JP4402134B2 - Multilayer secondary battery and manufacturing method thereof - Google Patents

Description

  The present invention relates to a stacked secondary battery in which a plurality of flat positive electrodes and negative electrodes are stacked with a separator interposed therebetween, and a method for manufacturing the same.

  In a laminated type secondary battery, a sheet-shaped positive electrode and a negative electrode having different active electrode layers formed on a current collector made of metal foil or the like are stacked with a separator and covered with an exterior material. It is configured with a sealing structure.

  In recent years, with the spread of electric vehicles and hybrid vehicles, there has been an increase in the capacity of secondary batteries and the demand for stacked secondary batteries capable of discharging at a high rate. Is also growing.

  A laminated type secondary battery that is packaged with a laminated film is easier to manufacture than a battery using a metal case, but a technique for forming the laminated position of the laminated body to be the power generating element with high accuracy is required. .

  That is, from the viewpoint of safety, conventionally, a positive electrode active material of a positive electrode is arranged inside a negative electrode active material of a negative electrode in a positive electrode and a negative electrode via a separator (for example, Patent Document 1). Such a structure is also preferable from the viewpoint of characteristics such as charge / discharge capacity.

  There are various methods for coating the positive electrode and the negative electrode, but the coating method using the slit die coater that coats the electrode slurry by coating from the slit is excellent in the uniformity of thin film coating and coating thickness. Therefore, it is often used. In addition, since the electrode coating method of a positive electrode and a negative electrode is the same, the coating method is demonstrated here using a negative electrode. FIG. 5 is a plan view illustrating a negative electrode applied to one side by a conventional coating method, FIG. 6 is a plan view illustrating a negative electrode applied to both sides by a conventional coating method, and FIG. 7 is a conventional coating method. It is a top view explaining the slit cutting of the negative electrode apply | coated to both surfaces by a construction method. In the conventional negative electrode coating, intermittent coating is performed. At the start of intermittent coating application, as shown in FIG. 5, the surface coating portion 1 on the current collector 10 (note that the surface coating portion on the drawing is hatched). A concave portion 11a is formed at the central portion in the width direction of the coating start portion 11 and the convex portion 12b is formed at the central portion in the width direction of the coating end portion 12 at the end of coating. There is a trend.

  After coating the surface and winding the negative electrode coated on one side as described above, coating the back surface, the surface coating portion 1 and the back surface coating portion 2 (the back surface coating portion on the drawing) as shown in FIG. (The same applies to the following.) The relationship between the front surface coating start portion and the back surface coating end portion, and the front surface coating end portion 12 and the back surface coating start portion 21 overlap. Therefore, the concave portion 11a on the front surface and the convex portion on the back surface, and the convex portion 12b on the front surface and the concave portion on the back surface overlap.

  After coating on both sides, in the laminated type secondary battery, as shown in FIG. 7, the negative electrode is slit into a strip shape so as to have a necessary dimension. FIG. 7 shows a case where the strip-shaped negative electrodes 3 and 5 at the end and the strip-shaped negative electrode 4 at the center are slit (the one-dot chain line indicates the slit line 71). 5 and the strip-shaped negative electrode 4 in the central portion are coated so that the coated portion on the front surface is shifted from the coated portion on the back surface. 8 is a front view of a conventional strip-shaped negative electrode, FIG. 8 (a) is a front view of the strip-shaped negative electrode at the end, and FIG. 8 (b) is a front view of the strip-shaped negative electrode at the center. As shown in FIG. 8 (a), in the strip-shaped negative electrodes 3, 5 at the end after the slit, the coated portion on the front surface is shifted to the left side with respect to the back surface, and as shown in FIG. On the contrary, in the strip-shaped negative electrode 4, the coating portion on the front surface is applied while being shifted to the right with respect to the back surface.

  Before laminating the strip-shaped negative electrode, cutting is performed to adjust the dimensions of each negative electrode. At this time, as shown in FIGS. 8A and 8B, the cutting lines 7 and 9 are provided at a certain distance with the surface coating start portion 11 as the reference points 6 and 8. . In this case, the negative electrode is cut in a state where the coating ends of the front surface and the back surface are shifted. In the strip-shaped negative electrode 3 at the end portion, as shown in FIG. The application part is cut in a short state, and the strip-like negative electrode 4 in the center part is cut in a state in which the application part on the back surface is longer than the application part on the front surface as shown in FIG. In addition, the non-coating part is provided in the coating start part side in order to connect an external connection terminal to a collector.

  FIG. 9 is a schematic front view of a laminate when a conventional positive electrode and negative electrode are laminated. When laminating a negative electrode having a different size of the coated portion on the front and back surfaces, and a positive electrode having a different coated portion size on the front and back surfaces, which are cut as described above, the non-coated portion of the current collector of the positive electrode and the negative electrode 9 are positioned so that the coating portion of the positive electrode and the negative electrode are positioned on the inner side of the coating portion of the negative electrode, as shown in FIG. The reference point 108 and the cutting line 109 on the surface of the strip-shaped positive electrode 104 fall between the reference points 6 and 8 on the surface of the strip-shaped negative electrodes 3 and 4 and the cutting lines 7 and 9, but the strip-shaped negative electrode at the end. 3 and the front surface of the strip-shaped positive electrode 104, and the positional relationship between the back surface of the strip-shaped positive electrode 104 and the surface of the strip-shaped negative electrode 4 at the center, the positive electrode application part is arranged inside the negative electrode application part. In some cases, reverse portions 14 and 15 are not formed. In this way, when the end face of the positive electrode coating part is not covered with the end face of the negative electrode coating part, it becomes a problem from the viewpoint of safety and performance, so it is handled as a defective product, and thus the production efficiency deteriorates. was there.

JP 2005-228537 A

  The object of the present invention is to produce a positive electrode and a negative electrode using a coating method that forms an excellent coating film such as a die coater, and even in the case of lamination, the negative electrode application part covers the positive electrode application part, and can be produced efficiently and reliable. An object of the present invention is to provide a laminated secondary battery having excellent properties and a method for manufacturing the same.

  In order to achieve the above object, the laminated secondary battery of the present invention has a non-coated portion at one end of a flat-plate negative electrode current collector, and a negative electrode active material layer is coated on both surfaces of the negative electrode current collector, A negative electrode having a coating area on the back surface larger than a coating area on the front surface, and a non-coated portion at one end of a flat plate-shaped positive electrode current collector, and a positive electrode active material layer is coated on both surfaces of the positive electrode current collector, The outer periphery position of the negative electrode active material layer on the surface of the negative electrode is outside the outer periphery position of the positive electrode active material layer on the surface of the positive electrode, as viewed from above, with the positive electrode having a smaller coating area on the back surface than the coated area of It is characterized by being laminated so as to be positioned.

  Further, in the multilayer secondary battery of the present invention, the outer periphery position of the negative electrode active material layer on the surface of the negative electrode is 0.5 to 5 mm outside the outer periphery position of the positive electrode active material layer on the surface of the positive electrode. It is preferable to be laminated so as to be positioned.

  Also, the method for manufacturing a laminated secondary battery of the present invention was formed intermittently by applying a negative electrode active material on the surface of a flat plate negative electrode current collector to form a negative electrode active material layer. A step of starting the application of the negative electrode active material on the back surface from a position of 0.1 to 5 mm from the end of each negative electrode active material layer on the surface to the start side, and forming a negative electrode active material layer; A step of intermittently applying a positive electrode active material to the surface of the body to form a positive electrode active material layer, and a step of 0. The process of starting the application of the positive electrode active material on the back surface from a position of 1 to 5 mm to form the positive electrode active material layer, and the start part of the surface of the negative electrode active material layer and the start part of the surface of the positive electrode active material layer, respectively Cut to a predetermined size as a reference point to form a strip-shaped negative electrode and a strip-shaped positive electrode The negative electrode and the positive electrode are arranged such that the outer peripheral position of the negative electrode active material layer on the surface of the negative electrode is located outside the outer peripheral position of the positive electrode active material layer on the surface of the positive electrode when viewed from above. Including a step of laminating the layers.

  According to the laminated secondary battery of the present invention and the method for manufacturing the same, even when a positive electrode and a negative electrode having different coated areas on the front and back surfaces are laminated, the end surface of the positive electrode coated portion is always inside from the end surface of the negative electrode coated portion. Therefore, it is possible to obtain a stacked secondary battery with high reliability and high production efficiency.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 2 is a plan view of the laminated battery according to the present invention after the double-side application of the negative electrode, and FIG. 3 is a plan view of the laminated battery according to the present invention after the double-side application of the positive electrode.

  As shown in FIG. 2, the negative electrode is composed of a front surface coating portion 1 and a back surface coating portion 2 in which a negative electrode active material is formed on a current collector 10 made of a negative electrode current collector, for example, a copper foil having a thickness of 10 μm. The negative electrode is a negative electrode active material composed of graphite powder, and a mixture prepared in a slurry state together with a binder composed of PVDF is applied onto both surfaces of the negative electrode current collector 10 on both sides by intermittent coating and dried. The surface application part 1 and the back surface application part 2 are formed, then rolled by a roll press, and slit-cut into a predetermined dimension to form a strip-shaped negative electrode.

  Further, as shown in FIG. 3, the positive electrode active material layer includes a front surface application portion 101 in which a positive electrode active material is formed on a positive electrode current collector 110 made of a strip-shaped aluminum foil having a thickness of 20 μm and a back surface application. Part 102. The positive electrode is a positive electrode active material made of lithium cobalt oxide, and a mixture prepared by adding a binder made of PVDF and a conductive agent made of acetylene black to form a slurry is placed on one side of the positive electrode current collector 110. By applying and drying on both sides by intermittent coating one after another, the front surface application part 101 and the back surface application part 102 are formed, then rolled by a roll press machine, and slit-cut into a predetermined dimension to form a strip-like positive electrode.

  Next, the formation of the negative electrode will be described in more detail. FIG. 4 is a front view of the strip-shaped negative electrode of the present invention, FIG. 4 (a) is a front view of the strip-shaped negative electrode at the end, and FIG. 4 (b) is a front view of the strip-shaped negative electrode at the center. . As shown in FIG. 2, in the formation of the negative electrode, a concave portion is formed in the central portion at the coating start portion 11 in the surface coating portion 1, and a convex portion is formed in the central portion at the coating end portion 12. After the coating of the front surface is finished, when the back surface is coated, the coating start portion is applied from a position shifted from the front surface coating end portion 12 to the coating start portion 11 side. The shifting distance is preferably 0.1 to 5 mm with the center as the base point. This is because of the structure in which the coating start portion is curved, the shift at the center portion is minimum and the end portion is maximum. When the distance shifted at the center is 0.1 to 5 mm, the shift at the end may be 0.1 to 10 mm. As shown in FIG. 4 (a), the strip-shaped negative electrode at the end obtained by the slit after the coating is applied is shifted to the right with respect to the back surface, and the strip-shaped negative electrode at the center is also illustrated in FIG. As shown in b), the coating portion on the front surface is applied while being shifted to the right side with respect to the back surface.

  Before laminating the strip-shaped negative electrode, cutting is performed to adjust the size of each negative electrode. At this time, as shown in FIGS. 4 (a) and 4 (b), the surface coating start portion 11 is used as a reference. When the cutting lines 7 and 9 are provided at a certain distance as the points 6 and 8, and the cut lines 7 and 9 are cut, the back surfaces of the reference points 6 and 8 of the coating start portion 11 on the surface of both the strip-shaped negative electrode at the end and the strip-shaped negative electrode at the center In the structure, there is always a structure with an application part. In this way, a negative electrode having a coating area on the back surface larger than that on the front surface is obtained.

  For the formation of the positive electrode, as shown in FIG. 3, the position where the coating start portion is shifted from the surface coating end portion to the opposite side of the coating start portion after the front surface coating is finished. Apply from. The shifting distance is preferably 0.1 to 5 mm. This is because the coating start portion is curved in the positive electrode as in the negative electrode. The strip-shaped positive electrode at the end obtained by the slit after coating is applied with the coating part on the front side shifted from the back side, and the cutting line is cut with a certain distance from the coating start part on the surface as the reference point Then, both the strip-shaped positive electrode at the end and the strip-shaped positive electrode at the center have a structure in which there is no application portion on the back surface of the reference point of the coating start portion on the surface. In this way, a positive electrode having a coating area on the back surface smaller than the coating area on the front surface is obtained. Here, the slit width of the positive electrode is narrower than that of the negative electrode, and the distance from the reference point on the surface of the positive electrode to the cutting line is set shorter than the distance from the reference point on the surface of the negative electrode to the cutting line.

  A battery element made of a laminate in which a predetermined number of layers are opposed to each other through a polyethylene nonwoven fabric as a separator between the positive electrode and the negative electrode produced as described above is produced. FIG. 1 is a schematic front view of a laminate when the positive electrode and the negative electrode of the present invention are laminated. Although the illustration of the separator is omitted in FIG. 1, when laminating the positive electrode and the negative electrode, the position of the coating outer periphery of the negative electrode active material layer on the surface of the negative electrode when viewed from above is the positive electrode active on the surface of the positive electrode. The material layer is laminated so as to be located outside the coating outer peripheral position. At this time, the lamination is preferably performed so that the coating outer peripheral position of the negative electrode active material layer on the surface of the negative electrode is positioned 0.5 to 5 mm outside the coating outer peripheral position of the positive electrode active material layer on the surface of the positive electrode. In the laminating operation, it is important that the positive electrode active material is always located inside the negative electrode active material, and the inner position is preferably about 1 to 2 mm from the negative electrode. Further, when the accuracy of the position in the laminating operation is ± 2 mm, the total is 4 mm, so it is preferable to take a margin of 5 mm.

  An external connection tab is joined to the non-application part of the electrode active material of a negative electrode and a positive electrode. The width of the external connection tab is preferably 4/5 to 2/5 of the length of the side of the exterior body of the tab drawer portion. In this case, when the heat-sealed portion of the joint portion of the exterior body is 1/5 of the exterior body, the tab width is maximized for all remaining widths, and 2/5 is minimized. This is because if the tab width is narrow, the current cannot be efficiently taken out by the resistance of the tab itself, and a tab width of a certain level or more is required. Then, exterior is performed. The exterior film is an aluminum laminate film having a three-layer structure of nylon / aluminum / polypropylene. In order to store the battery element, the film is provided with a storage portion by drawing so that the polypropylene side is concave. The battery element is housed in a battery element housing portion of the exterior film, the battery element is covered with the other exterior film, the joint portions are overlapped, and the three sides around the exterior body are fused by thermal fusion. An electrolyte solution is injected into the battery element housing portion from one side that is not fused, and then sealed with a heat fusion machine in a vacuum to produce a film-type laminated secondary battery.

The schematic front view of the laminated body at the time of laminating | stacking the positive electrode and negative electrode of this invention. The top view after double-sided coating of the negative electrode of the laminated battery by this invention. The top view after double-sided application | coating of the positive electrode of the laminated battery by this invention. The front view of the strip-shaped negative electrode of this invention, FIG. 4 (a) is a front view of the strip-shaped negative electrode of an edge part, FIG.4 (b) is the front view of the strip-shaped negative electrode of a center part. The top view explaining the negative electrode apply | coated to the single side | surface by the conventional coating method. The top view explaining the negative electrode apply | coated to both surfaces with the conventional coating method. The top view explaining the slit cutting of the negative electrode apply | coated to both surfaces by the conventional coating method. 8A is a front view of a conventional strip-shaped negative electrode, FIG. 8A is a front view of the strip-shaped negative electrode at the end, and FIG. 8B is a front view of the strip-shaped negative electrode at the center. The schematic front view of the laminated body at the time of laminating | stacking the conventional positive electrode and negative electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Surface application part 2,102 Back surface application part 3,5 (Strip shape of edge part) Negative electrode 4 (Strip shape of center part) Negative electrode 6, 8, 108 Reference point 7, 9, 109 Cutting line 10, 110 Collection Electrical bodies 11 and 21 Coating start part 11a Concave part 12 Coating end part 12b Convex parts 14 and 15 Reverse part 71 Slit wire 104 (strip shape) positive electrode

Claims (3)

A negative electrode active material layer having a non-applied portion on one end of a flat-plate negative electrode current collector and a negative electrode active material layer applied to both surfaces of the negative electrode current collector, and a coating area on the back surface larger than the surface coating area;
A positive electrode active material layer is applied to both sides of the positive electrode current collector having a non-applied portion at one end of a flat plate positive electrode current collector, and a positive electrode having a coating area on the back surface smaller than the coated area on the surface,
Layered type 2 characterized in that the outer periphery position of the negative electrode active material layer on the surface of the negative electrode viewed from above is positioned outside the outer periphery position of the positive electrode active material layer on the surface of the positive electrode. Next battery.   The negative electrode active material layer is coated such that the outer peripheral position of the negative electrode active material layer on the surface of the negative electrode is positioned 0.5 to 5 mm outside the outer peripheral position of the positive electrode active material layer on the surface of the positive electrode. The multilayer secondary battery according to claim 1. A step of intermittently applying a negative electrode active material to the surface of a flat negative electrode current collector to form a negative electrode active material layer, and a start side from the end of each negative electrode active material layer on the intermittently formed surface Starting the application of the negative electrode active material on the back surface from a position of 0.1 to 5 mm to form a negative electrode active material layer;
A step of intermittently applying a positive electrode active material to the surface of a flat positive electrode current collector to form a positive electrode active material layer, and a start side from the end of each positive electrode active material layer on the surface formed intermittently Starting the application of the positive electrode active material on the back surface from a position of 0.1 to 5 mm on the opposite side and forming a positive electrode active material layer;
Forming a strip-shaped negative electrode and a strip-shaped positive electrode by cutting each of the start portion of the surface of the negative electrode active material layer and the start portion of the surface of the positive electrode active material layer with predetermined dimensions as reference points;
The negative electrode and the positive electrode are stacked so that the outer periphery position of the negative electrode active material layer on the surface of the negative electrode is located outside the outer periphery position of the positive electrode active material layer on the surface of the positive electrode when viewed from above. And a process for producing a laminated secondary battery.

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