Method for manufacturing electrode, electrode current collector, and electrode

Abstract

This disclosure relates to a method for manufacturing an electrode, an electrode current collector, and an electrode. An active material layer is formed on the surface of the electrode current collector. A groove is formed on the surface of the active material layer. The electrode is manufactured by peeling off a portion 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. The adhesive layer covers the first region. In the second region, the metal foil is exposed. The active material layer includes a first portion covering the adhesive layer and a second portion covering the second region. Grooves are formed in both the first and second portions. The second portion is peeled off.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing an electrode, an electrode current collector, and an electrode. Background Technology

[0002] Japanese Patent Application Publication No. 2013-017962 discloses a coating apparatus for a functional sheet with excellent linearity at the beginning and end of the coating process during intermittent coating. Summary of the Invention

[0003] Electrodes can be manufactured by forming an active material layer on the surface of the electrode current collector. Sometimes, the active material layer is formed intermittently. Parts of the electrode current collector surface where no active material layer has been formed are exposed. Hereinafter, the exposed parts of the electrode current collector surface will also be referred to as "exposed areas." Exposed areas can function as electrode cut-off allowances, solder joints for current collector components, etc.

[0004] Sometimes, the intermittent formation of the active material layer can lead to irregularities in the shape of the active material layer's ends (periphery). Such irregularities can, for example, result in a decrease in battery performance.

[0005] This disclosure provides a method for manufacturing an electrode capable of intermittently forming an active material layer.

[0006] The technical structure and effects of this disclosure are described below. The mechanism of action described herein includes assumptions. This mechanism is not intended to limit the scope of this disclosure.

[0007] The electrode manufacturing method of the first aspect of this disclosure includes manufacturing an electrode by forming an active material layer on the surface of an electrode current collector, forming a groove on the surface of the active material layer, and peeling off a portion of the active material layer. The electrode current collector includes a metal foil and an adhesive layer. In planar 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.

[0008] The active material layer is formed comprising 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. Grooves are formed in both the first and second portions. As part of the active material layer, the second portion is peeled off.

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

[0010] The active material layer comprises a first part and a second part. The first part is formed on a first region (adhesive layer). The second part is formed on a second region (metal foil). Grooves are formed in the active material layer. Grooves are formed in both the first and second parts. An adhesive layer is present between the first part and the metal foil. The first part is firmly bonded to the metal foil due to the formation of the grooves. In other words, the peel strength of the first part is improved. On the other hand, no adhesive layer is present between the second part and the metal foil. The second part becomes fragile due to the formation of the grooves, therefore, the peel strength of the second part is reduced.

[0011] Because of the difference in peel strength between part 1 and part 2, part 2 can be easily peeled off. By peeling off part 2, part 1 (active material layer) is retained, maintaining the planar shape of region 1 (adhesive layer) and exhibiting less end shape disorder. In other words, the active material layer can be formed intermittently.

[0012] In the first embodiment described above, the formation of the active material layer may include: preparing a wetted powder, processing the wetted powder into an active material layer by roll forming, and disposing the active material layer on the surface of the electrode current collector.

[0013] In the above configuration, the active material layer can be formed by any method. For example, the active material layer can be formed by applying a slurry.

[0014] For example, the active material layer can also be formed by roll forming of moist powder. Moist powder is an aggregate of particles. In roll forming, a sheet (active material layer) is formed by the extension of the aggregate of particles, so there is a tendency for the shape at the ends to become disordered. In the manufacturing method described above, even when the workpiece is made of moist powder, the disorder of the end shape can be reduced.

[0015] In the first embodiment described above, a portion of the groove may be formed along the boundary between the first portion and the second portion.

[0016] The groove along the boundary between Part 1 and Part 2 functions as a cutting line (drill line) when peeling off Part 2. By using a portion of the groove as a cutting line, further reduction of end-shape irregularities can be expected in Part 1 (the final active material layer).

[0017] In the first scheme described above, a portion of the active material layer can be peeled off by applying vibration to the second part.

[0018] It is possible to expect that the second part can be stripped away through weak stimuli. For example, vibrations could be applied to the second part.

[0019] The electrode current collector of the second embodiment of this disclosure 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. In the second region, the metal foil is exposed.

[0020] The aforementioned electrode current collector is suitable as the electrode current collector of the first embodiment described above.

[0021] In the second embodiment described above, the metal foil, when viewed in a plane, has a strip-like planar shape. Along the length of the metal foil, the first and second regions can be arranged alternately.

[0022] In the second scheme described above, the first region may have a rectangular planar shape when viewed from a plane.

[0023] In the second scheme described above, the second region may surround the first region when viewed from a plane.

[0024] The electrode of the third embodiment disclosed herein includes an electrode current collector and an active material layer. The active material layer covers an 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 the electrode manufactured using the above method, the end shape of the active material layer (part 1) exhibits less irregularity. For example, the active material layer can have a steep end face. That is, the end face of the active material layer can have an inclination angle of 45 degrees or more. Due to the steep end face of the active material layer, an increase in energy density can be expected, for example.

[0026] Hereinafter, embodiments of the present disclosure (hereinafter, may be simply referred to as "the present embodiments") will be described. However, the present embodiments are not intended to limit the technical scope of the present disclosure. Attached Figure Description

[0027] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein similar reference numerals denote similar elements.

[0028] Figure 1 This is a simplified flowchart of the electrode manufacturing method in this embodiment.

[0029] Figure 2 This is a first schematic cross-sectional view showing the electrode manufacturing process.

[0030] Figure 3 This is a schematic plan view of an example of a metal foil.

[0031] Figure 4 This is a simplified flowchart illustrating an example of a method for forming an active substance layer.

[0032] Figure 5 This is a schematic diagram showing an example of a film-forming apparatus.

[0033] Figure 6 This is an image representing an example of an end shape.

[0034] Figure 7 This is the second schematic cross-sectional view showing the electrode manufacturing process.

[0035] Figure 8 This is the third schematic cross-sectional view showing the electrode manufacturing process.

[0036] Figure 9 This is a schematic plan view showing an example of a groove.

[0037] Figure 10 This is the fourth schematic cross-sectional view showing the electrode manufacturing process.

[0038] Figure 11 This is a schematic plan view showing an example of an electrode in this embodiment.

[0039] Figure 12 It is an image representing the actual partial stripping.

[0040] Figure 13 This is a schematic cross-sectional view showing the electrodes in this embodiment.

[0041] Figure 14 This is the first conceptual diagram illustrating the relationship between the tilt angle of the end face and the energy density.

[0042] Figure 15 This is the second conceptual diagram illustrating the relationship between the tilt angle of the end face and the energy density.

[0043] Figure 16 This is an image illustrating an applicable example of this embodiment.

[0044] Figure 17 It is an image representing the reference method. Detailed Implementation

[0045] Definition of terms

[0046] In this specification, the descriptions of "possessing," "comprises," "have," and variations thereof (e.g., "consisting of," etc.) are open-ended. Open-ended descriptions may include or exclude additional elements besides mandatory elements. The description of "composed of" is closed-ended. However, even in closed-ended descriptions, incidental or additional elements unrelated to the technology disclosed herein are generally not excluded. The description of "substantially composed of" is semi-closed-ended. In semi-closed-ended descriptions, the addition of elements that do not substantially affect the basic and novel characteristics of the technology disclosed herein is permitted.

[0047] In this specification, expressions such as "can" and "able" are used not with a mandatory meaning "must do this" but with a permissive meaning "possibly have this possibility".

[0048] In this specification, unless otherwise specified, the order of execution of multiple steps, actions, and operations included in various methods is not limited to the order in which they are described. For example, multiple steps may be performed simultaneously. For example, multiple steps may be performed sequentially.

[0049] In this specification, numerical ranges such as "m~n%" include both upper and lower limits unless otherwise specified. That is, "m~n%" represents a numerical range "above m% and below n%". Furthermore, "above m% and below n%" includes "more than m% and less than n%". Moreover, any value arbitrarily selected from the numerical range can also become a new upper or lower limit. For example, new numerical ranges can be set by arbitrarily combining values ​​within the numerical range with values ​​described in other parts of this specification, tables, and figures.

[0050] In this specification, all numerical values ​​are described using the term "approximately." "Approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​can be approximate values ​​that may vary depending on how the technology disclosed is used. All numerical values ​​can be expressed in significant figures. The measured value can be the average of multiple measurements. The number of measurements can be 3 or more, 5 or more, or 10 or more. Generally, the more measurements, the more reliable the average value is expected to be. The measured value can be rounded off based on the number of significant figures. The measured value may include, for example, errors associated with the detection limits of the measuring device.

[0051] The geometric terms used in this specification (such as "parallel," "perpendicular," "orthogonal," etc.) should not be interpreted strictly. For example, "parallel" can be interpreted slightly differently from the strict meaning of "parallel." The geometric terms used in this specification may include tolerances and errors in design, operation, manufacturing, etc. The dimensional relationships in the various figures may sometimes differ from the actual dimensional relationships. To aid in understanding the technology disclosed herein, the dimensional relationships (length, width, thickness, etc.) in the various figures have sometimes been altered. Furthermore, some components may sometimes be omitted.

[0052] In this manual, "planar view" means observing the object using a line of sight parallel to its thickness direction. Planar views are depicted using planar view diagrams. "Sectional view" in this manual means observing the object using a line of sight orthogonal to its thickness direction. Sectional views are depicted using sectional views.

[0053] In this specification, "tilt angle" refers to the angle (acute and right angle) formed by the end face of the active material layer and the surface of the electrode current collector in cross-section.

[0054] In this specification, when a compound is represented by a stoichiometric formula (e.g., "LiCoO2"), this stoichiometric formula is merely a representative example of the compound. Compounds may have non-stoichiometric compositions. For example, when lithium cobalt oxide is represented as "LiCoO2," unless otherwise specified, lithium cobalt oxide is not limited to a composition ratio of "Li / Co / O = 1 / 1 / 2," and any composition ratio can include Li, Co, and O. Furthermore, doping and substitution of trace elements are also permitted.

[0055] In this manual, "electrode" is a general term for both positive and negative electrodes. An electrode can be either a positive or negative electrode. Electrodes are suitable for any battery system. For example, electrodes can be used in lithium-ion batteries.

[0056] In this specification, "solid content" refers to the total mass fraction (percentage) of components other than the liquid material in a solid-liquid mixture. Solid content can also be referred to as "NV (Nonvolatile content)". Components dissolved in the liquid material (solute) are considered as components other than the liquid material.

[0057] In this specification, "slurry" refers to a dispersion system in which a solid material (powder) is dispersed in a liquid material. "Wet powder" refers to a dispersion system in which a liquid material is dispersed in a solid material (powder).

[0058] In this specification, "D50" is defined as the particle size at which the cumulative frequency, starting from the smallest particle size, reaches 50% in a volumetric particle size distribution. The volumetric particle size distribution can be determined using a laser diffraction particle size distribution measuring device.

[0059] Electrode manufacturing method

[0060] Figure 1 This is a simplified flowchart of the electrode manufacturing method in this embodiment. Hereinafter, "the electrode manufacturing method in this embodiment" may be simply referred to as "this manufacturing method". This manufacturing method includes "(a) formation of an active material layer", "(b) formation of a groove", and "(c) partial peeling".

[0061] (a) Formation of the active substance layer

[0062] This manufacturing method includes forming an active material layer on the surface of the electrode current collector.

[0063] Electrode current collector

[0064] Figure 2This is a first schematic cross-sectional view showing the electrode manufacturing process. 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.

[0065] The metal foil 11 has a current-collecting function. The metal foil 11 may, for example, have a thickness of 5 to 50 μm. The metal foil 11 may, for example, include 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, for example, include Al foil, Al alloy foil, Cu foil, Ni foil, stainless steel foil, etc.

[0066] Figure 3 This is a schematic planar view of an example of a metal foil. In planar view, the metal foil 11 may, for example, have a strip-like planar shape. The metal foil 11 includes a first region 11a and a second region 11b. Along the length direction (Y-axis direction) of the metal foil 11, the first region 11a and the second region 11b may be arranged alternately.

[0067] The first region 11a has an active material layer disposed on the electrode. The first region 11a can have any planar shape. When viewed in a planar view, the first region 11a can, for example, have a rectangular planar shape.

[0068] The second region 11b is the exposed area where the electrode is located. In the second region 11b, the metal foil 11 is exposed. The second region 11b is adjacent to the first region 11a. In planar view, the second region 11b may, for example, surround the first region 11a.

[0069] Adhesive layer 12 covers region 11a (refer to) Figure 2 The adhesive layer 12 bonds the active material layer to the metal foil 11. The adhesive layer 12 may, for example, have a thickness of 0.1 to 5 μm. The adhesive layer 12 can include any adhesive material. For example, the adhesive layer 12 may include 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 polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP). In addition to the adhesive material, the adhesive layer 12 may also include, for example, a conductive material. The conductive material may include, for example, carbon black.

[0070] The adhesive layer 12 can be formed by any method. For example, an adhesive material composition comprising an adhesive material can be prepared. For example, the adhesive material composition can be prepared by mixing a liquid material (solvent or dispersant) and an adhesive material. The adhesive material composition can be a solution or a particulate dispersion. The mass fraction of the adhesive material in the adhesive material composition can be adjusted to make the adhesive material composition exhibit the desired viscosity. The mass fraction of the adhesive material can be, for example, 1 to 50%. An appropriate liquid material can be selected depending on the type of adhesive material. The liquid material can, for example, include at least one selected from the group consisting of water, N-methyl-2-pyrrolidone (NMP), and butyl butyrate.

[0071] For example, the adhesive material composition can be intermittently applied to the surface of the metal foil 11 using a die coater or similar tool. The adhesive layer 12 can be formed by drying the adhesive material composition. That is, the first region 11a and the second region 11b can be formed.

[0072] slurry

[0073] For example, an active material layer can be formed by applying a slurry to the surface of the electrode current collector 10. The slurry can be applied using a molding compound or similar device. The slurry can be formed, for example, by mixing an active material, a conductive material, a binder, and a liquid material. The solid content of the slurry can be, for example, 50–70% or 50–65%.

[0074] Moistened powder

[0075] Figure 4 This is a schematic flowchart illustrating an example of a method for forming an active material layer. "(a) Formation of the active material layer" may include, for example, "(a1) Preparation of wet powder", "(a2) Roll forming" and "(a3) Transfer printing".

[0076] (a1) Preparation of moistened powder

[0077] This manufacturing method may include preparing a moist powder. For example, the moist powder can be formed by mixing an active substance, a binder, a conductive material, and a liquid material. For example, the materials can be mixed using a mixing granulator or the like. The solid content of the moist powder may be, for example, 70–99%, or 75–90%.

[0078] The active material can be in the form of spheres, blocks, flakes, columns, etc. The active material can have any size. For example, the active material can have a D50 of 1–30 μm, or even 5–20 μm.

[0079] The active material can 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 can include any components. For example, the positive electrode active material can include 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 total proportions of the components within the parentheses are 1. As long as the total is 1, the amounts of each component are arbitrary. Li(NiCoMn)O2 can include, for example, Li(Ni... 1 / 3 Co 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.

[0080] 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 include any composition. Examples of negative electrode active materials include graphite, soft carbon, hard carbon, silicon, silicon oxide, silicon-based alloys, tin, tin oxide, tin-based alloys, and Li₄Ti₅O₂. 12 At least one selected from the group.

[0081] The binder may be soluble or insoluble in the liquid material. The amount of binder incorporated may be, for example, 0.1 to 10 parts by weight relative to 100 parts by weight of the active material. The binder can include any components. For example, the binder may include at least one selected from the group consisting of PVdF, PTFE, PVdF-HFP, SBR, CMC, and PAA.

[0082] The amount of conductive material can be, for example, 0.1 to 10 parts by mass relative to 100 parts by mass of active material. The conductive material can include any composition. For example, the conductive material may include at least one selected from the group consisting of carbon black, vapor-grown carbon fibers, carbon nanotubes, and graphene sheets. 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.

[0083] (a2) Roll forming

[0084] This manufacturing method may include processing wet powder into an active material layer by roll forming.

[0085] Figure 5 This is a schematic diagram illustrating an example of a film-forming apparatus. The film-forming apparatus 300 can process wet powder 2 into an active material layer 20. The film-forming apparatus 300 includes a first roller 301, a second roller 302, and a third roller 303. Each roller rotates in the direction of the arrow. The rotation axes of each roller are parallel. When the rotational speed of the first roller 301 is ω1, the rotational speed of the second roller 302 is ω2, and the rotational speed of the third roller 303 is ω3, for example, the relationship "ω1 < ω2 < ω3" can be satisfied.

[0086] A gap AB is formed between the first roller 301 and the second roller 302. Wet powder 2 is supplied to the gap AB. In the gap AB, the wet powder 2 is compacted and extended, thereby forming an active material layer 20 (sheet). The active material layer 20 may have a thickness of, for example, 10 to 500 μm, or 50 to 200 μm.

[0087] (a3) Transfer

[0088] This manufacturing method may include disposing an active material layer 20 on the surface of the electrode current collector 10. For example, a film-forming apparatus 300 may be used to transfer the active material layer 20 onto the electrode current collector 10. A roll gap BC is formed between a second roller 302 and a third roller 303. The second roller 302 conveys the active material layer 20 into the roll gap BC. The third roller 303 conveys the electrode current collector 10 into the roll gap BC.

[0089] At the roll gap BC, the active material layer 20 is applied to the surface of the electrode current collector 10. Thus, the active material layer 20 adheres 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.

[0090] Figure 6 This is an image showing an example of an end shape. In Figure 6 The middle shows with Figure 5 Region VI is a significant portion. In the method of forming the active material layer 20 using wet powder, there is a tendency for the end shape to become disordered in the width direction (X-axis direction).

[0091] Figure 7 This is a second schematic cross-sectional view illustrating the electrode manufacturing process. The active material layer 20 is formed including 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 also be formed, for example, to cover the entire surface of the electrode current collector 10.

[0092] (b) Formation of the groove

[0093] Figure 8Fig. 3 is a schematic cross-sectional view showing the manufacturing process of the electrode. This manufacturing method includes forming a groove portion 21 on the surface of the active material layer 20. The groove portion 21 can be formed by, for example, embossing. That is, the groove portion 21 (recess) can be formed by pressing a convex mold against the surface of the active material layer 20. For example, an embossing roll or the like can be used.

[0094] The active material layer 20 can be dried after the formation of the groove portion 21. The active material layer 20 can be dried by any method. For example, a hot air drying furnace or the like can be used.

[0095] The groove portion 21 can function as a flow path for the electrolyte, for example. By forming the groove portion 21, an improvement in battery performance (such as cycle characteristics, etc.) is expected. The cross-sectional shape of the groove portion 21 is arbitrary. The cross-sectional shape of the groove portion 21 can be rectangular, U-shaped, or V-shaped. The groove portion 21 can have a depth of, for example, 10 to 150 μm. The ratio of the depth of the groove portion 21 to the thickness of the active material layer 20 can be, for example, 0.1 to 0.9, or 0.3 to 0.7.

[0096] The groove portion 21 can be formed in the first part 20a and the second part 20b, respectively. By forming the groove portion 21 in the first part 20a, the peeling strength of the first part 20a can be improved. By forming the groove portion 21 in the second part 20b, the peeling strength of the second part 20b can be reduced.

[0097] A part of the groove portion 21 can be formed along the boundary 20c between the first part 20a and the second part 20b. The part of the groove portion 21 along the boundary 20c functions as a cutting line of the active material layer 20. The boundary 20c can be located directly above the boundary between the first region 11a and the second region 11b. A part of the groove portion 21 can extend linearly along the boundary 20c. A part of the groove portion 21 can be substantially coincident with the position of the boundary 20c. Even if a part of the groove portion 21 is slightly separated from the boundary 20c, it can function as a cutting line. The distance between a part of the groove portion 21 and the boundary 20c can be, for example, 0 to 10 mm.

[0098] Figure 9 Fig. 4 is a schematic plan view showing an example of the groove portion. The groove portion 21 can have an arbitrary planar pattern. The groove portion 21 can be formed, for example, in a multi-line arrangement (Japanese: 万線状). The groove portion 21 can be formed, for example, in a lattice pattern. The pitch (interval between adjacent parallel lines) of the groove portion 21 can be, for example, 0.1 to 10 mm, or 0.5 to 5 mm.

[0099] (c) Partial peeling

[0100] Figure 10This is a fourth schematic cross-sectional view illustrating the electrode manufacturing process. The manufacturing method includes peeling off a portion of the active material layer 20. Specifically, it involves peeling off the second portion 20b. Because the peeling strength of the second portion 20b is low, it can be peeled off using weak stimulation. For example, vibration can be applied to the second portion 20b. Alternatively, a suction pump or similar device can be used to attract the second portion 20b. Furthermore, the peeled second portion 20b can be reused, for example, as a raw material for wetting powder.

[0101] Figure 11 This is a schematic plan view showing an example of the electrode in this embodiment. Hereinafter, the "electrode in this embodiment" may be simply referred to as "this electrode". The electrode 100 can be fabricated by peeling off the second part 20b. The electrode 100 includes an active material layer 20. The active material layer 20 corresponds to the first part 20a. The active material layer 20 can have a planar shape corresponding to the first region 11a (adhesive layer 12).

[0102] Figure 12 This is an image representing the actual partial stripping. Part 20b can be stripped in a cut-off manner. After the stripping of part 20b, the disorder of the end shape of part 10a is small. Part 10a can have a rectangular planar shape. The periphery of part 10a can be straight.

[0103] electrode

[0104] Figure 13 This is a schematic cross-sectional view showing the 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 side of the electrode current collector 10, or it may be disposed on both sides. Figure 13 active substance layer 20 and Figure 7 This corresponds to part 20a in the above. The active material layer 20 covers the adhesive layer 12. The exposed area of ​​the metal foil 11 is similar to... Figure 3 The second region 11b is equivalent to the first. A groove 21 is formed on the surface of the active material layer 20.

[0105] The end shape of this electrode 100 exhibits minimal irregularity. In this electrode 100, the active material layer 20 has a steep end face. The end face of the active material layer 20 can have a tilt angle θ of 45 degrees or more. The tilt angle θ can be, for example, 60–90 degrees, or 75–90 degrees. The closer the tilt angle θ is to 90 degrees, the greater the expected increase in energy density.

[0106] Figure 14 This is the first conceptual diagram illustrating the relationship between the tilt angle of the end face and energy density. Figure 14 , 15For simplicity, the groove and adhesive layer are omitted. The electrode 100 faces the counter electrode 200 across the diaphragm 400. The counter electrode 200 has the opposite polarity to the electrode 100. For example, when the electrode 100 is positive, the counter electrode 200 is negative. When the tilt angle θ of the end face is small, an ineffective space 20s is formed at the end of the electrode 100 facing the counter electrode 200. The energy density decreases due to the formation of the ineffective space 20s.

[0107] Figure 15 This is the second conceptual diagram illustrating the relationship between the tilt angle of the end face and energy density. The closer the tilt angle θ is to 90 degrees, the smaller the ineffective space 20s becomes. In other words, the closer the tilt angle θ is to 90 degrees, the more we can expect an increase in energy density.

[0108] Figure 16 This is an image illustrating an applicable example of this embodiment. In Figure 16 The image shows a cross-sectional SEM image of the electrode. Figure 16 The active material layer 20 is formed using moistened powder. The end face of the active material layer 20 is formed by partial peeling in this embodiment. The active material layer 20 has a steep end face. The inclination angle of the end face is 45 degrees or more.

[0109] Figure 17 This is an image representing the reference method. In Figure 17 The image shows a cross-sectional SEM image of the electrode. Figure 17 The active material layer 20 is formed using a slurry. In the reference embodiment, partial stripping was not performed. Because the slurry has high fluidity, it easily generates liquid droplets at the ends of the coating. The tilt angle of the end face decreases due to the liquid droplets. The tilt angle of the end face is less than 45 degrees.

[0110] This embodiment is illustrative in all respects. This embodiment is not restrictive. The scope of this disclosure includes all modifications equivalent to and within the scope of the claims. For example, it was originally intended that arbitrary components be extracted from this embodiment and combined arbitrarily.

Claims

1. A method of manufacturing an electrode, characterized by, An electrode is manufactured by forming an active material layer on a surface of an electrode current collector, forming a groove portion on a surface of the active material layer, and peeling off a part of the active material layer. In the electrode, The electrode current collector includes a metal foil and a bonding layer. The metal foil includes a first region and a second region in a plan view. The bonding layer covers the first region. The second region is adjacent to the first region. In the second region, the metal foil is exposed. The active material layer is formed to include a first part and a second part. The second part is adjacent to the first part. The first part covers the bonding layer, and the bonding layer has a thickness of 0.1 to 5 μm. The second part covers the second region. The groove portion is formed in the first part and the second part, respectively. A part of the groove portion is formed along a boundary between the first part and the second part, and the part of the groove portion extends linearly along the boundary so as to coincide with a position of the boundary. The second part is peeled off as a part of the active material layer. When the second part is peeled off, the part of the groove portion formed along the boundary between the first part and the second part functions as a cut line of the active material layer.

2. The manufacturing method of the electrode according to claim 1, wherein The forming of the active material layer includes preparing a wet powder, processing the wet powder into the active material layer by roll pressing, and disposing the active material layer on a surface of the electrode current collector.

3. The manufacturing method of the electrode according to claim 1 or 2, wherein The part of the active material layer is peeled off by imparting vibration to the second part.

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