Electrode and method for manufacturing electrode

Abstract

Provided is an electrode having improved tensile strength by improving the in-plane dispersibility of PTFE. An embodiment of the present disclosure relates to an electrode including a core material and an electrode composite laminated on a surface of the core material, the electrode composite including an active material and PTFE, wherein, in an image representing a composition distribution obtained when the surface of the electrode composite is measured using energy dispersive X-ray analysis, the standard deviation of the area ratio of PTFE in 30 adjacent regions each having a size of 150 μm x 133 μm is 6% or less, and when the electrode composite is divided into three equal parts in the thickness direction and designated as a first region, a second region, and a third region from the core material side, the content of PTFE in the first region (a), the content of PTFE in the second region (b), and the content of PTFE in the third region (c) satisfy (c-a) / (a+b+c) ≤ ±10%.

Description

Technical Field

[0001] This disclosure relates to electrodes and methods for manufacturing electrodes. Background Technology

[0002] Electrodes for non-aqueous electrolyte secondary batteries such as lithium-ion batteries are typically manufactured using a wet process by coating an electrode composite slurry containing active materials and binders onto the surface of a core material, which is a metal foil, followed by drying and compression of the coating. In this process, a technical problem arises where the binder material can migrate during the drying of the coating. When this migration occurs, the amount of binder material on the surface side of the coating (electrode composite layer) increases compared to the core side, resulting in a deviation in the distribution of binder material in the thickness direction of the electrode composite layer.

[0003] In recent years, research has been conducted on a dry method for manufacturing electrodes by stretching and shaping electrode composite materials into sheets, and then bonding these sheets onto a core material. Patent Document 1 discloses an electrode film (electrode composite material) produced by mixing active materials, fibrillable binders such as polytetrafluoroethylene (PTFE), and conductive materials using a mixer, followed by applying high pressure and a large shear force to the mixture for an extended period to fibrillate the PTFE. It describes that the fibrillated PTFE content in the electrode composite material is 5% to 7% by weight.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 2019-512872 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] Through research, the inventors found that when the PTFE content is set to a relatively high level, as disclosed in Patent Document 1, and a large shear force is applied to the electrode composite material for a long period of time, the conductive material adheres to the PTFE rather than the active material; the PTFE aggregates, and even when stretched and shaped into sheets, it cannot be uniformly dispersed. When the in-plane dispersibility of PTFE deteriorates, the tensile strength of the electrode composite material sometimes decreases. Patent Document 1 does not address how to suppress the decrease in the tensile strength of the electrode composite material, and there is room for improvement.

[0009] Therefore, the purpose of this disclosure is to provide an electrode that improves tensile strength by increasing the in-plane dispersion of PTFE.

[0010] Solution for solving the problem

[0011] One embodiment of the electrode disclosed herein is characterized by comprising a core material and an electrode composite material laminated on the surface of the core material. The electrode composite material comprises an active material and PTFE. In an image representing the compositional distribution obtained by measuring the surface of the electrode composite material using energy-dispersive X-ray analysis, the standard deviation of the area ratio of PTFE in 30 adjacent 150 μm × 133 μm regions is less than 6%. When the electrode composite material is divided into three equal parts in the thickness direction and designated as region 1, region 2, and region 3 from the core material side, the PTFE content (a) in region 1, the PTFE content (b) in region 2, and the PTFE content (c) in region 3 satisfy (ca) / (a+b+c)≤±10%.

[0012] One embodiment of the present disclosure relates to a method for manufacturing an electrode, characterized by comprising the following steps: a mixing step, mixing an active substance, a conductive material, and PTFE to produce electrode composite material particles with a solid component concentration substantially 100%; a stretching step, passing the electrode composite material particles between rollers more than twice, mixing and stretching simultaneously to produce an electrode composite material sheet; and a bonding step, bonding the electrode composite material sheet to a core material to produce an electrode.

[0013] The effects of the invention

[0014] According to one embodiment of this disclosure, the tensile strength of the electrode can be improved. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view of an electrode as an example of an implementation method.

[0016] Figure 2 In the electrode manufacturing process, which is an example of an implementation method, Figure 2 (a) is a diagram showing the mixing steps. Figure 2 (b) is a diagram showing the stretching steps.

[0017] Figure 3 A diagram illustrating the bonding step in the manufacturing process of an electrode, as an example of an implementation method. Detailed Implementation

[0018] The following provides a detailed description of embodiments of the electrodes and electrode manufacturing methods disclosed herein. The embodiments described below are merely examples, and this disclosure is not limited to these embodiments. Furthermore, the accompanying drawings referenced in the description of the embodiments are schematic representations; the dimensional ratios of the constituent elements depicted in the drawings should be determined with reference to the following description.

[0019] [electrode]

[0020] The electrodes disclosed herein are preferably applicable to non-aqueous electrolyte secondary batteries such as lithium-ion batteries, but can also be applied to energy storage devices such as batteries or capacitors containing aqueous electrolytes. It should be noted that the following description uses electrodes for non-aqueous electrolyte secondary batteries (especially those applicable to the positive electrode) as an example.

[0021] Figure 1 This is a cross-sectional view of an electrode as an example of an implementation. Electrode 10 includes a core material 11 and an electrode composite material 12 laminated on the surface of the core material. Figure 1 As shown, electrode 10 may also have electrode composite material 12 on both sides of core material 11. Electrode 10 may be a long strip electrode constituting a wound electrode body, or a rectangular electrode constituting a stacked electrode body. It should be noted that electrode 10 can be used as the positive electrode, negative electrode, or both of non-aqueous electrolyte secondary batteries.

[0022] The core material 11 can be a metal foil, a thin film with a metal layer formed on its surface, etc. The thickness of the core material 11 is, for example, 5 μm to 20 μm. In the case of a positive electrode, a metal foil with aluminum as the main component can be used as the core material 11. In the case of a negative electrode, a metal foil with copper as the main component can be used. In this specification, the main component refers to the component with the highest mass percentage. The core material 11 can be an aluminum foil that is substantially 100% aluminum, or a copper foil that is substantially 100% copper.

[0023] The electrode composite material 12 comprises an active material and polytetrafluoroethylene (PTFE). The thickness of the electrode composite material 12 is, for example, 30 μm to 120 μm, preferably 50 μm to 100 μm. The electrode composite material 12 may contain a conductive material. Examples of conductive materials included in the electrode composite material 12 include carbon black (CB), acetylene black (AB), Ketjen black, carbon nanotubes (CNTs), graphite, and other carbon materials. The particle size of the conductive material is, for example, 0.01 μm to 0.1 μm. This allows it to penetrate and adhere to the recesses on the surface of the positive electrode active material. The content of the conductive material in the electrode composite material 12 can be set to, for example, 0.5% by mass to 5.0% by mass.

[0024] The positive electrode active material (positive electrode active material) is typically a lithium transition metal composite oxide. Examples of metal elements contained in the lithium transition metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. Preferably, it contains at least one of Ni, Co, and Mn. The negative electrode active material (negative electrode active material) uses carbon-based active materials such as natural graphite (e.g., flake graphite, block graphite, amorphous graphite) or artificial graphite (e.g., blocky graphite (MAG) or graphitized mesophase carbon microspheres (MCMB)). Alternatively, a Si-based active material alloyed with lithium can also be used. The active material is the main component of the electrode composite material 12, and the content of the active material in the electrode composite material 12 is preferably 85% to 99% by mass, more preferably 90% to 99% by mass.

[0025] The positive electrode active material is, for example, a secondary particle composed of multiple primary particles aggregated together. Thus, the surface of the positive electrode active material has irregularities, allowing conductive materials to penetrate and adhere to the recesses within these irregularities, as described above. The particle size of the primary particles constituting the secondary particles is, for example, 0.05 μm to 1 μm. The particle size of the primary particles is measured as the diameter of the circumcircle in a particle image observed by a scanning electron microscope (SEM). The positive electrode active material has a median particle size (D50) in volumetric terms, for example, 3 μm to 30 μm, preferably 5 μm to 25 μm, and more preferably 7 μm to 15 μm. D50 refers to the particle size at which the frequency accumulation in the volumetric particle size distribution reaches 50% from the smallest particle size; it is also called the median diameter. The particle size distribution of the positive electrode active material can be measured using a laser diffraction-type particle size distribution measuring device (e.g., Microtracbel Co., Ltd., MT3000II) with water as the dispersion medium.

[0026] PTFE is a dry powder, not a powder dispersed in a dispersion such as water. Therefore, the electrode composite material can be manufactured using the dry process described later. It should be noted that, in addition to PTFE, the electrode composite material 12 may also contain binder materials such as unfibrillated polyvinylidene fluoride (PVdF). Furthermore, the electrode composite material 12 may contain fibrillated binder materials other than PTFE, without affecting the purpose of this disclosure.

[0027] The PTFE content in the electrode composite material 12 is preferably 0.05% to 5% by mass, more preferably 1% to 3% by mass. Within this range, the adhesion of conductive material to PTFE can be suppressed, resulting in a higher concentration of conductive material on the surface of the active material, which is preferred from the perspective of improving battery characteristics. PTFE adheres to the particle surface of the active material and intertwines with it. In other words, the active material is retained through the mesh-like structure of the PTFE.

[0028] PTFE includes fibrillated PTFE fibers. PTFE fibers are fibers produced by fibrillating fibrillable, fine-powdered PTFE raw materials (PTFE particles) through a mixing step described later. The median particle size of PTFE fibers is preferably 2 μm to 20 μm. The median particle size of PTFE fibers can be measured using a particle size analyzer. The median particle size of PTFE fibers, 2 μm to 20 μm, refers to the size of the PTFE fibers as micronized relative to PTFE particles.

[0029] As described above, many PTFE particles are fibrillated into PTFE fibers, and the PTFE may contain residual PTFE particles that have not been fibrillated. PTFE particles can be secondary particles. The average particle size of the PTFE particles is, for example, 100 μm to 700 μm, preferably 100 μm to 500 μm, and more preferably 100 μm to 400 μm. The average particle size of the PTFE particles can be determined by observing the particles of the PTFE raw material using SEM. Specifically, the morphology of 100 randomly selected particles is determined, and the major diameter (longest diameter) of each of the 100 particles is calculated. The average value of these values ​​is taken as the average particle size of the PTFE particles.

[0030] In the image representing the compositional distribution obtained when measuring the surface of the electrode composite material 12 using energy-dispersive X-ray diffraction (EDS), the standard deviation of the area ratio of PTFE in 30 adjacent 150 μm × 133 μm regions is 6% or less, preferably 5% or less, and more preferably 4% or less. When the standard deviation of the area ratio of PTFE is 6% or less, the tensile strength can be improved due to the good in-plane dispersion of PTFE. The lower limit of the standard deviation of the area ratio of PTFE is, for example, 1%.

[0031] The maximum area ratio of PTFE in 30 adjacent 150μm×133μm regions is 23% or less, and the minimum is preferably 0.1% or more. This maximum value is more preferably 21% or less, and particularly preferably 16% or less. This minimum value is more preferably 1% or more, and particularly preferably 3% or more.

[0032] The 30 adjacent regions, each 150μm × 133μm in size, can be, for example, arranged in a vertical direction (2 regions) and a horizontal direction (150μm × 133μm regions in size). For instance, an EDS analysis can be performed on a field of view measuring 300μm vertically and 399μm horizontally, and then the same analysis can be performed on five horizontally adjacent fields of view. By dividing a field of view into two vertically and three horizontally, 30 regions of 150μm vertically and 133μm horizontally are formed. It should be noted that when analyzing five fields of view, there can be overlap between adjacent fields of view.

[0033] The area ratio of PTFE in each region is calculated, for example, as follows.

[0034] <Method for calculating the area ratio of PTFE>

[0035] (1) Using EDS, a mapped image is obtained that maps the regions where carbon (C region) and fluorine (F region) are present. The magnification of the EDS is adjusted to obtain an image with a vertical dimension of 300 μm and a horizontal dimension of 399 μm.

[0036] (2) Import the mapped image into the computer and use image analysis software (e.g., ImageJ, made by the National Institutes of Health) to obtain a composite image in which the overlapping part of region C and region F is regarded as the region where PTFE exists (PTFE region).

[0037] (3) Use image analysis software to binarize the synthesized image to obtain a binarized image in which the PTFE region in the image is converted to green and the other regions (blank regions) are converted to black.

[0038] (4) By dividing the binarized image into 2 vertical regions and 3 horizontal regions, 6 regions are created, and the area of ​​the PTFE region and the area of ​​the blank region in each region are calculated.

[0039] (5) The area ratio of PTFE in each region is calculated according to the following formula.

[0040] PTFE area ratio = (Area of ​​PTFE region / (Area of ​​PTFE region + Area of ​​blank region)) × 100

[0041] When the electrode composite material 12 is divided into three equal parts along its thickness direction, designated as region 1, region 2, and region 3 from the core material 11 side, the PTFE content (a) in region 1, the PTFE content (b) in region 2, and the PTFE content (c) in region 3 preferably satisfy (ca) / (a+b+c)≤±10%, more preferably (ca) / (a+b+c)≤±5%. Thus, PTFE is distributed substantially uniformly throughout the electrode composite material 12 along its thickness direction, rather than being distributed locally. By using the dry process described later, it is possible to achieve a substantially uniform distribution of PTFE throughout the electrode composite material 12.

[0042] Electrode 10 may further include an adhesive layer between the core material 11 and the electrode composite material 12, which functions to bond the core material 11 and the electrode composite material 12. The thickness of the adhesive layer is, for example, 1 μm to 10 μm. The adhesive layer may contain a conductive material and a bonding material, and the conductive material may be conductive. Examples of conductive materials included in the adhesive layer include carbon black (CB), acetylene black (AB), Ketjen black, carbon nanotubes (CNTs), graphite, and other carbon materials. The conductive material is preferably a material with a small particle size and a large specific surface area. As a result, the adhesive layer is easy to form a structure. The specific surface area of ​​the conductive material is, for example, 100 m². 2 / g~150m 2 The range is / g. Examples of adhesive materials included in the adhesive layer include fluoropolymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide, acrylic resins, and polyolefins. PVdF is preferred as the adhesive material included in the adhesive layer. The adhesive layer can be manufactured, for example, by coating the surface of the core material 11 with a slurry containing conductive materials, adhesive materials, etc., drying the coating, and then compressing it. It should be noted that the adhesive layer can also be formed on the surface of the core material 11 by dip coating or spray coating.

[0043] The conductive material content in the adhesive layer is preferably 40% to 80% by mass, more preferably 45% to 75% by mass, and particularly preferably 50% to 71% by mass. This relatively high conductive material content in the adhesive layer reduces interfacial resistance. Excessive conductive material weakens the adhesive layer itself, making it fragile and hindering conductivity between the electrode composite material 12 and the core material 11.

[0044] [Electrode manufacturing method]

[0045] The manufacturing method of electrode 10 will be further described in detail below. The following example illustrates the manufacturing method of the positive electrode, which can also be applied to the manufacturing of the negative electrode. In the case of the negative electrode, a negative electrode active material is used instead of the positive electrode active material.

[0046] Figure 2 and Figure 3 The diagram illustrates the manufacturing process of electrode 10 as an example of an implementation. The method for manufacturing electrode 10 includes: Figure 2 The mixing steps shown in (a) Figure 2 The stretching steps shown in (b) and Figure 3 The bonding steps are shown below. In the mixing step, the active material and PTFE are mixed to produce electrode composite material particles 12a with a solid content of substantially 100%. In the stretching step, the electrode composite material particles 12a are simultaneously mixed and stretched into a sheet shape to produce an electrode composite material sheet 12b. In the bonding step, the electrode is fabricated by bonding the electrode composite material sheet 12b onto the core material 11.

[0047] The electrode 10 is manufactured using a dry process employing an electrode composite material 12 with a substantially 100% solids concentration. A dry process refers to a process in which the active material particles and binder material particles are mixed without the use of solvents; that is, the active material and binder material are mixed at a substantially 100% solids concentration. The electrode 10 manufacturing method disclosed herein does not require the use of solvents as in conventional electrode 10 manufacturing methods. Eliminating the need for solvents means that they are not only not used as a simple raw material, but also that a solvent drying process is unnecessary, as are exhaust equipment and other equipment required for drying processes.

[0048] In the mixing step, active materials, PTFE, conductive materials, and other raw materials are mixed using a mixer 20 to produce electrode composite material particles 12a. For example, a conventionally known mechanical mixing mixer can be used as the mixer 20. Preferred examples of the mixer 20 include shredders, pin mills, bead mills, microparticle compounding devices (devices that generate shear force between a rotor with a special shape rotating at high speed inside a tank and a collision plate), granulators, twin-screw extruders, and planetary mixers, etc., preferably shredders, microparticle compounding devices, granulators, or twin-screw extruders. This allows PTFE to be fibrillated while mixing the raw materials. The processing time of the mixing step (the time for applying shear force to the material) is preferably within a few minutes, for example, it can be set to 0.5 minutes to 10 minutes. If the processing time is too long, the amount of conductive material introduced into the PTFE will increase. In this case, the conductivity of the electrode composite sheet will decrease significantly, resulting in increased resistance, which adversely affects the battery characteristics.

[0049] The mixing step may include: a step of mixing an active material and a conductive material to prepare a coated active material; and a step of mixing the coated active material and PTFE. By using a coated active material prepared by mixing an active material and a conductive material, the mixing time of the coated active material and PTFE can be shortened. This reduces the amount of conductive material introduced into the PTFE. Preferably, the surface of the coated active material has irregularities, and the conductive material penetrates and adheres to the recesses in these irregularities. Therefore, during the mixing process of the coated active material and PTFE, the conductive material on the surface of the coated active material is less likely to be carried away by the PTFE.

[0050] As a method for dry mixing of active and conductive materials, mechanical fusion can be used, for example. Mechanical fusion refers to a dry processing method using a mechanical fusion reaction apparatus having a cylindrical chamber with a compression tool inside that rotates at high speed. The conductive material and active material are placed inside the chamber, and by rotating the chamber, the particles are compressed against each other and pressed against the chamber wall. The centrifugal force generated by the compression tool and high-speed rotation promotes the adhesion and bonding of the conductive and active materials. Examples of mechanical fusion reaction apparatus include the "Nobilta" (registered trademark) pulverizer or "mechanofusion" (registered trademark) pulverizer manufactured by Hosokawa Micron Co., Ltd. (Japan), the "Hybridizer" (trademark) pulverizer manufactured by Nara Machinery Manufacturing Co., Ltd., the "BALANCEGRAN" manufactured by Freund-turbo Co., Ltd., and the "COMPOSI" manufactured by Nippon Coke Industry Co., Ltd.

[0051] Next, in the stretching step, as... Figure 2 As shown in (b), electrode composite material particles 12a are simultaneously mixed and stretched using a pair of rollers 22 to form sheets. The pair of rollers 22 are spaced apart by a predetermined gap and rotate in the same direction. The electrode composite material particles 12a are supplied to the gap between the pair of rollers 22, and are compressed and stretched into sheets by the pair of rollers 22. The linear pressure generated by the pair of rollers 22 is, for example, 1 t / cm to 3 t / cm. The pair of rollers 22 have, for example, the same roller diameter. The temperature of the pair of rollers 22 is not particularly limited; for example, it can be at room temperature or heated to above room temperature.

[0052] By passing the obtained electrode composite sheet 12b between a pair of rollers 22 again, the PTFE is dispersed. In other words, by passing the electrode composite particles 12a between the pair of rollers 22 more than twice, the in-plane dispersibility of the PTFE is improved. The number of times the electrode composite particles 12a and the electrode composite sheet 12b formed from the electrode composite particles 12a pass between the pair of rollers 22 is preferably 2 to 50 times, more preferably 3 to 40 times, and particularly preferably 5 to 20 times. The stretching step is not limited to using only one pair of rollers, and may also include a step of stretching using other pairs of rollers with different roller diameters, circumferential speeds, gaps, etc.

[0053] The thickness of the electrode composite sheet 12b obtained after the stretching step can be controlled by, for example, the gap between the pair of rollers 22, the circumferential speed, and the number of stretching operations. In the stretching step, it is preferable to use a pair of rollers 22 with a circumferential speed ratio of at least 2 times to form the electrode composite particles 12a into a sheet. By using a different circumferential speed ratio between the pair of rollers 22, it is easier, for example, to thin the electrode composite sheet 12b, thereby improving productivity. The active material density of the electrode composite sheet 12b is, for example, 3.6 g / cm³. 3 ~4.0g / cm 3 .

[0054] Next, in the bonding step, such as Figure 3 As shown, by attaching the electrode composite sheet 12b to the core material 11, an electrode 10 can be obtained with a composite material layer composed of the electrode composite material 12 on the surface of the core material 11. Figure 3 The diagram shows a state where the electrode composite material 12 is bonded to only one side of the core material 11, but preferably the electrode composite material 12 is bonded to both sides of the core material 11. Two electrode composite materials 12 can be bonded to both sides of the core material 11 simultaneously, or one can be bonded to one side of the core material 11 and the other to the other side. Alternatively, the electrode composite material sheet 12b can be adhered to the core material 11 using an adhesive layer.

[0055] In the bonding step, a pair of rollers 24 are used to bond the electrode composite sheet 12b to the surface of the core material 11. The pair of rollers 24, for example, have the same diameter, are spaced apart by a predetermined gap, and rotate in the same direction at the same circumferential speed. The temperature of the pair of rollers 24 is, for example, 25°C to 300°C. The linear pressure applied by the pair of rollers 24 is preferably 0.1 t / cm to 5 t / cm, more preferably 0.2 t / cm to 3 t / cm.

[0056] Example

[0057] The present disclosure will be further described below through embodiments, but the present disclosure is not limited to these embodiments.

[0058] <Example 1>

[0059] [Preparation of Cathode Composite Material Particles (Mixing Steps)]

[0060] Lithium transition metal composite oxide, acetylene black (AB), and PTFE particles were added to a mixer (Osaka Chemical, Wonder Crusher) at a mass ratio of 100:1:2 and mixed for 5 minutes at room temperature and a rotation speed of scale 3. It should be noted that the maximum rotation speed of the Wonder Crusher at scale 10 is 28,000 rpm. This mixing process yielded cathode composite material particles with uniform dispersion of the positive electrode active material and PTFE. The solid content concentration of the obtained cathode composite material was 100%.

[0061] [Fabrication of Cathode Composite Material Sheets (Stretching Steps)]

[0062] The obtained cathode composite material particles are passed five times between a pair of rollers, simultaneously mixing and stretching to produce cathode composite material sheets. The circumferential speed ratio of the pair of rollers is set to 1:3, and the thickness of the cathode composite material sheet is adjusted to approximately 100 μm.

[0063] [Determination of tensile strength]

[0064] The tensile strength of the positive electrode composite sheet was evaluated using a universal testing machine (SDMK-1000-D) (20 mm / min). The test piece was set to be 12.5 mm wide and 122 mm long.

[0065] <Example 2>

[0066] Except that the number of times the positive electrode composite material particles pass between a pair of rollers is set to 10, the positive electrode composite material sheet is prepared in the same manner as in Example 1 and evaluated.

[0067] <Example 3>

[0068] Except that the number of times the positive electrode composite material particles passed between a pair of rollers was set to 20, the positive electrode composite material sheet was prepared in the same manner as in Example 1 and evaluated.

[0069] <Comparative Example>

[0070] Except that the number of times the positive electrode composite material particles pass between a pair of rollers is set to 1, the positive electrode composite material sheet is prepared in the same manner as in Example 1 and evaluated.

[0071] Table 1 shows the tensile strength results measured for the Examples and Comparative Examples. Additionally, Table 1 also shows the number of times the cathode composite material particles passed between a pair of rollers (roller passes) and the standard deviation, maximum, and minimum values ​​of the PTFE area ratio in the electrode composite material surface calculated by the above method. Furthermore, Table 2 shows the PTFE content (a) in region 1, the PTFE content (b) in region 2, the PTFE content (c) in region 3, and the value of (ca) / (a+b+c) for the Examples and Comparative Examples.

[0072] [Table 1]

[0073]

[0074] [Table 2]

[0075]

[0076] As shown in Table 1, the tensile strength of the cathode composite sheet of the Examples is higher than that of the comparative examples. The tensile strength of the cathode composite sheet of the Comparative Examples is low to an unmeasurable degree. Furthermore, as shown in Table 2, in the cathode composite sheet of the Examples, PTFE is also present in a substantially uniform manner throughout the electrode composite material along the thickness direction.

[0077] Explanation of symbols

[0078] 10: Electrode; 11: Core material; 12: Electrode composite material; 12a: Electrode composite material particles; 12b: Electrode composite material sheet; 20: Mixer; 22, 24: Rollers.

Claims

1. An electrode comprising a core material and an electrode composite material laminated on the surface of the core material, wherein, The electrode composite material contains active materials and PTFE. In the image representing the compositional distribution obtained when measuring the surface of the electrode composite material using energy-dispersive X-ray diffraction (EDXRD), the standard deviation of the area ratio of the PTFE in 30 adjacent 150 μm × 133 μm regions was less than 6%. When the electrode composite material is divided into three equal parts in the thickness direction and designated as region 1, region 2 and region 3 from the core material side, the PTFE content (a) in region 1, the PTFE content (b) in region 2 and the PTFE content (c) in region 3 satisfy -10%≤(ca) / (a+b+c)≤10%.

2. The electrode according to claim 1, wherein, The maximum area ratio of PTFE in the 30 adjacent 150μm×133μm regions is 23%, and the minimum area ratio is 0.1%.

3. The electrode according to claim 1, wherein, The PTFE content in the electrode composite material is 0.05% to 5% by mass.

4. The electrode according to claim 1, wherein, Between the core material and the electrode composite material, there is an adhesive layer that functions to bond the core material and the electrode composite material together.

5. A method for manufacturing an electrode according to any one of claims 1 to 4, comprising the following steps: The mixing step involves mixing active materials, conductive materials, and PTFE to produce electrode composite material particles with a solid component concentration of approximately 100%. The stretching step involves passing the electrode composite material particles between a pair of rollers more than twice, while simultaneously mixing and stretching, to produce electrode composite material sheets. as well as The bonding step involves bonding the electrode composite sheet onto the core material to fabricate the electrode.

6. The method for manufacturing an electrode according to claim 5, wherein, The mixing step includes the following steps: The step of preparing a coated active material by mixing the active material and the conductive material; and, The step of mixing the coated active material and the PTFE.

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