Battery

Abstract

To provide a battery in which an external short circuit with large heat hardly occurs between current collector foils of a plurality of current collectors when a load is received from a conductive member in a direction orthogonal to a lamination direction of a plurality of electrodes.SOLUTION: A battery includes a laminate 15 configured by laminating, in a predetermined lamination direction, a plurality of electrodes 17, 20, 23, each including a current collector 18 and at least one of a positive electrode active material layer 21 and a negative electrode active material layer 19 formed on each current collector, and a plurality of separators 25 located between the positive electrode active material layers and the negative electrode active material layers. The current collectors each have a portion made of a current collector foil 18-1 where the positive electrode active material layer and the negative electrode active material layer are not formed, and when the laminate is viewed in the lamination direction, outer peripheral end portions of current collector foils 18C that are located at a central portion in the lamination direction are located on outer peripheral sides of the outer peripheral end portions of the current collector foils that are located at end portions in the lamination direction.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a battery.

Background Art

[0002] Patent Document 1 below discloses a battery in which a plurality of electrodes including bipolar electrodes are stacked in a predetermined stacking direction.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the battery of Patent Document 1 above receives a load in a direction orthogonal to the stacking direction from a conductive member, there is a risk of an external short - circuit accompanied by a large amount of heat occurring between the current - collecting foils of the plurality of current - collectors.

[0005] In consideration of the above facts, an object of the present invention is to obtain a battery in which an external short - circuit accompanied by a large amount of heat is less likely to occur between the current - collecting foils of a plurality of current - collectors when the battery receives a load in a direction orthogonal to the stacking direction of the plurality of electrodes.

Means for Solving the Problems

[0006] The battery according to the first aspect includes a plurality of electrodes having a current collector and at least one of a positive electrode active material layer and a negative electrode active material layer formed on the current collector, and a plurality of separators positioned between the positive electrode active material layer and the negative electrode active material layer are laminated in a predetermined lamination direction to form a laminate. A part of the current collector is a current collector foil on which the positive electrode active material layer and the negative electrode active material layer are not formed. When the laminate is viewed along the lamination direction, an outer peripheral side end portion of the current collector foil positioned at a central portion in the lamination direction is positioned more on the outer peripheral side than an outer peripheral side end portion of the current collector foil positioned at an end portion in the lamination direction.

[0007] In the battery according to the first aspect, when the laminate is viewed along the lamination direction of the laminate, an outer peripheral side end portion of the current collector foil positioned at a central portion in the lamination direction is positioned more on the outer peripheral side than an outer peripheral side end portion of the current collector foil positioned at an end portion in the lamination direction. Therefore, when the battery receives a load in a direction orthogonal to the lamination direction from a conductive member, the possibility that this conductive member simultaneously contacts the current collector foil positioned at the central portion and the current collector foil positioned at the end portion in the lamination direction is small. In other words, in the battery according to the first aspect, it is difficult for an external short circuit accompanied by a large amount of heat to occur between the current collector foils of the plurality of current collectors.

[0008] The battery according to the second aspect is, in the first aspect, the electrode other than the electrode positioned at the end portion in the lamination direction is a bipolar electrode having the current collector, the positive electrode active material layer formed on one surface of the current collector, and the negative electrode active material layer formed on the other surface of the current collector.

[0009] The battery according to the second aspect can output a larger power compared to the case where no bipolar electrode is provided.

[0010] The battery according to the third aspect is, in the first aspect or the second aspect, the outer peripheral side end portion of the current collector foil positioned at the center in the lamination direction is positioned more on the outer peripheral side than the outer peripheral side end portion of the current collector foil positioned at the end portion in the lamination direction.

[0011] In the battery according to the third aspect, the outer peripheral side end portion of the current collector foil located at the center in the stacking direction is located on the outer peripheral side of the outer peripheral side end portion of the current collector foil located at the end in the stacking direction. According to this configuration, it is difficult for the conductive member in contact with the current collector foil located at the center to come into contact with the current collector foils located at both ends in the stacking direction.

[0012] When the total number of current collectors is odd, this "current collector foil located at the center" is the current collector foil of one current collector. When the total number of current collectors is even, this "current collector foil located at the center" is the current collector foils of two current collectors. Further, when the total number of current collectors is even, the outer peripheral side end portions of the current collector foils of the two current collectors may be located on the outer peripheral side of the outer peripheral side end portion of the current collector foil located at the end in the stacking direction, or only the outer peripheral side end portion of one of the current collector foils of the two current collectors may be located on the outer peripheral side of the outer peripheral side end portion of the current collector foil located at the end in the stacking direction.

[0013] In the battery according to the fourth aspect, in the first aspect or the second aspect, when viewing the laminate along the stacking direction, the distance between the outer peripheral side end portions of the current collector foils adjacent to each other in the stacking direction is larger than the dimension of the current collector in the stacking direction.

[0014] According to the fourth aspect, when the conductive member receives a load in a direction perpendicular to the stacking direction, it is difficult for an external short circuit to occur between the current collector foils adjacent to each other in the stacking direction.

[0015] In the battery according to the fifth aspect, in the first aspect or the second aspect, when defining the current collector having the outer peripheral side end portion located most on the outer peripheral side as the maximum protruding current collector when viewing the laminate along the stacking direction, each current collector other than the maximum protruding current collector has an outer peripheral side end portion located on the inner peripheral side of the outer peripheral side end portion of the current collector foil of the current collector located on the maximum protruding current collector side with respect to itself.

[0016] According to the fifth aspect, when the conductive member receives a load in a direction perpendicular to the stacking direction, it is difficult for an external short circuit to occur between the current collector foils.

Advantages of the Invention

[0017] As described above, the battery according to the present invention has an excellent effect that when a load in a direction orthogonal to the stacking direction of the plurality of electrodes is received from the conductive member, it is difficult for a large heat-generating external short circuit to occur between the current collector foils of the plurality of current collectors.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0019] Hereinafter, a bipolar lithium ion secondary battery according to an embodiment (hereinafter referred to as battery 10) will be described. The battery 10 can be mounted on various devices. The battery 10 of the present embodiment is mounted on a battery electric vehicle (BEV) and can supply power to an electric motor which is a drive source. The arrows UP, FR, and LH shown in each drawing indicate the upper side in the vertical direction, the front side in the front-rear direction, and the left side in the left-right direction, respectively.

[0020] First, the basic configuration of the battery 10 will be described. The battery 10 of the present embodiment includes a laminate 15 and a resin member 30.

[0021] The laminate 15 is formed by laminating a plurality of electrodes and a plurality of separators 25 in a predetermined lamination direction (the vertical direction in FIG. 1). As shown in FIG. 2, these electrodes include a negative terminal electrode 17, a positive terminal electrode 20, and a plurality of bipolar electrodes 23. The laminate 15 of the present embodiment includes 11 electrodes (negative terminal electrode 17, positive terminal electrode 20, bipolar electrode 23). That is, the laminate 15 has 11 current collectors 18. Note that in FIGS. 2 and 3, illustration of some of the bipolar electrodes 23 is omitted.

[0022] The negative terminal electrode 17 includes a current collector 18 and a negative electrode active material layer 19 provided on one surface (the upper surface in FIG. 1) of the current collector 18. The positive terminal electrode 20 includes a current collector 18 and a positive electrode active material layer 21 provided on one surface (the lower surface in FIG. 1) of the current collector 18. Each bipolar electrode 23 includes a current collector 18, a negative electrode active material layer 19 provided on one surface (the upper surface in FIG. 2) of the current collector 18, and a positive electrode active material layer 21 provided on the other surface (the lower surface in FIG. 2) of the current collector 18.

[0023] A separator 25 is provided between the negative electrode active material layer 19 of the negative terminal electrode 17 and the positive electrode active material layer 21 of the bipolar electrode 23 adjacent to the negative terminal electrode 17. Further, a separator 25 is provided between the positive electrode active material layer 21 of the positive terminal electrode 20 and the negative electrode active material layer 19 of the bipolar electrode 23 adjacent to the positive terminal electrode 20. Further, a separator 25 is provided between the negative electrode active material layer 19 of the adjacent bipolar electrodes 23 and the positive terminal electrode 20.

[0024] As shown in FIGS. 1 and 2, both end faces in the lamination direction of the laminate 15 including the negative terminal electrode 17, the positive terminal electrode 20, the bipolar electrode 23, and the separator 25 are constituted by the current collector 18. As shown in FIG. 2, the outer peripheral portion of each current collector 18 when the laminate 15 is viewed along the lamination direction is a current collector foil 18-1 located on the outer peripheral side from the outer peripheral side end portions of the negative electrode active material layer 19 and the positive electrode active material layer 21.

[0025] The shape (planar shape) of the laminate 15 of the present embodiment when viewed along the stacking direction is rectangular. That is, the shapes of the current collector 18, the negative electrode active material layer 19, the positive electrode active material layer 21, and the separator 25 when the laminate 15 is viewed along the stacking direction are rectangular. Further, as is clear from FIG. 2, when the laminate 15 is viewed along the stacking direction, the outer peripheral side end portions of each negative electrode active material layer 19 are located on the outer peripheral side of the outer peripheral side end portions of each positive electrode active material layer 21. Further, the shapes of the respective negative electrode active material layers 19 when the laminate 15 is viewed along the stacking direction are the same as each other, and the shapes of the respective positive electrode active material layers 21 when the laminate 15 is viewed along the stacking direction are the same as each other.

[0026] On the other hand, the shapes of the respective current collectors 18 when the laminate 15 is viewed along the stacking direction are different from each other. Here, the current collector 18 located at the center in the stacking direction is defined as the maximum protruding current collector 18C. That is, the sixth current collector 18 counted from the top and the sixth current collector 18 counted from the bottom are the maximum protruding current collector 18C. As is clear from FIG. 2, in the shape (outer shape) when viewed along the stacking direction, the maximum protruding current collector 18C is the largest among all the current collectors 18, and the shapes of the respective current collectors 18 gradually become smaller as they go upward and downward from the maximum protruding current collector 18C. In other words, the outer peripheral side end portions 18PE of each current collector 18 are gradually located on the inner peripheral side as they go upward and downward from the maximum protruding current collector 18C. Further, the distance DF in the direction orthogonal to the stacking direction between the outer peripheral side end portions 18PE of the current collectors 18 adjacent to each other in the stacking direction when the laminate 15 is viewed along the stacking direction (in FIG. 2, only some of the distances DF are shown) is larger than the dimension (thickness) of each current collector 18 in the stacking direction. For example, the distance DF in the front-rear direction between the front end face of the uppermost current collector 18 and the front end face of the second current collector 18 counted from the top, and the distance DF in the front-rear direction between the front end face of the second current collector 18 counted from the bottom and the front end face of the third current collector 18 counted from the bottom are larger than the dimension of the current collector 18 in the stacking direction.

[0027] The shapes of the separators 25 when viewed along the stacking direction of the laminate 15 are different from each other. That is, the shape of each separator 25 when viewed along the stacking direction is substantially the same as the current collector 18 facing from the side of the maximum protruding current collector 18 with respect to itself. Further, the outer peripheral side ends of the separators 25 are located on the outer peripheral side of the outer peripheral side ends of the negative electrode active material layer 19 and the positive electrode active material layer 21.

[0028] A resin member 30, which is an integrally molded product made of resin, is provided on the outer periphery of the laminate 15. The resin member 30 is integrated with the outer periphery of the laminate 15 in an airtight and liquidtight state so as to cover the outer periphery of the laminate 15. The shape of the resin member 30 when cut along a cross section orthogonal to the stacking direction is a rectangle with a rectangular opening formed in the central portion. The resin member 30 is composed of a resin material having insulating properties. The constituent material of the resin member 30 is, for example, polypropylene, polyethylene, polystyrene, ABS resin, acid-modified polypropylene, acid-modified polyethylene, or acrylonitrile styrene resin. For example, the resin member 30 may be integrally provided on the outer periphery of the laminate 15 by insert molding performed while placing the laminate 15 inside a molding die (not shown).

[0029] Although not shown, an electrolytic solution is provided inside the laminate 15, and the electrolytic solution is impregnated in the negative terminal electrode 17, the positive terminal electrode 20, and the bipolar electrode 23.

[0030] The battery 10 configured as described above is fixed via fixing means on the upper surface of a substantially horizontal plate material (not shown) that forms a part of the vehicle body constituent members of the electric vehicle.

[0031] As shown in FIGS. 1 and 2, the outer peripheral side ends 18PE of the current collectors 18 of the negative terminal electrode 17, the positive terminal electrode 20, and the bipolar electrode 23 and the outer peripheral side ends of the separators 25 are located inside the resin member 30. On the other hand, the outer peripheral side ends of the negative electrode active material layers 19 and the positive electrode active material layers 21 are located on the inner peripheral side of the inner peripheral surface of the central opening 30S of the resin member 30. Further, the current collector 18 of the negative terminal electrode 17 is exposed through one opening end of the central opening 30S, and the current collector 18 of the positive terminal electrode 20 is exposed through the other opening end of the central opening 30S. Therefore, the electric power generated by the battery 10 can be supplied to various electrical and electronic devices (not shown) provided in the electric vehicle through a conductive member (not shown) connected to the current collector 18 of the negative terminal electrode 17 through one opening end of the central opening 30S and a conductive member (not shown) connected to the current collector 18 of the positive terminal electrode 20 through the other opening end of the central opening 30S.

[0032] (Operation and Effect) Next, the operation and effect of this embodiment will be described.

[0033] Here, assume a case where a vehicle (not shown) traveling forward in the rear area of the electric vehicle collides with the rear end portion of the electric vehicle. As shown in FIG. 3, the electric vehicle includes a metal member (conductive member) 40 that is a part of the vehicle body component and is located immediately behind the battery 10. At the time before the collision occurs in the electric vehicle, the front end face 41 of the member 40 is constituted by a plane orthogonal to the front-rear direction. Further, the lower end of the member 40 is located below the lower end of the battery 10, the upper end of the member 40 is located above the upper end of the battery 10, the left end of the member 40 is located to the left of the left end of the battery 10, and the right end of the member 40 is located to the right of the right end of the battery 10.

[0034] When such a collision occurs in the electric vehicle, due to the impact generated in the electric vehicle, the member 40 moves forward relative to the battery 10, and while the member 40 breaks the rear portion 30R (see FIGS. 1 and 2) of the resin member 30, it may collide with the rear end portion (outer peripheral side end portion) of the laminate 15. FIG. 3 shows the rear portion of the laminate 15 and the member 40 when such a state occurs in the electric vehicle, while omitting the rear portion 30R (resin member 30).

[0035] In this case, as shown in FIG. 3, the front end face 41 of the member 40 contacts the rear end portion (outer peripheral side end portion 18PE) of the maximum protruding current collector 18C of the bipolar electrode 23 located at the center in the lamination direction. Further, the front end face 41 contacts the rear end portion (outer peripheral side end portion) of the separator 25 facing the maximum protruding current collector 18C from above and the rear end portion (outer peripheral side end portion 18PE) of the current collector 18U which is the current collector 18 facing the separator 25 from above. Further, the front end face 41 contacts the rear end portion (outer peripheral side end portion) of the separator 25 facing the maximum protruding current collector 18C from below and the rear end portion (outer peripheral side end portion 18PE) of the current collector 18D which is the current collector 18 facing the separator 25 from below.

[0036] Incidentally, as described above, the outer peripheral side end portion 18PE of each current collector 18 is gradually positioned more on the inner peripheral side as it goes upward and downward from the maximum protruding current collector 18C. That is, the rear end portion of each current collector 18 is gradually positioned more forward as it goes upward and downward from the maximum protruding current collector 18C. Therefore, in this case, the front end face 41 is unlikely to come into contact with the rear end portions of the current collectors 18 positioned above the current collector 18U and the rear end portions of the current collectors 18 positioned below the current collector 18D. That is, in this case, there is a high possibility that the maximum protruding current collector 18C, the two current collectors 18U and 18D positioned above and below the maximum protruding current collector 18C, are short-circuited externally through the conductive member 40. In this case, although the maximum protruding current collector 18C and the current collectors 18U and 18D generate heat, the possibility that this heat becomes a large amount of heat is low. That is, for example, when the member 40 comes into contact with the maximum protruding current collector 18C located at the center in the stacking direction and the current collector 18 located at the uppermost or lowermost position at the same time, these current collectors 18 generate an extremely large amount of heat. On the other hand, the amount of heat generated by the battery 10 when the maximum protruding current collector 18C and the two current collectors 18U and 18D positioned above and below the maximum protruding current collector 18C are short-circuited externally is smaller than the amount of heat generated when the maximum protruding current collector 18C located at the center and the current collector 18 located at the uppermost or lowermost position are short-circuited externally. That is, in the battery 10 of the present embodiment, it is difficult for an external short circuit accompanied by a large amount of heat to occur between the current collecting foils 18-1 of the plurality of current collectors 18.

[0037] Furthermore, the distance DF between the outer peripheral side end portions 18PE of the current collectors 18 adjacent to each other in the stacking direction when the laminate 15 is viewed along the stacking direction is larger than the dimension (thickness) of the current collector 18 in the stacking direction. That is, the distance between the outer peripheral side end portions 18PE of the adjacent current collectors 18 when the laminate 15 is viewed along the stacking direction is large. Therefore, compared with the case where the distance DF between the outer peripheral side end portions 18PE of the adjacent current collectors 18 is equal to or less than the dimension (thickness) of the current collector 18 in the stacking direction, the possibility that the member 40 (front end face 41) comes into contact with the outer peripheral side end portions 18PE of a large number (for example, 4 or more) of current collectors 18 at the same time is small.

[0038] Furthermore, since the battery 10 includes the bipolar electrodes 23, the battery 10 can generate greater power as compared to the case where the bipolar electrodes 23 are not provided. That is, since each bipolar electrode 23 can generate a large current (for example, 5 A or more), the degree of temperature rise of the battery 10 when an external short circuit occurs is higher than that of a battery without bipolar electrodes when an external short circuit occurs. Therefore, when the present invention is applied to the battery 10, greater usefulness can be obtained as compared to the case where the present invention is applied to a battery without the bipolar electrodes 23.

[0039] As described above, the battery 10 according to the embodiment has been described, but these can be appropriately modified within a range not departing from the gist of the present invention.

[0040] For example, the outer peripheral side end portions 18PE of two current collectors 18 adjacent to each other in the stacking direction may overlap each other in the vertical direction when the laminate 15 is viewed in the stacking direction.

[0041] The outer peripheral side end portion 18PE of the current collector 18 located at the central portion in the stacking direction may be located on the outermost peripheral side among all the current collectors 18. Here, the "central portion" means the range between the current collector 18 at the N / 3-th position counted from the uppermost current collector 18 and the current collector 18 at the N / 3-th position counted from the lowermost current collector 18 when the total number of current collectors 18 is N. For example, when the battery 10 includes 11 current collectors 18 as in the present embodiment, N / 3 = 3.666 ···. In this case, at least one outer peripheral side end portion 18PE of the current collector 18 located within the range between the fourth current collector 18 from the top and the fourth current collector 18 from the bottom is located on the outermost peripheral side. Further, for example, when the battery 10 includes 18 current collectors 18, the outer peripheral side end portion 18PE of the current collector 18 located within the range between the sixth current collector 18 from the top and the sixth current collector 18 from the bottom is located on the outermost peripheral side. Also in this modification, the possibility that the member 40 simultaneously contacts the current collector 18 having the outermost peripheral side end portion 18PE located on the outermost peripheral side and the current collector 18 located at the uppermost or lowermost position is small.

[0042] If the outer peripheral side end portion 18PE of at least one current collector 18 located at the central portion in the stacking direction is on the outer peripheral side of the outer peripheral side end portion 18PE of the current collector 18 located at the end portion in the stacking direction, the outer peripheral side end portions 18PE of the other current collectors 18 may be located on the inner peripheral side of the outer peripheral side end portion 18PE of the current collector 18 located at the end portion in the stacking direction.

[0043] The number of electrodes provided in the battery 10 may be any number as long as it is plural.

[0044] All the electrodes provided in the battery 10 may be constituted by electrodes that are not bipolar electrodes.

[0045] The battery 10 may be configured such that the laminate is covered with a container made of a laminate film.

[0046] The battery 10 may be provided in a device different from an electric vehicle.

Description of Reference Numerals

[0047] 10 Lithium ion secondary battery (battery) 15 Laminate 17 Negative terminal electrode (electrode) 18 Current collector 18-1 Current collecting foil 18C Maximum protruding current collector 18PE Outer peripheral side end portion 20 Positive terminal electrode (electrode) 23 Bipolar electrode (electrode) 25 Separator

Claims

1. A battery having a plurality of electrodes including a current collector and at least one of a positive electrode active material layer and a negative electrode active material layer formed on the current collector, and a plurality of separators positioned between the positive electrode active material layer and the negative electrode active material layer, the battery being configured by laminating in a predetermined lamination direction, A part of the current collector is a current collector foil on which the positive electrode active material layer and the negative electrode active material layer are not formed, A battery in which, when the laminate is viewed along the lamination direction, an outer peripheral side end portion of the current collector foil positioned at a central portion in the lamination direction is positioned more on the outer peripheral side than an outer peripheral side end portion of the current collector foil positioned at an end portion in the lamination direction.

2. The battery according to claim 1, wherein the electrodes other than the electrodes positioned at the end portions in the lamination direction are bipolar electrodes each having the current collector, a positive electrode active material layer formed on one surface of the current collector, and a negative electrode active material layer formed on the other surface of the current collector.

3. The battery according to claim 1 or claim 2, wherein the outer peripheral side end portion of the current collector foil positioned at the center in the lamination direction is positioned more on the outer peripheral side than the outer peripheral side end portion of the current collector foil positioned at the end portion in the lamination direction.

4. The battery according to claim 1 or claim 2, wherein a distance between the outer peripheral side end portions of the current collector foils adjacent to each other in the lamination direction when the laminate is viewed along the lamination direction is greater than a dimension of the current collector in the lamination direction.

5. When the current collector having the outermost peripheral side end portion positioned most on the outer peripheral side when the laminate is viewed along the lamination direction is defined as the maximum protruding current collector, The battery according to claim 1 or claim 2, wherein each of the current collectors other than the maximum protruding current collector has an outer peripheral side end portion positioned more on the inner peripheral side than the outer peripheral side end portion of the current collector foil of the current collector positioned on the maximum protruding current collector side with respect to itself.

Images