Bipolar type secondary battery

Abstract

To provide a bipolar type secondary battery that suppresses short circuits between electrodes and improves volumetric efficiency.SOLUTION: A bipolar type secondary battery 10 comprises: a stacked body 20 in which electricity storage modules 30 are stacked in the vertical direction of a vehicle with the wide surface of the electricity storage modules 30 facing the vertical direction of the vehicle, the electricity storage modules being modules in which a bipolar electrode 32 having a positive electrode active material layer 34 on one side of a current collector 33 and a negative electrode active material layer 35 on the other side of the current collector 33 and a separator 36 are stacked; and a dilatant buffer body 50 arranged to cover the side peripheral surface of the stacked body 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bipolar secondary battery. [Background technology]

[0002] Patent document 1 discloses a battery pack in which a battery assembly consisting of multiple connected single cells is housed inside an exterior body, and at least a portion of the multiple single cells is covered with a cushioning material having dilatancy properties. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2012 / 081173 Summary of the Invention [Problem to be solved by the invention]

[0004] In the bipolar secondary battery, it is preferable to suppress short circuits between electrodes and improve the volumetric efficiency.

[0005] An object of the present invention is to provide a bipolar secondary battery which suppresses short circuits between electrodes and improves volumetric efficiency. [Means for solving the problem]

[0006] The bipolar secondary battery of claim 1 comprises a bipolar electrode having a positive electrode active material layer on one side of a collector and a negative electrode active material layer on the other side of the collector, a stack in which a separator and an electricity storage module are stacked in the vertical direction of the vehicle with a wide surface of the module facing in the vertical direction of the vehicle, and a dilatant buffer body arranged to cover the side peripheral surface of the stack.

[0007] In the bipolar secondary battery according to claim 1, a dilatant buffer is provided so as to cover the side circumferential surface of the laminate, so that the periphery of the bipolar electrodes is covered with the dilatant buffer. Therefore, when a strong external force is input from the side of the bipolar secondary battery in a short time due to a collision, the dilatant buffer becomes solid and hard. As a result, deformation of the bipolar secondary battery is suppressed, and cracks in the separator are also suppressed. Therefore, short circuits between the electrodes can be suppressed.

[0008] Moreover, by disposing the buffer so as to cover the side peripheral surface of the stack, volumetric efficiency can be improved compared to a case in which the buffer is provided on the outside or inside of the case that contains the stack, and therefore a bipolar secondary battery can be obtained that suppresses short circuits between the electrodes and improves volumetric efficiency.

[0009] The bipolar secondary battery of claim 2 is the bipolar secondary battery of claim 1, further comprising a frame-shaped member that holds the periphery of the bipolar electrode, and the buffer is arranged to cover the side surface of the frame-shaped member.

[0010] In the bipolar secondary battery according to claim 2, the buffer is arranged to cover the side circumferential surface of the frame member that holds the periphery of the bipolar electrode, so that the bipolar electrode is covered by the buffer having dilatancy via the frame member. Therefore, an external force input from the side of the bipolar secondary battery is dispersed by the frame member. As a result, cracks in the separator are suppressed, and short circuits between the electrodes can be further suppressed.

[0011] A bipolar secondary battery according to a third aspect of the present invention is the bipolar secondary battery according to the first or second aspect, wherein the buffer body is configured by sealing a non-flammable liquid or a flame-retardant liquid in a bag-shaped container.

[0012] In the bipolar secondary battery according to claim 3, the buffer is formed by sealing a non-flammable or flame-retardant liquid in a bag-shaped container, and thus the buffer is formed with a simple structure. Moreover, since the buffer is non-flammable or flame-retardant, smoke generation and fire can be suppressed.

[0013] A bipolar secondary battery according to a fourth aspect of the present invention is the bipolar secondary battery according to any one of the first to third aspects, wherein the buffer supports the power storage module.

[0014] In the bipolar secondary battery according to claim 4, the buffer supports the power storage modules, and thus functions as a spacer that maintains the distance between the power storage modules. Therefore, even if a spacer is not provided, deformation of the bipolar secondary battery, such as denting caused by negative pressure, is suppressed. As a result, deformation of the bipolar secondary battery can be suppressed while improving volumetric efficiency.

[0015] A bipolar secondary battery according to a fifth aspect of the present invention is the bipolar secondary battery according to any one of the first to fourth aspects, which is an all-solid-state battery.

[0016] In the bipolar secondary battery according to claim 5, it is possible to provide an all-solid-state battery in which short circuits between electrodes are suppressed and volumetric efficiency is improved. Effect of the Invention

[0017] As described above, the bipolar secondary battery according to the present invention can suppress short circuits between electrodes and improve volumetric efficiency. [Brief description of the drawings]

[0018] [Figure 1] 1 is a perspective view showing a bipolar secondary battery according to an embodiment of the present invention; [Diagram 2] 2 is a cross-sectional view showing the bipolar secondary battery according to the embodiment, showing the AA cross section of FIG. [Diagram 3]1 is a cross-sectional view showing an electricity storage module according to an embodiment. [Figure 4] 1 is a graph showing the results of an effect confirmation test of a bipolar secondary battery. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a bipolar secondary battery according to an embodiment will be described with reference to the drawings. The bipolar secondary battery according to the embodiment is described as being mounted on a vehicle such as an electric vehicle or a hybrid vehicle and used as an on-board power source for the vehicle. In each drawing, the arrow UP indicates the upper side in the vertical direction of the bipolar secondary battery, the arrow FR indicates the front side in the front-rear direction of the bipolar secondary battery, and the arrow LH indicates the left side in the horizontal direction of the bipolar secondary battery. In addition, the upper side of the bipolar secondary battery coincides with the upper side of the vehicle on which the bipolar secondary battery is mounted.

[0020] [Configuration of bipolar secondary battery 10] As shown in FIG. 1, a bipolar secondary battery 10 includes a case 12, a laminate 20 housed in the case 12, and a buffer 50 disposed between the laminate 20 and the case 12.

[0021] <Laminate 20> 2, the laminate 20 has a plurality of (four in this embodiment) power storage modules 30 and a plurality of (five in this embodiment) conductive plates 40. The laminate 20 is formed by stacking the power storage modules 30 and the conductive plates 40 alternately in the vehicle vertical direction with the wide surfaces of the power storage modules 30 facing the vehicle vertical direction. That is, when the bipolar secondary battery 10 is mounted on the vehicle, the laminate 20 has a stacking direction that is the vehicle vertical direction. Note that it is sufficient for the bipolar secondary battery 10 to include at least one power storage module 30 and at least one conductive plate 40.

[0022] (Energy storage module 30) The power storage module 30 is formed in a rectangular plate shape with its plate thickness direction aligned in the vertical direction of the vehicle. The power storage module 30 is, for example, a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery.

[0023] As shown in FIG. 3, the electricity storage module 30 includes an electrode laminate 31 and a frame member 38 that surrounds the side peripheral surface of the electrode laminate 31.

[0024] <Electrode laminated portion 31> The electrode laminated portion 31 has a plurality of bipolar electrodes 32 laminated in the vehicle vertical direction with separators 36 interposed therebetween. The electrode laminated portion 31 is formed by laminating the bipolar electrodes 32 in the vehicle vertical direction with the wide surfaces of the bipolar electrodes 32 facing in the vehicle vertical direction. The bipolar electrodes 32 are formed in a rectangular plate shape with the plate thickness direction being the vehicle vertical direction.

[0025] The bipolar electrode 32 has a current collector 33, a positive electrode active material layer 34 formed on the upper surface (one side) of the current collector 33, and a negative electrode active material layer 35 formed on the lower surface (the other side) of the current collector 33.

[0026] The separator 36 is formed in a rectangular plate shape with the plate thickness direction being the vehicle vertical direction. The separator 36 is disposed between adjacent bipolar electrodes 32 in the stacking direction. The separator 36 isolates adjacent positive electrode active material layers 34 and negative electrode active material layers 35 in the electrode stacking portion 31, thereby preventing electrical short circuits between the electrodes. The bipolar electrodes 32 and the separator 36 are impregnated with an electrolyte.

[0027] <Frame-shaped member 38> The frame-shaped member 38 is formed in a frame shape so as to surround the side periphery of the electrode laminated portion 31. The frame-shaped member 38 can be formed in a frame shape, for example, by disposing molten thermoplastic resin on the peripheral surface of the electrode laminated portion 31 and cooling it. The frame-shaped member 38 holds the peripheries of the multiple bipolar electrodes 32 so that a space is formed between the bipolar electrodes 32 adjacent to each other in the vertical direction of the vehicle, and seals this space.

[0028] (Conductive plate 40) The conductive plate 40 is formed of a conductive material such as metal and has conductivity. The conductive plate 40 is electrically connected to the power storage modules 30 adjacent in the vertical direction of the vehicle, and the multiple power storage modules 30 are connected in series via the conductive plate 40. The multiple power storage modules 30 are charged and discharged via external terminals (not shown).

[0029] The conductive plate 40 also functions as a heat sink for dissipating heat generated in the power storage module 30. A plurality of gaps 41 extending in the left-right direction are provided in the conductive plate 40. Cooling air passes through the gaps 41, so that the heat generated in the power storage module 30 can be efficiently dissipated to the outside.

[0030] <Case 12> As shown in Fig. 2, the case 12 has a pair of upper and lower end plates 14. The pair of upper and lower end plates 14 are arranged to sandwich the stacked body 20. Bolts 18 and nuts 19 serving as restraining members are attached to the pair of upper and lower end plates 14, thereby compressing the stacked body 20 in the vertical direction of the vehicle (stacking direction). In other words, the stacked body 20 is housed in the case 12 in a state compressed in the vertical direction of the vehicle.

[0031] An electrically insulating film 42 is arranged on inner surfaces of the pair of end plates 14 in the vertical direction of the vehicle, providing insulation between the case 12 and the electricity storage module 30.

[0032] <Buffer 50> 1, the buffer 50 is made of a material having dilatancy, and is configured so that the rate of increase in shear stress (flow resistance) increases as the shear (flow) speed increases. In other words, the buffer 50 has speed-dependency in its deformability, and is configured so that it is easily deformed by a low-speed input, but is difficult to deform by a high-speed input.

[0033] The buffer 50 is made of a material having dilatancy, such as a suspension of fine powder such as potato starch or cornstarch, or a material made by impregnating ceramic particles into Kevlar (registered trademark) material.

[0034] The buffer 50 has a shear rate of 0.01 [S -1 ] at viscosity γ (γ = 0.01) vs shear rate 100 [S -1 It is preferable that the ratio of the viscosity γ (γ=100) at 25° C. is greater than 1000. In other words, it is preferable that the following relational expression (1) is satisfied at 25° C. γ(γ=100) / γ(γ=0.01)>1000 ···(1)

[0035] From the viewpoint of flame retardancy, the buffer 50 is preferably non-flammable or flame-retardant. From the viewpoint of suppressing electric leakage, the buffer 50 is preferably insulating.

[0036] From the viewpoint of lowering the flue gas temperature, the buffer 50 preferably has a specific heat of 1.4 [J / (g·K)] or more.

[0037] The thickness of the buffer 50 is preferably 60 mm or less from the viewpoint of preventing a decrease in volumetric efficiency. From the viewpoint of achieving both volumetric efficiency and impact resistance, the thickness of the buffer 50 is preferably 10 mm or more, and more preferably 20 mm or more.

[0038] 1 and 2, the buffer 50 is disposed so as to cover the side peripheral surface of the stack 20. The buffer 50 is attached to the frame-shaped member 38 by, for example, welding, and disposed so as to cover the side peripheral surface of the frame-shaped member 38. In this way, the buffer 50 is configured to support the power storage module 30. The buffer 50 has a height that extends from the lower surface to the upper surface of the stack 20.

[0039] The buffer 50 may be covered by a bag-like container such as an easily deformable film. Four bag-like containers may be provided corresponding to the respective side surfaces of the laminate 20, or the bag-like container may be formed in a frame shape surrounding the side surface of the laminate 20, or may be divided into a plurality of parts.

[0040] [Effectiveness verification test] A test was carried out to confirm the effect of impact resistance of the bipolar secondary battery 10 according to the embodiment.

[0041] In the test, Examples 1 to 5 and Comparative Examples 1 to 3 were prepared. The bipolar secondary batteries 10 of Examples 1 to 5 were formed by stacking four storage modules 30 each having 30 bipolar electrodes 32 stacked on top of each other. The bipolar secondary batteries 10 of Examples 1 to 5 were in a constrained form A in which the constraining load of the storage module 30 was approximately 40 kN. The bipolar secondary battery 10 of Example 1 was configured to include a buffer body 50 having a thickness of 10 mm. The bipolar secondary battery 10 of Example 2 was configured to include a buffer body 50 having a thickness of 20 mm. The bipolar secondary battery 10 of Example 3 was configured to include a buffer body 50 having a thickness of 35 mm. The bipolar secondary battery 10 of Example 4 was configured to include a buffer body 50 having a thickness of 50 mm. The bipolar secondary battery 10 of Example 5 was configured to include a buffer body 50 with a thickness of 60 mm.

[0042] The bipolar secondary batteries of Comparative Example 1 to Comparative Example 3 were formed by stacking four power storage modules 30, each of which had 30 bipolar electrodes 32 stacked on top of each other. The bipolar secondary batteries of Comparative Example 1 and Comparative Example 2 were in a constrained form A in which the constrained load of the power storage module 30 was approximately 40 [kN]. The bipolar secondary battery of Comparative Example 3 was in a constrained form B in which the constrained load of the power storage module 30 was approximately 90 [kN]. The bipolar secondary batteries of Comparative Example 1 and Comparative Example 2 were configured without a buffer body. The bipolar secondary battery of Comparative Example 3 was configured with a buffer body 50 having a thickness of 80 [mm].

[0043] (Crash test) In the collision test, a semi-cylindrical load having a diameter of 75 mm was collided from behind with each of the bipolar secondary batteries 10 of Examples 1 to 5 and the bipolar secondary batteries of Comparative Examples 1 to 3 at 50 G. Then, a cell whose cell voltage had decreased by 25% compared to before the test was determined to be a short-circuited cell, and the number of short-circuited cells was counted out of 120 cells. When ¼ or more of the total cells were short-circuited, the collision was determined to be ×.

[0044] (Smoke test) In the smoke generation test, a heater was installed between the second top storage module and the third top storage module in the center in the front-rear and left-right directions in each of the bipolar secondary batteries 10 of Examples 1 to 5 and the bipolar secondary batteries of Comparative Examples 1 to 3, and the batteries were heated to 600°C. The second top storage module and the third top storage module were heated until the temperature of the surface opposite to the side where the heater was installed exceeded 300°C. Then, the smoke generation temperature profile was measured at a position 80 [mm] away from the side of the storage module. When smoke generation of 900°C or more continued for 30 [sec] or more, the smoke generation was judged to be ×.

[0045] Fig. 4 is a graph showing the results of an effect confirmation test of bipolar secondary batteries. As can be seen from Fig. 4, the bipolar secondary batteries of Comparative Example 1 and Comparative Example 2 were judged as x in the collision test. On the other hand, the bipolar secondary batteries 10 of Examples 1 to 5 were judged as o in the collision test. Furthermore, the bipolar secondary batteries of Comparative Example 1 and Comparative Example 2 were judged as x in the smoke generation test. On the other hand, the bipolar secondary batteries 10 of Examples 1 to 5 were judged as o in the smoke generation test.

[0046] [Effect] However, when an external force is input from the side of the bipolar secondary battery 10, if the bipolar secondary battery 10 deforms and a crack occurs in the separator 36, there is a problem that a short circuit occurs between the electrodes due to the crack in the separator 36.

[0047] The bipolar secondary battery 10 according to the embodiment includes a bipolar electrode 32 having a positive electrode active material layer 34 on one side of a current collector 33 and a negative electrode active material layer 35 on the other side of the current collector 33, and a separator 36. The bipolar electrode 32 has a positive electrode active material layer 34 on one side of the current collector 33 and a negative electrode active material layer 35 on the other side of the current collector 33. The bipolar electrode 32 and the separator 36 are stacked in the vertical direction of the vehicle, with the wide side of the stacked energy storage module 30 facing in the vertical direction of the vehicle. A dilatant buffer 50 is arranged to cover the side peripheral surface of the stack 20 (see FIG. 1).

[0048] By providing the dilatant buffer 50 arranged to cover the side peripheral surface of the laminate 20, the periphery of the bipolar electrode 32 is covered with the dilatant buffer 50. Therefore, when a strong external force is input from the side of the bipolar secondary battery 10 in a short time due to a collision, the dilatant buffer 50 becomes solid and hardens. As a result, deformation of the bipolar secondary battery 10 is suppressed, and cracks in the separator 36 are also suppressed. Therefore, short circuits between the electrodes can be suppressed.

[0049] Moreover, the volumetric efficiency can be improved compared to a case where the buffer 50 is provided on the outside or inside of a case that accommodates the laminate 20. Therefore, the bipolar secondary battery 10 can be provided with improved volumetric efficiency by suppressing short circuits between the electrodes.

[0050] The bipolar secondary battery 10 according to this embodiment includes a frame member 38 that holds the periphery of the bipolar electrode 32, and the buffer 50 is disposed so as to cover the side peripheral surface of the frame member 38 (see FIG. 3).

[0051] The buffer 50 is disposed so as to cover the side peripheral surface of the frame member 38 that holds the periphery of the bipolar electrode 32, so that the bipolar electrode 32 is covered by the buffer 50 having dilatancy via the frame member 38. Therefore, an external force input from the side of the bipolar secondary battery 10 is dispersed by the frame member 38. As a result, cracks in the separator 36 are suppressed, and short circuits between the electrodes can be further suppressed.

[0052] In the bipolar secondary battery 10 according to the embodiment, the buffer 50 is configured by sealing a non-flammable liquid or a flame-retardant liquid in a bag-shaped container.

[0053] The buffer 50 is configured by sealing a non-flammable liquid or a flame-retardant liquid in a bag-shaped container, and thus the buffer 50 is formed with a simple configuration. Moreover, since the buffer 50 is non-flammable or flame-retardant, smoke generation and fire can be suppressed.

[0054] In the bipolar secondary battery 10 according to this embodiment, the buffer 50 supports the power storage module 30 (see FIG. 3).

[0055] The buffer 50 supports the power storage modules 30, and thus functions as a spacer that maintains the distance between the power storage modules 30. Therefore, even if a spacer is not provided, deformation such as denting of the bipolar secondary battery 10 due to negative pressure, for example, is suppressed. As a result, deformation of the bipolar secondary battery 10 can be suppressed while improving volumetric efficiency.

[0056] In the bipolar secondary battery 10 according to this embodiment, the buffer 50 has a height that reaches from the lower surface to the upper surface of the laminate 20 (see FIG. 2).

[0057] The buffer 50 has a height extending from the lower surface to the upper surface of the stack 20, so that the entire side peripheral surface of the stack 20 is covered with the buffer 50. Therefore, when an external force is input from the side of the bipolar secondary battery 10 due to a collision, the buffer 50 prevents the external force from being input to the stack 20. As a result, cracks in the separator are prevented, and short circuits between the electrodes can be further prevented.

[0058] The bipolar secondary battery according to the embodiment has been described above based on the embodiment. However, the specific configuration is not limited to this embodiment, and design changes and the like are permitted as long as they do not deviate from the gist of the invention according to each claim of the claims.

[0059] In the embodiment, an example has been shown in which the buffer 50 is disposed so as to cover the side peripheral surface of the laminate 20. However, the buffer may be disposed so as to cover at least a part of the side peripheral surface.

[0060] In the embodiment, an example has been shown in which the bipolar secondary battery 10 accommodates an electrolyte inside the power storage module 30. However, the bipolar secondary battery may be an all-solid-state battery. [Explanation of symbols]

[0061] 10 Bipolar secondary battery 30 Energy Storage Module 32 Bipolar Electrode 34 Cathode active material layer 35 Negative electrode active material layer 36 Separator 38 Frame-shaped member 50 Buffer

Claims

1. a bipolar electrode having a positive electrode active material layer on one surface of a current collector and a negative electrode active material layer on the other surface of the current collector, and a separator are stacked together, and the power storage modules are stacked in the vehicle vertical direction with a wide surface of the power storage module facing the vehicle vertical direction; a buffer body having dilatancy and arranged so as to cover a side peripheral surface of the laminate; A bipolar secondary battery comprising:

2. a frame-shaped member for holding a periphery of the bipolar electrode; The buffer is disposed so as to cover a side peripheral surface of the frame-shaped member. The bipolar secondary battery according to claim 1 .

3. The buffer body is configured by sealing a non-flammable liquid or a flame-retardant liquid in a bag-shaped container. The bipolar secondary battery according to claim 1 .

4. The buffer supports the power storage module. The bipolar secondary battery according to claim 1 .

5. All-solid-state battery The bipolar secondary battery according to claim 1 .

Images