Electrode body

Abstract

This invention provides a technology to improve the adhesion between the resin layer and the electrode layer of a current collector. [Solution] The electrode body may comprise an electrode layer and a current collector bonded to the surface of the electrode layer. The surface of the electrode layer may have a plurality of irregularities. The current collector may comprise a resin layer bonded to the surface of the electrode layer. The volume of the resin layer per unit area of ​​the surface to which the electrode layer and the resin layer are bonded may be greater than the spatial volume defined by the plurality of irregularities per unit area of ​​the surface to which the electrode layer and the resin layer are bonded.

Description

Technical Field

[0001] The technology disclosed in this specification relates to an electrode body.

Background Art

[0002] Patent Document 1 discloses an electrode body for a battery. The electrode body includes an electrode layer and a current collector joined to the electrode layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the electrode body as described above, a current collector having a resin layer may be used. Usually, there are a plurality of irregularities on the surface of the electrode layer. Due to the plurality of irregularities, a relatively large spatial volume is defined on the surface of the electrode layer. When the electrode layer having such a surface and the resin layer of the current collector are simply joined, the resin layer may not be able to enter to the bottom surface of the concave portion of the spatial volume of the electrode layer, and there is a possibility that a gap is formed between the resin layer and the electrode layer. As a result, the adhesion between the resin layer of the current collector and the electrode layer may be reduced.

[0005] This specification provides a technology for improving the adhesion between the resin layer of the current collector and the electrode layer.

Means for Solving the Problems

[0006] In a first aspect of this technology, the electrode body may comprise an electrode layer and a current collector bonded to the surface of the electrode layer. The surface of the electrode layer may have a plurality of irregularities. The current collector may comprise a resin layer bonded to the surface of the electrode layer. The volume of the resin layer per unit area of ​​the surface to which the electrode layer and the resin layer are bonded may be greater than the spatial volume defined by the plurality of irregularities per unit area of ​​the surface to which the electrode layer and the resin layer are bonded.

[0007] In the electrode body described above, the volume of the resin layer is greater than the spatial volume of the electrode layer per unit area of ​​the surface where the electrode layer and the resin layer are joined. With this configuration, when joining the electrode layer and the resin layer, the resin layer, which is present in a large amount relative to the spatial volume of the electrode layer, can penetrate to the bottom surface of the recess in the electrode layer. Therefore, it is difficult for a gap to form between the resin layer and the electrode layer, and the adhesion between the resin layer and the electrode layer of the current collector can be improved.

[0008] In a second aspect of this technology, in the first aspect described above, the spatial volume may be calculated based on the state of the plurality of irregularities on the surface of the electrode layer.

[0009] With this configuration, the spatial volume can be calculated from the state of multiple irregularities on the surface of the electrode layer, and therefore the amount of resin required to produce a resin layer with a volume that satisfies the relationship between the spatial volume of the electrode layer and the resin layer can be controlled.

[0010] In a third aspect of this technology, in the first or second aspect described above, the plurality of irregularities on the surface of the electrode layer may comprise a plurality of recesses, and the spatial volume may be calculated based on the integral of the depths of the plurality of recesses.

[0011] With this configuration, the spatial volume can be calculated from the integral of the depths of multiple recesses, allowing for precise control of the amount of resin required to produce a resin layer with a volume that satisfies the relationship between the spatial volume and the resin layer.

[0012] In a fourth aspect of this technology, in any one of the first to third aspects described above, the resin layer may contain a plurality of conductive additives.

[0013] This configuration allows multiple conductive additives, along with the resin layer, to reach the bottom surface of the recesses in the electrode layer. This improves the conductivity between the resin layer and the electrode layer. [Brief explanation of the drawing]

[0014] [Figure 1] A diagram showing the schematic configuration of the electrode body. [Figure 2] A diagram illustrating the method for fabricating electrode bodies. [Figure 3] A diagram illustrating the method for fabricating electrode bodies. [Figure 4] A diagram illustrating a method for calculating spatial volume, schematically showing the contour surfaces of multiple irregularities. [Figure 5] This diagram illustrates the method for calculating spatial volume, and shows the load area ratio relative to the height of the contour curved surface in Figure 4. [Modes for carrying out the invention]

[0015] Referring to the drawings, the electrode body 10 of this embodiment will be described. The electrode body 10 is used as a positive or negative electrode when manufacturing a battery. As shown in Figure 1, the electrode body 10 comprises an electrode layer 12 and a current collector 14.

[0016] The electrode layer 12 is formed using an electrode active material. When the electrode body 10 is used as the positive electrode, the electrode active material is, for example, LCO (LiCoO2), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 It can be formed from NCM-based materials such as O2, LFP (LiFePO4), LiMn2O4, etc. However, the electrode active material is not limited to these. For example, when electrode body 10 is used as a negative electrode, the electrode active material can be Si, SiO, graphite, LTO (Li4Ti5O4). 12)It may be formed by etc. Also, the electrode active material contained in the electrode layer 12 may be of one type, or a plurality of types of electrode active materials may be combined in any ratio. Further, the electrode active material may be solid particles, porous particles, or other shapes.

[0017] A current collector 14 is joined to the surface 12a of the electrode layer 12. The current collector 14 includes a metal foil 16 and a resin layer 18 disposed on the metal foil 16 (the resin layer 18 disposed below the metal foil 16 in the state shown in FIG. 1). In this embodiment, the metal foil 16 is a copper foil, and the electrode body 10 is used as a positive electrode. When the electrode body 10 is used as a negative electrode, the metal foil 16 may be an aluminum foil. Note that the metal foil 16 may be formed of a metal having high conductivity, and may be formed of other metals such as nickel and stainless steel.

[0018] The resin layer 18 is joined to the surface 12a of the electrode layer 12. The resin layer 18 is configured using a modified polyvinylidene fluoride (PVdF)-based resin. However, the type of resin constituting the resin layer 18 is not particularly limited. For example, the resin layer 18 may be configured using a resin such as a polyacrylic acid-based resin. When the electrode body 10 is used as a negative electrode, the material constituting the resin layer 18 may be a resin such as a polyacrylic acid-based resin, polyacrylic acid, polyamideimide, polyimide, styrene-butadiene rubber, etc.

[0019] The resin layer 18 contains a plurality of conductive aids 20. The plurality of conductive aids 20 are carbon materials. However, the shape and type of the conductive aid 20 are not particularly limited. For example, the carbon material has various shapes such as particulate (solid, hollow, porous), fibrous, tubular, brush-shaped, chip-shaped (or flat-shaped), etc., and any of them may be used as the carbon material. Also, metal-coated carbon may be used as the conductive aid 20. Note that the conductive aid 20 may be other metal materials other than carbon materials. Further, the plurality of conductive aids 20 may be of one type of conductive aid, or a plurality of types of conductive aids may be combined in any ratio.

[0020] Here, FIG. 2 shows the current collector 14 and the electrode layer 12 before joining. As shown in FIGS. 1 and 2, the surface 12a of the electrode layer 12 joined to the resin layer 18 has a plurality of fine irregularities 13. The plurality of irregularities 13 have a plurality of convex portions 13p and a plurality of concave portions 13r. In the electrode layer 12, a spatial volume is defined by the plurality of irregularities 13. The spatial volume described in this embodiment means, for example, as shown in FIG. 2, the volume of the space S defined between the surface 12a of the electrode layer 12 having the plurality of irregularities 13 and a plane PS that is perpendicular to the height direction of the plurality of convex portions 13p and passes through the topmost portions 13p1 of the plurality of convex portions 13p. That is, the space S refers to the region delimited by the solid line and the broken line of the electrode layer 12 in FIG. 2. The spatial volume is a finite volume and is represented by the volume per unit area on the surface where the electrode layer 12 and the resin layer 18 are joined.

[0021] Regarding the spatial volume of the electrode layer 12 described above, the volume of the resin layer 18 in this embodiment has the following magnitude relationship. That is, the resin layer 18 is formed such that the volume of the resin layer 18 per unit area is larger than the spatial volume per unit area of the electrode layer 12.

[0022] Here, a method for manufacturing the electrode body 10 will be described. In the method for manufacturing the electrode body 10, first, as shown in FIG. 2, the current collector 14 and the electrode layer 12 are prepared respectively. Subsequently, as shown in FIG. 3, the resin layer 18 of the current collector 14 and the electrode layer 12 are arranged so as to face each other, and the current collector 14 and the electrode layer 12 are pressure-bonded by a pressing process. In the pressing process, pressure is applied using a roll press device. Thereby, the resin layer 18 of the current collector 14 and the electrode layer 12 are joined, and the electrode body 10 shown in FIG. 1 is manufactured. The volume of the resin layer 18 per unit area and the spatial volume of the electrode layer 12 per unit area to which the resin layer 18 is joined satisfy the above-described magnitude relationship in any case before and after the joining of the current collector 14 and the electrode layer 12. That is, the volume of the resin layer 18 per unit area is larger than the spatial volume per unit area of the electrode layer 12 to which the resin layer 18 is joined.

[0023] The following describes the details of the spatial volume of the electrode layer 12.

[0024] The spatial volume of the electrode layer 12 is calculated based on the state of multiple irregularities 13 on the surface 12a of the electrode layer 12. The state of multiple irregularities 13 refers to the three-dimensional surface properties (surface roughness) as defined by ISO 25178. That is, the state of multiple irregularities 13 on the surface 12a of the electrode layer 12 can be measured using a three-dimensional surface measuring instrument. Specifically, by measuring the surface 12a of the electrode layer 12 using a three-dimensional surface measuring instrument before it is bonded to the resin layer 18, information on the curved surface (hereinafter also referred to as the contour surface) of the multiple irregularities 13 on the surface 12a of the electrode layer 12 can be obtained. In this embodiment, since the spatial volume can be calculated from the state of the multiple irregularities 13 in this way, the amount of resin required to produce a resin layer 18 that satisfies the size relationship with the spatial volume of the electrode layer 12 can be controlled.

[0025] Figure 4 schematically shows the contour surface of multiple irregularities 13 on the surface 12a of the electrode layer 12 based on information obtained by three-dimensional surface measurement. Note that the contour surface corresponds to the contour curve of two-dimensional surface measurement, and in Figure 4, the contour surface is schematically shown in two dimensions for simplicity of explanation. In Figure 5, the load curve showing the load area ratio with respect to the height of the contour surface is shown by a solid line. As shown in Figures 4 and 5, the multiple irregularities 13 on the surface 12a of the electrode layer 12 are divided in the height direction from highest to lowest into protruding peaks A1, cores A2, and protruding valleys A3. Of the three divisions of the multiple irregularities 13, the protruding peaks A1 are relatively prone to wear. Considering that the protruding peaks A1 will be crushed by wear, the spatial volume of the electrode layer 12 can be considered to be the area hatched with diagonal lines in Figure 4. Furthermore, as can be seen from Figure 4, the spatial volume of the electrode layer 12 can be considered as the void volume of the multiple recesses 13r among the multiple irregularities 13. From this, the spatial volume of the electrode layer 12 can be calculated based on the integral of the depth of the multiple recesses 13r among the multiple irregularities 13. More specifically, the void volume of the multiple recesses 13r shown in Figure 4 corresponds to the sum of the void volume Vvc of the core portion A2 derived from the load curve shown in Figure 5 and the void volume Vvv of the protruding valley portion A3 (the hatched area in Figure 5). That is, the spatial volume of the electrode layer 12 can be calculated from the sum of the void volume Vvc of the core portion A2 and the void volume Vvv of the protruding valley portion A3. With this configuration, the amount of resin required to produce the resin layer 18 can be controlled with greater precision.

[0026] In Figure 5, Smr1 represents the load area ratio that separates the protruding peaks A1 and the core A2 of the multiple irregularities 13, and Smr2 represents the load area ratio that separates the protruding valleys A3 and the core A2 of the multiple irregularities 13. In this embodiment, it is assumed that the protruding peaks A1 of the multiple irregularities 13 are infinitesimally small, and the spatial volume of the electrode layer 12 is calculated accordingly. In this case, for example, Smr1 is 0%. However, when calculating the spatial volume, Smr1 may be greater than 0%. For example, Smr1 may be 5% or less, 10% or less, or 20% or less. Smr1 may be set appropriately by the person measuring the multiple irregularities 13.

[0027] In this embodiment, a non-contact type is used as the three-dimensional surface measuring instrument. By using a non-contact measuring instrument, the surface 12a of the electrode layer 12 can be measured without damaging it. Furthermore, the non-contact type can measure finer irregularities compared to the contact type. For example, a laser microscope can be used as a non-contact measuring instrument. However, the type of measuring instrument used to measure the three-dimensional surface properties is not particularly limited, and other non-contact types such as a white light interferometer or contact types may also be used.

[0028] (effect) In this embodiment, the electrode body 10 is formed such that the volume of the resin layer 18 per unit area of ​​the surface to which the electrode layer 12 and the resin layer 18 are joined is larger than the spatial volume defined by the multiple irregularities 13 per unit area of ​​the surface to which the electrode layer 12 and the resin layer 18 are joined. With this configuration, when joining the electrode layer 12 and the resin layer 18, the resin layer 18, which is present in a large amount relative to the spatial volume of the electrode layer 12, can penetrate to the bottom surface of the multiple recesses 13r of the electrode layer 12. Therefore, it is difficult for a gap to form between the resin layer 18 and the electrode layer 12, and the adhesion between the resin layer 18 and the electrode layer 12 of the current collector 14 can be improved.

[0029] In this embodiment in particular, the resin layer 18 comprises a plurality of conductive additives 20. With this configuration, the plurality of conductive additives 20, along with the resin layer 18, can reach the bottom surface of the plurality of recesses 13r in the electrode layer 12. This improves the conductivity between the resin layer 18 and the electrode layer 12.

[0030] The volume of the resin layer 18 can be calculated from the weight of the resin layer 18 and the density of the resin layer 18, which has been calculated in advance. The density of the resin layer 18 can be calculated, for example, as follows.

[0031] First, a sample is prepared by forming a resin layer 18 of a predetermined thickness on a substrate. The substrate may be the same as the metal foil 16 used in the example. The resin layer 18 is formed by coating a slurry of resin, conductive additive, and solvent onto the substrate and drying it. The drying conditions here may be, for example, the time it takes for the resin layer 18 of a sample placed on a hot plate at a predetermined temperature in a local exhaust ventilation system to be visually confirmed to be dry after dropping one drop of solvent onto it. The drying conditions for the resin layer 18 may be appropriately changed depending on the solvent used to prepare the resin layer 18. For example, if water is used as the solvent, the drying conditions may be about 90°C for about 30 minutes. Alternatively, if ethanol is used as the solvent, the drying conditions may be about 70°C for about 30 minutes, or if 2-ethyl-1-hexanol is used as the solvent, the drying conditions may be about 180°C for about 30 minutes. The drying treatment of the resin layer 18 may be carried out under other drying conditions (temperature, time, atmosphere, etc.), not limited to the drying conditions described above.

[0032] The prepared sample is repeatedly adjusted to achieve a uniform resin layer thickness by alternating between film thickness measurement and pressing. This reduces the voids within the resin layer 18 and increases its density. For film thickness measurement, an electromagnetic film thickness gauge may be used, for example. Although not particularly limited, the pressing process may be performed under the same conditions as when the electrode layer 12 and the resin layer 18 are pressed together. Next, the sample with a uniformly thick resin layer 18 is punched out using a hand punch or the like. The area of ​​the resin layer 18 is then calculated from the size of the punched-out sample. Next, the film thickness of the resin layer 18 is measured from a cross-sectional image of the punched-out sample obtained with an electron microscope. The volume of the resin layer 18 of the sample is then calculated from the calculated area of ​​the resin layer 18 and the measured film thickness of the resin layer 18. The weight of the punched-out sample is weighed, and the weight of the resin layer 18 of the sample is calculated from the weighed sample weight and the previously calculated weight of the base material. Then, the density of the resin layer 18 is calculated from the volume and weight of the resin layer 18.

[0033] Next, a current collector 14 is fabricated, in which a resin layer 18 is formed on a metal foil 16. The fabricated current collector 14 may be subjected to drying, pressing, etc., in the same manner as the sample described above. Then, the fabricated current collector 14 is punched out using a hand punch or the like. The weight of the punched-out current collector 14 is weighed, and the weight of the resin layer 18 of the punched-out current collector 14 is calculated from the weight of the weighed resin layer 18 and the weight of the metal foil 16, which has been calculated in advance in the same manner as the substrate of the sample. From the above, the volume of the resin layer 18 of the current collector 14 fabricated in this case can be calculated from the calculated weight of the resin layer 18 and the density of the resin layer 18 calculated using the sample.

[0034] Although specific examples of the technology disclosed herein have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above.

[0035] In this embodiment, the electrode layer 12 was bonded to a resin layer 18 located on one side of the current collector 14, but the configuration of the electrode body 10 is not limited to this. In addition to the above configuration, the electrode body 10 may also have the electrode layer 12 bonded to the other side of the current collector 14 via the resin layer 18.

[0036] In a modified example, the current collector 14 does not need to include the metal foil 16. For example, the current collector 14 may consist only of, for example, a resin layer 18.

[0037] In the modified example, the resin layer 18 does not need to include the conductive additive 20.

[0038] The technical elements described herein or in the drawings demonstrate technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated herein or in the drawings achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness in itself. [Explanation of Symbols]

[0039] 10: Electrode body 12: Electrode layer 12a: Surface 13: Multiple bumps and irregularities 13p: Convex part 13r: recessed 14: Current collector 16: Metal foil 18: Resin layer 20: Conductive additive

Claims

1. Electrode layer and The electrode layer comprises a current collector bonded to the surface of the electrode layer, The surface of the electrode layer has a plurality of irregularities, The current collector comprises a resin layer bonded to the surface of the electrode layer, An electrode body in which the volume of the resin layer per unit area of ​​the surface to which the electrode layer and the resin layer are joined is greater than the spatial volume defined by the plurality of irregularities per unit area of ​​the surface to which the electrode layer and the resin layer are joined.

2. The electrode body according to claim 1, The spatial volume is calculated based on the state of the multiple irregularities on the surface of the electrode layer, in the electrode body.

3. An electrode body according to claim 1 or 2, The plurality of irregularities on the surface of the electrode layer comprises a plurality of recesses, The spatial volume is calculated based on the integral of the depths of the plurality of recesses, in the electrode body.

4. An electrode body according to claim 1 or 2, The aforementioned resin layer is an electrode body containing multiple conductive additives.

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