Collector

Abstract

To provide a collector which is hardly extended when joining an electrode layer.SOLUTION: A collector to which an electrode layer of a secondary battery is joined comprises: a conductive porous membrane including a first face at the side where the electrode layer is joined and a second face at an opposite side of the first face, the porous membrane including a plurality of first openings on the first face and including a plurality of cavities inside; and a resin layer consisting of a resin, which contains a conductive assistant, and at least partially disposed on the first face. The porous membrane includes a plurality of cavities, through which the resin layer can infiltrate, in a region closer to the second face than the resin layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a current collector. [Background technology]

[0002] Patent Document 1 discloses a resin current collector made of a resin to which a conductive material has been added. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-198197 A Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, in a secondary battery using a current collector, a negative electrode collector, a negative electrode layer, a separator, a positive electrode layer, and a positive electrode collector are stacked in the stacking direction. That is, the positive electrode collector is configured so that it does not come into contact with the negative electrode collector and the negative electrode layer by the separator. When manufacturing a secondary battery, a positive electrode layer is bonded to the separator side surface of the positive electrode collector. When bonding the positive electrode layer to the positive electrode collector, pressure is applied to the positive electrode collector. As a result, the positive electrode collector made of resin stretches to the periphery due to the pressure. In this case, the stretched portion of the positive electrode collector may enter the negative electrode layer side from the periphery of the separator beyond the separator, and the positive electrode collector and the negative electrode layer may come into contact with each other.

[0005] Disclosed herein is a current collector that is less prone to stretching when an electrode layer is bonded to it. [Means for solving the problem]

[0006] In a first aspect of the technology disclosed in the present specification, a current collector to which an electrode layer of a secondary battery is bonded may include a conductive porous membrane having a first surface on the side to which the electrode layer is bonded and a second surface opposite to the first surface, the porous membrane having a plurality of first openings on the first surface and a plurality of voids therein, and a resin layer made of a resin containing a conductive assistant, at least a portion of which is disposed on the first surface. The porous membrane may have a plurality of voids into which the resin layer can penetrate in a region closer to the second surface than the resin layer.

[0007] According to the above configuration, when the electrode layer is bonded to the porous membrane from the first surface side of the porous membrane, the resin layer disposed on the first surface of the porous membrane enters into the multiple voids inside the porous membrane through the multiple first openings. Therefore, it is possible to prevent the resin layer of the current collector from extending outside the porous membrane. As a result, for example, when the current collector having the above configuration is used as a positive electrode current collector of a secondary battery, even if pressure is applied to the positive electrode current collector, it is possible to prevent the positive electrode current collector from contacting the negative electrode layer.

[0008] In a second aspect, in the first aspect above, the total volume of the multiple voids between the first surface and the second surface in a specific area of ​​the first surface in which the resin layer is disposed may be larger than the volume of the resin layer.

[0009] According to the above-mentioned configuration, the entire resin layer can penetrate into the plurality of voids inside the porous film, and therefore the current collector can be further prevented from stretching.

[0010] In a third aspect, in the first or second aspect, the second surface may be provided with a plurality of second openings. An average value of the opening areas of the plurality of first openings may be greater than an average value of the opening areas of the plurality of second openings.

[0011] According to the above configuration, the resin layer is more likely to enter the multiple voids inside the porous membrane than in the configuration in which the resin layer is disposed on the second surface, and therefore, when the electrode layer is bonded to the porous membrane from the first surface side of the porous membrane, the amount of the resin layer that enters the multiple voids inside the current collector can be increased, and the current collector can be more effectively prevented from stretching. [Brief description of the drawings]

[0012] [Figure 1] FIG. [Diagram 2] 3A to 3C are diagrams showing a manufacturing process of the current collector 10. [Diagram 3] FIG. 1 shows a manufacturing process for a secondary battery 40 (1). [Figure 4] FIG. 2 shows the manufacturing process of the secondary battery 40. [Diagram 5] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Example) (Configuration of current collector 10; FIG. 1) The current collector 10 of this embodiment will be described with reference to Fig. 1. The up-down and left-right directions in each of the following figures are added for ease of understanding, and do not indicate the directions in the actual state of use.

[0014] As shown in FIG. 1, the current collector 10 includes a conductive porous film 12 having a plurality of holes (a plurality of voids S). The current collector 10 also includes an upper resin layer 14 and a lower resin layer 16. The porous film 12 in this embodiment is made of a conductive material such as tubular carbon, a carbon composite material, or a metal. In a modified example, the porous film 12 may be formed as a conductive film by coating a metal on the surface of a porous film made of a material having no conductivity such as cellulose, polyolefin, or polyimide. The porosity of the porous film 12 is, for example, 30 to 95%. Since the porous film 12 has a plurality of voids S, a plurality of upper surface openings 12b due to the plurality of voids S are formed on the upper surface 12a of the porous film 12, and a plurality of lower surface openings 12d due to the plurality of voids S are formed on the lower surface 12c of the porous film 12. The average value of the opening areas of the upper surface openings 12b is greater than the average value of the opening areas of the lower surface openings 12d.

[0015] The upper resin layer 14 and the lower resin layer 16 are each made of a resin 20 containing a conductive assistant 18. The conductive assistant 18 is, for example, particulate carbon, fibrous carbon, tubular carbon, porous carbon, chip-like carbon, metal-coated carbon, or metal particles. When the current collector 10 is used as a positive electrode current collector, the resin 20 is, for example, modified PVdf or an acrylic acid-based resin. When the current collector 10 is used as a negative electrode current collector, the resin 20 is, for example, polyacrylic acid, a polyacrylic acid-based resin, polyamide-imide, polyimide, or styrene-butadiene rubber.

[0016] The upper resin layer 14 is disposed on the upper surface 12a of the porous membrane 12, and a portion of it penetrates into the multiple voids S inside the porous membrane 12. The upper resin layer 14 that has penetrated into the multiple voids S inside the porous membrane 12 penetrates into the multiple voids S in the region above the central axis C in the thickness direction (i.e., the up-down direction) of the porous membrane 12. The other portion of the upper resin layer 14 (i.e., the upper resin layer 14 that has not penetrated into the multiple voids S inside the porous membrane 12) is disposed on the upper surface 12a of the porous membrane 12.

[0017] The lower resin layer 16 is disposed on the lower surface 12c of the porous membrane 12, and a part of it penetrates into the multiple voids S inside the porous membrane 12. The lower resin layer 16 that penetrates into the multiple voids S inside the porous membrane 12 penetrates into the multiple voids S in the region below the central axis C. The other part of the lower resin layer 16 (i.e., the lower resin layer 16 that does not penetrate into the multiple voids S inside the porous membrane 12) is disposed on the lower surface 12c of the porous membrane 12. The porous membrane 12 has multiple voids S into which the upper resin layer 14 can penetrate in a region on the lower surface 12c side of the upper resin layer 14. That is, the upper resin layer 14 and the lower resin layer 16 are not in contact with each other.

[0018] In this embodiment, the volume of the upper resin layer 14 is approximately the same as the volume of the lower resin layer 16. The distance L1 from the central axis C to the upper surface of the upper resin layer 14 is smaller than the distance L2 from the central axis C to the lower surface of the lower resin layer 16. That is, the amount of the upper resin layer 14 entering the multiple voids S inside the porous membrane 12 is greater than the amount of the lower resin layer 16 entering the multiple voids S inside the porous membrane 12.

[0019] (Manufacturing method of current collector 10; FIG. 2) A method for producing the current collector 10 will be described with reference to FIGS.

[0020] As shown in FIG. 2, first, the porous membrane 12, the upper resin layer 14, and the lower resin layer 16 are prepared (preparation step).

[0021] Next, the upper resin layer 14 is disposed on the upper surface 12a of the porous membrane 12, and the lower resin layer 16 is disposed on the lower surface 12c of the porous membrane 12. Then, a part of the upper resin layer 14 is infiltrated into the multiple voids S inside the porous membrane 12, and a part of the lower resin layer 16 is infiltrated into the multiple voids S inside the porous membrane 12 (resin layer infiltration process). As a method for infiltrating a part of the upper resin layer 14 into the multiple voids S inside the porous membrane 12, the upper resin layer 14 in a slurry form is disposed on the upper surface 12a of the porous membrane 12, and a part of the upper resin layer 14 in a slurry form is infiltrated into the multiple voids S inside the porous membrane 12 by its own weight. In this case, the upper resin layer 14 that has entered the multiple voids S inside the porous membrane 12 is fixed to the multiple voids S inside the porous membrane 12 by the anchor effect. Alternatively, a film-like upper resin layer 14 may be disposed on the upper surface 12a of the porous membrane 12, and then a part of the upper resin layer 14 may be infiltrated into the plurality of voids S inside the porous membrane 12 by thermocompression bonding. As described above, the average value of the opening area of ​​the plurality of upper openings 12b is larger than the average value of the opening area of ​​the plurality of lower openings 12d. Therefore, compared with the lower resin layer 16, the upper resin layer 14 is more likely to infiltrate into the plurality of voids S inside the porous membrane 12 through the upper openings 12b. Therefore, as shown in FIG. 1, the distance L1 from the central axis C to the upper surface of the upper resin layer 14 is smaller than the distance L2 from the central axis C to the lower surface of the lower resin layer 16. In this manner, the current collector 10 of FIG. 1 is completed.

[0022] In this embodiment, the amounts of the upper resin layer 14 and the lower resin layer 16 are adjusted so that the total volume of the multiple voids S between the upper surface 12a and the lower surface 12c in the specific area SA on the upper surface 12a of the porous membrane 12, where the upper resin layer 14 is disposed, is larger than the sum of the volume of the upper resin layer 14 and the volume of the lower resin layer 16. Therefore, the upper resin layer 14 and the lower resin layer 16 penetrate into only some of the multiple voids S in the specific area SA.

[0023] (Secondary battery manufacturing method; Figures 3 to 5) 3 to 5, a method for manufacturing a secondary battery 40 (see FIG. 5) that utilizes a positive electrode current collector 30 and a negative electrode current collector 32 having the same configuration as current collector 10 will be described.

[0024] First, as shown in Fig. 3, a positive electrode collector 30 and a positive electrode layer 34 are prepared (preparation step). In this state, a part of the upper resin layer 14 and a part of the lower resin layer 16 penetrate into a plurality of voids S inside the porous membrane 12. The resin 20 of the positive electrode collector 30 is, for example, modified PVdf or an acrylic acid-based resin. Other thermoplastic resins, thermosetting resins, conductive resins, etc. may also be used as the resin 20 of the positive electrode collector 30. The positive electrode layer 34 contains a positive electrode active material, a conductive assistant, and a binder.

[0025] Next, the positive electrode layer 34 is joined to the positive current collector 30 (positive electrode layer joining step). Specifically, pressure is applied to the positive electrode layer 34 from above the positive current collector 30 to join the positive electrode layer 34 to the positive current collector 30. In this case, the positive electrode layer 34 first comes into contact with the upper resin layer 14 of the positive current collector 30 from above. As described above, the upper resin layer 14 and the lower resin layer 16 have infiltrated only some of the multiple voids S in the specific region SA of the positive current collector 30, and there are multiple voids S between the upper resin layer 14 and the lower resin layer 16 that have not been infiltrated by the resin layers. Therefore, when pressure is applied to the positive electrode layer 34 from above the positive current collector 30, a part of the upper resin layer 14 disposed on the upper surface 12a of the positive current collector 30 can penetrate into the multiple voids S inside the porous membrane 12 without extending outside the porous membrane 12. Then, as the positive electrode layer 34 moves further downward, the upper resin layer 14 is pressed into the multiple voids S inside the porous membrane 12. As a result, the positive electrode layer 34 is joined to the positive current collector 30 as shown in FIG. 4.

[0026] As described above, when the positive electrode layer 34 is joined to the positive current collector 30, a part of the upper resin layer 14 disposed on the upper surface 12a of the positive current collector 30 further penetrates into the multiple voids S inside the porous membrane 12. On the other hand, a part of the lower resin layer 16 disposed on the lower surface 12c of the positive current collector 30 does not penetrate into the multiple voids S inside the porous membrane 12. Therefore, the distance L3 from the central axis C to the upper surface of the upper resin layer 14 is shorter than the distance L4 from the central axis C to the lower surface of the lower resin layer 16. That is, the upper resin layer 14 penetrates into the multiple voids S inside the porous membrane 12 by a larger amount than the lower resin layer 16. In this embodiment, even after the positive electrode layer 34 is joined to the positive current collector 30, the upper resin layer 14 and the lower resin layer 16 do not penetrate into some of the multiple voids S inside the porous membrane 12, specifically, into the multiple voids S between the lower surface of the upper resin layer 14 and the lower resin layer 16.

[0027] In addition, the negative electrode layer 36 in FIG. 5 can be joined to the negative electrode collector 32 in the same manner as above. The negative electrode collector 32 and the negative electrode layer 36 correspond to a configuration in which the positive electrode collector 30 and the positive electrode layer 34 in FIG. 4 are inverted upside down. The resin (not shown) of the negative electrode collector 32 is, for example, polyacrylic acid, polyacrylic acid-based resin, polyamide-imide, polyimide, or styrene-butadiene rubber. Other thermoplastic resins, thermosetting resins, conductive resins, and the like may also be used as the resin of the negative electrode collector 32. The negative electrode layer 36 contains a negative electrode active material, a conductive assistant, and a binder.

[0028] Thereafter, the positive electrode collector 30, the positive electrode layer 34, the separator 38, the negative electrode layer 36, and the negative electrode collector 32 are laminated by a known method to complete the secondary battery 40 of Fig. 5. In the secondary battery 40, the positive electrode collector 30, the positive electrode layer 34, the separator 38, the negative electrode layer 36, and the negative electrode collector 32 are laminated in the vertical direction. The separator 38 is made of, for example, polyethylene (PE) or polypropylene (PP).

[0029] (Effects of this embodiment) 3, the positive electrode current collector 30 (an example of a "current collector") to which the positive electrode layer 34 of the secondary battery 40 is bonded is a conductive porous membrane 12 having an upper surface 12a (an example of a "first surface") on the side to which the positive electrode layer 34 is bonded and a lower surface 12c (an example of a "second surface"), the porous membrane 12 having a plurality of upper surface openings 12b (an example of a "first opening") on the upper surface 12a and having a plurality of voids S therein, and an upper resin layer 14 made of a resin 20 containing a conductive assistant 18, at least a part of which is disposed on the upper surface 12a. The porous membrane 12 has a plurality of voids S into which the upper resin layer 14 can penetrate in a region of the lower surface 12c beyond the upper resin layer 14.

[0030] According to the above configuration, when the positive electrode layer 34 is bonded to the porous membrane 12 from the upper surface 12a side of the porous membrane 12, the upper resin layer 14 disposed on the upper surface 12a of the porous membrane 12 enters into the multiple voids S inside the porous membrane 12 through the multiple upper surface openings 12b. This makes it possible to suppress the positive electrode collector 30 from extending. As a result, when the positive electrode collector 30 having the above configuration is used as the positive electrode collector 30 of the secondary battery 40, it is possible to suppress the positive electrode collector 30 from coming into contact with the negative electrode layer 36.

[0031] Furthermore, the total volume of the plurality of voids S between the upper surface 12a and the lower surface 12c in the specific area SA on the upper surface 12a where the upper resin layer is disposed is larger than the volume of the upper resin layer .

[0032] According to the above-mentioned configuration, the entire upper resin layer 14 can enter into the multiple voids S inside the porous membrane 12. Therefore, the positive electrode current collector 30 can be further prevented from stretching.

[0033] Further, a plurality of lower surface openings 12d are provided on the lower surface 12c. The average value of the opening areas of the plurality of upper surface openings 12b is greater than the average value of the opening areas of the plurality of lower surface openings 12d.

[0034] According to the above configuration, the upper resin layer 14 is more likely to enter the multiple voids S inside the porous membrane 12 than in a configuration in which the upper resin layer 14 is disposed on the lower surface 12c. Therefore, when the positive electrode layer 34 is joined to the porous membrane 12 from the upper surface 12a side of the porous membrane 12, the amount of the upper resin layer 14 that enters the multiple voids S inside the positive current collector 30 can be increased, and the extension of the positive current collector 30 can be further suppressed.

[0035] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Modifications of the above-mentioned embodiments are listed below.

[0036] (First Modification) In the current collector 10 of Fig. 1 before the electrode layers are bonded, the upper resin layer 14 may be provided only on the upper surface 12a of the porous membrane 12. In other words, the upper resin layer 14 does not have to penetrate into the multiple voids S. The same applies to the lower resin layer 16.

[0037] (Second Modification) The total volume of multiple gaps S between the upper surface 12a and the lower surface 12c in a specific area SA of the upper surface 12a in Figure 1 where the upper resin layer 14 is arranged may be smaller than the volume of the upper resin layer 14.

[0038] (Third Variant) The average value of the opening area of ​​the multiple upper surface openings 12b in FIG. 1 may be the same as the average value of the opening area of ​​the multiple lower surface openings 12d, or the average value of the opening area of ​​the multiple upper surface openings 12b may be smaller than the average value of the opening area of ​​the multiple lower surface openings 12d.

[0039] (Fourth Modification) The current collector 10 in FIG.

[0040] (Fifth Modification) In the positive electrode current collector 30 to which the positive electrode layer 34 of FIG. 4 is bonded, the amounts of the upper resin layer 14 and the lower resin layer 16 may be adjusted so that the lower surface of the upper resin layer 14 and the upper surface of the lower resin layer 16 are in contact with each other.

[0041] The technical elements described in this specification or drawings have technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0042] 10: Current collector, 12: Porous membrane, 12a: Top surface, 12b: Top opening, 12c: Bottom surface, 12d: Bottom opening, 14: Upper resin layer, 16: Lower resin layer, 18 : Conductive aid, 20: Resin, 30: Positive electrode current collector, 32: Negative electrode current collector, 34: Positive electrode layer, 36: Negative electrode layer, 38: Separator, 40: Secondary battery, C: Central axis

Claims

1. A current collector to which an electrode layer of a secondary battery is joined, A conductive porous membrane having a first surface to which the electrode layer is bonded and a second surface opposite to the first surface, the porous membrane having a plurality of first openings on the first surface and a plurality of voids therein; a resin layer made of a resin containing a conductive assistant, at least a portion of which is disposed on the first surface; the porous film has a plurality of voids into which the resin layer can penetrate in a region closer to the second surface than the resin layer.

2. The current collector according to claim 1 , a total volume of the plurality of voids between the first surface and the second surface in a specific region of the first surface where the resin layer is disposed is larger than a volume of the resin layer.

3. The current collector according to claim 1 or 2, The second surface is provided with a plurality of second openings, a current collector, wherein an average value of an opening area of ​​the plurality of first openings is greater than an average value of an opening area of ​​the plurality of second openings.

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