Electrode manufacturing method

Abstract

To provide an electrode and a method of manufacturing the same capable of facilitating penetration of electrolyte.SOLUTION: An electrode 100 includes an active material layer 20. A first groove part 21 and a second groove part 22 are formed on a surface of the active material layer 20. The first groove part 21 has a first depth. The second groove part 22 has a second depth. The second depth is shallower than the first depth. Each of the first groove part 21 and the second groove part 22 extends linearly along the surface of the active material layer 20. The second groove part 22 is adjacent to the first groove part 21.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Japanese Patent Application Laid-Open No. 2018-041921 (Patent Document 1) discloses a method for cleaning active material pieces generated during groove formation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-041921 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, a secondary battery (hereinafter may be abbreviated as "battery") includes electrodes and an electrolyte. During the manufacturing process of the battery, the electrolyte is impregnated into the electrodes. If the electrolyte does not sufficiently permeate the electrodes, the battery performance may be reduced. In some cases, the permeation of the electrolyte takes a long time. There is a demand for a reduction in the permeation time.

[0005] To facilitate the penetration of the electrolyte, it has been proposed to form grooves on the surface of the electrode (active material layer), but there is still room for improvement.

[0006] The purpose of the present disclosure is to promote the penetration of the electrolyte. [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 electrode includes an active material layer. A first groove and a second groove are formed on the surface of the active material layer. The first groove has a first depth. The second groove has a second depth. The second depth is shallower than the first depth. Each of the first groove and the second groove extends linearly along the surface of the active material layer. The second groove is adjacent to the first groove.

[0009] Conventionally, grooves having a certain depth are formed on the surface of an active material layer, and it is believed that the deeper the grooves, the more advantageous they are for electrolyte penetration.

[0010] In the present disclosure, two types of grooves with different depths are formed. That is, a first groove portion (deep groove) and a second groove portion (shallow groove) are formed on the surface of the active material layer. According to the new findings of the present disclosure, the combination of deep grooves and shallow grooves can further promote the penetration of the electrolyte solution. That is, it is expected that the film flow of the electrolyte solution will spread over the surface of the active material layer in a short time through the shallow grooves. Furthermore, it is expected that the electrolyte solution that has spread over the surface of the active material layer will penetrate through the deep grooves in the thickness direction of the active material layer. It is believed that the synergistic effects of these actions can promote the penetration of the electrolyte solution.

[0011] 2. For example, a plurality of first grooves and a plurality of second grooves may be formed on the surface of the active material layer. In a plan view, the first grooves and the second grooves may be arranged alternately. This is because this may promote the penetration of the electrolyte solution.

[0012] 3. For example, the ratio of the first depth to the second depth may be 2 to 370. This is because there is a possibility that the penetration of the electrolyte is promoted.

[0013] 4. The first groove portion has a first width. The second groove portion has a second width. The ratio of the second width to the first width may be, for example, 10 to 100. This is because there is a possibility that the penetration of the electrolyte solution will be promoted.

[0014] 5. A secondary battery includes electrodes and an electrolyte. It is expected that the time required for the electrolyte to penetrate into the secondary battery during production will be shortened.

[0015] 6. A method for manufacturing an electrode includes the following steps (a) and (b): (a) Forming an active material layer. (b) An electrode is manufactured by forming a first groove portion and a second groove portion on the surface of the active material layer. The first groove portion has a first depth. The second groove portion has a second depth. The second depth is shallower than the first depth. Each of the first groove portion and the second groove portion extends linearly along the surface of the active material layer. The second groove portion is adjacent to the first groove portion.

[0016] In the manufacturing method of "6." above, the electrode of "1." above can be manufactured.

[0017] 7. (b) above may include, for example, pressing a concave-convex mold against the surface of the active material layer. The concave-convex mold includes protrusions and recesses. The recesses are adjacent to the protrusions. The protrusions may be pressed against the surface of the active material layer so as to form gaps between the recesses and the surface of the active material layer.

[0018] It is conceivable to form the grooves using a concave-convex mold (for example, an embossing roll, etc.). Usually, in order to form deep grooves and keep the surface of the active material layer flat, the bottom of the recesses is also pressed against the surface of the active material layer. In the manufacturing method of "7." above, a gap is formed between the recesses and the surface of the active material layer. A part of the active material layer is extruded into the gap. As a result, a protrusion (a projection) is formed adjacent to the first groove portion (a deep groove). A second groove portion (a shallow groove) can be formed between the projections.

[0019] 8. (b) above may include, for example, irradiating the surface of the active material layer with a laser. The active material layer is scraped with the laser to form first grooves. Shavings of the active material layer are deposited adjacent to the first grooves to form protrusions.

[0020] For example, the first groove portion (deep groove) may be formed by laser processing. Usually, shavings generated by the groove processing are removed. In the manufacturing method of "8." above, the shavings are not removed but are used as protrusions. The second groove portion (shallow groove) may be formed between the protrusions.

[0021] For example, the energy density may decrease if the shavings are cleaned (discarded) as in Patent Document 1. In the manufacturing method of "8." above, the shavings (part of the active material layer) are not discarded but remain in the active material layer, so it is thought that the energy density is less likely to decrease.

[0022] Hereinafter, an embodiment of the present disclosure (hereinafter may be abbreviated as "the present embodiment") and an example of the present disclosure (hereinafter may be abbreviated as "the present example") will be described. However, the present embodiment and the example do not limit the technical scope of the present disclosure. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic diagram showing an electrode according to this embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of an active material layer. [Figure 3] FIG. 3 is a schematic flowchart of a method for producing an electrode in this embodiment. [Figure 4] FIG. 4 is a schematic diagram showing a first example of groove machining. [Figure 5] FIG. 5 is a schematic diagram showing a second example of groove machining. [Figure 6] FIG. 6 is a schematic cross-sectional view showing the secondary battery of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] <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.

[0025] In this specification, expressions such as "may" and "can" are used in the permissive sense of "possibly" rather than the obligatory sense of "must."

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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. For example, viewing active material layer 20 from the Z-axis direction in FIG. 1 corresponds to a planar view of active material layer 20.

[0032] The "depth" of a groove in this specification refers to the maximum depth in a cross section perpendicular to the direction in which the groove extends (the axial direction of the groove). The "width" of a groove in this specification refers to the maximum width in a cross section perpendicular to the axial direction of the groove.

[0033] As used herein, "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. D50 can be measured using a laser diffraction particle size distribution analyzer.

[0034] In this specification, the term "electrode" is a general term for a positive electrode and a negative electrode. The electrode may be a positive electrode or a negative electrode.

[0035] In this specification, the term "secondary battery" refers to a battery that can be charged and discharged. The secondary battery may be any battery system as long as it contains an electrolyte. The secondary battery may be, for example, a lithium ion battery. This embodiment is an example of application to a lithium ion battery. However, the technology of the present disclosure may also be applied to battery systems other than lithium ion batteries.

[0036] <Electrode> FIG. 1 is a schematic diagram showing an electrode in this embodiment. Hereinafter, "the electrode in this embodiment" may be abbreviated as "the electrode." The electrode 100 is for a secondary battery. The secondary battery will be described later. The electrode 100 is in a sheet form. The electrode 100 includes an active material layer 20. The electrode 100 may further include a substrate 10, etc.

[0037] 《Base material》 The substrate 10 is a support for the active material layer 20. The substrate 10 may be, for example, in the form of a sheet or a mesh. The substrate 10 may have, for example, a strip-like planar shape. The substrate 10 may be conductive. The substrate 10 may function as a current collector. A portion of the substrate 10 may be exposed from the active material layer 20. For example, a current collecting member or the like may be joined to the exposed portion of the substrate 10.

[0038] The substrate 10 may have any thickness. For example, the substrate 10 may have a thickness of 5 to 50 μm, or may have a thickness of 5 to 20 μm.

[0039] The substrate 10 may include, for example, a metal foil. The substrate 10 may include, for example, at least one selected from the group consisting of aluminum (Al), copper (Cu), nickel (Ni), titanium (Ti), chromium (Cr), and iron (Fe). The substrate 10 may include, for example, at least one selected from the group consisting of Al foil, Al alloy foil, Cu foil, Cu alloy foil, Ni foil, Ni alloy foil, Ti foil, and stainless steel foil. When the electrode 100 is a positive electrode, the substrate 10 may include, for example, Al foil. When the electrode 100 is a negative electrode, the substrate 10 may include, for example, Cu foil.

[0040] 《Active material layer》 The active material layer 20 is a layer containing an active material. The active material layer 20 may be disposed on the surface of the substrate 10, for example. The active material layer 20 may be disposed on only one surface of the substrate 10, or on both the front and back surfaces. The active material layer 20 may have any thickness. The active material layer 20 may have a thickness of, for example, 5 to 1000 μm, 10 to 500 μm, or 50 to 250 μm.

[0041] <First and second grooves> First grooves 21 and second grooves 22 are formed on the surface of the active material layer 20. The first grooves 21 are relatively deep grooves. The first grooves 21 can promote the penetration of the electrolyte solution in the depth direction. The second grooves 22 are relatively shallow grooves. The second grooves 22 can promote the penetration of the electrolyte solution in the surface direction. The combination of the first grooves 21 and the second grooves 22 can synergistically promote the penetration of the electrolyte solution.

[0042] Each of the first groove portion 21 and the second groove portion 22 extends linearly along the surface of the active material layer 20. Each of the first groove portion 21 and the second groove portion 22 may extend linearly, for example. Each of the first groove portion 21 and the second groove portion 22 may be curved, for example. Each of the first groove portion 21 and the second groove portion 22 may be serpentine, for example.

[0043] Each of the first groove portion 21 and the second groove portion 22 can have any length. For example, each of the first groove portion 21 and the second groove portion 22 may have a length of 1 to 1000 mm, or may have a length of 1 to 100 mm.

[0044] Each of the first groove portion 21 and the second groove portion 22 may extend across the surface of the active material layer 20. Each of the first groove portion 21 and the second groove portion 22 may have an opening on the periphery (side surface) of the active material layer 20. The side surface of the active material layer 20 may be an inclined surface.

[0045] A single first groove portion 21 may be formed independently. A single second groove portion 22 may be formed independently. A plurality of first groove portions 21 and a plurality of second groove portions 22 may be formed independently.

[0046] The second groove portions 22 are adjacent to the first groove portions 21. In a plan view (XY plane), the first groove portions 21 and the second groove portions 22 may be arranged alternately.

[0047] FIG. 2 is a schematic cross-sectional view of the active material layer. FIG. 2 shows a cross section perpendicular to the axial direction of each groove. The first groove 21 has a first depth d1. The second groove 22 has a second depth d2. The second depth d2 is shallower than the first depth d1. The ratio of the first depth d1 to the second depth d2 (hereinafter also referred to as the "depth ratio") may be, for example, 2 to 370. The depth ratio may be, for example, 5 to 200, 5 to 100, or 5 to 10.

[0048] The first depth d1 may be, for example, 20 to 350 μm, 20 to 200 μm, or 20 to 100 μm. The second depth d2 may be, for example, 1 to 20 μm, or 1 to 10 μm.

[0049] The first groove portion 21 has a first width w1. The second groove portion 22 has a second width w2. The ratio of the second width w2 to the first width w1 (hereinafter also referred to as "width ratio") may be, for example, 10 to 100. The width ratio may be, for example, 20 to 80, or 40 to 60.

[0050] The first width w1 may be, for example, 40 to 400 μm, or 100 to 300 μm. The second width w2 may be, for example, 0.1 to 10 mm, 0.5 to 5 mm, or 1 to 2 mm.

[0051] The first groove portion 21 may have, for example, a tapered cross-sectional shape. That is, the deeper the position, the narrower the width of the first groove portion 21. The cross-sectional shape of the first groove portion 21 may be, for example, V-shaped, U-shaped, or rectangular.

[0052] The second groove 22 may have, for example, a flat bottom surface, or may have, for example, a curved bottom surface.

[0053] The second groove portion 22 is sandwiched between two protrusions 23. The height of the protrusions 23 corresponds to the second depth d2 of the second groove portion 22. The protrusions 23 have a third width w3. The third width w3 may be, for example, 5 to 60 μm, 5 to 30 μm, or 5 to 20 μm.

[0054] <composition> The active material layer 20 includes an active material. In addition to the active material, the active material layer 20 may further include, for example, a binder, a conductive material, and the like.

[0055] The active material may be, for example, particulate. The active material may have a D50 of, for example, 1 to 30 μm. The active material may include, 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 include any component. The positive electrode active material may include, 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 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.

[0056] The active material may include, for example, a negative electrode active material. 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 may include 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 conductive material can form an electron conduction path. The amount of the conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the active material. The conductive material may contain any component. For example, the conductive material may contain at least one material selected from the group consisting of carbon black, vapor-grown carbon fiber, carbon nanotubes, and graphene flakes.

[0058] The binder can bind solid materials together. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of active material. The binder may contain any component. For example, the binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyimide (PI), polyamideimide (PAI), and polyacrylic acid (PAA).

[0059] <Electrode manufacturing method> FIG. 3 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" and "(b) groove processing." The present electrode 100 may be manufactured by this manufacturing method.

[0060] (a) Formation of Active Material Layer The manufacturing method includes forming an active material layer 20. The active material layer 20 can be formed by any method. For example, a slurry containing an active material may be prepared. For example, the slurry may be prepared by mixing an active material, a conductive material, a binder, and a dispersion medium. For example, an appropriate dispersion medium may be selected depending on the types of active material, binder, etc. The dispersion medium may include, for example, water, N-methyl-pyrrolidone (NMP), etc.

[0061] For example, the active material layer 20 may be formed by applying the slurry to the surface of the substrate 10 using a die coater.

[0062] The present manufacturing method may include drying the active material layer 20. For example, the active material layer 20 may be dried using a hot air drying oven. The present manufacturing method may include compressing the active material layer 20. For example, the active material layer 20 may be compressed using a roll press.

[0063] 《(b) Grooving》 This manufacturing method includes producing the present electrode 100 by forming the first grooves 21 and the second grooves 22 on the surface of the active material layer 20. The first grooves 21 and the second grooves 22 can be formed by any method.

[0064] 4 is a schematic diagram showing a first example of groove processing. For example, a concave-convex mold 30 may be pressed against the surface of the active material layer 20. The concave-convex mold 30 may be, for example, in the form of a plate or a roll. The concave-convex mold 30 may be, for example, an embossing roll.

[0065] The concave-convex mold 30 includes a convex portion 31 and a concave portion 32. The convex portion 31 protrudes compared to the concave portion 32. The first groove portion 21 can be formed corresponding to the shape of the convex portion 31. The cross-sectional shape of the convex portion 31 may be, for example, tapered or rectangular. The concave portion 32 is recessed compared to the convex portion 31. The concave portion 32 is adjacent to the convex portion 31. The bottom surface of the concave portion 32 may be flat, curved, or tapered.

[0066] The protrusions 31 are pressed against the surface of the active material layer 20 so that gaps are formed between the recesses 32 and the surface of the active material layer 20. By pressing the protrusions 31 against the surface of the active material layer 20, first grooves 21 can be formed. Furthermore, parts of the active material layer 20 can be pushed out into the gaps between the recesses 32 and the surface of the active material layer 20. This can form protrusions 23. Second grooves 22 can be formed between the protrusions 23. That is, the first grooves 21 and the second grooves 22 can be formed.

[0067] 5 is a schematic diagram showing a second example of groove processing. For example, the grooves may be formed by laser processing. That is, a laser 40 may be irradiated onto the surface of the active material layer 20. The active material layer 20 is scraped by the laser 40, thereby forming the first groove portions 21. Furthermore, shavings of the active material layer 20 may accumulate adjacent to the first groove portions 21, thereby forming protrusions 23. The second groove portions 22 may be formed between the protrusions 23. That is, the first groove portions 21 and the second groove portions 22 may be formed.

[0068] For example, a laser processing machine such as a laser marker may be used. For example, a laser 40 that is well absorbed by the active material may be used. For example, a YAG laser or the like may be used. A fundamental wave (wavelength 1060 nm) or a harmonic wave may be used. For example, a triple wave (wavelength 355 nm) may be used. The output of the laser 40 may be, for example, 4 to 10 W.

[0069] The electrode 100 is manufactured by forming the first grooves 21 and the second grooves 22. The electrode 100 may be cut to fit the design of the secondary battery, for example.

[0070] <Secondary battery> 6 is a schematic cross-sectional view showing the secondary battery of this embodiment. Hereinafter, the "secondary battery of this embodiment" may be abbreviated as "the battery."

[0071] The battery 200 includes a case 260. The case 260 may be sealed. The case 260 may have any shape. For example, the case 260 may be a pouch made of a metal foil laminate film. The case 260 may be a metal container. The case 260 may be, for example, rectangular or cylindrical. The case 260 may contain, for example, Al.

[0072] The case 260 contains an electrode group 250 and an electrolyte (not shown). The electrolyte permeates the electrode group 250. A portion of the electrolyte may be stored in the bottom of the case 260. The electrode group 250 may have any shape. FIG. 6 shows a wound electrode group 250 as an example. The electrode group 250 may be, for example, a laminated type. The electrode group 250 includes a positive electrode 210 and a negative electrode 220. The electrode group 250 may further include a separator 230. At least one of the positive electrode 210 and the negative electrode 220 is the above-described present electrode 100. That is, the present battery 200 includes the present electrode 100 and an electrolyte.

[0073] The separator 230 may be interposed between the positive electrode 210 and the negative electrode 220. The separator 230 is electrically insulating. The separator 230 is porous. The separator 230 may be made of, for example, polyolefin.

[0074] 《Electrolyte》 The electrolyte is a liquid electrolyte. The electrolyte may be a viscous fluid. The electrolyte may have a viscosity of, for example, 500 to 2000 kg / cm. 3 The electrolyte may have a density of 1000 to 2000 kJ / cm. The electrolyte includes a lithium salt and a solvent. The electrolyte may further include an optional additive.

[0075] The lithium salt is dissolved in the solvent. The lithium salt may include at least one selected from the group consisting of LiPF6, LiBF4, and Li(FSO2)2N. The concentration of the lithium salt may be, for example, 0.5 to 2 mol / L.

[0076] The solvent may contain any component. For example, the solvent may contain at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). The additive may contain at least one selected from the group consisting of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), cyclohexylbenzene (CHB), tert-amylbenzene (TAB), and lithium bis(oxalato)borate (LiBOB). [Example]

[0077] <Experiment 1> Electrodes Nos. 1 to 3 shown in the following Table 1 were produced. Hereinafter, for example, "electrode No. 1" may be abbreviated as "No. 1."

[0078] A predetermined amount of electrolyte solution was dropped onto the surface of the active material layer. The electrolyte solution was allowed to permeate into the active material layer. The time required for the electrolyte solution to completely permeate the entire active material layer (total permeation time) was measured. Completion of permeation was confirmed visually. The results are shown in Table 1 below.

[0079] [Table 1]

[0080] A comparison of No. 1 and No. 2 shows that the formation of deep grooves in the active material layer tends to shorten the overall permeation time.

[0081] Comparing No. 2 and No. 3, it can be seen that the formation of shallow grooves in addition to deep grooves tends to further shorten the overall penetration time.

[0082] <Experiment 2> In a simplified model based on Experiments 2 and 3, the time required for the electrolyte to spread over the surface of the active material layer (surface penetration time) was calculated. The density of the electrolyte was set to 1300 kg / m 3 It was assumed that the results are shown in Table 2 below.

[0083] [Table 2]

[0084] The addition of shallow grooves reduced surface penetration time by 79%, a result similar to the reduction in overall penetration time between No. 2 and No. 3 in Experiment 1.

[0085] The present embodiment and examples are illustrative in all respects. The present embodiment and examples are not limiting. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is also intended from the beginning that any configuration may be extracted from the present embodiment and examples and that they may be combined in any desired manner. [Explanation of symbols]

[0086] 10 substrate, 20 active material layer, 21 first groove portion, 22 second groove portion, 23 protrusion portion, 30 uneven type, 31 convex portion, 32 concave portion, 40 laser, 100 electrode, 200 secondary battery, 210 positive electrode, 220 negative electrode, 230 separator, 250 electrode group, 260 case, d1 first depth, d2 second depth, w1 first width, w2 second width, w3 third width.

Claims

[Claim 1] (a) forming an active material layer; and (b) forming a first groove portion and a second groove portion on the surface of the active material layer to produce an electrode; Including, the first groove portion has a first depth; the second groove portion has a second depth; the second depth is shallower than the first depth; each of the first groove portion and the second groove portion extends linearly along the surface of the active material layer; the second groove portion is adjacent to the first groove portion, (b) includes irradiating the surface of the active material layer with a laser; the active material layer is removed by the laser to form the first groove portion; a protrusion is formed adjacent to the first groove portion by accumulation of shavings of the active material layer; Electrode manufacturing method.

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