JP2014056799A - Bipolar secondary battery and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bipolar secondary battery capable of sufficiently suppressing leakage of electrolytes that are enclosed in the battery.SOLUTION: A bipolar secondary battery in which electrolytes are enclosed comprises: bipolar electrodes each of which has a positive electrode on a first surface of a collector and a negative electrode on a second surface of the collector; separators each of which is sandwiched between the positive electrode and the negative electrode; sealing materials in frame-like shapes, surrounding peripheries of single cells each of which is constituted of the positive electrode, the negative electrode, and the separator, and being pressed between the collectors. The sealing materials surround the peripheries of the single cells, and partially include strongly press-bonded port which is divided.

Description

  The present invention relates to a bipolar secondary battery and a method for manufacturing the same. The bipolar secondary battery of the present invention is used, for example, to drive a driving motor for traveling in an electric vehicle.

  In recent years, various in-vehicle batteries have been developed along with the spread of electric vehicles. For example, in Patent Document 1 below, a substrate having electron conductivity in which a positive electrode material layer is disposed only on one surface, and at least one single surface. A positive electrode material layer, a substrate having electron conductivity with a negative electrode material layer disposed on the other surface, and a substrate having electron conductivity with a negative electrode material layer disposed on only one surface, via a lithium ion conductive electrolyte layer. All the positive electrode material layers are opposed to the negative electrode material layer, and each of the substrates and the laminated body laminated so that the positive electrode material layer and the negative electrode material layer do not directly contact each other, and at least the positive electrode material layer and the negative electrode material layer of the laminated body are provided. A bipolar secondary battery that shields the electrolyte layer from the outside air has been proposed.

JP 9-23003 A

  One of the characteristics required for an in-vehicle battery is a reduction in size and weight of the battery. If an in-vehicle battery is reduced in size and weight, the battery mounting amount increases, and accordingly the travelable distance is extended.

  Among them, the bipolar secondary battery has a structure in which a large number of stack components are stacked. Therefore, when the battery is reduced in size and weight, the thickness of each component tends to be reduced. On the other hand, an electrolyte solution is sealed in a bipolar secondary battery. Therefore, in the situation where the thickness of each component is reduced, leakage of the electrolyte must be sufficiently suppressed.

  In view of the above, it is an object of the present invention to provide a bipolar secondary battery and a method for manufacturing the same that can sufficiently suppress leakage of an electrolyte solution enclosed in the battery.

  In order to achieve the above object, a bipolar secondary battery according to claim 1 of the present invention is sandwiched between a positive electrode provided on one surface of the current collector and a negative electrode on the other surface, and the positive electrode and the negative electrode. And a bipolar secondary battery that encloses an electrolyte and includes a separator, and a frame-shaped sealing material that surrounds a cell constituted by the positive electrode, the negative electrode, and the separator and is pressed between current collectors. And the said frame-shaped sealing material has the high crimping | compression-bonding site | part which enclosed the circumference | surroundings of the said cell and was partly divided | segmented.

  A bipolar secondary battery according to claim 2 of the present invention is the bipolar secondary battery according to claim 1, wherein the bipolar electrode and the frame-shaped sealing material are planar squares, and the four sides thereof. It has the high crimping | compression-bonding site | part which continues on three sides among these.

  According to a third aspect of the present invention, there is provided a bipolar secondary battery manufacturing method comprising: a bipolar electrode having a positive electrode on one surface and a negative electrode on the other surface; and a separator sandwiched between the positive electrode and the negative electrode And a laminated product forming step of laminating a frame-shaped sealing material that surrounds a cell constituted by a positive electrode, a negative electrode, and a separator and is pressed between current collectors; and the frame-shaped sealing material is bipolar A crimping step of welding to the mold electrode, wherein the crimping step pressurizes and crimps a portion surrounding the unit cell and partly divided at a higher pressure than other portions.

  A bipolar secondary battery manufacturing method according to claim 4 of the present invention is the manufacturing method according to claim 3, wherein the position surrounds the unit cell and corresponds to a part of the cell. A pressure press bonding is performed using a hot press mold provided with a protruding portion.

  In the bipolar secondary battery of the present invention having the above-described configuration, the frame-shaped sealing material that seals the electrolytic solution inside the battery is provided with a high pressure bonding portion that surrounds the periphery of the unit cell. It is possible to sufficiently suppress leakage of the electrolyte due to the sealing action exhibited by the part. Here, the high pressure bonding portion refers to a portion that is pressure-bonded with a pressure higher than that of other portions. However, since the formation of the high pressure bonding portion is generally performed before the injection of the electrolytic solution, the injection operation of the electrolytic solution cannot be performed if the high pressure bonding portion is provided over the entire periphery of the unit cell. Therefore, in the present invention, the high pressure bonding part is provided in a shape in which a part (part of the entire circumference of the unit cell) is divided, and the part in which the part is divided is used as an electrolyte injection port at the time of electrolyte injection. I decided to use it. In the case where the bipolar electrode or the frame-shaped sealing material is a plane quadrangle, it is preferable in terms of manufacturing process and equipment that the high pressure bonding portion is continuously provided on three of the four sides. In this case, the remaining 1 The side is used as an electrolyte injection port when the electrolyte is injected.

  Since the frame-shaped sealing material is assembled in such a manner that it surrounds the unit cell and is crimped between the current collectors, it exerts a sealing action against the electrolyte by being crimped between the current collectors. . However, the crimping for assembling is performed for the purpose of laminating and integrating a large number of stack components, and the size of the press pressure at the time of crimping is set within a range where these can be integrated. However, there is a concern that such a large pressing pressure is insufficient to sufficiently suppress leakage of the electrolyte. Therefore, in the present invention, in addition to the pressure bonding for the assembly, a new high pressure bonding portion is newly provided, and in addition to the sealing action by the pressure bonding for the assembly, a new sealing action by the high pressure bonding portion is exhibited. Therefore, it is possible to sufficiently suppress leakage of the electrolytic solution by exhibiting this weighted sealing action. Since the high pressure bonding portion is formed at a higher pressing pressure than the other portions, the high pressure bonding portion is often formed in a shape in which the thickness of the sealing material is reduced as compared with the other portions.

  As a method for manufacturing a bipolar secondary battery, when performing a crimping process of welding a frame-shaped sealing material to a bipolar electrode, a part of the cell surrounding the cell and partially separated from other parts It is preferable to form a high pressure bonding part by pressurizing and pressing at a high pressure, and according to this, the pressure bonding for the assembly and the formation of the high pressure bonding part are performed at the same time, so that the work efficiency is good. As the heat press mold used for the crimping, it is preferable to use a mold that surrounds the unit cell and has a protrusion at a position corresponding to a part of the cell part. Since the pressure bonding for assembly and the formation of the high pressure bonding portion are performed at the same time, the work efficiency is good.

  The present invention has the following effects.

  That is, in the present invention, as described above, the frame-shaped sealing material that seals the electrolyte inside the battery is provided with a high pressure bonding portion that surrounds the periphery of the unit cell. Electrolyte leakage can be sufficiently suppressed. Since a part of the high pressure bonding part is divided, the injection operation of the electrolytic solution is not hindered. Further, according to the manufacturing method of the present invention, the pressure bonding for assembling and the formation of the high pressure bonding portion can be performed simultaneously, and the working efficiency is good.

FIG. 2 is a plan view of a bipolar electrode, a first sealing material and a second sealing material in a bipolar secondary battery according to an embodiment of the present invention, and a plan view of an electrode sheet obtained by combining them. Cross section of electrode sheet Sectional drawing which shows the laminated structure of a bipolar secondary battery Plan view of bipolar secondary battery Explanatory drawing of processing steps for high pressure bonding parts Manufacturing process explanatory diagram of bipolar secondary battery

The present invention includes the following embodiments.
(1) A bipolar electrode (current collector foil with electrode) is bonded to both sides in the thickness direction to form an electrode sheet, and a plurality of the electrode sheets are stacked with a separator interposed therebetween to form a laminate, and the laminate In a bipolar secondary battery (lithium ion battery) in which a peripheral part other than the electrolyte injection port in FIG. 2 is heat-press welded (crimped) to form a laminated product stack, the peripheral part of the laminated product stack that is hot-press welded is A bipolar secondary battery (lithium ion battery) comprising a high pressure bonding part (seal line) for sealing a leak of electrolyte injected into the laminated product stack.
(2) In the bipolar secondary battery (lithium ion battery) described in the above item (1), the high pressure bonding part (seal line) is set so that the press pressure of the hot press welding (crimping) is larger than other parts. Thus, the bipolar secondary battery (lithium ion battery) is formed as a three-dimensional shape having a thickness reduced from that of the other part.
(3) In the method of manufacturing the bipolar secondary battery (lithium ion battery) described in the above (1) or (2), a mold protrusion is provided at a portion corresponding to the high pressure bonding portion (seal line). A method of manufacturing a bipolar secondary battery (lithium ion battery), wherein the hot press welding (crimping) is performed using a hot press mold.

  Next, embodiments of the present invention will be described with reference to the drawings.

  The embodiment relates to a lithium ion battery which is a kind of bipolar secondary battery. The lithium ion battery according to this example is configured as follows.

overall structure····
That is, as shown in FIG. 1 and FIG. 2, the electrode sheet 11 is configured by sticking frame-shaped sealing materials 16 and 17 to both surfaces in the thickness direction of the bipolar electrode (current collector foil with electrode) 12. As shown in FIG. 3, a plurality of electrode sheets 11 are stacked with a separator 18 interposed therebetween to form a laminated product 21 </ b> A of electrode sheets 11. As shown in FIG. 4, a laminated product 21 </ b> A is formed. A laminated product stack 21B of the electrode sheet 11 is configured by hot press welding (crimping) the peripheral edge portion other than the electrolyte solution injection port 23 in FIG. The laminated product 21A is a bipolar secondary battery before hot press welding, and the laminated product stack 21B is a bipolar secondary battery after hot press welding. As shown in FIG. 3, the unit cell includes a positive electrode 14 of one electrode sheet 11 </ b> D, a negative electrode 15 of the other electrode sheet 11 </ b> C, and both electrodes 14, 15 in two sets of electrode sheets (for example, 11D and 11C) stacked on each other. One single battery is constituted by the separator 18C. Further, as shown in FIG. 4, a high pressure bonding part (seal) for sealing a leakage of an electrolyte solution (not shown) injected into the laminated product stack 21B at the peripheral portion of the hot-press welded laminated product stack 21B. Line) 24 is formed.

Configuration of electrode sheet 11
The bipolar electrode 12 shown in FIG. 1 and FIG. 2 has a current collector (current collector foil) 13 with a positive electrode 14 disposed on one surface in the thickness direction and a negative electrode 15 disposed on the other surface. The current collector 13 is formed into a planar quadrangular (rectangular) film shape (about 300 × 350 × 0.05 mm) from a material obtained by depositing a metal thin film (such as Cu) on conductive polyimide, and one surface in the thickness direction thereof. The positive electrode 14 is fixed at the center of the plane of the electrode, and the negative electrode 15 is fixed at the center of the plane of the other surface.

  One sealing material 16 is formed into a film shape of a plane square (rectangular) that is slightly larger than the current collector 13 by a thermosetting resin and a thermoplastic resin, and a hollow portion 16b penetrating in the thickness direction is formed at the center of the plane. The current collector 13 is fixed to one surface in the thickness direction so as to surround the positive electrode 14. The other sealing material 17 is formed into a frame-like shape by forming a flat square (rectangular) film that is slightly larger than the current collector 13 with a thermoplastic resin, and having a hollow portion 17b penetrating in the thickness direction at the center of the plane. The current collector 13 is fixed to the other surface in the thickness direction so as to surround the negative electrode 15. These frame-shaped sealing materials 16 and 17 surround the cell and are welded between the current collectors 13.

  Positioning holes 12a, 16a, and 17a in the form of circular small holes penetrating in the thickness direction are provided on the planes of the bipolar electrode 12 and the sealing materials 16 and 17 so as to align the planes when they are overlapped with each other. The bipolar electrode 12 and the sealing materials 16 and 17 are overlapped at the positions of the positioning holes 12a, 16a, and 17a. The sealing members 16 and 17 are fixed to the bipolar electrode 12 by, for example, temporarily fixing by pinpoint welding at a plurality of locations.

Structure of laminated product (laminated product before welding) 21A ...
A laminated product 21A shown in FIG. 3 is configured as a laminated product having three layers by alternately stacking four electrode sheets 11 and three separators 18. Positioning holes 11a (see FIG. 1) as the electrode sheet 11 are provided on the plane of the electrode sheet 11 by overlapping the positioning holes 12a, 16a, and 17a. The holes 11a are overlapped at the same position. On the other hand, since the separator 18 has a relatively small plane area, it is aligned by being arranged at the center position on the plane of the electrode sheet 11 and is not added to the alignment by the positioning hole. Note that the above three layers in the number of stacked layers are merely examples, and may be four or more layers, for example, eight layers. Prior to superposition, voltage monitoring terminals (FPC) 25 are attached to the electrode sheets 11.

Structure of laminated product stack (laminated product after welding) 21B
The laminated product stack 21B shown in FIG. 4 is produced by hot press welding the laminated product 21A shown in FIG. As described above, the electrode sheet 11 and the laminated product 21A obtained by superimposing a plurality of the electrode sheets 11 are planar quadrangular (rectangular), and one side of the four sides of the peripheral portion is the electrolyte injection port 23 and remains open. Therefore, the laminated product 21A is hot press welded on the remaining three sides, and in FIG. 4, the hot press welded regions are indicated by dots. The sealing material 17 in the welding region is welded to the current collector 13 of the bipolar electrode 12 at a portion overlapping with the bipolar electrode 12, and is welded to the sealing material 16 at a portion not overlapping with the bipolar electrode 12.

  Further, in FIG. 4, the high pressure bonding portion 24 is indicated by a thick black line, and as is clear from the arrangement, the high pressure bonding portion 24 is a single piece continuous over the three sides of the peripheral edge portion subjected to hot press welding. It is formed in a line shape (band shape). The high pressure bonding portion 24 is provided on the plane of the sealing materials 16 and 17 along the frame shape of the sealing materials 16 and 17 and surrounds the periphery of the unit cell and a part thereof (a part of the entire periphery of the unit cell, electrolytic The portion corresponding to the liquid injection port 23 is divided into a planar shape.

  Further, as shown in FIG. 5, the high pressure bonding portion 24 is formed as a three-dimensional shape having a thickness reduced from the other portions by setting the press pressure at the time of hot press welding larger than the other portions. Yes. Accordingly, the high pressure bonding portion 24 is formed in a groove-like shape on one surface in the thickness direction of the laminated product stack 21B, or is recessed in a groove shape on one surface in the thickness direction of the laminated product stack 21B and has a bowl shape on the other surface. Or a shape recessed in a groove shape on both one and other surfaces in the thickness direction of the laminated product stack 21B.

  Further, as shown in FIG. 5, the high pressure bonding portion 24 is formed by performing hot press welding with a hot press mold 31 provided with a protrusion 32 at a portion corresponding to the high pressure bonding portion 24. The protruding portion 32 is provided at a position corresponding to a part of the battery that surrounds the unit cell and is partially divided. Further, the protrusion 32 is provided on one split mold in the hot press mold 31 or is provided on both one and the other split mold.

  Next, a method for producing the lithium ion battery will be described.

As shown in FIG. 6A, a current collector 13 cut into a predetermined planar shape (square) is prepared, and a positive electrode 14 is applied to one surface in the thickness direction of the current collector 13. The negative electrode 15 is applied to the other surface to produce the bipolar electrode 12 (FIG. 6B).
On the other hand, as shown in FIG. 6 (C), seal materials 16 and 17 cut into a planar shape (square) of a predetermined size are prepared, and the seal materials 16 and 17 are punched and pressed into a frame shape. Processing is performed (FIG. 6D).

  Next, as shown in FIG. 6 (E), the bipolar electrode 12 and the two sealing materials 16 and 17 are overlapped and temporarily fixed by hot press welding to produce the electrode sheet 11 (FIG. 6 (F)). ). At the time of superimposition, in order to ensure the positional accuracy and minimize the positional deviation error, an alignment means by image processing is used. The positioning holes 12a, 16a and 17a are used for alignment.

  Next, as shown in FIG. 6 (G), a plurality of electrode sheets 11 are overlaid with a separator 18 sandwiched therebetween to form a laminated product 21A, and three peripheral edge portions other than the electrolyte solution inlet 23 in the laminated product 21A. Are heat-press welded with a mold 31 to produce a laminated product stack 21B (FIG. 6 (H)), and at this time, a high pressure bonding part 24 is formed. At the time of superimposition, in order to ensure the positional accuracy and minimize the positional deviation error, an alignment means by image processing is used. The positioning hole 11a is used for alignment. As described above, the high pressure bonding portion 24 is formed by performing hot press welding with the hot press mold 31 provided with the protrusion 32 at a position corresponding to the high pressure bonding portion 24. Further, the high pressure bonding portion 24 is formed by press-bonding a line-shaped portion surrounding the periphery of the unit cell and partly divided at a higher pressure than other portions when performing the hot press welding of the laminated product 21A. Form. Next, although not shown, an electrolytic solution is injected into each layer of the laminated product stack 21 </ b> B, and the injection port 23 is closed to complete.

  6E to 6G, the “multiple bipolar type in which a positive electrode is provided on one surface of the current collector and a negative electrode is provided on the other surface” according to the third aspect. An electrode, a separator sandwiched between the plurality of bipolar electrodes, a frame-shaped sealing material that surrounds a unit cell constituted by the positive electrode, the negative electrode, and the separator and is pressure-bonded between the current collectors A laminated product forming step of laminating the sealing material (in this embodiment, the sealing materials 16 and 17 are temporarily fixed to the bipolar electrode 12). 6 (H), the “crimping step of welding the frame-shaped sealing material to the bipolar electrode” described in claim 3 is performed (in this embodiment, the sealing materials 16 and 17 are This is fixed to the bipolar electrode 12).

  In the lithium ion battery having the above configuration, since the high pressure bonding portion 24 surrounding the periphery of the unit cell is provided in the frame-shaped sealing materials 16 and 17 for sealing the electrolyte inside the battery, The leakage of the electrolytic solution can be sufficiently suppressed by the sealing action exerted. Since a part of the high pressure bonding portion 24 is divided, the electrolyte injection operation is not hindered.

  Further, as a method of manufacturing a lithium ion battery, when performing hot press welding of the laminated product 21A, a high pressure bonding portion 24 is formed by pressure-bonding a line-shaped portion surrounding the periphery of the unit cell at a pressure higher than other portions. Therefore, the hot press welding of the laminate 21A and the formation of the high pressure bonding portion 24 can be performed simultaneously. Therefore, a battery product excellent in sealing properties can be manufactured without increasing new processes.

DESCRIPTION OF SYMBOLS 11 Electrode sheet 11a, 12a, 16a, 17a Positioning hole 12 Bipolar electrode 13 Current collector 14 Positive electrode 15 Negative electrode 16, 17 Sealing material 16b, 17b Hollow part 18 Separator 21A Laminated product 21B Laminated product stack 23 Electrolyte inlet 24 High pressure Placement area 25 Terminal 31 Heat press mold 32 Protrusion

Claims (4)

A bipolar electrode having a positive electrode on one surface of the current collector and a negative electrode on the other surface, a separator sandwiched between the positive electrode and the negative electrode, and surrounding a unit cell composed of the positive electrode, the negative electrode, and the separator A bipolar secondary battery including a frame-shaped sealing material that is crimped between current collectors and enclosing an electrolyte solution,
The frame-shaped sealing material has a high pressure bonding portion that surrounds the unit cell and is partially divided, and is a bipolar secondary battery.   2. The bipolar secondary battery according to claim 1, wherein the bipolar electrode and the frame-shaped sealing material are planar quadrilaterals and have a high pressure bonding portion that is continuous on three of the four sides. 3. A bipolar electrode having a positive electrode on one surface of the current collector and a negative electrode on the other surface, a separator sandwiched between the positive electrode and the negative electrode, and surrounding a unit cell constituted by the positive electrode, the negative electrode, and the separator. A laminated product forming step of laminating a frame-shaped sealing material to be crimped between electric bodies, and a pressure-bonding step of welding the frame-shaped sealing material to a bipolar electrode,
The method of manufacturing a bipolar secondary battery, wherein the crimping step includes pressurizing and crimping a portion of the cell surrounding the unit cell and a part of the cell being cut at a higher pressure than other portions.   4. The bipolar type according to claim 3, wherein pressure bonding is performed using a hot press mold that surrounds the unit cell and has a protrusion at a position corresponding to a part of the cell. A method for manufacturing a secondary battery.

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