Bipolar battery

Abstract

To provide a bipolar battery in which heat generation caused by an abnormality occurring in a first cell within a first battery module or a second cell within a second battery module is suppressed from being transmitted to the other battery module.SOLUTION: The bipolar battery includes a first battery module including multiple first cells stacked together, a cathode current collector foil, an expansion member, an anode current collector foil, and a second battery module including multiple second cells stacked together, all stacked in this order. The expansion member is composed of a conductive material. The first cells and the second cells each have a gas discharge pipe for discharging gas from the inside when internal pressure rises. The expansion member is a portion to which the gas discharge pipes connected to the first cells and the second cells are connected.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to bipolar batteries. [Background technology]

[0002] 2. Description of the Related Art Bipolar batteries have conventionally been used, in which a plurality of battery modules each having a plurality of stacked cells are further stacked.

[0003] For example, Patent Document 1 discloses a current collector for a bipolar battery including a conductive resin layer and at least one conductive ion-blocking layer that suppresses ion permeation in a direction perpendicular to the surface, wherein the resin layer and the ion-blocking layer are electrically joined so that the conductivity in the direction perpendicular to the surface of the current collector is higher than the conductivity in the planar direction.

[0004] Patent Document 2 also discloses a power supply device that includes a plurality of rectangular battery cells, a fixing member that fixes the plurality of battery cells in a stacked state, and a heat insulating sheet that is sandwiched between the stacked surfaces of the battery cells to insulate adjacent battery cells, where the heat insulating sheet is an inorganic fiber sheet that is made of inorganic fibers that are gathered three-dimensionally with no direction and have fine gaps between the inorganic fibers. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-277862 [Patent Document 2] International Publication No. 2019 / 187313 Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure aims to provide a bipolar battery in which heat generated due to an abnormality occurring in a first cell in a first battery module or a second cell in a second battery module is prevented from being transferred to the other battery module. [Means for solving the problem]

[0007] Means for solving the above problems include the following aspects. <1> a first battery module in which a plurality of first cells are stacked, a positive electrode current collector foil, an expansion member, a negative electrode current collector foil, and a second battery module in which a plurality of second cells are stacked, stacked in this order; the expansion member is made of a conductive material; the first cell and the second cell each have a gas exhaust pipe that exhausts gas from the inside when the internal pressure increases, The expansion member is connected to the gas exhaust pipe that is connected to the first cell and the second cell. [Effects of the Invention]

[0008] According to the present disclosure, a bipolar battery is provided in which heat generated due to an abnormality occurring in a first cell in a first battery module or a second cell in a second battery module is prevented from being transferred to the other battery module. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of a bipolar battery according to an embodiment of the present disclosure. [Figure 2] 2 is a schematic plan view showing an expansion member, a negative electrode current collector foil, and a gas exhaust pipe of the bipolar battery according to the embodiment of the present disclosure shown in FIG. 1. FIG. [Figure 3] 2 is a schematic cross-sectional view showing a state in which an expansion member is expanded in the bipolar battery according to the embodiment of the present disclosure shown in FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Bipolar battery> A bipolar battery according to an embodiment of the present disclosure is formed by stacking a first battery module, a positive electrode current collector foil, an expansion member, a negative electrode current collector foil, and a second battery module in this order. The first battery module is formed by stacking a plurality of first cells, and the second battery module is formed by stacking a plurality of second cells. The expansion member is made of a conductive material. The first cell and the second cell have gas exhaust pipes that exhaust gas from the inside when the internal pressure increases. A gas exhaust pipe that connects the first cell and the second cell is connected to the expansion member.

[0011] Here, the configuration of a bipolar battery according to an embodiment of the present disclosure will be described by way of an example with reference to the drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0012] Fig. 1 is a schematic cross-sectional view showing an example of a bipolar battery according to an embodiment of the present disclosure, and Fig. 2 is a schematic plan view showing an expansion member, a negative electrode current collector foil, and a gas exhaust pipe of the bipolar battery shown in Fig. 1.

[0013] The bipolar battery 10A shown in FIG. 1 includes a first battery module 21, a positive electrode current collector foil 4A, an expansion member 2a, a negative electrode current collector foil 4B, and a second battery module 22 stacked in this order. The first battery module 21 includes a plurality of first cells 61 stacked together. The second battery module 22 includes a plurality of second cells 62 stacked together. Each of the first cells 61 in the first battery module 21 and each of the second cells 62 in the second battery module 22 has a structure in which, for example, a positive electrode and a negative electrode are stacked with a separator interposed therebetween. Current collector foils (not shown) are interposed between the first cells 61 in the first battery module 21 and between the second cells 62 in the second battery module 22. Furthermore, a terminal current collecting foil (not shown) is provided at the end opposite the positive electrode current collecting foil 4A in the first battery module 21 (i.e., the end in the stacking direction, the upper end in FIG. 1), and at the end opposite the negative electrode current collecting foil 4B in the second battery module 22 (i.e., the end in the stacking direction, the lower end in FIG. 1).

[0014] The expansion member 2a is a bag-shaped member having an internal space. The expansion member 2a has a structure that allows it to expand when, for example, a gas is injected into the internal space. The expansion member 2a is made of a conductive material, such as Cu or Al. Because the expansion member 2a is made of a conductive material, electronic conductivity is ensured between the positive electrode current collector foil 4A and the negative electrode current collector foil 4B that are stacked via the expansion member 2a.

[0015] Each first cell 61 in the first battery module 21 and each second cell 62 in the second battery module 22 are connected to a gas exhaust pipe 8 that exhausts gas from the inside when the internal pressure increases. Therefore, when an abnormality occurs in the first cell 61 or the second cell 62 and the internal pressure increases, gas is exhausted from the first cell 61 or the second cell 62 through the gas exhaust pipe 8.

[0016] The gas exhaust pipes 8 connected to each of the first cells 61 and each of the second cells 62 are both connected to the expansion member 2a. Therefore, gas exhausted from the first cells 61 or the second cells 62 due to an increase in internal pressure is injected into the internal space of the expansion member 2a through the gas exhaust pipes 8.

[0017] The bipolar battery 10A shown in FIG. 1 has the above-described configuration, which prevents heat generated due to an abnormality occurring in the first cell in the first battery module or the second cell in the second battery module from being transferred to the other battery module.

[0018] Conventionally, bipolar batteries have been used, in which multiple battery modules, each of which has multiple stacked cells, are further stacked. In such bipolar batteries, an abnormality may occur in one cell within a battery module (i.e., the first cell within the first battery module or the second cell within the second battery module), causing an increase in the cell's internal pressure and further heat generation. However, in bipolar batteries, in order to ensure electronic conductivity between the battery modules, it is not possible to provide insulating material between the battery modules. Therefore, if an abnormality occurs in a cell within one battery module and heat is generated, the heat may be transferred to other adjacent battery modules, causing these battery modules to heat up as well. Then, as the other adjacent battery modules are heated, the internal pressure of the cells within these other battery modules may increase, further generating heat. In this way, the increase in internal pressure may propagate, leading to a chain reaction of heat generation.

[0019] In contrast, the bipolar battery 10A shown in FIG. 1 has a gas exhaust pipe 8 that exhausts gas from the inside of the first cell 61 and the second cell 62 when the internal pressure of the first cell 61 and the second cell 62 increases. The gas exhaust pipe 8 is connected to an expansion member 2a interposed between the positive and negative current collector foils 4A and 4B. Therefore, when an abnormality occurs in the first cell 61 or the second cell 62 and the internal pressure of the cell increases, the gas exhausted from the abnormal cell is injected into the expansion member 2a through the gas exhaust pipe 8. As in the bipolar battery 10B shown in FIG. 3, the expansion member 2b expands and becomes thicker, increasing the distance between the positive and negative current collector foils 4A and 4B. As a result, even if an abnormality occurs in the first cell 61 in the first battery module 21 or the second cell 62 in the second battery module 22 and generates heat, the increased distance between the two suppresses heat transfer to the other battery module. This prevents the other battery module from being heated, and prevents the rise in internal pressure from spreading to other battery modules, resulting in a chain reaction of heat generation.

[0020] Note that by filling the inside of the gas exhaust pipe 8 with a gas (such as Ar gas) that has higher thermal insulation properties than air, the thermal insulation properties can be improved, and heat transfer to the other battery module can be further suppressed.

[0021] As shown in Fig. 2, the expansion member 2a preferably has a smaller area than the negative electrode current collector foil 4B (and the positive electrode current collector foil 4A). To reduce electrical resistance, the expansion member 2a is preferably bonded to the negative electrode current collector foil 4B (and the positive electrode current collector foil 4A) with a conductive adhesive (e.g., silver paste). In this case, taking into account the expansion margin of the bonded portion, it is preferable to provide an unbonded region of 3 mm to 5 mm from the end of the negative electrode current collector foil 4B (and the positive electrode current collector foil 4A).

[0022] 1 and 2, the gas discharge pipe 8 passes through the negative electrode current collector foil 4B and the positive electrode current collector foil 4A and is connected to the expandable member 2a. Connecting holes 80 are provided at the connecting portion between the expandable member 2a and the gas discharge pipe 8, and gas is injected into the internal space of the gas discharge pipe 8 through the connecting holes 80. In order to prevent uneven distribution of the injected gas, the number of connecting holes 80 is set to 20 / m. 2 It is preferable that this is equal to or greater than this.

[0023] When gas is injected into the expandable member 2a and the expandable member 2a expands, the thickness of the expandable member 2a (that is, the distance between the negative electrode current collector foil 4B and the positive electrode current collector foil 4A) is preferably 3 mm or more from the viewpoint of suppressing heat transfer.

[0024] (Application) Examples of applications of the bipolar battery according to the embodiment of the present disclosure include power sources for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicles (BEVs). [Example]

[0025] The present disclosure will be described below based on examples, but the present disclosure is not limited to these examples in any way.

[0026] Example 1 A bipolar battery with the same configuration as shown in FIG. 1 was prepared. Specifically, a bipolar battery 10A was prepared by stacking a first battery module 21, in which multiple first cells 61 were stacked, a positive electrode current collector foil 4A, an expansion member 2a (a member made of Al), a negative electrode current collector foil 4B, and a second battery module 22, in which multiple second cells 62 were stacked, in this order. The first cells 61 and the second cells 62 were configured as follows: a positive electrode active material: Ni-Co-Mn oxide, a positive electrode current collector foil: Al, a negative electrode active material: carbon, a negative electrode current collector foil: Cu, and a separator: polyethylene (PE, thickness: 20 μm). Gas exhaust pipes 8 were connected to the first cells 61 and the second cells 62, which exhaust gas from the inside when the internal pressure increased. The gas exhaust pipes 8 were connected to the internal space of the expansion member 2a. The expansion member in the bipolar battery prepared in Example 1 was an expansion member whose thickness became 3 mm when gas was injected.

[0027] (Comparative Example 1) A bipolar battery was prepared in the same manner as in Example 1, except that no expansion member was provided between the positive electrode current collector foil and the negative electrode current collector foil, and the gas discharged from the second cell when the internal pressure increased was discharged into the second battery module.

[0028] Example 2 A bipolar battery was prepared in the same manner as in Example 1, except that an expansion member having a thickness of 1 mm when gas was injected was used.

[0029] Example 3 A bipolar battery was prepared in the same manner as in Example 1, except that the inside of the gas exhaust pipe was filled with Ar gas.

[0030] [Test method] A heating test was conducted on each of the bipolar batteries prepared in Examples 1 to 3 and Comparative Example 1 by installing a heater on the end face of the second battery module opposite the expansion member (the lower end face of second battery module 22 in FIG. 1). Heating was performed at 200°C using the heater, and it was confirmed that gas was being discharged from at least one second cell in the second battery module. Thereafter, while continuing heating, the highest temperature reached was measured for each bipolar battery on the end face of the first battery module opposite the expansion member (the upper end face of first battery module 21 in FIG. 1). The measurement results of the reached temperatures and an evaluation based on the following evaluation criteria are shown in Table 1. -Evaluation criteria- A(◎): Reached temperature is less than 55℃ B (○): Reached temperature is 55°C or higher and less than 100°C C (△): Reached temperature is 100℃ or more and less than 180℃ D(×): Reached temperature is 180℃ or higher

[0031] [Table 1]

[0032] Comparing Example 1 with Comparative Example 1, it can be seen that by providing an expansion member connected to a gas exhaust pipe that connects the first cell and the second cell, heat generated due to an abnormality occurring in the second cell in the second battery module is prevented from being transferred to the first battery module. Comparing Example 1 and Example 2, it can be seen that the thicker the expansion member, the greater the effect, and that when the expansion member has a thickness of 3 mm or more in its expanded state, heat transfer from an abnormal battery module to other adjacent battery modules is further suppressed. Comparing Example 1 and Example 3, it can be seen that by filling the inside of the gas exhaust pipe with a gas that has higher insulating properties than air, such as Ar gas, the heat transfer from the battery module in which an abnormality has occurred to other adjacent battery modules is further suppressed. [Explanation of symbols]

[0033] 2a, 2b expansion member, 4A positive electrode current collector foil, 4B negative electrode current collector foil, 8 gas exhaust pipe, 10A, 10B bipolar battery, 21 first battery module, 22 second battery module, 61 first cell, 62 second cell, 80 connecting hole

Claims

[Claim 1] a first battery module in which a plurality of first cells are stacked, a positive electrode current collector foil, an expansion member, a negative electrode current collector foil, and a second battery module in which a plurality of second cells are stacked, stacked in this order; the expansion member is made of a conductive material; the first cell and the second cell each have a gas exhaust pipe that exhausts gas from the inside when the internal pressure increases, The expansion member is connected to the gas exhaust pipe that is connected to the first cell and the second cell.

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