Bipolar secondary battery

Abstract

The present invention relates to a bipolar secondary battery. This bipolar secondary battery is provided with: a laminate in which a power storage module, in which a bipolar electrode having a positive electrode active material layer on one surface of a current collector and a separator having a negative electrode active material layer on the other surface of the current collector are laminated, is laminated in the vertical direction of the vehicle in such a manner that the wide surface of the power storage module faces the vertical direction of the vehicle; a negative electrode active material layer on the other surface of the current collector; and a buffer body that is disposed so as to cover the side peripheral surface of the laminate and has expansibility.

Description

Technical Field

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

[0002] The following technique is disclosed in International Publication No. 2012 / 081173: A battery pack is configured by housing a battery module formed by connecting a plurality of single cells in an outer package, wherein at least a part of the plurality of single cells is covered with a buffer member having an expansion property. Summary of the Invention

[0003] However, in a bipolar secondary battery, it is preferable to suppress a short circuit between electrodes and improve volumetric efficiency.

[0004] An object of the present invention is to provide a bipolar secondary battery that suppresses a short circuit between electrodes and improves volumetric efficiency.

[0005] The bipolar secondary battery according to Technical Solution 1 includes:

[0006] A laminate in which the power storage modules are stacked in the vehicle up-and-down direction with the wide surface of the power storage module facing the vehicle up-and-down direction, the power storage modules being stacked with bipolar electrodes and separators, the bipolar electrodes having a positive electrode active material layer on one surface of the current collector and a negative electrode active material layer on the other surface of the current collector; and

[0007] A buffer body disposed so as to cover the side peripheral surface of the laminate and having expansibility.

[0008] In the bipolar secondary battery according to Technical Solution 1, by including a buffer body having expansibility disposed so as to cover the side peripheral surface of the laminate, the periphery of the bipolar electrode is covered with the buffer body having expansibility. 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 buffer body having expansibility becomes solid and hardens. As a result, deformation of the bipolar secondary battery is suppressed, and cracking of the separator is also suppressed. Therefore, a short circuit between electrodes can be suppressed.

[0009] Moreover, by disposing the buffer body so as to cover the side peripheral surface of the laminate, volumetric efficiency can be improved as compared with the case where the buffer body is provided outside and inside the housing for housing the laminate. Therefore, a bipolar secondary battery that suppresses a short circuit between electrodes and improves volumetric efficiency can be formed.

[0010] The bipolar secondary battery according to Technical Solution 2 further includes a frame member that holds the periphery of the bipolar electrode, on the basis of the bipolar secondary battery according to Technical Solution 1,

[0011] The buffer body is disposed so as to cover the side peripheral surface of the frame member.

[0012] In the bipolar secondary battery of Technical Solution 2, the buffer body is arranged so as to cover the side peripheral surface of the frame-like member that holds the periphery of the bipolar electrode. Thus, the bipolar electrode is covered by the expandable buffer body with the frame-like member in between. Therefore, the external force input from the side of the bipolar secondary battery is dispersed by the frame-like member. As a result, cracking of the separator is suppressed, and short circuit between electrodes can be further suppressed.

[0013] Based on the bipolar secondary battery described in Technical Solution 1 or Technical Solution 2, the bipolar secondary battery of Technical Solution 3 is formed by enclosing a non-combustible liquid or a flame-retardant liquid in a bag-like container to form the buffer body.

[0014] In the bipolar secondary battery of Technical Solution 3, the buffer body is formed by enclosing a non-combustible liquid or a flame-retardant liquid in a bag-like container, thereby forming the buffer body with a simple structure. Moreover, since the buffer body is non-combustible or flame-retardant, smoking and fire can be suppressed.

[0015] Based on the bipolar secondary battery described in any one of Technical Solutions 1 to 3, the bipolar secondary battery of Technical Solution 4 is such that the buffer body supports the power storage module.

[0016] In the bipolar secondary battery of Technical Solution 4, the buffer body supports the power storage module. Thus, the buffer body functions as a spacer for maintaining the interval between the power storage modules. Therefore, even without newly providing a spacer, deformation such as the bipolar secondary battery being indented due to negative pressure can be suppressed. As a result, deformation of the bipolar secondary battery can be suppressed while improving the volume efficiency.

[0017] Based on the bipolar secondary battery described in any one of Technical Solutions 1 to 4, the bipolar secondary battery of Technical Solution 5 is an all-solid-state battery.

[0018] In the bipolar secondary battery of Technical Solution 5, an all-solid-state battery that suppresses short circuit between electrodes and improves volume efficiency can be formed.

[0019] As described above, according to the bipolar secondary battery of the present invention, short circuit between electrodes can be suppressed and volume efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Hereinafter, the features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described with reference to the drawings. In the drawings, the same reference numerals denote the same elements, and:

[0021] Figure 1 is a perspective view schematically showing the bipolar secondary battery of the embodiment;

[0022] Figure 2 is a cross-sectional view showing the bipolar secondary battery of the embodiment, showingFigure 1 Cross-section II-II;

[0023] Figure 3 is a cross-sectional view of a power storage module showing an embodiment; and

[0024] Figure 4 is a graph showing the results of an effect confirmation test of a bipolar secondary battery. Detailed Embodiment

[0025] Hereinafter, a bipolar secondary battery according to an embodiment will be described with reference to the accompanying drawings. As an example, the bipolar secondary battery according to the embodiment is mounted on a vehicle such as a battery electric vehicle or a hybrid electric vehicle and used as an in-vehicle power source for the vehicle. In each figure, 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 left-right 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.

[0026] Structure of the Bipolar Secondary Battery 10

[0027] As Figure 1 shown, the bipolar secondary battery 10 includes a housing 12, a laminate 20 housed in the housing 12, and a buffer 50 disposed between the laminate 20 and the housing 12.

[0028] Laminate 20

[0029] As Figure 2 shown, the laminate 20 has a plurality (four in this embodiment) of power storage modules 30 and a plurality (five in this embodiment) of conductive plates 40. The laminate 20 is formed by alternately laminating the power storage modules 30 and the conductive plates 40 in the vertical direction of the vehicle with the wide surface of the power storage module 30 facing the vertical direction of the vehicle. That is, in the state where the bipolar secondary battery 10 is mounted on the vehicle, the lamination direction of the laminate 20 is the vertical direction of the vehicle. It should be noted that the bipolar secondary battery 10 only needs to include at least one power storage module 30 and at least one conductive plate 40.

[0030] Power Storage Module 30

[0031] The power storage module 30 is formed in a rectangular plate shape with the vertical direction of the vehicle as the plate thickness direction. 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.

[0032] As Figure 3As shown, the power storage module 30 includes an electrode laminate portion 31 and a frame member 38 that surrounds the side peripheral surface of the electrode laminate portion 31.

[0033] Electrode laminate portion 31

[0034] In the electrode laminate portion 31, a plurality of bipolar electrodes 32 are laminated in the vehicle up-down direction with a separator 36 interposed therebetween. The electrode laminate portion 31 is formed by laminating the bipolar electrodes 32 in the vehicle up-down direction with the wide surface of the bipolar electrode 32 facing the vehicle up-down direction. The bipolar electrode 32 is formed in a rectangular plate shape with the vehicle up-down direction as the plate thickness direction.

[0035] The bipolar electrode 32 has a current collector 33, a positive electrode active material layer 34 formed on the upper surface (one surface) of the current collector 33, and a negative electrode active material layer 35 formed on the lower surface (the other surface) of the current collector 33.

[0036] The separator 36 is formed in a rectangular plate shape with the vehicle up-down direction as the plate thickness direction. The separator 36 is disposed between the bipolar electrodes 32 adjacent in the lamination direction. The separator 36 prevents electrical short-circuit between the electrodes by separating the adjacent positive electrode active material layer 34 and negative electrode active material layer 35 in the electrode laminate portion 31. The bipolar electrode 32 and the separator 36 are impregnated with an electrolyte.

[0037] Frame member 38

[0038] The frame member 38 is formed in a frame shape so as to surround the side periphery of the electrode laminate portion 31. The frame member 38 can be formed in a frame shape, for example, by disposing molten thermoplastic resin on the peripheral surface of the electrode laminate portion 31 and cooling it. The frame member 38 holds the peripheries of a plurality of bipolar electrodes 32 so as to form a space between the bipolar electrodes 32 adjacent to each other in the vehicle up-down direction, and seals the space.

[0039] Conductive plate 40

[0040] 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 to each other in the vehicle up-down direction, and a plurality of power storage modules 30 are connected in series via the conductive plate 40. Further, charging and discharging of the plurality of power storage modules 30 are performed via an external terminal (not shown).

[0041] In addition, the conductive plate 40 also functions as a heat dissipation plate for releasing 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, whereby heat generated in the power storage module 30 can be efficiently released to the outside.

[0042] Housing 12

[0043] As Figure 2As shown, the housing 12 includes a pair of upper and lower end plates 14. The pair of upper and lower end plates 14 are arranged with the laminate 20 therebetween. Bolts 18 and nuts 19, which are restraint members, are attached to the pair of upper and lower end plates 14, whereby the laminate 20 is compressed in the vehicle up-down direction (lamination direction). In other words, the laminate 20 is housed in the housing 12 in a state of being compressed in the vehicle up-down direction.

[0044] A film 42 having electrical insulation properties is disposed on the surfaces of the pair of end plates 14 on the vehicle up-down direction inner sides, and insulation is provided between the housing 12 and the power storage module 30.

[0045] Buffer body 50

[0046] As Figure 1 shown, the buffer body 50 is formed of a material having expansibility, and is configured such that the higher the shear (flow) velocity, the greater the increase rate of the shear stress (flow resistance). That is, the buffer body 50 has a structure in which the ease of deformation is velocity-dependent, and it is easily deformed by an input at a low speed, while it is difficult to be deformed by an input at a high speed.

[0047] The buffer body 50 is an expansible material such as a suspension in which fine powders such as potato starch and corn starch are suspended, or a material in which ceramic particles are infiltrated into a Kevlar (registered trademark) raw material.

[0048] At 25°C, the ratio of the viscosity γ (γ = 100) of the buffer body 50 at a shear velocity of 100 [S -1 to the viscosity γ (γ = 0.01) at a shear velocity of 0.01 [S -1 is preferably greater than 1000. That is, at 25°C, it is preferable to satisfy the following relational expression (1).

[0049] γ (γ = 100) / γ (γ = 0.01) > 1000…(1)

[0050] From the viewpoint of flame retardancy, the buffer body 50 is preferably non-combustible or flame retardant. From the viewpoint of suppressing leakage current, the buffer body 50 preferably has insulation properties.

[0051] From the viewpoint of reducing the temperature of the exhaust gas, the specific heat of the buffer body 50 is preferably 1.4 [J / (g·K)] or more.

[0052] From the viewpoint of not deteriorating the volume efficiency, the thickness of the buffer body 50 is preferably 60 [mm] or less. From the viewpoint of achieving both volume efficiency and impact resistance, the buffer body 50 is preferably 10 [mm] or more, and more preferably 20 [mm] or more.

[0053] As Figure 1 and Figure 2As shown, the buffer body 50 is arranged so as to cover the side peripheral surface of the laminate 20. The buffer body 50 is, for example, installed on the frame member 38 by welding and is arranged so as to cover the side peripheral surface of the frame member 38. Thus, the buffer body 50 is configured to support the power storage module 30. The buffer body 50 has a height reaching from the lower surface to the upper surface of the laminate 20.

[0054] The buffer body 50 may also be covered with a bag-shaped container such as a film that is easily deformable. Four bag-shaped containers may be provided corresponding to the respective side surfaces of the laminate 20, or may be formed in a frame shape surrounding the side surface of the laminate 20, or may be divided into a plurality of pieces.

[0055] [Effect Confirmation Test]

[0056] A test was conducted to confirm the effect of the impact resistance of the bipolar secondary battery 10 of the embodiment.

[0057] 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 power storage modules 30 in which 30 bipolar electrodes 32 were laminated. In addition, the bipolar secondary batteries 10 of Examples 1 to 5 were set to a constraint form A in which the constraint load of the power storage module 30 was about 40 [kN]. The bipolar secondary battery 10 of Example 1 was set to have a structure with a buffer body 50 having a thickness of 10 [mm]. The bipolar secondary battery 10 of Example 2 was set to have a structure with a buffer body 50 having a thickness of 20 [mm]. The bipolar secondary battery 10 of Example 3 was set to have a structure with a buffer body 50 having a thickness of 35 [mm]. The bipolar secondary battery 10 of Example 4 was set to have a structure with a buffer body 50 having a thickness of 50 [mm]. The bipolar secondary battery 10 of Example 5 was set to have a structure with a buffer body 50 having a thickness of 60 [mm].

[0058] The bipolar secondary batteries of Comparative Examples 1 to 3 were formed by stacking four power storage modules 30 in which 30 bipolar electrodes 32 were laminated. In addition, the bipolar secondary batteries of Comparative Examples 1 and 2 were set to a constraint form A in which the constraint load of the power storage module 30 was about 40 [kN]. The bipolar secondary battery of Comparative Example 3 was set to a constraint form B in which the constraint load of the power storage module 30 was about 90 [kN]. The bipolar secondary batteries of Comparative Examples 1 and 2 were set to have a structure without a buffer body. The bipolar secondary battery of Comparative Example 3 was set to have a structure with a buffer body 50 having a thickness of 80 [mm].

[0059] Collision Test

[0060] In the impact test, a semi-cylindrical load element with a diameter of φ75 [mm] was made to impact the bipolar secondary batteries 10 of Examples 1 to 5 and the bipolar secondary batteries of Comparative Examples 1 to 3 from the rear at 50 [G]. Then, among the battery cells, those with a cell voltage reduced by 25% compared to before the test were determined as short-circuited battery cells, and the number of short-circuited battery cells was counted among 120 battery cells. When more than 1 / 4 of all the battery cells were short-circuited, the impact determination was set to ×.

[0061] Smoke test

[0062] In the smoke test, in each of the bipolar secondary batteries 10 of Examples 1 to 5 and the bipolar secondary batteries of Comparative Examples 1 to 3, a heater was provided at the center in the front-rear direction and the left-right direction between the second power storage module from the top and the third power storage module from the top, and heated to 600 °C. The temperature of the surfaces of the second power storage module and the third power storage module from the top on the side opposite to the side where the heater was provided exceeded 300 °C. Then, at a position 80 [mm] away from the side surface of the power storage module, the smoke temperature curve was measured. When the smoke at 900 °C or higher continued for 30 [sec] or more, the smoke determination was set to ×.

[0063] Figure 4 is a graph showing the results of the effect confirmation test of the bipolar secondary battery. It can be seen from Figure 4 that the impact determinations of the bipolar secondary batteries of Comparative Examples 1 and 2 were × in the impact test. On the other hand, the impact determinations of the bipolar secondary batteries 10 of Examples 1 to 5 were 〇 in the impact test. In addition, the smoke determinations of the bipolar secondary batteries of Comparative Examples 1 and 2 were × in the smoke test. On the other hand, the smoke determinations of the bipolar secondary batteries 10 of Examples 1 to 5 were 〇 in the smoke test.

[0064] Function

[0065] However, when an external force is input from the side of the bipolar secondary battery 10, if the bipolar secondary battery 10 is deformed and cracks are generated in the separator 36, there is a problem of short-circuit between the electrodes due to the cracks in the separator 36.

[0066] The bipolar secondary battery 10 of the embodiment includes:

[0067] A laminate 20, with the wide surface of the power storage module 30 facing the vehicle up-down direction, the power storage modules 30 are laminated in the vehicle up-down direction, and the power storage module 30 is laminated with a bipolar electrode 32 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; and

[0068] The buffer body 50 is disposed so as to cover the side peripheral surface of the laminate 20 and has expansibility (see Figure 1 ).

[0069] By providing the buffer body 50 having expansibility and disposed so as to cover the side peripheral surface of the laminate 20, the periphery of the bipolar electrode 32 is covered with the buffer body 50 having expansibility. 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 buffer body 50 having expansibility becomes solid and hardens. As a result, the deformation of the bipolar secondary battery 10 is suppressed, and the cracking of the separator 36 is also suppressed. Therefore, a short circuit between the electrodes can be suppressed.

[0070] Moreover, compared with the case where the buffer body 50 is provided on the outer side and the inner side of the housing for housing the laminate 20, the volumetric efficiency can be improved. Therefore, the bipolar secondary battery 10 that suppresses a short circuit between the electrodes and improves the volumetric efficiency can be formed.

[0071] In the bipolar secondary battery 10 of the embodiment, a frame member 38 that holds the periphery of the bipolar electrode 32 is provided, and the buffer body 50 is disposed so as to cover the side peripheral surface of the frame member 38 (see Figure 3 ).

[0072] The buffer body 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. Thus, the bipolar electrode 32 is covered with the buffer body 50 having expansibility with the frame member 38 interposed therebetween. Therefore, the external force input from the side of the bipolar secondary battery 10 is dispersed by the frame member 38. As a result, the cracking of the separator 36 is suppressed, and a short circuit between the electrodes can be further suppressed.

[0073] In the bipolar secondary battery 10 of the embodiment, the buffer body 50 is formed by enclosing a nonflammable liquid or a flame retardant liquid in a bag-like container.

[0074] By forming the buffer body 50 by enclosing a nonflammable liquid or a flame retardant liquid in a bag-like container, the buffer body 50 can be formed with a simple structure. Moreover, since the buffer body 50 is nonflammable or flame retardant, smoking and ignition can be suppressed.

[0075] In the bipolar secondary battery 10 of the embodiment, the buffer body 50 supports the power storage module 30 (see Figure 3 ).

[0076] The buffer body 50 supports the power storage module 30. Thus, the buffer body 50 functions as a spacer for maintaining the interval between the power storage modules 30. Therefore, even if a new spacer is not provided, deformation such as the bipolar secondary battery 10 being recessed due to negative pressure can be suppressed. As a result, the deformation of the bipolar secondary battery 10 can be suppressed while improving the volumetric efficiency.

[0077] In the bipolar secondary battery 10 of the embodiment, the buffer body 50 has a height reaching from the lower surface to the upper surface of the laminate 20 (see Figure 2 ).

[0078] Since the buffer body 50 has a height reaching from the lower surface to the upper surface of the laminate 20, the entire side circumferential surface of the laminate 20 is covered by the buffer body 50. Therefore, when an external force is input from the side of the bipolar secondary battery 10 due to a collision, the buffer body 50 suppresses the input of the external force to the laminate 20. As a result, the cracking of the separator is suppressed, and the short circuit between the electrodes can be further suppressed.

[0079] As described above, the bipolar secondary battery of the embodiment has been described based on the embodiment. However, the specific structure is not limited to this embodiment, and design changes and the like are permitted as long as they do not depart from the gist of the invention related to each claim of the claims.

[0080] In the embodiment, an example in which the buffer body 50 is arranged so as to cover the side circumferential surface of the laminate 20 is shown. However, the buffer body may also be arranged so as to cover at least a part of the side circumferential surface.

[0081] In the embodiment, an example in which the bipolar secondary battery 10 stores an electrolytic solution inside the power storage module 30 is shown. However, the bipolar secondary battery may also be an all-solid-state battery.

Claims

1. A bipolar secondary battery, wherein: The bipolar secondary battery has: A stacked body in which the storage modules are stacked in the vehicle vertical direction with the wide faces of the storage modules facing the vehicle vertical direction, the storage modules being stacked with bipolar electrodes and separators, the bipolar electrodes having a positive electrode active material layer on one side of a current collector and a negative electrode active material layer on the other side of the current collector; and The buffer body is arranged so as to cover the side peripheral surface of the stacked body and has expandability.

2. The bipolar secondary battery according to claim 1, wherein: A frame-shaped member for holding the periphery of the bipolar electrode, The buffer body is arranged so as to cover the side peripheral surface of the frame-shaped member.

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

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

5. The bipolar secondary battery according to claim 1, wherein: This bipolar secondary battery is an all-solid-state battery.

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