since the branch points are arranged at equal intervals, it can be approximated that the electrical resistance in the Y direction at each branch point is always a constant value regardless of the distance from the junction 27 '.

The respective currents flowing in the X direction and the Y direction after branching at each branch point depend on the electric resistances in the X direction and the Y direction at each branch point. That is, the current flowing into a certain branch point is I, the electrical resistance in the X direction at the branch point is R _X , the electrical resistance in the Y direction at the branch point is R _Y , and the current flowing in the X direction after the branch is I _X If the current that subsequently flows in the Y direction is I _Y , these satisfy the following equations 2 and 3:

Here, as described above, the electrical resistance in the X direction and the electrical resistance in the Y direction at each branch point are constant values. Therefore, R _Y / R _X is a constant value, and according to Equation 3, I _X / I _Y is also a constant value.

From the above, in the outermost layer current collector 11b of the conventional bipolar battery, it is considered that the current flowing into each branch point always branches in the X direction and the Y direction at a constant ratio. If the ratio value (I _X / I _Y ) is assumed to be I _X / I _Y = 9 and the current flowing from the negative electrode tab 27 is assumed to be 10 A, the current branched at each branch point is The values are shown in Table 1 below. These assumptions are merely for convenience of calculation, and are different from actual values. Further, no consideration is given to the attenuation of current due to the internal resistance of the outermost layer current collector 11b.

  The relative value of the current flowing in the Y direction at each branch point is shown by the length of the arrow in FIG. 2 and as a graph in FIG.

  From the results shown in Table 1, FIG. 2 and FIG. 4, the current branched in the Y direction in the negative electrode side outermost current collector 11 b of the conventional bipolar battery has a bottom of 0 as the distance from the junction 27 ′ of the negative electrode tab 27 increases. It can be seen that it decreases to an exponential function of .9.

  Then, the case of the bipolar battery of this embodiment is demonstrated. FIG. 3 is a conceptual diagram for explaining how a current flows in the negative electrode side outermost layer current collector 11b of the bipolar battery 10 of the present embodiment (first embodiment).

  The negative electrode side outermost layer current collector 11b of the bipolar battery of this embodiment shown in FIG. 3 is the same as the conventional outermost layer current collector in that it is made of a homogeneous material. However, as described above, it differs from the outermost layer current collector of the conventional bipolar battery in that the thickness decreases linearly as the distance from the junction 27 ′ with the negative electrode tab 27 increases.

  Here, also in the present embodiment, nine branch points are assumed in the same manner as described above for the outermost current collector of a conventional bipolar battery (see points a to i in FIG. 3). . Also in the present embodiment, as in the case of the above, the relationship of Equation 2 and Equation 3 is established between the current and the electrical resistance.

As shown in FIG. 3, the thickness of the negative electrode side outermost layer current collector 11 b of the bipolar battery of the present embodiment linearly decreases as the distance from the junction 27 ′ with the negative electrode tab 27 increases. Thus, the cross-sectional area A in the X direction of the current collector 11b also decreases linearly. Therefore, according to Equation 1, the electric resistance (R _X ) in the planar direction (X direction) of the negative electrode side outermost layer current collector 11 b increases linearly as the distance from the junction 27 ′ with the negative electrode tab 27 increases. Will do. In the present embodiment, it is possible to assume that the electrical resistance in the Y direction at each branch point is always a constant value regardless of the distance from the joint portion 27 ′ to the negative electrode tab 27, as described above. .

As described above, the value of R _Y / R _X at each branch point decreases linearly as the distance from the junction with the tab increases (as the travel proceeds from the branch point a → i). Therefore, according to Equation 3, the value of I _X / I _Y also decreases linearly as the distance from the joint with the tab increases.

Here, it is assumed that the negative electrode side outermost layer current collector 11b of the bipolar battery of the present embodiment is made of the same material as the negative electrode side outermost layer current collector 11b of the conventional form shown in FIG. Furthermore, it is assumed that the value of R _Y / R _X decreases linearly by 0.2 as the branch point is advanced by one in the X direction. Then, since the thickness of the branch point E which is the central branch point becomes the average value of the thickness of the current collector, the value of R _Y / R _{X at} the branch point E is 9.0 which is the same as the conventional case. Thus, the values of R _Y / R _X at other branch points are the values shown in Table 2 below. Moreover, since it consists of the same material, the value of _RY becomes the same in this embodiment and the conventional form. Furthermore, since the ratio of the electrical resistance (R _X ) in the X direction at each branch point is directly the ratio of the thickness of the current collector 11b at each branch point, the thickness at each branch point of this embodiment (FIG. 2). The relative value with respect to the thickness of the current collector in the form shown in FIG.

  Similarly to the above, assuming that the current flowing from the negative electrode tab 27 is 10 A, the current branched at each branch point has the values shown in Table 2 below. Further, the current flowing in the Y direction at each branch point is indicated by the length of the arrow in FIG. 3 and as a graph in FIG.

  From the results shown in Table 2, FIG. 3, and FIG. 4, the current branching in the Y direction at each branch portion of the negative electrode side outermost layer current collector 11b of the bipolar battery of this embodiment is compared with that of the conventional bipolar battery. Thus, although it decreases on the side closer to the joint 27 ′ of the negative electrode tab 27, the difference decreases as the distance from the joint 27 ′ increases, and the distance reverses and increases as the distance further increases. In other words, the current density distribution in the Y direction, which showed an exponential decrease in the case of the conventional bipolar battery, will show a more linear decrease by adopting the configuration of this embodiment. I understand. From this, in the configuration of the present embodiment, in the conventional bipolar battery, the current in the Y direction that is biased toward the junction 27 ′ side with the negative electrode tab 27 is dispersed over the entire surface of the outermost current collector, It can be seen that the current density distribution in the Y direction is relaxed.

  Therefore, according to the bipolar battery of the present embodiment, the current flowing in the stacking direction of the battery elements 21 is concentrated on a specific portion without increasing the amount of the material constituting the outermost current collector in the conventional bipolar battery. Can be mitigated, and deterioration of the battery element due to the consumption of the active material and the generation of heat at the specific site can be suppressed. As a result, it can greatly contribute to the improvement of the life characteristics of the bipolar battery.

  The current flowing in the stacking direction of the battery element 21 at the interface between the outermost current collector and the adjacent active material layer has been described above by taking the negative electrode side outermost current collector 11b as an example. For the current collector 11a, the same theory can be established except that the current flow is in the opposite direction (positive electrode active material layer 13 → positive electrode side outermost layer current collector 11a). Therefore, it is preferable that the outermost layer current collectors (11a, 11b) on both the positive electrode side and the negative electrode side have a configuration as in this embodiment shown in FIG. However, even if only one of the outermost layer current collectors has the configuration of the present embodiment, it is included in the technical scope of the present invention as long as the effects of the present invention are exhibited.

  In the present embodiment, the positive electrode tab 25 and the negative electrode tab 27 are led out from opposite sides of the substantially rectangular bipolar battery. In other words, the direction in which the thickness of the positive electrode side outermost layer current collector 11a decreases and the direction in which the thickness of the negative electrode side outermost layer current collector 11b decreases are opposite. Therefore, according to the bipolar battery of this embodiment, the thickness of the entire surface of the battery element 21 sealed with the laminate sheet 29 can be maintained uniformly. As a result, a bipolar battery excellent in space efficiency can be provided. However, in some cases, a form in which both the positive electrode tab 25 and the negative electrode tab 27 are derived from the same side of the substantially rectangular bipolar battery may be employed.

  Hereinafter, although the member which comprises the bipolar battery 10 of this embodiment is demonstrated easily, it is not restrict | limited only to the following form, A conventionally well-known form can be employ | adopted similarly.

[Current collector (including outermost layer current collector)]
The current collector 13 and the outermost layer current collector (11a, 11b) are made of a conductive material such as an aluminum foil, a copper foil, or a stainless steel (SUS) foil. The general thickness of the current collector other than the outermost layer current collector is 1 to 30 μm. However, a current collector having a thickness outside this range may be used. When the thickness of the outermost layer current collector is changed as in this embodiment, the thickness at the thickest part is preferably about 10 to 1000 μm, and the thickness at the thinnest part is preferably about 1 to 100 μm. It is.

  The size of the current collector is determined according to the use application of the bipolar battery 10. If a large electrode used for a large battery is manufactured, a current collector having a large area is used. If a small electrode is produced, a current collector with a small area is used.

[Active material layer]
The positive electrode active material layer 15 includes a positive electrode active material. As the positive electrode active material, a lithium-transition metal composite oxide is preferable, and examples thereof include a Li—Mn composite oxide such as LiMn ₂ O ₄ and a Li—Ni composite oxide such as LiNiO ₂ . In some cases, two or more positive electrode active materials may be used in combination.

  The negative electrode active material layer 17 includes a negative electrode active material. As the negative electrode active material, the above lithium transition metal-composite oxide or carbon is preferable. Examples of carbon include graphite-based carbon materials such as natural graphite and artificial graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, and hard carbon.

  The positive electrode active material layer 15 and the negative electrode active material layer 17 may contain other materials if necessary. For example, a binder, a conductive additive, a lithium salt (supporting electrolyte), an ion conductive polymer, and the like can be included. When an ion conductive polymer is included, a polymerization initiator for polymerizing the polymer may be included.

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

  The conductive assistant refers to an additive that is blended in order to improve the conductivity of the positive electrode active material layer 13 or the negative electrode active material layer 15. Examples of the conductive aid include carbon powder such as graphite.

As a lithium salt (supporting electrolyte), LiBETI (lithium bis (perfluoroethylenesulfonylimide); Li (C ₂ F ₅ SO ₂ ) ₂ N), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ Etc.

  Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers. Here, the ion conductive polymer may be the same as or different from the ion conductive polymer used as the electrolyte in the electrolyte layer 17 of the bipolar battery 10, but is preferably the same.

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

  The compounding ratio of the components contained in the positive electrode active material layer 13 and the negative electrode active material layer 15 is not particularly limited. The blending ratio can be adjusted by appropriately referring to known knowledge about lithium ion secondary batteries.

[Electrolyte layer]
In general, the electrolyte constituting the electrolyte layer 17 includes a liquid electrolyte or a polymer electrolyte. In the present invention, a polymer electrolyte is preferably used. By using the polymer electrolyte, leakage of electrolyte and the like can be prevented, and the safety of the bipolar battery 10 can be improved.

  The polymer electrolyte is composed of an ion conductive polymer, and the material is not limited as long as it exhibits ion conductivity. Made by forming a cross-linked structure by polymerizing a polymerizable polymer for forming a polymer electrolyte by thermal polymerization, ultraviolet polymerization, radiation polymerization, or electron beam polymerization because it can exhibit excellent mechanical strength. Are preferably used. In the electrolyte layer formed of such a polymer electrolyte, liquid leakage does not occur, so that the reliability of the battery is improved and the bipolar battery 10 having a simple configuration and excellent output characteristics is formed.

  Examples of the polymer electrolyte include an intrinsic polymer electrolyte and a gel polymer electrolyte.

  The intrinsic polymer electrolyte is not particularly limited, and examples thereof include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. In such polyalkylene oxide polymers, electrolyte salts such as lithium salts can be well dissolved. In addition, these polymers can exhibit excellent mechanical strength by forming a crosslinked structure. In the present invention, it is preferable that the all solid polymer electrolyte is contained in both the positive electrode active material layer 13 and the negative electrode active material layer 15 in order to further improve the electrode characteristics.

The gel polymer electrolyte generally refers to an electrolyte solution held in an all-solid polymer electrolyte having ion conductivity. In the present application, a polymer gel electrolyte also includes a polymer skeleton that does not have lithium ion conductivity and that holds a similar electrolyte solution. The type of electrolyte solution (electrolyte salt and plasticizer) used is not particularly limited. Examples of the electrolyte salt include lithium salts such as LiBETI, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F ₅ ) ₂ . Examples of the plasticizer include carbonates such as propylene carbonate and ethylene carbonate.

  When the electrolyte layer is made of a gel polymer electrolyte, the electrolyte layer is formed by impregnating a polymer gel raw material solution into a separator such as a nonwoven fabric and then polymerizing using the various methods described above. There may be. By using the separator, the filling amount of the electrolytic solution can be increased, and the thermal conductivity inside the battery is ensured.

[Insulation layer]
In the bipolar battery 10, an insulating layer 31 is usually provided around each unit cell layer 19. The insulating layer 31 is provided for the purpose of preventing short-circuiting due to a slight unevenness of the end portions of the battery cell layer 19 in the battery element 21 due to contact between adjacent current collectors 13 in the battery. The installation of such an insulating layer 31 ensures long-term reliability and safety, and can provide a high-quality bipolar battery 10.

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

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

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

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

(Second Embodiment)
The bipolar battery of the second embodiment is different from the first embodiment only in the shape of the outermost layer current collector and the joining position of the tab, and the other configurations are the same as in the first embodiment. It is. Accordingly, the same members as those in the first embodiment are denoted by the same reference numerals, and detailed description of the same components as those in the first embodiment is omitted. The same applies to other forms described later.

  FIG. 5 is a schematic perspective view of the negative electrode side outermost layer current collector 11b of the bipolar battery 10 of this embodiment (second embodiment), and FIG. 6 is a cross-sectional view taken along line 6-6 shown in FIG. FIG. 7 is a cross-sectional view showing the bipolar battery 10 of the present embodiment (second embodiment). The surface along line 6-6 shown in FIG. 5 corresponds to the cross section of FIG.

  In the present embodiment, the negative electrode side outermost layer current collector 11b is substantially rectangular, and the joint portion 27 'of the negative electrode tab 27 is located at the center of the rectangle (see the hatched portion in FIG. 5). As the distance from the joint portion 27 ′ with the negative electrode tab 27 increases in the planar direction of the current collector 11b, specifically, the negative electrode side outermost portion extends from the joint portion 27 ′ with the negative electrode tab 27 toward the four sides of the rectangle. The thickness of the outer layer current collector 11b decreases linearly. As shown in FIG. 7, the tabs (25, 27) are covered with a heat-resistant insulating resin 33. This can prevent a short circuit between the tabs (25, 27) and the outermost current collector (11a, 11b) at a place other than the joints (25 ', 27').

  By having the configuration as described above, the bipolar battery 10 of the present embodiment exhibits the same operations and effects as the bipolar battery of the first embodiment. That is, as the thickness of the negative electrode side outermost layer current collector 11b as described above decreases, the electric resistance in the direction in which the thickness decreases linearly increases. Thereby, the bias of the density distribution of the current flowing in the stacking direction of the battery element 21 from the negative electrode side outermost layer current collector 11b is alleviated by the same mechanism as described in the first embodiment. As a result, the deterioration of the battery element due to the consumption of the active material or the generation of heat at the specific part is suppressed, and the life characteristics of the bipolar battery can be improved.

(Third embodiment)
The bipolar battery of the third embodiment is different from the first embodiment only in the configuration of the outermost layer current collector, and the other configurations are the same as those in the first embodiment.

  FIG. 8 is a plan view of the negative electrode side outermost layer current collector 11b of the bipolar battery 10 of the present embodiment (third embodiment) as seen from the side where the negative electrode tab 27 is joined, and FIG. It is the side view seen from the A direction shown in FIG.

  In the present embodiment, the negative electrode side outermost layer current collector 11b is substantially rectangular, and the joint portion 27 'of the negative electrode tab 27 is located at the edge of one side of the rectangle (see the hatched portion in FIG. 8). Then, on the surface to which the negative electrode tab 27 is joined, there are four groove portions from the side where the joint portion 27 ′ is located toward the side facing this side, in other words, along the longitudinal direction of the current collector 11 b. 35 is formed. The depth and width of each groove portion 35 increase from the side where the joint portion 27 ′ is located toward the side facing this side. That is, each groove part 35 has a triangular pyramid shape. The dimensions and number of the groove portions 35 are not particularly limited to the forms shown in FIGS. 8 and 9 and can be changed as appropriate. Moreover, there is no restriction | limiting in particular also about the formation method of the groove part 35, For example, the method of using an electric cutter etc. is illustrated.

  Even with the bipolar battery 10 of the present embodiment having the above-described configuration, the same operations and effects as those of the above-described embodiment can be obtained.

(Fourth embodiment)
The bipolar battery of the fourth embodiment is different from the third embodiment only in the configuration of the groove portion of the outermost layer current collector, and the other configurations are the same as those in the third embodiment. .

  FIG. 10 is a plan view of the negative electrode side outermost layer current collector 11b of the bipolar battery 10 of the present embodiment (fourth embodiment) as viewed from the side where the negative electrode tab 27 is joined. It is the side view seen from the B direction shown in FIG.

  In the present embodiment, the negative electrode side outermost layer current collector 11b is substantially rectangular, and the joint portion 27 'of the negative electrode tab 27 is located at the edge of one side of the rectangle (see the hatched portion in FIG. 10). On the surface to which the negative electrode tab 27 is bonded, five parallel groove portions 35 are formed at equal intervals from the side where the bonding portion 27 ′ is located toward the side facing this side. The depth of each groove portion 35 is shallower as the groove portion 35 is closer to the side where the joint portion 27 ′ is located, and deeper as the groove portion 35 is farther from the side where the joint portion 27 ′ is located.

  As described above, in the form shown in FIG. 11, the groove portions 35 are formed at equal intervals. However, according to circumstances, the interval between adjacent groove portions 35 may be varied. For example, the interval between the adjacent groove portions 35 may be narrowed from the side where the joint portion 27 ′ is located toward the side facing this side.

  Even with the bipolar battery 10 of the present embodiment having the above-described configuration, the same operations and effects as those of the above-described embodiment can be obtained.

(Fifth embodiment)
The bipolar battery of the fifth embodiment is different from the fourth embodiment only in the configuration of the outermost layer current collector, and the other configurations are the same as those in the fourth embodiment.

  FIG. 12 is a plan view of the bipolar battery 10 according to the present embodiment (fifth embodiment) as viewed from the side of the surface to which the negative electrode tab 27 of the negative electrode side outermost current collector 11b is joined, and FIG. 12 is a side view seen from the C direction shown in FIG.

  In the present embodiment, the negative electrode side outermost layer current collector 11b is substantially rectangular, and the joint portion 27 'of the negative electrode tab 27 is located at the edge of one side of the rectangle (see the hatched portion in FIG. 12). And on the surface where the negative electrode tab 27 is joined, six notches 37 are formed in parallel to the side where the joined portion 27 ′ is located. Each notch 37 is alternately cut out from two opposing sides of the current collector 11b in the longitudinal direction of the rectangle. Further, the length of each notch portion 37 increases from the side where the joint portion 27 ′ is located toward the side facing this side, and the interval between adjacent notch portions 37 is narrowed.

  In the form shown in FIG. 13, the depth of each notch 37 is constant in all notches 37. However, depending on the case, the depth of each notch 37 may be varied. As such a form, for example, a notch part 37 closer to the side where the joint part 27 ′ is located is shallower and a notch part 37 farther from the side where the joint part 27 ′ is located is deeper. According to such a form, the flat surface of the current collector 11b is further away from the joint part 27 ′ of the negative electrode tab 27 than in the form in which each notch part 37 as shown in FIGS. 12 and 13 has a certain depth. The rate of increase when the electrical resistance in the direction increases can increase.

  The form in which the notch 37 is provided on the surface to which the negative electrode tab 27 is joined is not limited to the above form, and the electrical resistance in the planar direction of the current collector 11b as the distance from the joint 27 'with the negative electrode tab 27 increases. Any form that can increase is sufficient. As another form in which the notch part 37 is provided, the form shown in FIG. 14 is mentioned, for example. In the form shown in FIG. 14, each notch 37 is notched at equal intervals from both of the two opposite sides in the longitudinal direction of the current collector 11b. Further, the length of each cutout portion 37 increases from the side where the joint portion 27 ′ is located toward the side facing this side.

  There is no restriction | limiting in particular about the formation method of the notch part 37, The method of using the electric cutter etc. which were mentioned above about formation of the groove part 35 is illustrated.

  Even with the bipolar battery 10 of the present embodiment having the above-described configuration, the same operations and effects as those of the above-described embodiment can be obtained.

(Sixth embodiment)
In the sixth embodiment, an assembled battery is configured by connecting a plurality of the bipolar batteries of the first to fifth embodiments in parallel and / or in series.

  FIG. 15 is a perspective view showing the assembled battery of the present embodiment (sixth embodiment).

  As shown in FIG. 15, the assembled battery 40 is configured by connecting a plurality of bipolar batteries described in any of the first to fifth embodiments. Each bipolar battery 10 is connected by connecting the positive electrode tab 25 and the negative electrode tab 27 of each bipolar battery 10 using a bus bar. On one side surface of the assembled battery 40, electrode terminals (42, 43) are provided as electrodes of the entire assembled battery 40.

  The connection method when connecting the plurality of bipolar batteries 10 constituting the assembled battery 40 is not particularly limited, and a conventionally known method can be appropriately employed. For example, a technique using welding such as ultrasonic welding or spot welding, or a technique of fixing using rivets, caulking, or the like can be employed. According to such a connection method, the long-term reliability of the assembled battery 40 can be improved.

  According to the assembled battery 40 of the present embodiment, a battery having a high capacity and / or high output can be provided by using the bipolar battery 10 of the first to fifth embodiments as an assembled battery. And since each bipolar battery 10 which comprises the assembled battery 40 is excellent in durability, according to the assembled battery 40 of this embodiment, the battery excellent in durability can also be provided.

  The connection of the bipolar batteries 10 constituting the assembled battery 40 may be all connected in parallel, all may be connected in series, or a combination of series connection and parallel connection may be used. Also good.

(Seventh embodiment)
In the seventh embodiment, the bipolar battery 10 of the first to fifth embodiments or the assembled battery 40 of the sixth embodiment is mounted as a motor driving power source to constitute a vehicle. As a vehicle using the bipolar battery 10 or the assembled battery 40 as a motor power source, for example, a complete electric vehicle that does not use gasoline, a hybrid vehicle such as a series hybrid vehicle or a parallel hybrid vehicle, and a fuel cell vehicle, etc. A driving car can be mentioned.

  For reference, FIG. 16 shows a schematic diagram of an automobile 50 on which the assembled battery 40 is mounted. The assembled battery 40 mounted on the automobile 50 has the characteristics as described above. For this reason, the automobile 50 equipped with the assembled battery 40 is excellent in durability, and can provide a sufficient output even after being used for a long period of time.

  As described above, some preferred embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and various modifications, omissions, and additions can be made by those skilled in the art. It is.

It is sectional drawing which shows the bipolar battery of 1st Embodiment. It is a conceptual diagram for demonstrating a mode that an electric current flows in the negative electrode side outermost layer collector of the conventional bipolar battery. The relative value of the current in the Y direction at each branch point is indicated by the length of the arrow. It is a conceptual diagram for demonstrating a mode that an electric current flows in the negative electrode side outermost layer electrical power collector of the bipolar battery of 1st Embodiment. The relative value of the current in the Y direction at each branch point is indicated by the length of the arrow. It is a graph which shows the relative value of the electric current of the Y direction in each branch point of the conventional bipolar battery and the bipolar battery of 1st Embodiment. It is a model perspective view of the negative electrode side outermost layer electrical power collector of the bipolar battery of 2nd Embodiment. FIG. 6 is a cross-sectional view taken along line 6-6 shown in FIG. It is sectional drawing which shows the bipolar battery of 2nd Embodiment. It is the top view seen from the surface side where the negative electrode tab is joined of the negative electrode side outermost layer collector of the bipolar battery of 3rd Embodiment. It is the side view seen from the A direction shown in FIG. It is the top view seen from the surface side where the negative electrode tab is joined of the negative electrode side outermost layer collector of the bipolar battery of 4th Embodiment. It is the side view seen from the B direction shown in FIG. It is the top view seen from the surface side where the negative electrode tab is joined of the negative electrode side outermost layer collector of the bipolar battery of 5th Embodiment. It is the side view seen from the C direction shown in FIG. It is a top view which shows the modification of the negative electrode side outermost layer collector of the bipolar battery of 5th Embodiment. It is a perspective view which shows the assembled battery of 6th Embodiment. It is the schematic which shows the motor vehicle of 7th Embodiment.

Explanation of symbols

10 Bipolar battery,
11 Current collector,
11a Positive electrode side outermost layer current collector,
11b The negative electrode side outermost layer current collector,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 electrolyte layer,
19 cell layer,
21 battery elements,
25 positive electrode tab,
25 'joint between the positive electrode tab and the positive electrode side outermost layer current collector,
27 negative electrode tab,
27 'junction of the negative electrode tab and the negative electrode side outermost layer current collector,
29 Laminate sheet,
31 insulating layer,
33 resin,
35 groove,
37 Notch,
40 battery packs,
50 cars.

Claims (6)

The positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer is a single cell which are laminated in this order, and further layered with a current collector, made and the outermost current collector and the tab is joined at the junction A bipolar battery,
The bipolar battery according to claim 1, wherein the outermost layer current collector has at least one portion having an electrical resistance in a planar direction higher than that of the junction . In the outermost layer current collector, it has at least two parts having an electrical resistance in a planar direction higher than that of the joint part
2. The electrical resistance in a planar direction at a portion where the electrical resistance in the planar direction is higher than that of the joint is increased as the distance from the joint in the planar direction of the outermost layer current collector is increased. The bipolar battery described. 3. The bipolar battery according to claim 1, wherein a portion where the electric resistance in the planar direction is higher than that of the junction is formed by reducing the thickness of the outermost layer current collector. 3. The bipolar battery according to claim 1, wherein a portion where the electrical resistance in the planar direction is higher than that of the joint is formed by providing a groove or a notch in the outermost layer current collector.   The thickness of the outermost layer current collector monotonously decreases as the distance from the junction between the outermost layer current collector and the tab increases in the planar direction of the outermost layer current collector. 2. The bipolar battery according to 1. The outermost layer current collector is substantially rectangular,
The joint between the tab and the outermost layer current collector is located on one side of the outermost layer current collector,
The bipolar battery according to claim 5 , wherein a thickness of the outermost layer current collector decreases from the one side where the joint portion is located toward an opposite side.

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