Electrode manufacturing method

Abstract

To provide a method of manufacturing an electrode capable of forming an active material layer intermittently.SOLUTION: An active material layer is formed on a surface of an electrode current collector. A groove part is formed on a surface of the active material layer. An electrode is manufactured by peeling a part of the active material layer. The electrode current collector includes a metal foil and an adhesive layer. The metal foil includes a first region and a second region in a plan view. The adhesive layer covers the first region. The second region is adjacent to the first region. The metal foil is exposed in the second region. The active material layer is formed so as to include a first portion and a second portion. The second portion is adjacent to the first portion. The first portion covers the adhesive layer. The second portion covers the second region. The groove part is formed on each of the first portion and the second portion. The second portion is peeled off.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electrode, an electrode current collector, and an electrode. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2013-017962 (Patent Document 1) discloses a functional sheet coating device that has excellent linearity at the start and end of coating during intermittent coating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-017962 Summary of the Invention [Problem to be solved by the invention]

[0004] An electrode can be manufactured by forming an active material layer on the surface of an electrode current collector. The active material layer may be formed intermittently. In areas where the active material layer is not formed, the surface of the electrode current collector is exposed. Hereinafter, the exposed surface of the electrode current collector is also referred to as an "exposed region." The exposed region can function as a cutting margin for the electrode, a welding part for the current collecting member, etc.

[0005] The intermittent formation of the active material layer may cause the shape of the edge (periphery) of the active material layer to become irregular, which may result in, for example, a decrease in battery performance.

[0006] An object of the present disclosure is to provide a method for manufacturing an electrode that can form an active material layer intermittently. [Means for solving the problem]

[0007] The technical configuration and effects of the present disclosure will be described below. However, the mechanism of action in this specification includes speculation. The mechanism of action does not limit the technical scope of the present disclosure.

[0008] 1. The method for producing an electrode includes the following steps (a) to (c): (a) An active material layer is formed on the surface of an electrode current collector. (b) Grooves are formed on the surface of the active material layer. (c) A portion of the active material layer is peeled off to produce an electrode. The electrode current collector includes a metal foil and an adhesive layer. In a plan view, the metal foil includes a first region and a second region. The adhesive layer covers the first region. The second region is adjacent to the first region. The metal foil is exposed in the second region. In the above (a), the active material layer is formed to include a first portion and a second portion. The second portion is adjacent to the first portion. The first portion covers the adhesive layer. The second portion covers the second region. In the above (b), a groove portion is formed in each of the first portion and the second portion. In the above (c), the second portion is peeled off.

[0009] The electrode current collector includes a first region and a second region. The first region is a region of the electrode where an active material layer is disposed. The second region is a region of the electrode that is exposed. The first region is covered with an adhesive layer.

[0010] The active material layer includes a first portion and a second portion. The first portion is formed on a first region (adhesive layer). The second portion is formed on a second region (metal foil). A groove is formed in the active material layer. The groove is formed in each of the first portion and the second portion. An adhesive layer is interposed between the first portion and the metal foil. The formation of the groove allows the first portion to be firmly adhered to the metal foil. In other words, the peel strength of the first portion can be improved. On the other hand, no adhesive layer is interposed between the second portion and the metal foil. The formation of the groove makes the second portion brittle, and therefore the peel strength of the second portion can actually be reduced.

[0011] Because there is a difference in peel strength between the first portion and the second portion, the second portion can be easily peeled off. By peeling off the second portion, the first portion (active material layer) remains with little disturbance in the edge shape according to the planar shape of the first region (adhesive layer). In other words, the active material layer can be formed intermittently.

[0012] 2. The above (a) may include the following (a1) to (a3): (a1) Prepare a wet powder. (a2) The wet powder is processed into an active material layer by roll molding. (a3) An active material layer is disposed on the surface of an electrode current collector.

[0013] In the above "1.", the active material layer can be formed by any method. For example, the active material layer may be formed by coating a slurry.

[0014] For example, the active material layer may be formed by roll molding of a wet powder. The wet powder is an aggregate of particles. In roll molding, a sheet (active material layer) is formed by spreading the aggregate of particles, so there is a tendency for the edge shape to become irregular. In the manufacturing method described in "1." above, even when the workpiece is a wet powder, the irregularity of the edge shape can be reduced.

[0015] 3. In the above (b), a part of the groove may be formed along the boundary between the first portion and the second portion.

[0016] The groove along the boundary between the first and second portions can function as a perforation line when the second portion is peeled off. By having part of the groove function as a perforation line, it is expected that the distortion of the edge shape of the first portion (final active material layer) will be further reduced.

[0017] 4. (c) above may include imparting vibration to the second portion.

[0018] The second portion is expected to be peeled off by a weak stimulus, for example, vibration may be applied to the second portion.

[0019] 5. The electrode current collector includes a metal foil and an adhesive layer. In plan view, the metal foil includes a first region and a second region. The adhesive layer covers the first region. The second region is adjacent to the first region. The metal foil is exposed in the second region.

[0020] The electrode current collector of "5." above is suitable as the electrode current collector of "1." above.

[0021] 6. The metal foil may have a band-like shape in plan view. The first regions and the second regions may be arranged alternately in the longitudinal direction of the metal foil.

[0022] 7. In plan view, the first region may have a rectangular planar shape.

[0023] 8. In plan view, the second region may surround the periphery of the first region.

[0024] 9. The electrode includes an electrode current collector and an active material layer. The active material layer covers the adhesive layer. A groove is formed on the surface of the active material layer. The end face of the active material layer has an inclination angle of 45 degrees or more.

[0025] In an electrode manufactured by the manufacturing method described in "1." above, the edge shape of the active material layer (first portion) is less disordered. The active material layer may have, for example, a steep edge. That is, the edge of the active material layer may have an inclination angle of 45 degrees or more. The steep edge of the active material layer is expected to improve, for example, the energy density.

[0026] Hereinafter, an embodiment of the present disclosure (hereinafter may be abbreviated as "the present embodiment") will be described. However, the present embodiment does not limit the technical scope of the present disclosure. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic flowchart of a method for producing an electrode according to this embodiment. [Figure 2] FIG. 2 is a first schematic cross-sectional view showing a manufacturing process of an electrode. [Figure 3] FIG. 3 is a schematic plan view showing an example of a metal foil. [Figure 4] FIG. 4 is a schematic flow chart showing an example of a method for forming an active material layer. [Figure 5] FIG. 5 is a schematic diagram showing an example of a film forming apparatus. [Figure 6] FIG. 6 is an image showing an example of the end shape. [Figure 7] FIG. 7 is a second schematic cross-sectional view showing the manufacturing process of the electrode. [Figure 8] FIG. 8 is a third schematic cross-sectional view showing the manufacturing process of the electrode. [Figure 9] FIG. 9 is a schematic plan view showing an example of a groove portion. [Figure 10] FIG. 10 is a fourth schematic cross-sectional view showing the manufacturing process of the electrode. [Figure 11] FIG. 11 is a schematic plan view showing an example of an electrode in this embodiment. [Figure 12] FIG. 12 is an image showing actual partial peeling. [Figure 13] FIG. 13 is a schematic cross-sectional view showing an electrode in this embodiment. [Figure 14] FIG. 14 is a first conceptual diagram illustrating the relationship between the inclination angle of the end face and the energy density. [Figure 15] FIG. 15 is a second conceptual diagram illustrating the relationship between the inclination angle of the end face and the energy density. [Figure 16] FIG. 16 is an image showing an application example of this embodiment. [Figure 17] FIG. 17 is an image showing a reference form. DETAILED DESCRIPTION OF THE INVENTION

[0028] <Terminology> In this specification, the terms "comprise," "include," "have," and variations thereof (e.g., "consisting of") are open-ended. Open-ended terms may or may not include additional elements in addition to the required elements. The term "consisting of" is closed-ended. However, even in closed-ended terms, additional elements that are normally incidental impurities or unrelated to the disclosed technology are not excluded. The term "consisting essentially of..." is semi-closed. Semi-closed terms allow for the addition of elements that do not substantially affect the basic and novel characteristics of the disclosed technology.

[0029] In this specification, expressions such as "may" and "can" are used in the permissive sense of "possibly" rather than the obligatory sense of "must."

[0030] In this specification, the order of execution of multiple steps, actions, operations, etc. included in various methods is not limited to the order described unless otherwise specified. For example, multiple steps may proceed simultaneously. For example, multiple steps may occur one after the other.

[0031] In this specification, unless otherwise specified, a numerical range such as "m to n%" includes both the upper and lower limits. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "more than m% and less than n%." Furthermore, a numerical value arbitrarily selected from within the numerical range may be set as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described elsewhere in this specification, in a table, a figure, or the like.

[0032] In this specification, all numerical values ​​are modified by the term "about." The term "about" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximate values ​​that may vary depending on the application of the disclosed technology. All numerical values ​​may be expressed with significant figures. Measured values ​​may be the average value of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. In general, the more measurements are made, the more reliable the average value is expected to be. Measured values ​​may be rounded off based on the number of significant figures. Measured values ​​may include errors, such as those associated with the detection limits of the measuring device.

[0033] Geometric terms used in this specification (e.g., "parallel," "perpendicular," "orthogonal," etc.) should not be interpreted in a strict sense. For example, "parallel" may deviate slightly from the strict meaning of "parallel." Geometric terms used in this specification may include, for example, tolerances, errors, etc. in design, work, manufacturing, etc. The dimensional relationships in each drawing may not match the actual dimensional relationships. To facilitate understanding of the disclosed technology, the dimensional relationships (length, width, thickness, etc.) in each drawing may be changed. Furthermore, some configurations may be omitted.

[0034] In this specification, the term "planar view" refers to viewing an object from a line of sight parallel to the thickness direction of the object. A planar view is depicted in a plan view. In this specification, the term "cross-sectional view" refers to viewing an object from a line of sight perpendicular to the thickness direction of the object. A cross-sectional view is depicted in a cross-sectional view.

[0035] In this specification, the term "tilt angle" refers to the angle (acute angle or right angle) formed between the end face of the active material layer and the surface of the electrode current collector in a cross-sectional view.

[0036] In this specification, when a compound is expressed by a stoichiometric formula (e.g., "LiCoO2"), the stoichiometric formula is merely a representative example of the compound. The compound may have a non-stoichiometric composition. For example, when lithium cobalt oxide is expressed as "LiCoO2," unless otherwise specified, the lithium cobalt oxide is not limited to a composition ratio of "Li / Co / O = 1 / 1 / 2" and may contain Li, Co, and O in any composition ratio. Furthermore, doping or substitution with trace elements may be permitted.

[0037] As used herein, the term "electrode" refers collectively to a positive electrode and a negative electrode. The electrode may be a positive electrode or a negative electrode. The electrode may be applied to any battery system. For example, the electrode may be for a lithium-ion battery.

[0038] As used herein, the term "solid content" refers to the total mass fraction (percentage) of components other than the liquid material in a solid-liquid mixture. The solid content may also be referred to as "NV (Nonvolatile Content)." Components dissolved in the liquid material (solutes) are considered to be components other than the liquid material.

[0039] In this specification, "slurry" refers to a dispersion system in which a solid material (powder) is dispersed in a liquid material, and "wet powder" refers to a dispersion system in which a liquid material is dispersed in a solid material (powder).

[0040] In this specification, "D50" is defined as the particle size at which the cumulative frequency of smaller particle sizes reaches 50% in a volume-based particle size distribution. The volume-based particle size distribution can be measured using a laser diffraction particle size distribution analyzer.

[0041] <Electrode manufacturing method> Fig. 1 is a schematic flowchart of a method for manufacturing an electrode according to this embodiment. Hereinafter, the "method for manufacturing an electrode according to this embodiment" may be abbreviated as "the present manufacturing method." The present manufacturing method includes "(a) forming an active material layer," "(b) forming grooves," and "(c) partial peeling."

[0042] (a) Formation of Active Material Layer The manufacturing method includes forming an active material layer on the surface of an electrode current collector.

[0043] <Electrode current collector> 2 is a first schematic cross-sectional view showing the manufacturing process of an electrode. An electrode current collector 10 is prepared. The electrode current collector 10 is a sheet-like substrate. The electrode current collector 10 includes a metal foil 11 and an adhesive layer 12.

[0044] The metal foil 11 has a current collecting function. The metal foil 11 may have a thickness of, for example, 5 to 50 μm. The metal foil 11 may contain, for example, at least one selected from the group consisting of aluminum (Al), copper (Cu), nickel (Ni), iron (Fe), chromium (Cr), and titanium (Ti). The metal foil 11 may contain, for example, Al foil, Al alloy foil, Cu foil, Ni foil, stainless steel foil, etc.

[0045] 3 is a schematic plan view showing an example of a metal foil. In a plan view, the metal foil 11 may have, for example, a strip-like planar shape. The metal foil 11 includes first regions 11a and second regions 11b. The first regions 11a and the second regions 11b may be arranged alternately in the longitudinal direction (Y-axis direction) of the metal foil 11.

[0046] The first region 11a is where the active material layer is disposed in the electrode. The first region 11a may have any planar shape. In plan view, the first region 11a may have, for example, a rectangular planar shape.

[0047] The second region 11b is an exposed region of the electrode. In the second region 11b, the metal foil 11 is exposed. The second region 11b is adjacent to the first region 11a. In a plan view, the second region 11b may, for example, surround the periphery of the first region 11a.

[0048] The adhesive layer 12 covers the first region 11a (see FIG. 2). The adhesive layer 12 bonds the active material layer to the metal foil 11. The adhesive layer 12 may have a thickness of, for example, 0.1 to 5 μm. The adhesive layer 12 may contain any adhesive material. The adhesive layer 12 may contain, for example, at least one selected from the group consisting of styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP). The adhesive layer 12 may further contain, in addition to the adhesive material, a conductive material, for example. The conductive material may include, for example, carbon black, etc.

[0049] The adhesive layer 12 can be formed by any method. For example, an adhesive composition containing an adhesive may be prepared. For example, the adhesive composition may be prepared by mixing a liquid material (solvent or dispersion medium) with an adhesive. The adhesive composition may be a solution or a particle dispersion. The mass fraction of the adhesive in the adhesive composition can be adjusted so that the adhesive composition exhibits a desired viscosity. The mass fraction of the adhesive may be, for example, 1 to 50%. An appropriate liquid material can be selected depending on the type of adhesive. The liquid material may include, for example, at least one selected from the group consisting of water, N-methyl-2-pyrrolidone (NMP), and butyl butyrate.

[0050] For example, an adhesive composition may be intermittently applied to the surface of the metal foil 11 using a die coater or the like. The adhesive composition is dried to form the adhesive layer 12. That is, the first region 11a and the second region 11b may be formed.

[0051] <slurry> For example, the active material layer may be formed by applying a slurry to the surface of the electrode current collector 10. For example, the slurry may be applied using a die coater or the like. The slurry may be formed by mixing an active material, a conductive material, a binder, and a liquid material, for example. The solid content of the slurry may be, for example, 50 to 70%, or 50 to 65%.

[0052] <Wet powder> 4 is a schematic flowchart showing an example of a method for forming an active material layer. "(a) Formation of an active material layer" may include, for example, "(a1) Preparation of wet powder," "(a2) Roll molding," and "(a3) Transfer."

[0053] (a1) Preparation of wet powder The manufacturing method may include preparing a wet powder. For example, the wet powder may be formed by mixing an active material, a binder, a conductive material, and a liquid material. For example, the materials may be mixed using a stirring granulator or the like. The solid content of the wet powder may be, for example, 70 to 99% or 75 to 90%.

[0054] The active material may be, for example, spherical, blocky, flake-like, columnar, etc. The active material may have any size. The active material may have a D50 of, for example, 1 to 30 μm, or 5 to 20 μm.

[0055] The active material may be, for example, a positive electrode active material. The positive electrode active material can absorb and release lithium (Li) ions at a higher potential than the negative electrode active material. The positive electrode active material may contain any component. The positive electrode active material may contain, for example, at least one selected from the group consisting of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. For example, "(NiCoMn)" in "Li(NiCoMn)O2" indicates that the sum of the composition ratios in parentheses is 1. As long as the sum is 1, the amounts of the individual components are arbitrary. Li(NiCoMn)O2 may be, for example, Li(Ni 1 / 3Co 1 / 3 Mn 1 / 3 )O2, Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, Li(Ni 0.8 Co 0.1 Mn 0.1 ) O2, etc.

[0056] The negative electrode active material can absorb and release Li ions at a lower potential than the positive electrode active material. The negative electrode active material can contain any component. Examples of the negative electrode active material include graphite, soft carbon, hard carbon, silicon, silicon oxide, silicon-based alloys, tin, tin oxide, tin-based alloys, and Li4Ti5O. 12 It may contain at least one selected from the group consisting of:

[0057] The binder may be soluble or insoluble in the liquid material. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the active material. The binder may contain any component. For example, the binder may contain at least one selected from the group consisting of PVdF, PTFE, PVdF-HFP, SBR, CMC, and PAA.

[0058] The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of active material. The conductive material may contain any component. The conductive material may include, for example, at least one selected from the group consisting of carbon black, vapor-grown carbon fiber, carbon nanotubes, and graphene flakes. The carbon black may include, for example, at least one selected from the group consisting of acetylene black, furnace black, channel black, and thermal black.

[0059] (a2) Roll forming The method may include converting the wet powder into the active material layer by roll forming.

[0060] FIG. 5 is a schematic diagram showing an example of a film-forming apparatus. The film-forming apparatus 300 can process the wet powder 2 into an active material layer 20. The film-forming apparatus 300 includes a first roll 301, a second roll 302, and a third roll 303. Each roll rotates in the direction of the arrow. The rotation axes of the rolls are parallel to each other. When the rotation speed of the first roll 301 is ω1, the rotation speed of the second roll 302 is ω2, and the rotation speed of the third roll 303 is ω3, the relationship "ω1<ω2<ω3" may be satisfied, for example.

[0061] A gap AB is formed between a first roll 301 and a second roll 302. A wet powder 2 is supplied to the gap AB. In the gap AB, the wet powder 2 is consolidated and spread to form an active material layer 20 (sheet). The active material layer 20 may have a thickness of, for example, 10 to 500 μm, or may have a thickness of 50 to 200 μm.

[0062] (a3) Transcription The present manufacturing method may include disposing the active material layer 20 on the surface of the electrode current collector 10. For example, the active material layer 20 may be transferred to the electrode current collector 10 by a film-forming apparatus 300. A gap BC is formed between a second roll 302 and a third roll 303. The second roll 302 transports the active material layer 20 into the gap BC. The third roll 303 transports the electrode current collector 10 into the gap BC.

[0063] In the gap BC, the active material layer 20 is rubbed against the surface of the electrode current collector 10. This causes the active material layer 20 to adhere to the surface of the electrode current collector 10. In other words, the active material layer 20 is disposed on the surface of the electrode current collector 10.

[0064] Fig. 6 is an image showing an example of the edge shape. Fig. 6 shows a portion corresponding to region VI in Fig. 5. In the method of forming active material layer 20 using wet powder, there is a tendency for the edge shape in the width direction (X-axis direction) to become distorted.

[0065] 7 is a second schematic cross-sectional view showing the manufacturing process of the electrode. The active material layer 20 is formed to include a first portion 20a and a second portion 20b. The second portion 20b is adjacent to the first portion 20a. The first portion 20a covers the adhesive layer 12 (first region 11a). The second portion 20b covers the second region 11b. The active material layer 20 may be formed to cover, for example, the entire surface of the electrode current collector 10.

[0066] (b) Groove formation 8 is a third schematic cross-sectional view showing the manufacturing process of the electrode. This manufacturing method includes forming grooves 21 in the surface of the active material layer 20. The grooves 21 can be formed, for example, by stamping. That is, the grooves 21 (recesses) may be formed by pressing a convex mold against the surface of the active material layer 20. For example, an embossing roll or the like may be used.

[0067] After the grooves 21 are formed, the active material layer 20 may be dried. The active material layer 20 may be dried by any method. For example, a hot air drying oven or the like may be used.

[0068] The grooves 21 can function as, for example, flow paths for the electrolyte. The formation of the grooves 21 is expected to improve battery performance (for example, cycle characteristics, etc.). The cross-sectional shape of the grooves 21 is arbitrary. The cross-sectional shape of the grooves 21 may be rectangular, U-shaped, or V-shaped. The grooves 21 may have a depth of, for example, 10 to 150 μm. The ratio of the depth of the grooves 21 to the thickness of the active material layer 20 may be, for example, 0.1 to 0.9, or 0.3 to 0.7.

[0069] The grooves 21 may be formed in each of the first portion 20a and the second portion 20b. By forming the grooves 21 in the first portion 20a, the peel strength of the first portion 20a may be improved. By forming the grooves 21 in the second portion 20b, the peel strength of the second portion 20b may be reduced.

[0070] A portion of groove 21 may be formed along boundary 20c between first portion 20a and second portion 20b. A portion of groove 21 along boundary 20c can function as a cutting line for active material layer 20. Boundary 20c can be located directly on the boundary between first region 11a and second region 11b. A portion of groove 21 may extend linearly along boundary 20c. A portion of groove 21 may substantially coincide with the position of boundary 20c. A portion of groove 21 can function as a cutting line even if it is somewhat separated from boundary 20c. The distance between the portion of groove 21 and boundary 20c may be, for example, 0 to 10 mm.

[0071] 9 is a schematic plan view showing an example of a groove portion. The groove portion 21 can have any planar pattern. For example, the groove portion 21 may be formed in a line pattern. For example, the groove portion 21 may be formed in a lattice pattern. The pitch of the groove portion 21 (the distance between adjacent parallel lines) may be, for example, 0.1 to 10 mm, or 0.5 to 5 mm.

[0072] 《(c) Partial peeling》 FIG. 10 is a fourth schematic cross-sectional view showing the manufacturing process of the electrode. This manufacturing method includes peeling off a part of the active material layer 20. That is, the second portion 20b is peeled off. Because the peel strength of the second portion 20b is low, the second portion 20b can be peeled off by a weak stimulus. For example, vibration may be applied to the second portion 20b. For example, the second portion 20b may be sucked by a suction pump or the like. The peeled second portion 20b may be reused, for example, as a raw material for a wet powder.

[0073] FIG. 11 is a schematic plan view showing an example of an electrode in this embodiment. Hereinafter, "the electrode in this embodiment" may be abbreviated as "the present electrode." The present electrode 100 may be produced by peeling off the second portion 20b. The present electrode 100 includes an active material layer 20. The active material layer 20 corresponds to the first portion 20a. The active material layer 20 may have a planar shape corresponding to the first region 11a (adhesive layer 12).

[0074] 12 is an image showing actual partial peeling. The second portion 20b can be peeled off as if being cut away. After the second portion 20b is peeled off, there is little distortion in the edge shape of the first portion 20a. The first portion 20a can have a rectangular planar shape. The periphery of the first portion 20a can be straight.

[0075] <Electrode> Fig. 13 is a schematic cross-sectional view showing an electrode in this embodiment. The electrode 100 includes an electrode current collector 10 and an active material layer 20. The active material layer 20 may be disposed on only one surface of the electrode current collector 10, or on both the front and back surfaces. The active material layer 20 in Fig. 13 corresponds to the first portion 20a in Fig. 7 and other figures. The active material layer 20 is coated with an adhesive layer 12. The region where the metal foil 11 is exposed corresponds to the second region 11b in Fig. 3 and other figures. A groove portion 21 is formed on the surface of the active material layer 20.

[0076] The electrode 100 has small irregularities in the edge shape. In the electrode 100, the active material layer 20 may have steep edge faces. The edge faces of the active material layer 20 may have an inclination angle θ of 45 degrees or more. The inclination angle θ may be, for example, 60 to 90 degrees, or 75 to 90 degrees. The closer the inclination angle θ is to 90 degrees, the more improved the energy density is expected to be.

[0077] FIG. 14 is a first conceptual diagram illustrating the relationship between the inclination angle of the end face and energy density. For convenience, the groove and adhesive layer are omitted from FIGS. 14 and 15. The present electrode 100 faces a counter electrode 200 across a separator 400. The counter electrode 200 has the opposite polarity to the present electrode 100. For example, when the present electrode 100 is a positive electrode, the counter electrode 200 is a negative electrode. If the inclination angle θ of the end face is small, a dead space 20s may be formed at the end of the present electrode 100 facing the counter electrode 200. The formation of the dead space 20s may reduce the energy density.

[0078] 15 is a second conceptual diagram illustrating the relationship between the inclination angle of the end face and the energy density. As the inclination angle θ approaches 90 degrees, the dead space 20s can become smaller. In other words, as the inclination angle θ approaches 90 degrees, it is expected that the energy density will improve.

[0079] Fig. 16 is an image showing an application example of this embodiment. Fig. 16 shows a cross-sectional SEM image of an electrode. The active material layer 20 in Fig. 16 is formed from a wet powder. The end faces of the active material layer 20 are formed by partial peeling according to this embodiment. The active material layer 20 has steep end faces. The inclination angle of the end faces is 45 degrees or more.

[0080] FIG. 17 is an image showing a reference embodiment. FIG. 17 shows a cross-sectional SEM image of an electrode. The active material layer 20 in FIG. 17 is formed from a slurry. In the reference embodiment, the partial peeling of this embodiment is not performed. Because the slurry has high fluidity, dripping easily occurs at the edge of the coating film. Dripping can reduce the inclination angle of the end face. The inclination angle of the end face is less than 45 degrees.

[0081] The present embodiment is illustrative in all respects. The present embodiment is not restrictive. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the description of the claims. For example, it is also intended from the beginning that any configuration may be extracted from the present embodiment and arbitrarily combined. [Explanation of symbols]

[0082] 2 wet powder, 10 electrode current collector, 11 metal foil, 11a first region, 11b second region, 12 adhesive layer, 20 active material layer, 20a first portion, 20b second portion, 20c boundary, 20s dead space, 21 groove portion, 100 electrode, 200 counter electrode, 300 film forming device, 301 first roll, 302 second roll, 303 third roll, 400 separator, AB, BC gap, θ tilt angle.

Claims

1. (a) forming an active material layer on the surface of an electrode current collector; (b) forming a groove on the surface of the active material layer; and (c) producing an electrode by peeling off a portion of the active material layer; Including, the electrode current collector includes a metal foil and an adhesive layer, In a plan view, the metal foil includes a first region and a second region, the adhesive layer covers the first region; the second region is adjacent to the first region, In the second region, the metal foil is exposed, In the above (a), the active material layer is formed to include a first portion and a second portion, the second portion is adjacent to the first portion; the first portion covers the adhesive layer; the second portion covers the second region; In (b), the groove portion is formed in each of the first portion and the second portion; In the step (c), the second portion is peeled off. Electrode manufacturing method.

2. The (a) is (a1) providing a wet powder; (a2) processing the wet powder into the active material layer by roll forming; and (a3) disposing the active material layer on the surface of the electrode current collector; Including, A method for manufacturing the electrode according to claim 1.

3. In (b), a part of the groove is formed along the boundary between the first portion and the second portion. The method for manufacturing the electrode according to claim 1 or 2.

4. (c) includes applying vibration to the second portion. The method for manufacturing the electrode according to any one of claims 1 to 3.

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