Method for manufacturing electrode and electrode manufactured thereby

Abstract

A method for manufacturing an electrode according to one embodiment of the present invention may comprise the steps of: coating a first coating layer including an active material on at least one surface of a current collector including a metal material; coating a plurality of second coating layers including an active material on at least one surface of the first coating layer; and rolling the current collector, the first coating layer, and the second coating layers by means of a rolling device.

Description

Electrode manufacturing method and electrode manufactured thereby

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0179051, filed December 11, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a method for manufacturing an electrode and an electrode manufactured thereby.

[0005] To address environmental pollution caused by the use of petroleum resources and the resulting energy shortage resulting from petroleum depletion, research and development are underway on power generation based on eco-friendly energy sources. In particular, active research is being conducted on secondary batteries, which offer high utility due to their ability to be repeatedly charged and discharged. Research is also being conducted on various aspects of secondary batteries, including their materials, structure, processes, and stability.

[0006] Common types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. These batteries are used not only in small products such as digital cameras, DVDs, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also in larger products requiring high output, such as electric and hybrid vehicles, as well as in power storage devices that store surplus power or renewable energy, and as backup power storage devices.

[0007] To manufacture these secondary batteries, first, an electrode active material slurry is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and these are laminated on both sides of a separator to form an electrode assembly of a predetermined shape. Then, the electrode assembly is housed in a battery case, filled with electrolyte, and sealed.

[0008] Secondary batteries manufactured in this manner are utilized in a variety of industries. To further enhance their performance, active research is underway to increase their capacity. A common method for increasing secondary battery capacity is to press electrodes under high pressure to increase their density when manufacturing electrode assemblies.

[0009] However, the problem of reduced electrolyte impregnation in high-pressure electrodes arises. This reduced electrolyte impregnation prevents the electrolyte from quickly reaching the electrode active material particles, hindering the smooth movement of lithium ions and potentially degrading secondary battery performance. Furthermore, reduced electrolyte impregnation slows the impregnation rate, making secondary battery manufacturing time-consuming and potentially reducing secondary battery productivity.

[0010] Therefore, there is a need for technology to manufacture a secondary battery with high capacity and excellent electrolyte impregnation properties.

[0011] The problem to be solved by the present invention is to provide a method for manufacturing an electrode by coating a plurality of second coating layers on a first coating layer so that regions having different active material densities and electrolyte impregnation properties are formed, and an electrode manufactured thereby.

[0012] A method for manufacturing an electrode according to one embodiment of the present invention may include a step of coating a first coating layer including an active material on at least one surface of a current collector including a metal material, a step of coating a plurality of second coating layers including an active material on at least one surface of the first coating layer, and a step of rolling the current collector, the first coating layer, and the second coating layer by a rolling device.

[0013] In the step of coating the second coating layer, the plurality of second coating layers can be coated at a constant interval from each other.

[0014] In the step of rolling by the above rolling device, a first active material layer in which the first coating layer and the second coating layer are rolled together and a second active material layer in which the first coating layer is rolled alone can be formed.

[0015] In the step of rolling by the above rolling device, the active material density of the first active material layer may be higher than the active material density of the second active material layer.

[0016] In the step of rolling by the above rolling device, the electrolyte impregnation property of the second active material layer may be higher than the electrolyte impregnation property of the first active material layer.

[0017] In the step of rolling by the rolling device, the electrode, the first coating layer, and the second coating layer can be rolled so that the outer surface of the first active material layer and the outer surface of the second active material layer are positioned on the same surface.

[0018] In the step of coating the second coating layer, the second coating layer can be coated along the width direction of the entire body.

[0019] An electrode according to another embodiment of the present invention includes a current collector including a metal material and an active material layer coated on at least one surface of the current collector, wherein the active material layer may include a first active material layer and a second active material layer that is alternately positioned with the first active material layer and has an active material density lower than that of the first active material layer.

[0020] The electrolyte impregnation property of the second active material layer may be higher than the electrolyte impregnation property of the first active material layer.

[0021] The first active material layer and the second active material layer can be formed along the width direction of the current collector.

[0022] According to a preferred embodiment of the present invention, by coating a plurality of second coating layers on a first coating layer so that regions having different active material densities and electrolyte impregnation properties are formed, a high-capacity electrode can be manufactured while at the same time having excellent electrolyte impregnation properties.

[0023] In addition, the configurations according to preferred embodiments of the present invention may include effects that can be easily predicted by those skilled in the art.

[0024] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0025] Figure 1 is a flowchart of an electrode manufacturing method according to one embodiment of the present invention.

[0026] FIG. 2 is a perspective view showing a second coating layer coated on the outer surface of a first coating layer according to an electrode manufacturing method according to one embodiment of the present invention.

[0027] FIG. 3 is a cross-sectional view showing a first coating layer, a second coating layer, and a current collector being rolled according to an electrode manufacturing method according to one embodiment of the present invention.

[0028] Figure 4 is a perspective view of an electrode according to another embodiment of the present invention.

[0029] Figure 5 is a perspective view of an electrode according to another embodiment of the present invention.

[0030] Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited or restricted by the following examples.

[0031] In order to clearly explain the present invention, a detailed description of a part that is irrelevant to the description or a related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and when adding reference signs to components of each drawing in this specification, the same or similar reference signs are attached to the same or similar components throughout the specification.

[0032] In addition, terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0033] Figure 1 is a flowchart of an electrode manufacturing method according to one embodiment of the present invention.

[0034] Referring to FIG. 1, an electrode (1) can be manufactured through an electrode manufacturing method according to one embodiment of the present invention. For example, according to the electrode manufacturing method, a coating layer including an active material can be coated on at least one surface of a current collector (10). In a state where the coating layer is coated on at least one surface of the current collector (10), the current collector (10) and the coating layer are rolled by a rolling device, thereby manufacturing an electrode (1) according to another embodiment of the present invention, which will be described later.

[0035] Specifically, through the electrode manufacturing method, a first coating layer (11a) and a second coating layer (11b) are sequentially coated on at least one surface of a current collector (10), and then the current collector (10), the first coating layer (11a), and the second coating layer (11b) can be rolled by a rolling device.

[0036] The current collector (10) may refer to a thin film used to form an electrode assembly, including a structure made of a plate-shaped material, rolled or cut into rolls, and laminated. The current collector (10) may play a role in transferring electrons from the outside to the active material or releasing them from the active material to the outside so that an electrochemical reaction occurs during the charging and discharging process of a secondary battery.

[0037] The current collector (10) may include a metallic material. Specifically, the material of the current collector (10) may vary depending on the type of the electrode plates divided into the negative electrode and the positive electrode. For the negative electrode current collector (10), copper foil, which is stable in electrochemical reactions within the operating range of the carbon electrode (1) and has good electrical conductivity, may be primarily used. On the other hand, for the positive electrode current collector (10), aluminum foil, which is stable in electrochemical reactions even at high potentials and has good electrical conductivity, may be used.

[0038] The manufacturing method of the current collector (10) may vary depending on the type of electrode plate. Aluminum foil may be manufactured by thinning an aluminum piece through a rolling process. On the other hand, copper foil may be manufactured by melting a copper wire through an electrolytic plating process.

[0039] The first coating layer (11a) and the second coating layer (11b) may include an active material slurry. The active material slurry may refer to a material that is applied to the outer surface of the current collector (10) and generates electrical energy through a chemical reaction. In addition, the active material slurry may include an active material, a conductive material, and a binder. That is, the first coating layer (11a) and the second coating layer (11b) may include an active material.

[0040] Active materials can chemically react to generate electrical energy. Active materials may include positive electrode active materials or negative electrode active materials.

[0041] The cathode active material may be, for example, a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium manganese oxide such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; or a compound having the chemical formula LiNi. 1-x M x Ni-site lithium nickel oxide represented by O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01 to 0.3); chemical formula LiMn 2-x M x Lithium manganese complex oxides expressed as O2 (M = Co, Ni, Fe, Cr, Zn or Ta, x = 0.01 to 0.1) or Li2Mn3MO8 (M = Fe, Co, Ni, Cu or Zn); LiNi x Mn 2-x Lithium manganese composite oxide with spinel structure represented by O4; Li x CoPO4(0.5 <x<1.3) 등의 리튬 전이금속 인산화물, 화학식의 Li 일부가 알칼리토금 속 이온으로 치환된 LiMn2O4; 디설파이드 화합물; Fe2(MoO4)3등을 포함할 수 있지만, 이들만으로 한정되는 것은 아니다.

[0042] The negative active material is a carbonaceous material such as artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, etc.; a metallic compound that can be alloyed with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO x(0 < x < 2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of coating and decoating lithium; lithium titanium oxide, metal composite oxides containing two or more metals, or composites containing the above metal compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. Additionally, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0043] The conductive agent can promote electron transfer between the positive and negative active materials. For example, the conductive agent can include a small amount of finely powdered carbon to improve the conductivity between active material particles or the current collector (10) and prevent the binder from acting as an insulator.

[0044] The conductive material is not particularly limited, but specific examples thereof include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; graphite such as natural graphite or artificial graphite; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 1 wt% to 30 wt%, specifically 1 wt% to 10 wt%, and more specifically 1 wt% to 5 wt%, based on the total weight of the solid content of the active material slurry.

[0045] A binder can bond an active material and a conductive material to each other. For example, the binder can function to facilitate the mixing of the active material and the conductive material. Accordingly, the binder can function to uniformly coat the active material and the conductive material on the current collector (10). As the secondary battery is repeatedly charged and discharged, the bond between the active material and the conductive material weakens, causing volume changes in the current collector (10), thereby reducing the lifespan and function of the secondary battery. However, the binder can improve this problem by enhancing the bonding strength of the active material and the conductive material.

[0046] The binder is not particularly limited, but specific examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 1 wt% to 30 wt%, specifically 1 wt% to 10 wt%, and more specifically 1 wt% to 5 wt%, based on the total weight of the solid content in the active material slurry.

[0047] According to the electrode manufacturing method, a coating layer is coated multiple times on the outer surface of the current collector and a second coating layer (11b) is coated in a specific structure, so that multiple regions with different active material densities and electrolyte impregnation properties can be formed on the electrode (1). In other words, a region with a relatively higher active material density than other regions can be formed on the electrode (1), and a region with a relatively higher electrolyte impregnation property than other regions can be formed.

[0048] FIG. 2 is a perspective view showing a second coating layer (11b) coated on the outer surface of a first coating layer (11a) according to an electrode manufacturing method according to one embodiment of the present invention.

[0049] Referring to FIG. 2, the electrode manufacturing method may include a step (S10) of coating a first coating layer (11a), a step (S20) of coating a second coating layer (11b), and a step (S30) of rolling by a rolling device.

[0050] In the step (S10) of coating the first coating layer (11a), the first coating layer (11a) may be coated on at least one surface of the current collector (10) including a metal material. For example, the first coating layer (11a) may be coated on one surface of the current collector (10) or both surfaces of the current collector (10). In addition, the first coating layer (11a) may be formed only on a specific portion of the current collector (10), rather than on the entire current collector (10).

[0051] The first coating layer (11a) can be coated on at least one surface of the current collector (10) along the longitudinal direction of the current collector (10). For example, the first coating layer (11a) can be coated on the outer surface of the current collector (10) so as to have a longitudinal direction parallel to the longitudinal direction of the current collector (10).

[0052] When the electrode (1) is manufactured, a portion of the current collector (10) on which the first coating layer (11a) is formed may be a holding portion containing an active material slurry. The other portion of the current collector (10) on which the first coating layer (11a) is not formed may be a non-conductive portion not containing an active material slurry.

[0053] In the step (S20) of coating the second coating layer (11b), a plurality of second coating layers (11b) containing an active material may be coated on at least one surface of the first coating layer (11a). For example, the second coating layer (11b) may be coated on one surface of the first coating layer (11a), and the other surface of the first coating layer (11a) may be coated on the current collector (10). In other words, the first coating layer (11a) may be coated on the upper surface of the current collector (10), and the second coating layer (11b) may be coated on the upper surface of the first coating layer (11a).

[0054] In the step (S20) of coating the second coating layer (11b), a plurality of second coating layers (11b) may be coated so as to form a space between each other. For example, the second coating layer (11b) may be coated along the width direction of the current collector (10), and the plurality of second coating layers (11b) may be formed so as to be spaced apart from each other at a constant space. That is, the longitudinal direction of the second coating layer (11b) may be parallel to the width direction of the current collector (10). In other words, the plurality of second coating layers (11b) may be coated in a stripe shape on the outer surface of the first coating layer (11a).

[0055] However, the direction in which the second coating layer (11b) is coated is not limited to this, and the second coating layer (11b) may be coated perpendicular to the width direction of the current collector (10).

[0056] The second coating layer (11b) may be formed to be spaced apart from both ends of the first coating layer (11a). For example, a pair of second coating layers (11b) located at the outermost end among a plurality of second coating layers (11b) may be spaced apart from both ends of the first coating layer (11a) by a certain distance.

[0057] According to the structure of the second coating layer (11b) as described above, since the second coating layer (11b) is not formed at both ends of the first coating layer (11a), the active material slurry is prevented from being formed at a high level at both ends of the first coating layer (11a), and thus problems such as the sliding phenomenon of the active material slurry can be prevented.

[0058] In the step (S30) of rolling by a rolling device, the collector (10), the first coating layer (11a), and the second coating layer (11b) can be rolled by the rolling device. For example, the rolling device can include a roller press.

[0059] Specifically, a current collector (10) coated with a first coating layer (11a) and a second coating layer (11b) can be moved between a pair of roller presses. The first coating layer (11a), the second coating layer (11b), and the current collector (10) can be rolled by being pressed by the pair of roller presses.

[0060] By the rolling process of such a rolling device, the density of the electrode (1) manufactured can be increased, and the adhesive strength and bonding strength between the current collector (10) and the active material slurry can be enhanced. In addition, by the rolling process, directionality is created in the crystal structure of the electrode (1), so that electric energy can be generated from the electrode (1) with a greater output. Consequently, the performance of the electrode (1) manufactured by the rolling process can be enhanced.

[0061] FIG. 3 is a cross-sectional view showing a first coating layer (11a), a second coating layer (11b), and a current collector (10) being rolled according to an electrode manufacturing method according to one embodiment of the present invention.

[0062] Referring to FIG. 3, in the step (S30) of rolling by a rolling device, a first active material layer (110) in which a first coating layer (11a) and a second coating layer (11b) are rolled together, and a second active material layer (111) in which the first coating layer (11a) is rolled alone can be formed. For example, when a plurality of second coating layers (11b) are coated on one surface of the first coating layer (11a) at regular intervals from each other, the first coating layer (11a) and the second coating layer (11b) are rolled by the rolling device, thereby forming an area in which the first coating layer (11a) and the second coating layer (11b) overlap. That is, the first active material layer (110) can be formed only on a specific portion of the first coating layer (11a) on which the second coating layer (11b) is coated.

[0063] The first active material layer (110) and the second active material layer (111) are formed in multiple numbers, and the multiple first active material layers (110) and the multiple second active material layers (111) can be formed along the current collector (10). For example, the first active material layers (110) and the second active material layers (111) can be formed alternately along the longitudinal direction of the current collector (10).

[0064] Additionally, the first active material layer (110) and the second active material layer (111) may be formed along the width direction of the current collector (10). In other words, the first active material layer (110) and the second active material layer (111) may be formed in a direction parallel to the width direction of the current collector (10).

[0065] In the step (S30) of rolling by the rolling device, the electrode (1), the first coating layer (11a), and the second coating layer (11b) can be rolled so that the outer surface of the first active material layer (110) and the outer surface of the second active material layer (111) are positioned on the same surface.

[0066] In the step (S30) of rolling by the rolling device, the active material density of the first active material layer (110) may be higher than the active material density of the second active material layer (111). In other words, since the first active material layer (110) is a portion in which the first coating layer (11a) and the second coating layer (11b) are overlapped and rolled, it may contain a larger amount of active material, unlike the second active material layer (111) in which the first coating layer (11a) is formed alone. That is, since the first active material layer (110) contains a larger amount of active material per same volume, the active material density of the first active material layer (110) may be higher than the active material density of the second active material layer (111).

[0067] Therefore, unlike the case where only the first coating layer (11a) is coated on the current collector (10) and then rolled, the second coating layer (11b) is secondarily coated on the first coating layer (11a) and then rolled, so that according to the electrode manufacturing method according to one embodiment of the present invention, an active material region with a higher density is formed, and thus an electrode (1) with higher capacity and higher performance can be manufactured.

[0068] Conversely, in the step (S30) of being rolled by a rolling device, the electrolyte impregnation property of the second active material layer (111) may be higher than the electrolyte impregnation property of the first active material layer (110). In other words, since the second active material layer (111) is a layer formed only by the first coating layer (11a) that does not overlap with the second coating layer (11b), it can impregnate the electrolyte more.

[0069] Accordingly, since the second active material layer (111) has relatively high electrolyte impregnation property, when manufacturing a secondary battery using the electrode (1), the electrolyte impregnation speed is increased, so that the productivity of the secondary battery can be further increased. In addition, because the second active material layer (111) has high electrolyte impregnation property, the electrolyte can quickly reach the electrode active material particles, so that lithium ions can move more smoothly, so that the performance of the secondary battery manufactured using the electrode (1) can be improved.

[0070] As a result, by forming the first active material layer (110) and the second active material layer (111) by the electrode manufacturing method according to one embodiment of the present invention, an electrode (1) is manufactured, thereby manufacturing a high-capacity electrode (1), and thus an electrode (1) with excellent electrolyte impregnation properties can be manufactured.

[0071] Hereinafter, an electrode (1) according to another embodiment of the present invention will be described. The electrode (1) according to another embodiment of the present invention can be manufactured through an electrode manufacturing method according to one embodiment of the present invention, as described above.

[0072] Figure 4 is a perspective view of an electrode according to another embodiment of the present invention.

[0073] Referring to Fig. 4, the electrode (1) can be manufactured by coating an active material layer (11) on a current collector (10). For example, the current collector (10) includes a metal material, and an active material layer (11) can be coated on at least one surface of the current collector (10).

[0074] The active material layer (11) may include a first active material layer (110) and a second active material layer (111) that is alternately positioned with the first active material layer (110). For example, the first active material layer (110) and the second active material layer (111) may be formed in multiple numbers, and the multiple first active material layers (110) and the multiple second active material layers (111) may be formed along the current collector (10). The first active material layers (110) and the second active material layers (111) may be alternately formed along the longitudinal direction of the current collector (10).

[0075] Additionally, the first active material layer (110) and the second active material layer (111) may be formed along the width direction of the current collector (10). In other words, the first active material layer (110) and the second active material layer (111) may be formed in a direction parallel to the width direction of the current collector (10).

[0076] The first active material layer (110) and the second active material layer (111) can be formed on the outer surface of the current collector (10) so that the outer surface of the first active material layer (110) and the outer surface of the second active material layer (111) are positioned on the same surface.

[0077] The active material density of the first active material layer (110) may be higher than the active material density of the second active material layer (111). In addition, the electrolyte impregnation property of the second active material layer (111) may be higher than the electrolyte impregnation property of the first active material layer (110).

[0078] Figure 5 is a perspective view of an electrode according to another embodiment of the present invention.

[0079] Referring to FIG. 5, an electrode (1) according to another embodiment of the present invention may include a first active material layer (110) formed along the longitudinal direction of a current collector (10). For example, the first active material layer (110) according to another embodiment of the present invention may be formed to be parallel to the longitudinal direction of the current collector (10). Accordingly, the second active material layer (111) may also be formed to be parallel to the longitudinal direction of the current collector (10). In other words, the first active material layer (110) and the second active material layer (111) according to another embodiment of the present invention may be formed to be perpendicular to the width direction of the current collector (10).

[0080] The above description is merely an example of the technical idea of ​​the present invention, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present invention.

[0081] Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of ​​the present invention but to explain it, and the scope of the technical idea of ​​the present invention is not limited by these embodiments.

[0082] The scope of protection of the present invention should be interpreted by the claims below, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the rights of the present invention.

[0083] [Explanation of symbols]

[0084] 1: Electrode

[0085] 10: Whole house

[0086] 11: Active material layer

[0087] 110: First active material layer

[0088] 111: Second active material layer

[0089] 11a: First coating layer

[0090] 11b: Second coating layer

Claims

1. A step of coating a first coating layer including an active material on at least one surface of a current collector including a metal material; A step of coating a plurality of second coating layers containing an active material on at least one surface of the first coating layer; and A method for manufacturing an electrode, comprising a step of rolling the entire body, the first coating layer and the second coating layer by a rolling device.

2. In paragraph 1 A method for manufacturing an electrode, wherein, in the step of coating the second coating layer, the plurality of second coating layers are coated so as to have a set interval between them.

3. In paragraph 2 A method for manufacturing an electrode, wherein, in the step of rolling by the rolling device, a first active material layer in which the first coating layer and the second coating layer are rolled together and a second active material layer in which the first coating layer is rolled alone are formed.

4. In paragraph 3 A method for manufacturing an electrode, wherein, in the step of rolling by the rolling device, the active material density of the first active material layer is higher than the active material density of the second active material layer.

5. In paragraph 3 A method for manufacturing an electrode, wherein, in the step of rolling by the rolling device, the electrolyte impregnation property of the second active material layer is higher than the electrolyte impregnation property of the first active material layer.

6. In paragraph 3 A method for manufacturing an electrode, wherein, in the step of rolling by the rolling device, the electrode, the first coating layer and the second coating layer are rolled so that the outer surface of the first active material layer and the outer surface of the second active material layer are located on the same plane.

7. In paragraph 2 A method for manufacturing an electrode, wherein in the step of coating the second coating layer, the second coating layer is coated along the width direction of the current collector.

8. A current collector comprising a metal material; and Comprising an active material layer coated on at least one surface of the above-mentioned collector, The above active material layer is, first active material layer; and An electrode comprising a second active material layer alternately positioned with the first active material layer and having a lower active material density than the first active material layer.

9. In Article 8 An electrode wherein the electrolyte impregnation property of the second active material layer is higher than the electrolyte impregnation property of the first active material layer.

10. In Article 8 An electrode wherein the first active material layer and the second active material layer are formed along the width direction of the current collector.

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