Electrode and method for manufacturing the electrode

Abstract

The present application relates to an electrode, a manufacturing method thereof, and uses thereof. The present application can provide an electrode having an insulating layer that stably ensures the desired insulating properties, exhibits excellent adhesive strength, and does not induce cracks at the boundary between the coated and uncoated parts of the electrode, and a manufacturing method thereof. The present application can also provide uses of the electrode.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0157005 filed on November 15, 2021 and Korean Patent Application No. 10-2022-0151950 filed on November 14, 2022, and all the contents disclosed in the corresponding patent applications are included as part of this specification.

[0002] This application relates to an electrode and a method for manufacturing the electrode.

Background Art

[0003] As the demand for mobile devices and electric vehicles increases, the demand for secondary batteries as an energy source is also increasing. Known secondary batteries include nickel-metal hydride batteries, lithium batteries, and lithium-ion batteries.

[0004] Generally, a secondary battery includes an electrode assembly in which a positive electrode and a negative electrode, on which a positive electrode active material and a negative electrode active material are respectively coated, are disposed with a separator interposed therebetween, and an exterior material for sealing and housing the electrode assembly together with an electrolytic solution.

[0005] In a secondary battery, the separator located between the positive electrode and the negative electrode maintains electrical insulation, but problems with stability due to a short circuit between the positive electrode and the negative electrode may occur in an abnormal state. Such abnormal states include overcharging, over-discharging, dendritic growth of electrode materials, internal short circuit due to foreign substances, external force applied from the outside, and penetration of the battery by a sharp object such as a nail or a screw.

[0006] As the separator, a porous membrane of a polymer material such as polyolefin is mainly used, but the heat resistance temperature of such a porous membrane is not sufficient. Therefore, when the short circuit occurs, the separator shrinks due to the heat of reaction and the short circuit portion expands, thereby generating more heat of reaction and causing a problem of thermal runaway. y) may occur.

[0007] To address this problem, a technique is known in which an insulating layer is formed on the uncoated portion of the positive electrode and / or on the boundary between the coated and uncoated portions (Patent Document 1).

[0008] The uncoated portion refers to a region on the current collector where no electrode active material layer is formed, and the coated portion refers to a region on the current collector where an electrode active material layer is formed.

[0009] In the conventional technology, an insulating layer is formed by coating a polymer solution such as PVDF (poly(vinylidene fluoride)) and drying it. However, this method can cause the polymer to penetrate into the active material layer after coating but before drying, making it difficult to form an insulating layer with suitable performance.

[0010] A method of coating the solution forming the insulating layer and then rapidly drying it before the polymer penetrates into the active material layer may be considered, but in this case, the adhesive strength of the formed insulating layer may be reduced, which may also result in a decrease in the performance of the insulating layer. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Korean Patent Publication No. 10-2019-0093522 [Non-patent literature]

[0012] [Non-Patent Document 1] Yanlong Luo et al., 2017, J. Phys. Chem. C, 2017, 121, 10163-10173, DOI: 10.1021 / acs.jpcc.7b01583 Summary of the Invention [Problem to be solved by the invention]

[0013] This application aims to provide an electrode having an insulating layer that stably ensures the intended insulation, exhibits excellent adhesive strength, and does not induce cracks or the like at the boundary between the grounded and ungrounded portions of the electrode, and a method for manufacturing the same.

[0014] In this application, it is a further object to provide the use of the above electrode.

Means for Solving the Problems

[0015] Among the physical properties mentioned in this specification, when the measurement temperature affects the relevant physical property, unless otherwise specified, the physical property is the physical property measured at room temperature.

[0016] In this specification, the term "room temperature" is the natural temperature without being particularly heated or cooled, and is any one temperature within the range of about 10°C to 30°C, for example, about 15°C or higher, 18°C or higher, 20°C or higher, or about 23°C or higher, and can mean a temperature within the range of about 27°C or lower. Unless otherwise specified, the unit of temperature mentioned in this specification is °C.

[0017] Among the physical properties mentioned in this specification, when the measurement pressure affects the relevant physical property, unless otherwise specified, the physical property is the physical property measured at normal pressure.

[0018] In this specification, the term "normal pressure" is the pressure in a state where it is not particularly pressurized or depressurized, and means a pressure of about 740 mmHg to 780 mmHg, which is usually at the atmospheric pressure level.

[0019] Among the physical properties mentioned in this specification, when the measurement humidity affects the relevant physical property, unless otherwise specified, the physical property is the physical property measured at the natural humidity at the above room temperature and normal pressure.

[0020] The term "thickness" used in this application means the average thickness unless otherwise mentioned.

[0021] An electrode according to an example of the present application can include a current collector and an active material layer formed on at least one surface of the current collector. The active material layer can be formed on one or both surfaces of the current collector. The electrode can be, for example, a negative electrode or a positive electrode of a secondary battery.

[0022] As the current collector, a known current collector for a positive electrode or a current collector for a negative electrode can be used.

[0023] As the current collector for the positive electrode, one that does not induce unnecessary chemical changes in the secondary battery and has appropriate conductivity can be used. Its type, size, shape, etc. are not particularly limited and can be determined according to the application. As the current collector for the positive electrode, for example, films, sheets, foils, nets, porous bodies, foams, or non-woven fabrics made of stainless steel, aluminum, nickel, titanium, or fired carbon, etc., or those with surfaces of films, sheets, foils, nets, porous bodies, foams, or non-woven fabrics made of aluminum, stainless steel, etc. surface-treated with carbon, nickel, titanium, silver, etc. can be used. In some cases, fine irregularities can be formed on the surface of the current collector for the positive electrode to enhance the adhesive force with the positive electrode active material, etc. The current collector can be in the form of a film, sheet, foil, net, porous body, foam, or non-woven fabric body, etc.

[0024] The thickness of the current collector for the positive electrode is usually in the range of 3 μm to 500 μm, but is not limited thereto.

[0025] For the current collector for the negative electrode, those that do not induce chemical changes unnecessary for the secondary battery and have appropriate conductivity can be used. Their type, size, shape, etc. are not particularly limited and can be selected according to the purpose. Examples of the current collector for the negative electrode include films, sheets, foils, nets, porous bodies, foams, or non-woven fabrics made of copper, stainless steel, aluminum, nickel, titanium, or fired carbon, etc., or those in which films, sheets, foils, nets, porous bodies, foams, or non-woven fabrics made of copper, stainless steel, etc. are surface-treated with carbon, nickel, titanium, silver, etc., or films, sheets, foils, nets, porous bodies, foams, or non-woven fabrics made of aluminum-cadmium alloys, etc. can be used. Similar to the current collector for the positive electrode, the current collector for the negative electrode may also be subjected to a treatment that can strengthen the bonding force with the negative electrode active material, such as unevenness on the surface. The current collector can be in the form of a film, sheet, foil, net, porous body, foam, or non-woven fabric body, etc.

[0026] The thickness of the current collector for the negative electrode is usually in the range of 3 μm to 500 μm, but is not limited thereto.

[0027] In this application, there are no special restrictions on the type and form of the active material layer either.

[0028] For example, as the active material layer, a layer containing an electrode active material can be applied.

[0029] The electrode active material contained in the active material layer can be a positive electrode active material or a negative electrode active material depending on the type of the electrode.

[0030] Examples of the positive electrode active material include layered compounds such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), and compounds in which the oxide is substituted with one or more transition metals; lithium iron oxides such as LiFe3O4; lithium iron phosphate such as LiFePO4; chemical formula Li 1+c1 Mn 2-c1O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3 or LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5 or Cu2V2O7; chemical formula LiNi 1-c2 M c2 O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦c2≦0.3 is satisfied); 2-c3 M c3 Lithium manganese composite oxides expressed as Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfying 0.01≦c3≦0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion, etc., can be used, but are not limited to these.

[0031] The negative electrode active material can be any compound capable of reversible intercalation and deintercalation of lithium. Examples of the negative electrode active material include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metal compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; SiO β(0 < β < 2), metal oxides such as SnO2, vanadium oxides or lithium vanadium oxides that can be doped and de-doped with lithium; or composites containing a metal and a carbon material such as Si-C composites or Sn-C composites, etc. There are such materials, and one or a mixture of two or more of these can be used. As the active material for the negative electrode, a thin film of metallic lithium may be used, and all of low-crystalline carbon and highly crystalline carbon, etc. can also be used for the carbon material. Soft carbon and hard carbon are typically known as low-crystalline carbon, and amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, Kish graphite, pyrolytic carbon, pitch-based carbon fibers (e.g., mesophase pitch based carbon fiber), carbon microspheres (e.g., mesocarbon microbeads), mesophase pitches and high-temperature calcined carbons such as petroleum or coal tar pitch derived cokes are known as highly crystalline carbon. In addition to the above, various materials can be used as the active material for the negative electrode.

[0032] The ratio of the electrode active material in the active material layer is also adjusted according to the purpose, and usually the electrode active material can be contained within a range of about 80 to 99.5% by weight or 88 to 99% by weight based on the total weight of the active material layer.

[0033] The active material layer may include a binder as an additional component, which may improve adhesion between active materials and / or between the active material layer and the current collector. The binder is typically PVDF (poly(vinylidene fluoride), PVA (poly(vinyl alcohol), polyvinyl alcohol), PI (polyimide), PAI (polyamideimide), SBR (styrene butadiene rubber), PEO (poly(ethylene oxide), polyethylene oxide), CMC (carboxyl methyl cellulose), CA (cellulose acetate), CAB (cellulose acetate butyrate), CAP (cellulose acetate propionate), cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, cyanoethyl cellulose ... One or more of the following may be used, but is not limited to: sucrose, pullulan, PMMA (poly(methylmethacrylate), polybutylacrylate), polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, EVA (polyethylene-co-vinyl acetate), and polyarylate.

[0034] In one example, PVDF (poly(vinylidene fluoride)) can be used as the binder. In such a case, as the PVDF, those having a weight-average molecular weight (Mw) in the range of 400,000 to 1,500,000 g / mol or 600,000 to 1,200,000 g / mol can be used. The weight-average molecular weight can be measured using GPC (Gel Permeation Chromatograph). Also, as the PVDF, those having a melting point measured by a DSC (Differential Scanning Calorimetry) instrument within the range of 150°C to 180°C or 165°C to 175°C can be used considering solubility and the like.

[0035] The ratio of the binder in the active material layer can also be adjusted according to the purpose and application. Usually, the binder can be included in a ratio of 0.1 to 10 parts by weight or 0.5 to 5 parts by weight relative to 100 parts by weight of the electrode active material.

[0036] The active material layer may contain a conductive material as an additional component. As the conductive material, those that do not induce unnecessary chemical changes and have appropriate conductivity can be used. For example, as the conductive material, graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black or thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes (CNT); metal powders such as fluorocarbon, aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or one or more of conductive materials such as polyphenylene derivatives can be used, but it is not limited thereto.

[0037] The ratio of the conductive material in the active material layer can also be adjusted according to the purpose and application. Usually, the conductive material can be included in a ratio of 0.1 to 20 parts by weight or 0.3 to 10 parts by weight relative to 100 parts by weight of the electrode active material.

[0038] Such an active material layer can usually have a thickness in the range of 50 to 100 μm or 70 to 80 μm, but is not limited thereto.

[0039] The electrode of the present application can additionally include an insulating layer formed on the current collector on which the active material layer is formed. Although not particularly limited, the insulating layer can be present, for example, on the non-patterned portion on the current collector and / or at the boundary between the non-patterned portion and the patterned portion on the current collector. For example, the insulating layer may be positioned to cover at least a part of the surface of the current collector where the active material layer is located and at least a part of the surface of the non-patterned portion of the current collector where the active material layer is not located.

[0040] That is, the insulating layer may be formed on the surface of the current collector on which the active material layer is formed. In one example, the active material layer is formed on a part of the surface of the current collector, and the insulating layer may be formed on the surface of the current collector where the active material layer is formed and on at least a part of the surface of the current collector where the active material layer is not formed and on at least a part of the surface of the active material layer.

[0041] The above-mentioned non-patterned portion is a region on the current collector where the active material layer is not formed, and the patterned portion means a region on the current collector where the active material layer is formed.

[0042] Such an insulating layer can minimize possible short circuits that may occur between the positive electrode and the negative electrode in a secondary battery and ensure stability.

[0043] FIG. 1 is a cross-sectional view of the electrode of the present application including the insulating layer 30 as described above, showing a case where the current collector 10, the active material layer 20, and the insulating layer 30 are formed. In the drawing, the insulating layer 30 and the active material layer 20 overlap to form an overlapping region AOL with a width L'.

[0044] Such an insulating layer can have controlled surface characteristics. At this time, the surface characteristics of the insulating layer correspond to the surface opposite to the surface facing the current collector of the insulating layer.

[0045] For example, the insulating layer can have an arithmetic mean height (Sa) within a predetermined range. The arithmetic mean height is a variable with respect to the surface roughness. Such an arithmetic mean height (Sa) is known as the average of the absolute values of the height differences between points with respect to the average plane of the target surface. In this application, the lower limit of the arithmetic mean height can be about 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.01 μm, 3.02 μm, 3.03 μm, 3.04 μm, 3.05 μm, 3.06 μm, 3.07 μm, 3.08 μm, 3.09 μm, 3.1 μm, 3.15 μm or 3.5 μm, and the upper limit can be about 5 μm, 4.5 μm, 4 μm, 3.5 μm, 3.475 μm, 3.45 μm, 3.425 μm, 3.4 μm, 3.375 μm, 3.35 μm, 3.325 μm, 3.3 μm or 3.275 μm. The arithmetic mean height (Sa) can be equal to or greater than any one of the above-mentioned lower limits, or while being equal to or greater than any one of the above-mentioned lower limits, it can be within the range less than or equal to any one of the above-mentioned upper limits.

[0046] Through the above-mentioned surface characteristics, the desired insulation and adhesion can be ensured, and defects such as cracks that may occur in the electrodes can also be prevented. The above-mentioned surface characteristics are derived through the application of the characteristic materials of this application described below. Through such materials, the desired insulation and adhesion can be ensured, and defects such as cracks that may occur in the electrodes can also be prevented.

[0047] The insulating layer may also satisfy one or more additional conditions selected from the group consisting of a maximum height roughness (Sz) within a predetermined range (condition (i)), an arithmetic mean peak curvature (Spc) within a predetermined range (condition (ii)), and a developed interfacial area ratio (Sdr) within a predetermined range (condition (iii)).

[0048] Sz related to the above condition (i) is the maximum height roughness of the surface to be measured, and means the distance between the highest point and the lowest point within a single surface.

[0049] The lower limit of Sz of the insulating layer surface of the present application may be about 13 μm, 14 μm, 15 μm, 15.25 μm, 15.5 μm, 15.75 μm, 16 μm, 16.25 μm, 16.5 μm, 16.75 μm, or 17 μm, and the upper limit may be about 40 μm, 35 μm, 30 μm, 25 μm, 24.5 μm, 24 μm, 23.5 μm, 23 μm, 22.5 μm, 22 μm, 21.5 μm, 21 μm, 20.5 μm, or 20 μm. Sz may be equal to or greater than any one of the lower limits, equal to or less than any one of the upper limits, or equal to or greater than any one of the lower limits but equal to or less than any one of the upper limits.

[0050] The Spc is the arithmetic mean of the principal curvature of the peaks on the surface. The upper limit of the Spc of the insulating layer of the present application is 40 mm. -1 , 39mm -1 , 38mm -1 , 37mm -1 , 36mm -1 , 35mm -1 , 34mm -1 , 33mm -1 , 32mm -1 , 31mm-1 、30 mm -1 、29 mm -1 、28 mm -1 、27 mm -1 、26 mm -1 、25 mm -1 、24 mm -1 、23 mm -1 、22 mm -1 、21 mm -1 、20 mm -1 、19 mm -1 、18 mm -1 、17 mm -1 、16 mm -1 、15 mm -1 、14 mm -1 、13 mm -1 、12 mm -1 、11 mm -1 、10 mm -1 、9 mm -1 、8 mm -1 or 7 mm -1 and its lower limit can be about 1 mm -1 、2 mm -1 、3 mm -1 、4 mm -1 、5 mm -1 、6 mm -1 、7 mm -1 、8 mm -1 、9 mm -1 、10 mm -1 、15 mm -1 、20 mm -1 、25 mm -1 、30 mm -1 or 35 mm -1 and can be about that. The Spc can be greater than or exceeding any one of the aforementioned lower limits, less than or below any one of the aforementioned upper limits, or within the range that is greater than or exceeding any one of the aforementioned lower limits while being less than or below any one of the aforementioned upper limits.

[0051] Sdr (Developed Interfacial Area Ratio) is the developed interfacial area ratio, which indicates how much the developed area (surface area of the measured shape) has increased compared to the area when the measurement area is viewed vertically from above. In the insulating layer of the present application, the upper limit of Sdr may be about 0.01, 0.009, 0.0085, 0.008, 0.0075, 0.007, 0.0065, 0.006, 0.0055, 0.005, 0.004, 0.003, 0.002, 0.001, or 0.00095, and the lower limit may be about 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004, or 0.005. The Sdr may be greater than or equal to any one of the lower limits, less than or equal to any one of the upper limits, or greater than or equal to any one of the lower limits but less than or equal to any one of the upper limits.

[0052] When the insulating layer has surface properties that satisfy one, two, or all of the above conditions (i) to (iii), the desired insulating and adhesive properties can be ensured and defects such as cracks that may occur in the electrode can be prevented. Such surface properties are achieved by applying the characteristic materials of the present application, which will be described later, and these materials can ensure the desired insulating and adhesive properties and prevent defects such as cracks that may occur in the electrode.

[0053] There is no particular limitation on the method for measuring Sa, Sz, Spc, and Sdr. For example, Sa, Sz, Spc, and Sdr can be measured by scanning the surface of the insulating layer using a known 3D scanner and then analyzing the scan results.

[0054] The insulating layer having the above-described characteristic surface properties of the present application can be formed using the specific insulating layer materials provided in the present application.

[0055] The insulating layer may include an aqueous binder. In this application, the term aqueous binder may refer to a binder having a solubility parameter within a certain range. The solubility parameter is a value known as the Hansen Solubility Parameter, and is a value confirmed through literature (e.g., Non-Patent Document 1) or by a method described in the literature.

[0056] In this application, the lower limit of the solubility parameter of the aqueous binder is 10 MPa. 1 / 2 , 11 MPa 1 / 2 , 12 MPa 1 / 2 , 13 MPa 1 / 2 , 14 MPa 1 / 2 , 15 MPa 1 / 2 or 16 MPa 1 / 2 The upper limit is about 30 MPa. 1 / 2 , 28 MPa 1 / 2 , 26 MPa 1 / 2 , 24 MPa 1 / 2 , 22 MPa 1 / 2 , 20 MPa 1 / 2 or 18 MPa 1 / 2 The solubility parameter of the binder may be equal to or greater than any one of the lower limits described above, equal to or less than any one of the upper limits described above, or equal to or greater than any one of the lower limits but equal to or less than any one of the upper limits described above.

[0057] By applying a solution in which the aqueous binder is dispersed in a specific solvent in a specific manner, the particle size distribution of the aqueous binder in the solution can be controlled, and as a result, a desired insulating layer can be obtained.

[0058] The specific type of the aqueous binder is not particularly limited as long as it has the above-mentioned solubility parameter. A representative example of a binder having the above-mentioned solubility parameter is SBR (Styrene Butadiene Rubber), but is not limited thereto.

[0059] The lower limit of the content of the aqueous binder in the insulating layer may be about 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 99 wt%, or 100 wt%, based on the total weight of the insulating layer, and the upper limit may be about 100 wt%, 95 wt%, 92.5 wt%, 90 wt%, 87.5 wt%, 85 wt%, 82.5 wt%, or 80 wt%, based on the total weight of the insulating layer. The content of the binder may be equal to or greater than any one of the lower limits, or equal to or less than any one of the upper limits, or may be equal to or greater than any one of the lower limits but equal to or less than any one of the upper limits.

[0060] The insulating layer may include particles, such as inorganic particles having insulating properties, including ceramic particles, along with the aqueous binder, thereby improving the safety of the battery and the strength of the insulating layer.

[0061] The particles may be ceramic particles such as metal oxides, semi-metal oxides, metal fluorides, or metal hydroxides, and may be any one or a combination of two or more selected from the group consisting of boehmite, γ-AlO(OH), Al(OH), AlO(OH), Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, YO3, SrTiO3, BaTiO3, and Mg(OH).

[0062] In order to contribute to the desired surface properties of the insulating layer, the particles may have a predetermined average particle size.

[0063] For example, the lower limit of the average particle size of the particles may be about 0.01 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm, and the upper limit may be about 100 μm, 90 μm, 80 μm, 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, or 1.5 μm. The average particle size may be equal to or greater than any one of the lower limits, equal to or less than any one of the upper limits, or equal to or greater than any one of the lower limits but equal to or less than any one of the upper limits.

[0064] The average particle size referred to above is the so-called D50 particle size (median diameter), which can refer to the particle size at 50% cumulative volume of the particle size distribution. The particle size distribution is calculated based on volume, and the particle size at the point where the cumulative value reaches 50% on the cumulative curve with the total volume set to 100% can be regarded as the average particle size. The D50 particle size can be measured by laser diffraction.

[0065] The lower limit of the ratio of the particles in the insulating layer may be about 1 part by weight, 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, or 25 parts by weight relative to 100 parts by weight of the aqueous binder, and the upper limit may be about 100 parts by weight, 80 parts by weight, 60 parts by weight, 40 parts by weight, 35 parts by weight, or 30 parts by weight relative to 100 parts by weight of the aqueous binder. The ratio may be equal to or greater than any one of the lower limits, equal to or less than any one of the upper limits, or equal to or greater than any one of the lower limits but equal to or less than any one of the upper limits.

[0066] The insulating layer is also a compound and may contain a solvent component. Such a solvent component was contained in the solution for forming the insulating layer. Such a solvent is usually removed in the drying process for forming the insulating layer, but a trace amount of residual component may be present in the insulating layer.

[0067] The solvent can be, for example, a solvent having a dipole moment within a predetermined range. Through the application of such a solvent, the dispersion state of the aqueous binder in the solution can be adjusted to be suitable. For example, the lower limit of the dipole moment of the solvent at 20°C can be about 2.2D, 2.4D, 2.6D, 2.8D, 3.0D, 3.2D, 3.4D, 3.6D, 3.8D or 4.0D, and the upper limit can be about 6D, 5.8D, 5.6D, 5.4D, 5.2D, 5.0D, 4.8D, 4.6D, 4.4D or 4.2D. The dipole moment is greater than or exceeds any one of the lower limits described above, less than or below any one of the upper limits described above, or may be within the range that is greater than or exceeds any one of the lower limits described above while being less than or below any one of the upper limits described above.

[0068] As the solvent, various types can be used without particular limitation as long as they have the dipole moment. For example, non-aqueous organic solvents can be used. Typically, amide series solvents such as N-methyl-2-pyrrolidone (NMP) can be used, but it is not limited thereto.

[0069] The content of the solvent in the insulating layer is small. That is, as described above, since the step of removing the solvent proceeds during the formation process of the insulating layer, the solvent may not be present in the insulating layer. If it is present, the lower limit of the content of the solvent in the insulating layer can be about 0 parts by weight relative to 100 parts by weight of the binder, and the upper limit can be about 20 parts by weight, 15 parts by weight, 10 parts by weight, 9 parts by weight, 8 parts by weight, 7 parts by weight, 6 parts by weight, 5 parts by weight, 4 parts by weight, 3 parts by weight, 2 parts by weight, 1 part by weight or 0.5 parts by weight. The content is either equal to or greater than any one of the lower limits described above, or less than or equal to any one of the upper limits described above, or within the range of being equal to or greater than any one of the lower limits described above while being less than or equal to any one of the upper limits described above.

[0070] Such an insulating layer can be formed with an appropriate thickness.

[0071] For example, the lower limit of the thickness of the insulating layer can be about 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm or 7 μm, and the upper limit can be about 50 μm, 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm or 15 μm. The thickness is either equal to or greater than any one of the lower limits described above, or less than or equal to any one of the upper limits described above, or within the range of being equal to or greater than any one of the lower limits described above while being less than or equal to any one of the upper limits described above. When the thickness of the insulating layer satisfies the above range, the movement of lithium ions can be restricted to improve the problem of capacity expression, and an appropriate charge-discharge capacity can be ensured.

[0072] The above-mentioned insulating layer can be manufactured using an insulating layer solution as a material. At this time, the insulating layer solution can contain the above-mentioned aqueous binder dispersed in a solvent having the above-mentioned dipole moment.

[0073] In the insulating layer solution, the aqueous binder may be dispersed so as to exhibit a substantially monodisperse particle size distribution. At this time, showing a substantially monodisperse particle size distribution means that substantially one main peak is confirmed in the volume ratio particle size distribution curve. Such a dispersion state of the aqueous binder cannot be achieved by dispersing the aqueous binder in the solvent in a normal manner, and it is necessary to produce the solution by the method described later.

[0074] The lower limit of the content of the aqueous binder in the solution (solid content = 100 × weight of aqueous binder / (weight of aqueous binder + weight of solvent)) can be about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, and the upper limit can be about 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15% or 12%. The solid content is either above or exceeding any one of the lower limits described above, or below or less than any one of the upper limits described above, or within the range of being above or exceeding any one of the lower limits described above while being below or less than any one of the upper limits described above.

[0075] The solution may contain the particles described above as an additional component. At this time, the solution can exhibit the above-described substantially monodisperse particle size distribution even in a state containing the particles. At this time, the specific types and ratios of the particles that can be applied are as described above.

[0076] The insulating layer solution (which may also be referred to as a composition for an insulating layer) as described above can be produced by a method of adding a second solvent different from the first solvent while removing the first solvent in a solution containing the aqueous binder and the first solvent in which the aqueous binder is dispersed (hereinafter, may also be referred to as a first solution).

[0077] That is, the insulating layer solution can be produced by a method of adding another solvent while removing the solvent in a solution in which the aqueous binder is dispersed. At this time, as the second solvent to be added, the solvent that can remain in the insulating layer described above can be used.

[0078] If the aqueous binder is directly dispersed in the second solvent, the substantial monodisperse particle size distribution described above cannot be obtained, and it is difficult to form the target insulating layer when using such a material.

[0079] As the first solvent, a solvent having a lower dipole moment than the second solvent can be used. For example, the upper limit of the dipole moment of the first solvent at 20 °C can be about 2.5 D, 2.4 D, 2.3 D, 2.2 D, 2.1 D, 2.0 D, 1.9 D or 1.85 D, and the lower limit can be about 0 D, 0.5 D, 1 D or 1.5 D. The dipole moment of the first solvent is lower than that of the second solvent, and is greater than or exceeds any one of the lower limits described above, or less than or below any one of the upper limits described above, or is within the range that is greater than or exceeds any one of the lower limits described above while being less than or below any one of the upper limits described above.

[0080] As the first solvent, any solvent having the above-described dipole moment can be used without particular limitation. For example, an aqueous solvent such as water can be used.

[0081] The lower limit of the content of the aqueous binder (solid content = 100 × weight of aqueous binder / (weight of aqueous binder + weight of first solvent)) in the first solution containing such a first solvent and the aqueous binder can be about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40%, and the upper limit can be about 100%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50% or 45%. The solid content is greater than or exceeds any one of the lower limits described above, or less than or below any one of the upper limits described above, or is within the range that is greater than or exceeds any one of the lower limits described above while being less than or below any one of the upper limits described above.

[0082] Removal of the first solvent in the first solution as described above can be carried out while maintaining the first solution at a predetermined temperature and volatilizing the first solution. Since there is a section where the removal of the first solvent and the addition of the second solvent are carried out simultaneously, a solvent having a boiling point higher than that of the first solvent can be used as the second solvent. In this case, the temperature for removing the first solvent can be between the boiling point of the first solvent and the boiling point of the second solvent.

[0083] For example, the lower limit of the boiling point of the first solvent can be about 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or 95°C, and the upper limit can be about 150°C, 145°C, 140°C, 135°C, 130°C, 125°C, 120°C, 115°C, 110°C or 105°C. The boiling point is either equal to or higher than any one of the lower limits described above, or equal to or lower than any one of the upper limits described above, or may be within the range that is equal to or higher than any one of the lower limits described above while being equal to or lower than any one of the upper limits described above.

[0084] The second solvent can have a boiling point higher than that of the first solvent. For example, the lower limit of the difference (BP2 - BP1) between the boiling point (BP2) of the second solvent and the boiling point (BP1) of the first solvent can be about 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or 95°C, and the upper limit can be about 150°C, 145°C, 140°C, 135°C, 130°C, 125°C, 120°C, 115°C, 110°C or 105°C. The difference in boiling points is either equal to or higher than any one of the lower limits described above, or may be within the range that is equal to or higher than any one of the lower limits described above while being equal to or lower than any one of the upper limits described above.

[0085] In the step of manufacturing the insulating layer solution, the removal of the first solvent can proceed at a constant rate. That is, the lower limit of the removal rate of the first solvent can be about 0.5 g / min, 1 g / min, 1.5 g / min, 2 g / min, 2.5 g / min, 5 g / min, 10 g / min, 50 g / min, 100 g / min, 500 g / min, 1 kg / min, 50 kg / min, 100 kg / min, 150 kg / min, 200 kg / min, 250 kg / min, 300 kg / min, 350 kg / min, 400 kg / min, 450 kg / min, 500 kg / min, 550 kg / min or 600 kg / min, and the upper limit thereof can be about 700 kg / min, 650 kg / min, 600 kg / min, 550 kg / min, 500 kg / min, 450 kg / min, 400 kg / min, 350 kg / min, 300 kg / min, 250 kg / min, 200 kg / min, 150 kg / min, 100 kg / min, 50 kg / min, 10 kg / min, 1 kg / min, 500 g / min, 100 g / min, 50 g / min, 10 g / min, 5 g / min, 4 g / min or 3 g / min. The removal rate of the first solvent is greater than or exceeds any one of the lower limits described above, less than or below any one of the upper limits described above, or may be within the range of greater than or exceeding any one of the lower limits described above and less than or below any one of the upper limits described above. Such a removal rate can be adjusted by adjusting the drying temperature of the first solution. The removal rate described above is the average rate.

[0086] In the step of manufacturing the insulating layer solution, the addition of the second solvent can also be performed at a constant rate. That is, the lower limit of the addition rate of the second solvent can be about 0.01 kg / min, 0.05 kg / min, 0.1 kg / min, 0.15 kg / min or 0.2 kg / min, and the upper limit thereof can be about 250 kg / min, 200 kg / min, 150 kg / min, 50 kg / min, 10 kg / min, 9 kg / min, 8 kg / min, 7 kg / min, 6 kg / min, 5 kg / min, 4 kg / min or 3 kg / min. The addition rate is the average rate.

[0087] In the manufacturing process, the removal of the first solvent and the addition of the second solvent can be carried out after the first solvent is substantially removed from the first solution until the solid content of the solution containing the second solvent and the aqueous binder reaches a predetermined range.

[0088] That is, the process is carried out until the solid content corresponding to the content of the aqueous binder in the solution (= 100 × weight of the aqueous binder / (weight of the aqueous binder + weight of the second solvent)) reaches a predetermined range. At this time, the lower limit of the solid content can be about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, and the upper limit can be about 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15% or 12%. The solid content is either equal to or greater than any one of the lower limits described above, or equal to or less than any one of the upper limits described above, or within the range that is equal to or greater than any one of the lower limits described above while being equal to or less than any one of the upper limits described above.

[0089] The insulating layer solution in the desired dispersed state can be manufactured in the above-described manner.

[0090] As described above, the removal of the first solvent and the addition of the second solvent can be carried out at a temperature at which the removal rate of the first solvent can be achieved within the temperature range between the boiling point of the first solvent and the boiling point of the second solvent.

[0091] On the other hand, at least a part of the process of removing the first solvent and the process of removing the second solvent in the process overlap. That is, the removal of the first solvent and the addition of the second solvent can be started simultaneously, and in some cases, one of the processes may proceed to the other process during the progress of one of the processes, and in any case, they overlap in a certain part.

[0092] In the manufacturing process of the insulating layer solution, after replacing the first solvent with the second solvent in the first solution as described above, the step of adding the above-described particles to the solution containing the second solvent may be performed.

[0093] Such an insulating layer solution allows the formation of an insulating layer with desired characteristics. For example, the insulating layer solution forms an insulating layer that ensures insulating performance and wet peel strength during the insulating layer formation process, while preventing swelling at high temperatures. The use of the insulating layer solution suppresses gelation of the active material layer, preventing cracks at the interface between the insulating layer and the active material layer.

[0094] For example, the insulating layer solution may form an insulating layer having a predetermined range of percentage (R1) of difference in arithmetic mean surface height (Sa) according to the following Equation 1. The upper limit of the percentage (R1) may be about 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, or 5%, and the lower limit may be about 0.01%, 0.05%, 0.1%, 0.5%, or 1%. The percentage (R1) may be equal to or greater than any one of the lower limits, equal to or less than any one of the upper limits, or equal to or greater than any one of the lower limits but equal to or less than any one of the upper limits.

[0095] [Formula 1] R1 = |Sa1-Sa2| / Sa2×100

[0096] In Equation 1, Sa1 is the arithmetic mean height (Sa) of the surface of the insulating layer formed by drying the insulating layer solution at 130°C, and Sa2 is the arithmetic mean height (Sa) of the surface of the insulating layer formed by drying the insulating layer solution at room temperature (approximately 25°C).

[0097] The insulating layer solution can also form an insulating layer in which the ratio (R2) of the adhesion force difference according to the following formula 2 is within a predetermined range. The lower limit of the ratio (R2) of the adhesion force difference according to the formula 2 can be about 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86% or 88%, and the upper limit thereof can be about 100%, 99%, 98%, 97%, 96% or 95%. The ratio is greater than or exceeds any one of the lower limits described above, less than or below any one of the upper limits described above, or within a range that is greater than or exceeds any one of the lower limits described above while being less than or below any one of the upper limits described above.

[0098] [Formula 2] R2 = Aw / Ad × 100

[0099] In Formula 2, Aw means the peeling force (wet peeling force) of the insulating layer with respect to the metal specimen measured through a 90-degree peel test in a state where the insulating layer adhered to the metal specimen is impregnated with an electrolytic solution at room temperature (about 25°C), and Ad means the peeling force (dry peeling force) of the insulating layer with respect to the metal specimen measured through a 90-degree peel test at room temperature (about 25°C).

[0100] The wet peeling force described above can mean the peeling force of the insulating layer measured in a state impregnated with an electrolytic solution. The wet peeling force can mean the peeling force measured through a 90-degree peel test after impregnating a metal specimen with an insulating layer formed on one side with an electrolytic solution. The metal specimen can mean a current collector used during electrode manufacturing in the space where the insulating layer is formed, and can be a current collector punched out to have a predetermined width and length.

[0101] The insulating layer according to an example of the present application can block the movement of lithium ions in the overlay region of the electrode and suppress capacitance expression and the like by satisfying the range of the ratio (R2) of the adhesion force difference according to the formula 2.

[0102] The overlay area may mean an area where an insulating layer is formed on an electrode. The insulating layer may be positioned to cover at least a part of the surface on the active material layer and at least a part of the surface of the current collector in the plain area where the active material layer is not located. However, the area where the insulating layer is formed on the active material layer can be referred to as the overlay area.

[0103] The insulating layer according to an example of the present application has a wet peel force (Aw) of the insulating layer peeled from a metal specimen measured through a 90-degree peel test in a state where the insulating layer attached to the metal specimen is impregnated with an electrolytic solution at room temperature of 15 gf / 20 mm or more, 15.5 gf / 20 mm or more, 16 gf / 20 mm or more, 16.5 gf / 20 mm or more, 17 gf / 20 mm or more, 17.5 gf / 20 mm or more, 18 gf / 20 mm or more, 18.5 gf / 20 mm or more, or 19 gf / 20 mm or more. In another example, the wet peel force of the insulating layer can be 50 gf / 20 mm or less, 48 gf / 20 mm or less, 46 gf / 20 mm or less, 44 gf / 20 mm or less, 42 gf / 20 mm or less, 40 gf / 20 mm or less, 38 gf / 20 mm or less, 36 gf / 20 mm or less, 34 gf / 20 mm or less, 32 gf / 20 mm or less, or 30 gf / 20 mm or less. The wet peel force of the insulating layer can be within a range formed by appropriately selecting the above-mentioned upper and lower limits.

[0104] The measurement of the wet peel force (Aw) of the insulating layer can be carried out by applying a tensile force to one side of the insulating layer (for example, the self-standing area) in a state where the metal specimen with the insulating layer formed is fixed, and measuring the force at which the insulating layer is peeled from the metal specimen. At this time, the metal specimen with the insulating layer formed can be in a state of being impregnated with an electrolytic solution at room temperature, and the wet peel force can be measured as the force at which the insulating layer is peeled from the metal specimen in a state of being impregnated with the electrolytic solution. The wet peel force of the insulating layer can be measured by a 90-degree peel test. For example, after setting the load of a UTM device (supplier: TA) to 0, the load speed can be set in the range of 10 - 200 mm / min to measure the peel force on the metal specimen.

[0105] The electrolytic solution used for measuring the wet peeling force (Aw) of the insulating layer may contain an organic solvent and an electrolyte salt, and the electrolyte salt may be a lithium salt. The lithium salt that is usually used in the non-aqueous electrolytic solution for lithium secondary batteries can be used without limitation. For example, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. As the organic solvent contained in the electrolytic solution, those usually used in the electrolytic solution for lithium secondary batteries can be used without limitation. For example, ether, ester, amide, linear carbonate or cyclic carbonate, etc. can be used alone or in combination of two or more. Among these, typically, it can contain a carbonate compound which is a cyclic carbonate, a linear carbonate or a mixture thereof.

[0106] The dry peeling force (Ad) of the insulating layer can also be measured by a 90-degree peel test at room temperature.

[0107] Generally, in a secondary battery, the electrodes exist in a state impregnated with the electrolytic solution. However, in the case of a conventional insulating coating, the wet peeling force in the state impregnated with the electrolytic solution decreases, and the movement of lithium ions cannot be prevented in the overlay region of the electrodes, resulting in a problem of capacity manifestation. In particular, lithium ions can be deposited during capacity manifestation in the overlay region of the electrodes, which can lead to a decrease in the stability of the battery.

[0108] When the wet peeling force of the insulating layer satisfies the above range, the movement of lithium ions can be suppressed in the overlay region of the electrodes, preventing the deposition of lithium ions and improving the stability of the battery.

[0109] In the electrode of the present application, the insulating layer can exhibit excellent peel strength with respect to the current collector. The peel strength can be a wet peel strength. Such a wet peel strength can be the peel strength measured by impregnating an electrode including the current collector and the insulating layer into an electrolytic solution, which can be the peel strength of the insulating layer with respect to the current collector. The wet peel strength can be the peel strength of the insulating layer with respect to the current collector measured at a peel angle of 90 degrees and a peel rate of 100 mm / min. At this time, the peel strength can be the peel strength measured after impregnating the electrode including the insulating layer and the current collector into an electrolyte at a temperature of 25°C for 1 hour. The lower limit of the peel strength (Aw) can be 15 gf / 20 mm, 15.5 gf / 20 mm, 16 gf / 20 mm, 16.5 gf / 20 mm, 17 gf / 20 mm, 17.5 gf / 20 mm, 18 gf / 20 mm, 18.5 gf / 20 mm or 19 gf / 20 mm, and the upper limit thereof can be 50 gf / 20 mm, 48 gf / 20 mm, 46 gf / 20 mm, 44 gf / 20 mm, 42 gf / 20 mm, 40 gf / 20 mm, 38 gf / 20 mm, 36 gf / 20 mm, 34 gf / 20 mm, 32 gf / 20 mm or 30 gf / 20 mm. The peel strength can be equal to or greater than any one of the lower limits described above, less than or below any one of the upper limits described above, or within the range of being equal to or greater than any one of the lower limits described above and less than or below any one of the upper limits described above. The type of electrolytic solution applied in the process is the same as that applied when measuring Aw of Formula 2. Such a method for measuring the peel strength specifically follows the content described in the example items.

[0110] The method for manufacturing the electrode of the present application as described above is not specifically limited as long as the insulating layer solution described above is used.

[0111] For example, the method for manufacturing the electrode may include a step of forming an insulating layer on at least one surface of the current collector using the insulating layer solution described above. In this process, the insulating layer solution may be a solution manufactured by the method described above. Further, the insulating layer may be formed on the current collector on which the active material layer is formed, or may be formed on the current collector on which the active material layer is not formed. Usually, however, it is formed on the current collector on which the active material layer is formed.

[0112] When forming an insulating layer on the current collector on which the active material layer is formed, the insulating layer can be formed so as to cover at least a part of the surface on the active material layer and at least a part of the surface of the plain part of the current collector where the active material layer is not located. The insulating layer can exhibit the surface characteristics described above.

[0113] The method for manufacturing the electrode may additionally include a step of forming the active material layer on at least one surface of the current collector.

[0114] At this time, there are no special restrictions on the method for forming the active material layer. For example, the active material layer can be formed by applying an active material composition (slurry) for forming the active material layer on the current collector and performing a drying and / or rolling process as necessary.

[0115] The application described above can be performed in various known ways such as slot die coating, slide coating, and curtain coating.

[0116] The active material layer may mean the active material composition (slurry) applied to at least one surface of the current collector, and in other examples, it may mean the state in which the drying of the applied active material composition (slurry) is completed. Specifically, when the active material composition is dried simultaneously with the insulating layer solution, the active material layer means the applied active material composition, and when the drying time of the active material composition is different from that of the insulating layer solution described later, the active material layer may mean the state in which the applied active material composition is dried and the drying is completed.

[0117] The above-mentioned active material composition (slurry) can be coated partially or entirely on one side of the current collector by a secondary battery model. For example, the active material composition may be applied only partially (patterned area) to one side of the current collector to be coated, and not applied to the other part (non-patterned area) to form a predetermined pattern. However, considering the introduction of an insulating layer to prevent short circuits between the positive and negative electrodes, it is preferable that the active material composition is applied only partially so that a patterned area and a non-patterned area are formed on one side of the current collector to be coated.

[0118] The type of current collector applied in the above process is as described above.

[0119] The above-mentioned active material composition (slurry) can be manufactured by dispersing the above-mentioned electrode active material and other necessary components (for example, binder and / or conductive material, etc.) in an appropriate solvent. At this time, the types and ratios of the applied electrode active material, binder for the active material, conductive material, etc. are as described above. Also, known solvents can be applied to the solvent, for example, water, isopropyl alcohol, N-methyl-2-pyrrolidone (NMP) and / or acetone, etc. can be applied.

[0120] The insulating layer can be formed on the current collector on which the active material layer is or is not formed in the above-described manner using the insulating layer solution. In case the active material layer exists, the insulating layer can be formed to cover at least a part of the surface on the active material layer and at least a part of the surface of the non-patterned area where the active material layer is not located on the current collector. Here, the insulating layer can mean a state where the applied insulating composition is dried and the drying is completed.

[0121] At this time, there is no particular limitation on the coating method for forming the insulating layer. For example, the same method as the coating method for forming the active material layer can be applied.

[0122] After applying the insulating layer solution as described above, an insulating layer can be formed through a drying process or the like. When the applied active material composition is present in this process, the drying may be performed simultaneously on the applied active material composition and the insulating layer solution. In some cases, the active material composition can be dried first, and then the insulating composition can be dried.

[0123] The temperature of the drying is not particularly limited. For example, the lower limit of the drying temperature can be about 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, and the upper limit can be about 200°C, 190°C, 180°C, 170°C, 160°C, 150°C, 140°C, 135°C, 130°C, 125°C, 120°C, 115°C, 110°C, 105°C, 100°C, 95°C, 90°C, 85°C, 80°C, 75°C, 70°C, 65°C, 60°C, 55°C, 50°C, 45°C or 40°C. The temperature can be equal to or higher than any one of the aforementioned lower limits, or equal to or lower than any one of the aforementioned upper limits, or within the range that is equal to or higher than any one of the aforementioned lower limits while being equal to or lower than any one of the aforementioned upper limits.

[0124] The drying time can be appropriately adjusted according to the drying temperature and is not particularly limited. For example, the lower limit of the drying time can be about 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 40 minutes or 50 minutes, and the upper limit can be about 200 minutes, 180 minutes, 150 minutes, 100 minutes, 90 minutes, 80 minutes, 70 minutes, 60 minutes, 50 minutes, 40 minutes, 30 minutes, 20 minutes or 10 minutes. The drying time can be equal to or higher than any one of the aforementioned lower limits, or equal to or lower than any one of the aforementioned upper limits, or within the range that is equal to or higher than any one of the aforementioned lower limits while being equal to or lower than any one of the aforementioned upper limits.

[0125] In the manufacturing method of an electrode according to an example of the present application, even when the insulating composition is dried at room temperature, the increase rate of the surface roughness is not high compared to that dried at high temperature. Here, the increase rate of the surface roughness not being high means that the percentage (R1) of the difference in the arithmetic mean height (Sa) of the surface according to the above-described formula 1 is 20% or less, 19% or less, 18% or less, 17% or less, 16% or less, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less.

[0126] As described above, in the manufacturing method of an electrode according to an example of the present application, since the increase rate of the surface roughness is not high, it is possible to manufacture even with high-temperature and room-temperature drying, and when drying at room temperature, drying can be completed in a short time to minimize penetration in the active material layer.

[0127] The manufacturing method of the electrode of the present application may include any known steps (for example, rolling, etc.) that are additionally required in the above process.

[0128] The electrode according to an example of the present application can be a positive electrode or a negative electrode. Usually, the insulating layer is formed on the positive electrode.

[0129] A secondary battery according to an example of the present application can include the electrode according to an example of the present application. The secondary battery can be a lithium-ion battery. Further, the secondary battery can include a positive electrode, a negative electrode positioned opposite to the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolytic solution. At this time, the secondary battery can optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0130] The separator separates the negative electrode and the positive electrode and provides a migration path for lithium ions. Any separator commonly used in the art can be used without particular limitation. In particular, a separator with low resistance to the migration of ions in the electrolyte and excellent electrolyte moisture retention ability is preferred. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene polymer, a propylene polymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof can be used. Also, a normal porous non-woven fabric, for example, a non-woven fabric made of high-melting glass fibers, polyethylene terephthalate fibers, etc. may be used. Further, a coated separator containing a ceramic component or a polymer substance may be used to ensure heat resistance or mechanical strength, and it can be selectively used in a single-layer or multi-layer structure.

[0131] The electrolyte can be an organic liquid electrolyte, an inorganic liquid electrolyte, a gel-type polymer electrolyte, a molten inorganic electrolyte, etc. commonly used in the art, but is not limited thereto. Specifically, the electrolyte can contain an organic solvent and a lithium salt.

[0132] As the organic solvent, any substance can be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double bond, aromatic ring, or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (such as ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant, which can enhance the charge-discharge performance of the battery, and a low-viscosity linear carbonate compound (such as ethylmethylcarbonate, dimethylcarbonate, or diethylcarbonate) is more preferred.

[0133] The lithium salt may be any compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt may be adjusted within a range of 0.1M to 2.0M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion migration.

[0134] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. In this case, the additives may be included in an amount of 0.1 wt % to 5 wt % based on the total weight of the electrolyte.

[0135] The secondary battery can be applied to portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs). [Effects of the Invention]

[0136] This application can provide an electrode having an insulating layer that stably ensures the intended insulation, exhibits excellent adhesion, and does not induce cracks or the like at the boundary between the grounded and ungrounded portions of the electrode, and a method for manufacturing the same. In this application, the use of the electrode can be provided.

Brief Description of the Drawings

[0137]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0138] Hereinafter, the electrode and the like will be specifically described through examples and the like, but the scope of the electrode is not limited by the following examples.

[0139] 1. Particle Size Distribution Evaluation The average particle size (D50 particle size) or particle size distribution was measured using a Malvern MASTERSIZER 3000 instrument in accordance with the ISO-13320 standard. When a laser is irradiated onto the particles dispersed in a solvent, the laser is scattered by the particles, and since the intensity and directionality values of the scattered laser vary depending on the size of the particles, the average diameter can be obtained by analyzing this using Mie theory.

[0140] Through the above analysis, a volume-based cumulative graph of the particle size distribution was obtained by converting to the diameter of a sphere having the same volume as the dispersed particles, and the particle size (median diameter) at 50% cumulative of the graph was designated as the average particle size (D50 particle size).

[0141] Production Example 1. Production of Composition for Insulating Layer The solvent in an SBR aqueous solution in which SBR (Styrene Butadiene Rubber) is dispersed in water was replaced with NMP (N-methyl pyrrolidone) to produce NMP-substituted SBR. The water is a solvent having a dipole moment of about 1.84 D (20 °C) and a boiling point of about 100 °C, and NMP is a solvent having a dipole moment of about 4.1 D (20 °C) and a boiling point of about 202 °C, and SBR is a binder having a solubility parameter of about 16.9 MPa 1 / 2 The solubility parameter of the SBR is a value confirmed in Non-Patent Document 1.

[0142] The SBR aqueous solution contains about 100 g of SBR and about 150 g of water, and the solid content of SBR is about 40%.

[0143] The SBR aqueous solution was maintained at a temperature higher than the boiling point of water and lower than that of NMP, and NMP was dropped while evaporating water with the aqueous solution. The temperature was set so that substantially all of the water in the SBR aqueous solution would evaporate over about 60 minutes. That is, the temperature was set so that the water removal rate would be about 2.5 g / min. NMP was dropped at a constant rate such that ultimately about 1000 g of NMP could be introduced over 5 minutes. Accordingly, the addition rate of NMP was about 0.2 kg / min, and through the above process, the solid content of SBR in the solution in which water was replaced with NMP (= 100×SBR / (SBR + NMP)) was approximately 10%.

[0144] Water in the SBR aqueous solution was replaced with NMP in the above-described manner to obtain a solution (SBR solution in NMP) having a solid content of about 10%.

[0145] Figure 2 is a graph analyzing the particle size distribution of SBR in the SBR solution in NMP formed by the above method. The portion showing a monodisperse particle size distribution in Figure 2 is the particle size distribution of SBR in the SBR solution in NMP. It can be seen through the drawing that the particle size distribution of the SBR solution in NMP shows a distribution in a monodisperse form with an average particle size (D50 particle size) of the SBR binder at about 180 nm level. In Figure 2, the bimodal particle size distribution is not for the SBR solution in NMP formed by the above method, but for the case where SBR obtained by drying the SBR aqueous solution is redispersed in NMP. In the case of the powder redispersion, the particle size distribution showed a bimodal distribution, and it was also confirmed that the average particle size (D50) was very large due to the aggregation of SBR.

[0146] Boehmite (average particle size (D50): about 1 μm) was blended as ceramic particles into the manufactured SBR solution in NMP to produce a composition for an insulating layer. At this time, the blending was carried out so that the weight ratio of the SBR to the boehmite would be about 4:1 (SBR: boehmite).

[0147] Figure 3 shows the particle size analysis results for the composition for the insulating layer. Figure 3 shows the case where a monodisperse particle size distribution is obtained when the boehmite is dispersed in the SBR solution in NMP. From Figure 3, it was confirmed that the D50 particle size of the composition for the insulating layer was at about 1.1 μm level, and it can be seen that it shows a monodisperse form of distribution. The particle size distribution confirmed when the same content of boehmite was blended in the solution showing a bimodal particle size distribution in Figure 2 is also shown in Figure 3, which is a graph showing a bimodal distribution in Figure 3. In the case of the powder redispersion, the particle size distribution showed a bimodal distribution, and the D50 particle size was also confirmed to be large.

[0148] Such results indicate that the particle size distribution of the particulate components in the composition varies depending on the manufacturing method of the composition for the insulating layer.

[0149] Example 1 (1) Fabrication of the electrode A slurry (active material composition) was applied to one side of an aluminum foil (current collector). The application was carried out such that the slurry was applied to a part of the aluminum foil, so that a coated part (the part where the slurry was applied) and an uncoated part (the part where the slurry was not applied) were formed on the aluminum foil.

[0150] Subsequently, after applying the insulating layer solution of Production Example 1 so as to cover all of the uncoated part and the coated part adjacent to the uncoated part on the aluminum foil, it was dried in a convection oven at a temperature of 130 °C for about 10 to 20 minutes, and then a positive electrode in which an active material layer and an insulating layer were formed was manufactured through a rolling process.

[0151] The thickness of the formed active material layer was about 75 μm, and the thickness of the insulating layer was about 7 μm. As the slurry, a positive electrode active material (LiNi 0.65 Co 0.15 Mn 0.2O2), binder (PVDF, poly(vinylidene fluoride)), and carbon black (C) were mixed in a weight ratio of 97.5:1.66:0.7 (positive electrode active material:PVDF:C).

[0152] (2) Manufacturing of coin-shaped half-cells The lithium metal plate, separator, and cathode were stacked to form an electrode assembly, which was then placed in a case. An electrolyte was then injected into the case and sealed to form a coin-shaped half cell. The electrolyte used was a mixture of EC (Ethyl carbonate) and EMC (Ethyl Methyl carbonate) in a volume ratio of 3:7 (EC:EMC), containing lithium salt (LiPF6) at a concentration of 1M.

[0153] Example 2 A positive electrode and a coin-type half cell were manufactured in the same manner as in Example 1, except that the insulating layer composition was applied and then dried in a dry room at a temperature of 25°C for about 90 minutes to manufacture a positive electrode.

[0154] Comparative Example 1 An electrode and a coin-type half cell were manufactured in the same manner as in Example 1, except that an insulating layer was not formed.

[0155] Comparative Example 2 An electrode and a coin-type half cell were manufactured in the same manner as in Example 1, except that a composition in which PVDF (poly(vinylidene fluoride)) was dissolved in NMP (N-methyl-2-pyrrolidone) was used as the insulating layer composition.

[0156] Comparative Example 3 As an insulating layer composition, except that a solution in which SBR (Styrene Butadiene Rubber) dried in NMP (N-methyl-2-pyrrolidone) described in Production Example 1 was dispersed and boehmite was added, and a solution showing a bimodal particle size distribution in FIGS. 2 and 3 was used, electrodes and coin-type half cells were produced in the same manner as in Example 2.

[0157] Test Example 1. Surface Evaluation of Insulating Layer The results of observing the surfaces of the insulating layers of the electrodes of Example, Comparative Example 2, and Comparative Example 3 using an SEM (Scanning Electron Microscope) are shown in FIGS. 4 to 8. FIG. 4 is the surface of the insulating layer of Example 1, FIG. 5 is the surface of the insulating layer of Example 2, FIG. 6 is the surface of the active material layer of Comparative Example 1, FIG. 7 is the surface of the insulating layer of Comparative Example 2, and FIG. 8 is the surface of the insulating layer of Comparative Example 3.

[0158] After scanning the surface of the insulating layer using a 3D scanner (VR-500, manufactured by KEYENCE), the characteristics analyzed by software were tabulated in Table 1. By using the 3D scanner to scan the surface of the insulating layer, the surface characteristics can be obtained through the analysis software built into the scanner. In Table 1 below, Sa is the arithmetical mean height (unit: μm) of the insulating layer surface, Sz is the maximum height roughness (unit: μm) of the insulating layer surface, Spc is the arithmetic mean peak curvature (unit: mm -1 ) of the insulating layer surface, and Sdr is the developed interfacial area ratio of the insulating layer surface.

[0159]

Table 1

[0160] Test Example 2. Measurement of Peel Force of Insulating Layer (1) Dry peeling force (Ad) The insulating layer solution applied in each of the examples or comparative examples was coated on aluminum foil and sufficiently dried at room temperature (about 25°C) to form an insulating layer of about 10 μm on the foil. Subsequently, the foil with the insulating layer formed thereon was punched out using a punching machine to produce test pieces having a size of about 20 mm in width and about 125 mm in length. The test pieces were attached to a slide glass using double-sided tape. When attaching, the side without the insulating layer formed was attached to the slide glass. As the double-sided tape, one having a high peeling force for comparing the peeling force between the aluminum foil and the insulating layer was used.

[0161] The attachment was performed by attaching the test piece to the slide glass with double-sided tape and reciprocating a roller of about 2 kg 10 times.

[0162] Subsequently, using a UTM (Universal Testing Machine) device of TA Co., one side of the insulating layer was pulled at a peeling angle of 90 degrees and a peeling speed of 100 mm / min to measure the peeling force.

[0163] (2) Measurement of wet peeling force (Aw) The insulating layer solution applied in each of the examples or comparative examples was coated on aluminum foil and sufficiently dried at room temperature (about 25°C) to form an insulating layer with a thickness of about 10 μm on the foil. Subsequently, the foil with the insulating layer formed thereon was punched out using a punching machine to produce test pieces having a size of about 20 mm in width and about 125 mm in length.

[0164] The wet peeling force was evaluated by the method shown in FIG. [[ID=..]]

[0165] Referring to Fig. 9, first, one side end of the insulating layer was peeled off from the foil with a test piece to form a self-standing region of the insulating layer (Fig. 9a). Subsequently, although the test piece was impregnated with the electrolyte, the self-standing region was not impregnated with the electrolyte (Fig. 9b). As the electrolyte, a mixture of DMC (Dimethyl Carbonate) and EC (Ethylene Carbonate) mixed at a weight ratio of 1:1 and in which 1M concentration of LiPF6 was dissolved was used. During the impregnation, the temperature of the electrolyte was maintained at about 25°C, and the impregnation was carried out for about 1 hour.

[0166] After impregnation, the test piece was attached to a slide glass using double-sided tape. When attaching, the surface where the insulating layer was not formed was attached to the slide glass. As the double-sided tape, one having a high peeling force compared to the peeling force between the aluminum foil and the insulating layer was used.

[0167] The attachment was performed by attaching the test piece with double-sided tape on the slide glass and reciprocating a roller of about 2 kg 10 times.

[0168] Subsequently, using a UTM (Universal Testing Machine) device of TA company, one side (standing region) of the insulating layer was pulled at a peeling angle of 90 degrees and a peeling speed of 100 mm / min to measure the peeling force (Figs. 9c and 9d). The measurement results are shown in Table 2 below.

[0169] In Table 2 below, R2 is a numerical value obtained by substituting the measured dry peeling force (A d ) and wet peeling force (A w ) into the formula R2 = 100A w / A d . Also, in Table 2 below, the units of the dry and wet peeling forces are gf / 20 mm.

[0170]

Table 2

[0171] Test Example 3. Characteristics Evaluation of Coin-Type Half-Cell For the coin-type half-cells manufactured in the examples and comparative examples, the discharge rate was evaluated under the 0.1C discharge condition, and the results are shown in Table 3 below. Further, the discharge characteristics were measured at 25°C and 45°C, respectively.

[0172] Figures 10 and 11 show the evaluation results of the discharge characteristics.

[0173] [Table 3]

Claims

1. A current collector, an active material layer formed on at least one surface of the current collector, and an insulating layer formed on the surface of the current collector on which the active material layer is formed, wherein the active material layer is formed in a partial region of the surface of the current collector, and the insulating layer is formed on at least a partial region of the surface of the current collector where the active material layer is not formed and on at least a partial surface of the active material layer, wherein an arithmetic mean height (Sa) of the surface of the insulating layer is 3 μm or more, wherein the surface of the insulating layer satisfies one or more of the following conditions (i) to (iii): Condition (i): The maximum height roughness (Sz) of the surface of the insulating layer ≧ 15 μm, Condition (ii): The arithmetic mean peak curvature (Spc) of the surface of the insulating layer ≦ 40 mm−1, Condition (iii): The developed area ratio (Sdr) of the interface of the surface of the insulating layer ≦ 0.0009, an electrode.

2. The electrode according to claim 1, satisfying two or more of the conditions (i) to (iii).

3. The electrode according to claim 1, satisfying all of the conditions (i) to (iii).

4. The insulating layer contains a binder having a solubility parameter in the range of 10 MPa １／２ to 30 MPa １／２ The electrode according to any one of claims 1 to 3.

5. The electrode according to claim 4, wherein a content of the binder in the insulating layer is in a range of 50 to 100% by weight.

6. The electrode according to claim 4, wherein the insulating layer further contains ceramic particles.

7. The electrode according to claim 6, wherein an average particle diameter of the ceramic particles is in a range of 0.01 μm to 100 μm.

8. The electrode according to claim 6, wherein the ceramic particles are metal oxides, semi-metal oxides, metal fluorides or metal hydroxides.

9. The electrode according to claim 6, wherein the insulating layer contains 1 to 100 parts by weight of ceramic particles with respect to 100 parts by weight of the binder.

10. The electrode according to claim 4, further containing a compound having a dipole moment at 20° C. in a range of 2.2 D to 6 D.

11. including a step of forming an insulating layer using an insulating layer solution on at least one surface of a current collector on which an active material layer is formed, wherein the insulating layer solution is produced by a step of producing a second solution by adding a second solvent at a constant addition rate while removing the first solvent at a constant removal rate in a first solution containing a first solvent and a binder, The dipole moment of the first solvent at 20°C is more than 0 D and 2.5 D or less, the dipole moment of the second solvent at 20°C is in the range of 2.2 D to 6 D, and the solubility parameter of the binder is 10 MPa １／２ to 30 MPa １／２ within the range of, a method for manufacturing an electrode.

12. The method for manufacturing an electrode according to claim 11, wherein a solid content of the first solution is in a range of 1% to 100%.

13. The method for manufacturing an electrode according to claim 11, wherein the removal of the first solvent or the addition of the second solvent is performed until the solid content of the second solution is within the range of 1% to 50%.

14. The method for manufacturing an electrode according to claim 11, wherein the boiling point of the first solvent is within the range of 50°C to 150°C.

15. The method for manufacturing an electrode according to claim 14, wherein the difference (BP2 - BP1) between the boiling point (BP2) of the second solvent and the boiling point (BP1) of the first solvent is within the range of 50°C to 150°C.

16. The method for manufacturing an electrode according to claim 11, wherein the removal rate of the first solvent is adjusted within the range of 0.5 g / min to 700 kg / min.

17. The method for manufacturing an electrode according to claim 11, wherein the addition rate of the second solvent is adjusted within the range of 0.01 kg / min to 250 kg / min.

18. A battery comprising the electrode according to claim 1.

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