Electrode group and secondary battery

Abstract

An electrode group according to an embodiment includes a positive electrode and a negative electrode. The electrode group is obtained by winding the positive electrode and the negative electrode with a separator therebetween. In the electrode group, at least part of the electrode group from a start point in the winding to an end point in the winding is provided with a portion in which four or more layers of the positive electrode and the negative electrode are wound in combination.

Description

Electrode group and secondary battery

[0001] An embodiment of the present invention relates to an electrode group and a secondary battery.

[0002] In recent years, secondary batteries such as lead-acid batteries and nickel-metal hydride batteries have been used as power sources for electric vehicles, hybrid vehicles, electric motorcycles, forklifts, etc. Recently, there has been active development toward the adoption of lithium-ion secondary batteries, which have high energy density, and development is being carried out while taking into consideration factors such as long life and safety.

[0003] For example, an electrode assembly used in a lithium ion secondary battery (hereinafter referred to as a secondary battery) may be manufactured by winding a positive electrode and a negative electrode with a separator interposed therebetween. In manufacturing such an electrode assembly, one layer of positive electrode and one layer of negative electrode may be combined and wound, but in this case, there is a concern that manufacturing the electrode assembly may take a long time.

[0004] International Publication No. 2012 / 014422

[0005] The problem to be solved by the present invention is to provide an electrode group and a secondary battery that can be manufactured in a short manufacturing time.

[0006] In order to solve the above problem, the electrode group of the embodiment is an electrode group that includes a positive electrode and a negative electrode, and the positive electrode and the negative electrode are wound with a separator interposed therebetween, and at least a portion of the electrode group from the starting point of the winding to the end point of the winding has a portion where four or more layers of the positive electrode and the negative electrode are combined and wound.

[0007] Fig. 1 is a perspective view schematically showing an electrode group according to a first embodiment. Fig. 2 is a partially developed perspective view of the electrode group according to the first embodiment as seen from above. Fig. 3 is a cross-sectional view of the electrode group according to the first embodiment taken along line II in Fig. 1. Fig. 4 is a cross-sectional view schematically showing an electrode group according to a modified example of the first embodiment. Fig. 5 is a perspective view schematically showing a secondary battery according to a second embodiment.

[0008] Hereinafter, an electrode group and a secondary battery according to an embodiment of the present invention will be described with reference to the drawings. The disclosure is merely an example, and appropriate modifications that are easily conceivable by those skilled in the art while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, in order to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals, and detailed descriptions may be appropriately simplified or omitted.

[0009] First Embodiment An electrode group 5 of a first embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view that schematically shows the electrode group 5 according to the first embodiment, and Fig. 2 is a perspective view of the electrode group 5 according to the first embodiment, seen from above, with the electrode group 5 being partially developed. The electrode group 5 of this embodiment is a combination of four or more layers of positive electrodes 13 and negative electrodes 15, and Fig. 2 shows two layers of positive electrodes 13 and negative electrodes 15.

[0010] 1 and 2 , the electrode group 5 is produced, for example, by winding a positive electrode 13 and a negative electrode 15 with a separator 4 sandwiched therebetween, and then pressure-molding the entire wound body into a flat shape in the stacking direction (Y direction) of the positive electrode 13 and the negative electrode 15. This pressure molding reduces the space within the electrode group 5, so that, for example, when the electrode group 5 is housed in a case of a secondary battery, many positive electrodes 13 and negative electrodes 15 can be housed in the limited space within the case. However, the method for producing the electrode group 5 is not limited to this, and any method may be used as long as the positive electrode 13 and the negative electrode 15 are wound with the separator 4 interposed therebetween.

[0011] The positive electrode 13 has a strip-shaped positive electrode current collector 13a having a long side 90 (Z direction) and a short side 92 (X direction). A positive electrode mixture layer 130, to which a positive electrode material is applied parallel to the long side 90, and an uncoated portion 70a of the positive electrode mixture layer, to which the positive electrode material is not applied, are formed on the positive electrode current collector 13a. The negative electrode 15 has a strip-shaped negative electrode current collector 15a having a long side 90 and a short side 92. A negative electrode mixture layer 150, to which a negative electrode material is applied parallel to the long side 90, and an uncoated portion 70b of the negative electrode mixture layer, to which the negative electrode material is not applied, are formed on the negative electrode current collector 15a. A separator 4 is disposed over the positive electrode mixture layer 130, and a separator 4 is disposed over the negative electrode mixture layer 150.

[0012] In the electrode group 5 having the wound structure of this embodiment, the uncoated portion 70a of the positive electrode current collector 13a protrudes in the opposite direction to the protruding direction of the uncoated portion 70b of the negative electrode current collector 15a. As a result, the uncoated portion 70a and the uncoated portion 70b are provided at both ends of the electrode group 5 in the X direction. The protruding directions of the uncoated portion 70a of the positive electrode mixture layer and the uncoated portion 70b of the negative electrode mixture layer are not limited to these. The uncoated portion 70a and the uncoated portion 70b may protrude in the same direction and both may be provided at one end of the electrode group 5.

[0013] The electrode group 5 will be further described with reference to Fig. 3. Fig. 3 is a cross-sectional view schematically showing the electrode group 5 according to the first embodiment, taken along line II in Fig. 1. Note that Fig. 3 does not illustrate the separator 4 disposed between the positive electrode 13 and the negative electrode 15.

[0014] In the electrode group 5 of this embodiment, as shown in Fig. 3, four or more layers of positive electrodes 13 and negative electrodes 15 are wound in combination in at least a portion from the start point P to the end point P' of winding the electrode group 5. In the illustrated example, only two layers of positive electrodes 13 and negative electrodes 15 are wound in one turn from the start point P of winding, and four layers of positive electrodes 13 and negative electrodes 15 are wound in combination from the second turn to the end point P'. In this way, by combining four or more layers of positive electrodes 13 and negative electrodes 15 in at least a portion of the electrode group 5, the manufacturing time of the electrode group 5 can be shortened when manufacturing an electrode group 5 having the same battery capacity as an electrode group 5 manufactured by combining and winding one layer of positive electrode 13 and one layer of negative electrode 15. Here, it is sufficient that at least a part of the electrode group 5 has four or more layers of positive electrodes 13 and negative electrodes 15 combined together, and several turns from the starting point P, several turns in the middle, or several turns around the outermost periphery may be wound with only two layers of positive electrodes 13 and negative electrodes 15.

[0015] The electrode group 5 of this embodiment has a configuration in which four or more layers of positive electrodes 13 and negative electrodes 15 are combined in at least a portion of the electrode group 5, but it is preferable that the number of layers of the positive electrodes 13 and the negative electrodes 15 is equal. For example, two layers of positive electrodes 13 may be combined with two layers of negative electrodes 15, or three layers of positive electrodes 13 with three layers of negative electrodes 15. As a result, in the electrode group 5 after winding, the positive electrodes 13 and the negative electrodes 15 face each other with the separator 4 interposed therebetween, and an electrode group 5 that ensures battery capacity can be obtained.

[0016] Furthermore, in FIG. 3, the positive electrode 13 is arranged on the innermost periphery of the electrode group 5, but this is not limiting, and the electrode arranged on the innermost periphery may be either the positive electrode 13 or the negative electrode 15.

[0017] A modified example of the electrode group 5 will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view (cross-section II shown in Fig. 1) that schematically shows a modified example of the electrode group 5 according to the first embodiment. Note that Fig. 4 does not illustrate the separator 4 disposed between the positive electrode 13 and the negative electrode 15.

[0018] In the modified electrode group 5, as shown in Fig. 4 , two layers of positive electrodes 13 and two layers of negative electrodes 15 are combined and wound from a start point P to an end point P' of the winding of the electrode group 5. By combining two layers of positive electrodes 13 and two layers of negative electrodes 15 from the start point P to the end point P' of the electrode group 5, the manufacturing time of the electrode group 5 can be shortened when manufacturing an electrode group 5 having the same battery capacity as an electrode group 5 manufactured by combining and winding one layer of positive electrodes 13 and one layer of negative electrodes 15. Specifically, in the modified electrode group 5, when manufacturing an electrode group 5 having the same battery capacity as an electrode group 5 manufactured by combining and winding one layer of positive electrodes 13 and one layer of negative electrodes 15, the manufacturing time of the electrode group 5 is approximately half.

[0019] In the modified example of the electrode group 5, two layers of positive electrodes 13 and two layers of negative electrodes 15 are combined from the start point P to the end point P' of the electrode group 5, but by combining the positive electrodes 13 and negative electrodes 15 continuously from the start point P to the end point P', there is no need for a process of increasing or decreasing the number of positive electrodes 13 or negative electrodes 15 during winding, and the electrode group 5 can be easily manufactured from the start point P to the end point P'.

[0020] Furthermore, in the modified example of the electrode group 5, the positive electrode 13 and the negative electrode 15 each have two layers, and therefore, compared to a combination of five or more layers of positive electrodes 13 and negative electrodes 15, misalignment of the electrode group 5 due to the combination of the positive electrodes 13 and the negative electrodes 15 is less likely to occur. As a result, for example, when the electrode group 5 is housed in a case of a secondary battery, the electrode group 5 can be housed appropriately in the case, and short-circuiting between the positive electrodes 13 and the negative electrodes 15 due to misalignment can also be suppressed.

[0021] In the electrode group 5 of the first embodiment described above, four or more layers of positive electrodes 13 and negative electrodes 15 are combined and wound in at least a portion from the start point P to the end point P′ in the winding of the electrode group 5. This allows the manufacturing time of the electrode group 5 to be shortened when manufacturing an electrode group 5 having the same battery capacity as an electrode group 5 manufactured by combining and winding one layer of positive electrode 13 and one layer of negative electrode 15, making it possible to provide an electrode group 5 that can be manufactured in a short manufacturing time.

[0022] Second Embodiment A secondary battery 1 according to a second embodiment will be described with reference to Fig. 5. Fig. 5 is a perspective view schematically showing the secondary battery 1 according to the second embodiment.

[0023] As shown in FIG. 5 , the secondary battery 1 has an exterior case 3, and the electrode group 5 having the wound structure of the first embodiment is housed inside the exterior case 3. Inside the exterior case 3, the electrode group 5 is impregnated with an electrolyte solution (not shown). The electrolyte solution is injected, for example, through a liquid injection port (not shown) provided in a lid member 7, and the liquid injection port is closed with a sealing plate 19 after the electrolyte solution has been injected. The electrolyte solution used is a non-aqueous electrolyte solution prepared by dissolving an electrolyte (e.g., a lithium salt) in a non-aqueous solvent. The non-aqueous solvent may be used alone or in combination of two or more types.

[0024] A gas exhaust valve 21 may be provided on the surface of the lid member 7 together with a sealing plate 19. Furthermore, for example, a pair of a positive electrode external terminal 23a and a negative electrode external terminal 23b are attached to the surface of the lid member 7. The positive electrode external terminal 23a and the negative electrode external terminal 23b are electrically connected to the uncoated portion 70a of the positive electrode mixture layer and the uncoated portion 70b of the negative electrode mixture layer of the electrode group 5, respectively. Terminal insulators 35 may be provided between the positive electrode external terminal 23a, the negative electrode external terminal 23b, and the lid member 7 to maintain insulation therebetween.

[0025] The secondary battery 1 of the second embodiment described above includes the electrode group 5 of the first embodiment. The electrode group 5 of the first embodiment can be manufactured in a short manufacturing time, and therefore, when this electrode group 5 is used in the secondary battery 1, the manufacturing time of the secondary battery 1 can also be shortened. This makes it possible to provide a secondary battery 1 that can be manufactured in a short manufacturing time.

[0026] According to the electrode group 5 of at least one embodiment described above, four or more layers of positive electrodes 13 and negative electrodes 15 are combined and wound in at least a portion from the start point P to the end point P′ in the winding of the electrode group 5. This allows the manufacturing time of the electrode group 5 to be shortened when manufacturing an electrode group 5 having the same battery capacity as an electrode group 5 manufactured by combining and winding one layer of positive electrode 13 and one layer of negative electrode 15, making it possible to provide an electrode group 5 and a secondary battery 1 that can be manufactured in a short manufacturing time.

[0027] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are within the scope and spirit of the invention, and are also within the scope of the inventions described in the claims and their equivalents.

Claims

1. An electrode group comprising a positive electrode and a negative electrode, the positive electrode and the negative electrode being wound with a separator interposed therebetween, wherein at least a portion of the electrode group from the starting point of the winding to the end point of the winding has a portion where four or more layers of the positive electrode and the negative electrode are combined and wound.

2. The electrode group according to claim 1, wherein two layers of the positive electrode and two layers of the negative electrode are combined and wound from the start point of the winding of the electrode group to the end point of the winding.

3. A secondary battery comprising the electrode group according to any one of claims 1 and 2 and an electrolyte solution.

4. The secondary battery according to claim 3, further comprising an outer case that houses the electrode group and an electrolyte.

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