JP2011192540A - Bipolar secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent battery capacity deterioration when a bipolar secondary battery is deformed by an external force. <P>SOLUTION: This bipolar secondary battery includes a power generating element 7 which is provided by laminating a plurality of bipolar electrodes 5 in series with electrolyte layers 4 therebetween, wherein the bipolar electrode 5 is constituted by forming a positive electrode active material layer 2 on one surface of a collector 1 and forming a negative electrode active material layer 3 on the other surface, two sheets of current collectors 9 and 10 which are arranged at both end parts in the laminating direction of the power generating element 7 so as to sandwich the power generating element 7, and an insulating portion 8 constituted by laminating insulating members 8a-8e arranged in the outer periphery of the part where the positive electrode active material layer 2 or the negative electrode active material layer 3 of the collector 1 is formed. The insulating portion 8 has a part having a thickness equal to or more than an interval between the two sheets of current collectors 9 and 10 on the outer side from the periphery of the current collectors 9 and 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a seal structure for a bipolar secondary battery in which a positive electrode and a negative electrode are disposed so as to sandwich a current collector from both sides.

  As a secondary battery used to drive a motor of an electric vehicle or a hybrid vehicle, a power generation element is formed by stacking a plurality of bipolar electrodes in series, each having a positive electrode on one side and a negative electrode on the other side of a current collector. Bipolar secondary batteries that are formed are known.

  For example, Patent Document 1 discloses a bipolar secondary battery in which positive and negative current collector plates are arranged at both ends in the stacking direction of power generation elements.

JP 2009-016235 A

  However, in the bipolar secondary battery of Patent Document 1, when a force is applied from the outside, particularly when an external force is applied from a direction crossing the bipolar electrode stacking method, the power generation element is deformed and the current collector plate There is a risk of contact with each other. When the current collector plates come into contact with each other, a large current flows, and heat is generated accordingly.

  Accordingly, an object of the present invention is to prevent the battery capacity from being deteriorated when an external force is applied to the bipolar secondary battery.

  The bipolar secondary battery of the present invention includes a power generation element in which a plurality of bipolar electrodes each having a positive electrode active material layer and a negative electrode active material layer formed on both sides of a current collector are stacked in series with an electrolyte layer interposed therebetween. And two current collector plates arranged so as to sandwich the power generation element at both ends in the stacking direction of the power generation element. And the insulating part formed by laminating | stacking the insulating member arrange | positioned in the outer peripheral part of the part which formed the positive electrode or the negative electrode of the electrical power collector is provided. Furthermore, the insulating portion has a portion that is thicker than the distance between the two current collector plates outside the outer periphery of the current collector plates.

  According to the present invention, even if the bipolar secondary battery is deformed so that the current collector plates approach each other due to an external force, the interval between the current collector plates is expanded by pushing the insulating portion into the inside of the battery element. The contact resistance between the element and the current collector increases. Therefore, even if the current collector plates come into contact with each other, the current flowing at that time can be suppressed, thereby preventing the battery capacity from deteriorating.

1 is a schematic cross-sectional view schematically showing the overall structure of a bipolar battery according to a first embodiment. It is the schematic sectional drawing which represented the structure of the bipolar electrode typically. It is a schematic sectional drawing which represented typically the structure of the cell layer. It is the figure which looked at the bipolar battery from the lamination direction. It is a schematic sectional drawing which represented typically the whole structure of the bipolar battery of 2nd Embodiment. It is a schematic sectional drawing which represented typically the whole structure of the bipolar battery of 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
First, the structure of a bipolar secondary battery (hereinafter simply referred to as a bipolar battery) will be described.

  FIG. 1 is a schematic cross-sectional view schematically showing the entire structure of the bipolar battery according to the first embodiment. FIG. 2 is a schematic cross-sectional view schematically showing the structure of a bipolar electrode constituting the bipolar battery. FIG. 3 is a schematic cross-sectional view schematically showing the structure of the single battery layer constituting the bipolar battery. FIG. 4 is a view of the bipolar battery as viewed from above in the stacking direction.

  As shown in FIG. 1, a bipolar battery has a power generation element (battery element) 7 in which a plurality of bipolar electrodes 5 are stacked in series with an electrolyte layer 4 interposed therebetween, and electrolyte leakage from the electrolyte layer 4 is prevented. And a seal portion 8 disposed around the battery element 7. The seal part 8 is a part constituted by a plurality of seal materials 8a to 8e as will be described later. Positive and negative current collecting plates 9 and 10 that are electrically connected to each other and take out current flowing in the surface direction are disposed at both ends of the battery element 7 in the stacking direction. The details of the bipolar electrode 5, the electrolyte layer 4, and the seal portion 8 will be described later.

  As shown in FIG. 2, the bipolar electrode 5 has a positive electrode 2 on one surface of the current collector 1 and a negative electrode 3 on the other surface.

  As shown in FIG. 3, the battery element 7 includes a plurality of bipolar electrodes 5 and electrolyte layers 4 alternately arranged in series so that the positive electrodes 2 and the negative electrodes 3 of the adjacent bipolar electrodes 5 face each other with the electrolyte layer 4 interposed therebetween. Are laminated. Then, current collector plates 9 and 10 are disposed at both ends of the battery element 7 in the stacking direction. The current collector plates 9 and 10 may have a structure in which an electrode (positive electrode 2 or negative electrode 3) only on one side necessary for the current collector 1 is formed. That is, the basic configuration of the bipolar battery can be said to be a configuration in which a plurality of single cell layers 6 are connected in series.

  The current collector plates 9, 10 have a smaller area than the current collector 1, and as shown in FIG. 4, when viewed from above in the stacking direction, the outer periphery of the current collector plates 9, 10 is a frame-shaped film. The structure is surrounded by.

  Here, a configuration of each component and a method for manufacturing a bipolar battery will be described.

[Current collector]
A conductive polymer material in which a carbon material is dispersed in a conductive polyethylene (PE) resin is formed into a film having a thickness of about 100 [μm] by stretching. This is cut into an appropriate size (for example, 140 × 90 mm) to obtain a current collector 1.

[Positive electrode]
The following materials are mixed at a predetermined ratio to produce a positive electrode slurry.

First, LiMn ₂ O ₄ [85% by mass] as a positive electrode active material, acetylene black [5% by mass] as a conductive additive, polyvinylidene fluoride (PVDF) [10% by mass] as a binder, and N as a slurry viscosity adjusting solvent A material made of methyl-2-pyrrolidone (NMP) is mixed at the above ratio to prepare a positive electrode slurry.

  The positive electrode slurry is applied to one side of the current collector 1 and dried in a vacuum oven. And it presses so that it may become thickness 60 [micrometer], and forms a positive electrode.

  The positive electrode slurry is not applied to a predetermined range (for example, about 10 mm from the outer periphery) on the outer peripheral side of the current collector 1. The seal portion 8 is formed in a frame shape that matches the range where the positive electrode slurry is not applied.

[Negative electrode]
The following materials are mixed at a predetermined ratio to prepare a negative electrode slurry.

  First, a negative electrode slurry is prepared by mixing hard carbon [90 mass%] as a negative electrode active material, PVDF [10 mass%] as a binder, and NMP as a slurry viscosity adjusting solvent in the above ratio. This negative electrode slurry is applied to the surface of the current collector 1 opposite to the surface on which the positive electrode slurry is applied, and dried in a vacuum oven. And it presses so that it may become thickness 50 [micrometer], and forms a negative electrode. The application range of the negative electrode slurry is the same as that of the positive electrode described above.

  In the above-described production of the positive electrode and the negative electrode, since NMP is completely volatilized and removed when the electrode is dried, an appropriate amount is added so as to obtain an appropriate slurry viscosity, not an electrode constituent material. Moreover, the said ratio shows the ratio converted with the component except a slurry viscosity adjustment solvent.

  By the above-described method, the bipolar electrode 5 having the positive electrode on one surface of the conductive polymer film as the current collector 1 and the negative electrode on the opposite surface is completed.

[Electrolyte layer]
The electrolyte layer 4 is formed by impregnating a PE separator (thickness: 35 μm) with an electrolytic solution. The electrolyte is a mixed solvent of diethyl carbonate (DEC) and ethylene carbonate (EC) in a volume ratio of 1: 1, and 1M LiPF ₆ as an electrolyte.

  In addition, electrolyte solution is injected in the lamination process mentioned later.

[Seal part]
As shown in FIG. 1, the seal portion 8 includes a plurality of seal materials 8 a to 8 e. The sealing materials 8a to 8e are frame-shaped films made of an insulating resin material such as polyolefin, polyester, polyimide, or polyamide, for example, and are arranged in a range where the above-described positive electrode slurry is not applied. Since these materials are electrically stable in the operating potential of the battery, they can be reliably insulated without adversely affecting the battery. Note that other than the above may be used as long as they have similar properties.

  The sealing materials 8a to 8e are characterized by being higher in rigidity than the battery element 7. Specifically, it is formed so that the Young's modulus is 0.1 to 120 GPa.

  Further, the adhesive strength by fusion described later is defined by the tensile strength, and is set to 0.2 [N / mm] or more, for example. However, it is not limited to this.

[Lamination method]
The bipolar electrode 5 and the electrolyte layer 4 described above are alternately stacked, and heat and pressure are applied to the three sides of the sealing materials 8a to 8e from both sides in the stacking direction, so that the sealing materials 8a to 8e are fused to the current collector 1. . As the conditions for the fusion, heat of 140 ° C. and pressure of 0.2 MPa are applied for 5 seconds. One side which is not fused serves as a liquid injection part for injecting the electrolytic solution.

  After the fusion, the electrolytic solution is injected from the injection portion, and the battery element 7 is sandwiched from both ends in the stacking direction by current collector plates 9 and 10 (130 × 80 mm, thickness 100 μm) formed of aluminum plates. Vacuum seal with aluminum laminate to cover. Thus, a bipolar battery in which the contact between the battery element 7 and the current collector plates 9 and 10 is enhanced by the atmospheric pressure is completed.

  Examples of the adhesive that bonds the battery element 7 and the current collector plates 9 and 10 include, but are not limited to, rubber, silicon, olefin, and acrylic.

  Moreover, the adhesive force between the battery element 7 and the current collector plates 9 and 10 is weaker than the adhesive force between the adjacent bipolar electrodes 5 and the adhesive force between the adjacent sealing materials 8a to 8e.

  Returning to the description of FIG.

  As described above, the current collector plates 9 and 10 have a smaller area than the seal portion 8, and the seal portion 8 protrudes in the left-right direction from the current collector plates 9 and 10 in FIG. 1.

  When an external force is applied to the bipolar battery from the direction crossing the stacking direction (the lateral direction in FIG. 1), the portion to which the external force is applied (input part) is pushed inward of the battery element 7, and the bipolar battery The side surface on the input part side has a convex shape in the center direction of the battery element 7 with the input part at the top. That is, the entire bipolar type is deformed so that the current collector plate 9 and the current collector plate 10 on the input portion side are close to each other.

  When the degree of deformation is large, if the seal portion 8 has an area equivalent to that of the current collector plates 9 and 10, or the areas of the seal materials 8 a to 8 e are smaller than those of the current collector plates 9 and 10 (for example, Japanese Patent Laid-Open Publication No. FIG. 3 of No. 16235), there is a possibility that the ends of the current collector plate 9 and the current collector plate 10 on the input portion side come into contact with each other. When the current collector plate 9 and the current collector plate 10 are in contact with each other, a large current flows to generate heat and promote deterioration of the battery capacity.

  However, according to the configuration of FIG. 1, when the current collector plate 9 and the current collector plate 10 are deformed so as to approach each other, the end portions on the input portion side of the current collector plate 9 and the current collector plate 10 are respectively adjacent seal members 8a. And it will sink into the sealing material 8e. This makes it difficult for the current collector plate 9 and the end of the current collector plate 10 on the input side to come into contact with each other. Moreover, even if it contacts, the sealing material 8a-8e will be pushed in into the inside of a battery element, the space | interval of the current collecting plates 9 and 10 will spread, and the contact resistance of the battery element 7 and the current collecting plates 9 and 10 will increase. Therefore, the electric current which flows when contacting can be suppressed.

  In addition, the current collecting plates 9 and 10 are less likely to penetrate the seal portion 8 by chamfering the outer peripheral portions of the current collecting plates 9 and 10.

  Moreover, since the rigidity of the sealing materials 8a to 8e is higher than the rigidity of the battery element 7 as described above, the amount of deformation of the entire bipolar battery when an external force is applied can be suppressed. As a result, contact between the current collector plate 9 and the current collector plate 10 can be prevented.

  Furthermore, since the adhesive force between the battery element 7 and the current collector plates 9 and 10 is weaker than the adhesive force between the stacked bipolar electrodes 5 and between the sealing materials 8a to 8e, when the external force acts and deforms First, the current collector plates 9 and 10 are peeled off from the battery element 7 and no current flows. Thereby, the heat_generation | fever by the adhesion | attachment between the bipolar type electrodes 5 peeling can be prevented.

  These effects also appear in the capacity retention rate and resistance change rate after the vibration test. The vibration test is a test in which a bipolar battery is vibrated by constantly applying vibration of a predetermined input acceleration and frequency. The capacity maintenance rate and resistance change rate after the vibration test are 100% of the capacity before vibration. The resistance change rate is represented as 1.

  As a result of the test, in the configuration of the present embodiment, the capacity retention rate after the vibration test was about 70%, and the resistance change rate was about 0.9.

  As a comparison object, when the same test was performed on a configuration in which the seal portion 8 did not protrude from the outer periphery of the current collector plates 9 and 10, the capacity maintenance rate was about 50% and the resistance change rate was about 0.7. there were.

  In addition, in this embodiment, the sealing material 8a-8e provided on the electrical power collector 1 is laminated | stacked, and it becomes the sealing part 8 and fulfill | performs a sealing function, In addition, the contact between the current collecting plate 9 and the current collecting plate 10 is performed. It also functions as an insulating part to prevent. However, the sealing materials 8a to 8e may perform only a sealing function, and may be provided with an insulating portion that performs an insulating function.

  As described above, in the present embodiment, the following effects can be obtained.

  (1) Since the seal portion 8 has a portion that is outside the outer periphery of the current collector plates 9 and 10 and has a thickness that is equal to or greater than the distance between the current collector plates 9 and 10, an external force acts to bring the current collector plates 9 and 10 closer. Even when it deform | transforms like this, it can prevent that the current collecting plate 9 and the current collecting plate 10 contact. Moreover, even if it contacts, the sealing material 8a-8e will be pushed in into the inside of a battery element, the space | interval of the current collecting plates 9 and 10 will spread, and the contact resistance of the battery element 7 and the current collecting plates 9 and 10 will increase. Therefore, the current flowing at that time can be suppressed. Therefore, deterioration of the battery capacity can be prevented.

  (2) Since the seal portion 8 formed by laminating the seal materials 8a to 8e also functions as an insulating portion for preventing the current collector plates 9 and 10 from contacting, it is necessary to provide an insulating portion in addition to the seal materials 8a to 8e. No cost and manufacturing man-hours can be reduced.

(Second Embodiment)
FIG. 5 is a schematic cross-sectional view schematically showing the entire structure of the bipolar battery according to the second embodiment.

  Compared with the first embodiment, the structure of the bipolar electrode 5, the electrolyte layer 4, the lamination method, and the like are the same, but the areas of the current collector plates 9 and 10 and the structure of the seal portion 8 are different.

  In the present embodiment, the current collecting plates 9 and 10 have the same area as the electrolyte layer 4, the positive electrode 2, and the negative electrode 3. The seal portion 8 is thick enough that the seal portions 8a and 8e at both ends in the stacking direction protrude in the stacking direction from the end portions in the stacking direction of the current collector plates 9 and 10. That is, the seal portion 8 is thicker in the stacking direction than the battery element 7.

  In the configuration as shown in FIG. 5, the entire bipolar battery is deformed so that the current collector plate 9 and the current collector plate 10 approach each other when an external force is applied from the direction intersecting the stacking direction as described in the first embodiment. As a result, the seal portion 8 is also deformed so as to bend around the input portion. For this reason, the sealing materials 8 a and 8 e are surely present between the current collector plate 9 and the current collector plate 10. That is, as in the first embodiment, the current collector plate 9 and the current collector plate 10 can be prevented from contacting each other.

  The battery capacity retention rate and resistance change rate after the vibration test were about 80% and about 1.0, respectively.

  As described above, in the present embodiment, the same effects as in the first embodiment can be obtained.

(Third embodiment)
FIG. 6 is a schematic cross-sectional view schematically showing the entire structure of the bipolar battery according to the third embodiment.

  Compared to the first embodiment, the structure of the bipolar electrode 5, the electrolyte layer 4, the lamination method, and the like are the same, but the structure of the seal portion 8 is different.

  In the present embodiment, the sealing materials 8 a and 8 e have a “wedge shape” that gradually increases in thickness in the stacking direction as they are separated from the battery element 7. For this reason, when an external force in the direction of pushing the seal portion 8 toward the inside of the battery element 7 is applied, the seal portion 8 is pushed in such a way that the distance between the current collector plate 9 and the current collector plate 10 is widened. The current collector plate 10 is peeled from the battery element 7.

  As a result, not only the heat generation due to the contact between the current collector plate 9 and the current collector plate 10 is prevented, but also the current collector plates 9 and 10 are electrically separated from the battery element 7 and the seal portion 8 to cause current concentration and heat generation. Can be prevented.

  The battery capacity retention rate and resistance change rate after the vibration test were about 90% and about 10 times, respectively.

  As described above, in the present embodiment, in addition to the same effects as those in the first embodiment, the following effects can also be obtained.

  Since the seal portion 8 has a so-called wedge shape in which the thickness increases as the distance from the outer periphery of the current collector plates 9 and 10 increases, the wedge portion becomes the battery element 7 and the current collector plates 9 and 10 when an external force is applied. The current collector plates 9 and 10 are easily peeled off from the battery element 7. Thereby, current concentration and heat generation can be prevented.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

DESCRIPTION OF SYMBOLS 1 Current collector 2 Positive electrode 3 Negative electrode 4 Electrolyte layer 5 Bipolar electrode 6 Single cell layer 7 Battery element 8 Seal part 9 Current collector plate 10 Current collector plate

Claims (3)

A power generation element formed by laminating a plurality of bipolar electrodes each having a positive electrode active material layer formed on one surface of a current collector and a negative electrode active material layer formed on the other surface, with an electrolyte layer interposed therebetween;
Two current collector plates disposed so as to sandwich the power generation element at both ends in the stacking direction of the power generation element;
An insulating portion formed by laminating insulating members disposed on the outer peripheral portion of the positive electrode active material layer or the negative electrode active material layer of the current collector; and
With
The bipolar secondary battery, wherein the insulating portion has a portion outside the outer periphery of the current collector plate and having a thickness greater than or equal to the interval between the two current collector plates.   The bipolar secondary battery according to claim 1, wherein the thickness of the insulating portion increases as the distance from the outer periphery of the current collector plate increases.   The insulating member is a seal member disposed between the current collectors so as to surround the periphery of a unit cell layer including the adjacent positive electrode active material, the electrolyte layer, and the negative electrode active material. The bipolar secondary battery according to 1 or 2.

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