Method for manufactruring of electrod

Abstract

A method for manufacturing an electrode according to the present invention comprises the steps of: applying a coating material onto an electrode current collector to form a coating layer; and applying an electrode slurry onto the electrode current collector on which the coating layer is formed to form an electrode composite layer, wherein the coating layer is formed along the longitudinal direction of the electrode current collector and is formed to be in contact with the end portion of the electrode composite layer, and the coating material is an organic solvent having opposite polarity to the solvent contained in the electrode slurry and having a boiling point difference of 10°C to 50°C with the solvent contained in the electrode slurry.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing an electrode. Specifically, it relates to a method for manufacturing an electrode that can mitigate electrode slurry loading deviations occurring during the electrode manufacturing process. Background Technology

[0002] The secondary battery electrode manufacturing process includes a coating process in which an electrode slurry, mixed with an electrode active material, a conductive material, a binder, and a solvent, is applied to a current collector and then dried. When the electrode slurry is uniformly applied to the current collector, charges and lithium ions diffuse uniformly, which is advantageous for the performance efficiency of the secondary battery.

[0003] Typically, an electrode slurry is coated on one or both sides of a current collector through comma coating and slot die coating, etc. FIG. 1 is a cross-section of a current collector coated with an electrode slurry according to the prior art. As can be seen in FIG. 1, due to the contact angle occurring at the interface between the electrode slurry (20) and the current collector (10) during the coating process, loading failure occurs at both ends of the electrode slurry (20) coated with the electrode slurry centered on the direction perpendicular to the coating direction. If the electrode slurry is applied unevenly, there is a problem in that the capacity decreases at the positive electrode and the possibility of lithium precipitation increases at the negative electrode. Prior art literature

[0004] Korean Published Patent No. 10-2022-0057309 The problem to be solved

[0005] The present invention aims to solve the above-mentioned problems and provides a method for manufacturing an electrode that can improve the loading failure phenomenon occurring during electrode slurry coating. means of solving the problem

[0006] [1] The present invention provides a method for manufacturing an electrode comprising the steps of: applying a coating material onto an electrode current collector to form a coating layer; and applying an electrode electrode slurry onto the electrode current collector on which the coating layer is formed to form an electrode composite layer, wherein the coating layer is formed along the longitudinal direction of the electrode current collector and is formed to be in contact with the end portion of the electrode composite layer, and the coating material has opposite polarity to the solvent contained in the electrode electrode slurry and is an organic solvent having a boiling point difference of 50°C or less with respect to the solvent contained in the electrode electrode slurry.

[0007] [2] The present invention provides a method for manufacturing an electrode in which, in [1] the boiling point of the coating material is 90 to 150 ℃.

[0008] [3] The present invention provides a method for manufacturing an electrode, wherein the coating material in [1] or [2] comprises one or more selected from the group consisting of heptane, isooctane, butanol, butyl acetate, toluene and xylene.

[0009] [4] The present invention provides a method for manufacturing an electrode in which, in at least one of [1] to [3], the width of the coating layer is 1 / 6,000 to 1 / 30 of the width of the electrode composite layer.

[0010] [5] The present invention provides a method for manufacturing an electrode in which, in at least one of [1] to [4], the width of the coating layer is 0.1 mm to 5.0 mm.

[0011] [6] The present invention provides a method for manufacturing an electrode in which, in at least one of [1] to [5], the height of the coating layer is 50% to 150% of the height of the electrode composite layer.

[0012] [7] The present invention provides a method for manufacturing an electrode in which, in at least one of [1] to [6], the height of the coating layer is 50 μm to 1,000 μm.

[0013] [8] The present invention provides a method for manufacturing an electrode in which, in at least one of [1] to [7], the electrode slurry is a water-based electrode slurry.

[0014] [9] The present invention provides a method for manufacturing an electrode in which, in at least one of [1] to [8], the coating layer volatilizes during the step of drying the electrode slurry. Effects of the invention

[0015] The method for manufacturing an electrode according to the present invention can alleviate the loading drop phenomenon occurring at both ends of the coating portion during electrode slurry coating.

[0016] The cathode manufactured by the above manufacturing method may have a reduced lithium precipitation amount, and the anode manufactured by the above manufacturing method may prevent capacity degradation. Brief explanation of the drawing

[0017] Figure 1 is a cross-section of a current collector coated with an electrode slurry according to the prior art. FIG. 2 is a cross-sectional view of a current collector coated with an electrode slurry according to one embodiment of the present invention. Figure 3 is a partial enlarged view of Figure 2. Specific details for implementing the invention

[0018] The present invention will be described in more detail below.

[0020] In conventional electrode manufacturing methods, when coating an electrode slurry onto a current collector, the loading amount is uneven at both ends of the coated electrode slurry centered on the direction perpendicular to the coating direction due to the contact angle between the slurry and the current collector. If the loading amount of the electrode slurry applied to the current collector is uneven, there is a problem that the capacity of the secondary battery decreases or lithium deposition increases.

[0021] As a result of continuous research to solve such problems, the inventors discovered that by forming a coating layer in which a coating material having opposite polarity to the solvent contained in the electrode slurry comes into contact with the end portion of the electrode slurry in the longitudinal direction of the current collector, and then applying the electrode slurry, the contact angle between the electrode slurry and the current collector can be increased, and as the contact angle increases, the loading amount at both end portions of the electrode slurry can be uniformized, and thus completed the present invention.

[0023] Method for manufacturing an electrode

[0024] A method for manufacturing an electrode according to the present invention comprises the steps of: applying a coating material onto an electrode current collector to form a coating layer; and applying an electrode slurry onto the electrode current collector on which the coating layer is formed to form an electrode composite layer.

[0025] As shown in the cross-sectional view of FIGS. 2 and 3, the electrode manufactured by the above method of manufacturing the electrode has a coating layer (200) and an electrode composite layer (300) disposed on the upper surface of the electrode current collector (100), and one surface of the coating layer (200) can come into contact with the end portion of the electrode composite layer (300).

[0027] The method for manufacturing the electrode of the present invention will be described in detail below.

[0029] Step of forming a coating layer

[0030] In this step, a coating material may be applied to the electrode current collector (100) along the length direction of the electrode current collector, to the portion in contact with the end portion of the electrode composite layer (300).

[0032] The above electrode current collector (100) is not particularly limited as long as it is conductive without causing chemical and electrochemical changes in the battery. As a positive current collector, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. As a negative current collector, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy may be used.

[0033] The above electrode current collector can typically have a thickness of 3 μm to 500 μm.

[0034] The above electrode current collector may form fine irregularities on its surface to strengthen the bonding force of the electrode active material. For example, the above electrode current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0036] The coating material may have opposite polarity to the solvent included in the electrode slurry of the electrode composite layer formation step described later, and the coating layer (200) formed by the coating material may also have opposite polarity to the solvent included in the electrode slurry. As the coating layer (200) has opposite polarity to the solvent included in the electrode slurry, the end portion of the electrode slurry may form a repulsive force due to the difference in polarity with the coating layer (200), thereby limiting the flowability of the electrode slurry and inducing aggregation.

[0037] For example, if the solvent included in the electrode slurry is water-based, the coating material may include one or more non-polar solvents selected from the group consisting of heptane, isooctane, butanol, butyl acetate, toluene, and xylene, but is not limited thereto. Any solvent that can volatilize during the drying process and does not affect the operation of the battery may be used without limitation.

[0039] The coating material may be an organic solvent having a boiling point difference of 50°C or less with respect to the solvent included in the electrode slurry, or between 1°C and 45°C or between 2°C and 40°C. If the difference between the boiling point of the coating material and the solvent included in the electrode slurry is too large, and the boiling point of the coating material is very high, the coating layer (200) may not volatilize during the drying step of the electrode slurry, and side reactions may form during the electrode assembly step. If the boiling point of the coating material is very low, the coating layer (200) may volatilize before the drying step of the electrode slurry, and the un-dried electrode slurry may penetrate into unintended parts and not be uniformly coated on the electrode current collector (100).

[0040] The boiling point of the coating material may be 90°C to 150°C, 95°C to 145°C, or 98°C to 140°C. Within the boiling point range of the coating material, the coating layer (200) may be maintained when the electrode slurry is applied, and the coating layer (200) may volatilize and be removed when the electrode slurry is dried. If the boiling point of the coating material exceeds the above range, the coating layer (200) may not be removed when the electrode slurry is dried, which may cause problems during subsequent electrode assembly and cell operation processes. If the boiling point of the coating material is below the above range, the coating layer (200) may be removed before the electrode slurry is applied to the electrode current collector (100).

[0042] Meanwhile, the width of the coating layer (200) may be 1 / 6,000 to 1 / 30, 1 / 4,000 to 1 / 50, or 1 / 2,000 to 1 / 100 of the width of the electrode composite layer. If the width ratio of the coating layer (200) is too small, the coating layer may not properly support the electrode slurry. If the width ratio of the coating layer (200) is too large, the area occupied by the coating layer (200) on the electrode current collector (100) increases, and the electrode composite layer (300) may not be formed in an appropriate size.

[0043] The coating layer (200) may have a width of 0.1 μm to 5.0 μm. If the width of the coating layer (200) is less than the above range, the coating layer (200) may not support the electrode slurry, and the electrode slurry may be applied to the upper surface of the coating layer (200). If the width of the coating layer (200) exceeds the above range, the area on which the electrode slurry can be applied to the electrode current collector (100) is reduced, and thus the electrode performance may be reduced.

[0045] The height of the coating layer (200) may be 50% to 150% of the height of the electrode composite layer (300). Due to the difference in polarity between the coating layer (200) and the electrode composite layer (300), a contact angle and mutual repulsion may occur, so the height of the coating layer may be maintained at 50% to 150% of the height of the electrode composite layer (300). If the height ratio of the coating layer (200) is too low, when the electrode slurry is applied to the electrode current collector (100), the electrode slurry may be applied to the upper surface of the coating layer (200). If the height ratio of the coating layer (200) is too high, there is a possibility that some of the coating layer (200) may remain when the slurry is dried later.

[0047] Additionally, the height of the coating layer (200) may be 50 μm to 1,000 μm, 70 μm to 800 μm, or 100 μm to 600 μm. Within the height range, a repulsive force between the coating layer (200) and the electrode composite layer (300) may be appropriately generated so that the coating layer (200) and the electrode composite layer (300) do not mix. If the height range is exceeded, the coating layer (200) or the electrode composite layer (300) may move out of the designated area.

[0049] Step of forming a composite layer

[0050] In this step, an electrode slurry can be applied to the electrode current collector (100) on which the coating layer (200) is formed to form an electrode composite layer (300).

[0052] The above electrode slurry can be prepared by mixing an electrode active material, optionally a binder, a conductive material, and a dispersant in a solvent.

[0053] The above electrode active material may be a positive electrode active material or a negative electrode active material.

[0054] The above-mentioned cathode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), or a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2(here, 0 <Y<1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2(here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r )O2(where, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2 Examples include )O2(wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r2 and s2 are each atomic fractions of independent elements, such that 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc., and any one or more of these compounds may be included.

[0055] The above positive active material may be included in an amount of 60 to 99 weight%, preferably 70 to 99 weight%, and more preferably 80 to 98 weight% based on the total weight of the positive composite layer.

[0057] The above negative electrode active material may be a carbon-based active material, a silicon-based active material, or a mixture of a carbon-based active material and a silicon-based active material.

[0058] The above carbon-based active material may include various carbon-based active materials used in the industry, such as graphite-based materials like natural graphite, artificial graphite, and Kish graphite; pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon, soft carbon, and hard carbon such as petroleum or coal tar pitch-derived cokes. The shape of the above carbon-based active material is not particularly limited, and materials of various shapes such as amorphous, plate-like, flake-like, spherical, or fibrous can be used.

[0059] Specifically, the carbon-based active material may be either natural graphite or artificial graphite, and natural graphite and artificial graphite may be used together to increase adhesion with the current collector and suppress the detachment of the active material.

[0060] In addition, the silicon-based active material is, for example, metallic silicon (Si) or silicon oxide (SiO). x, here 0 <x<2) 실리콘 탄화물(Si / C) 및 Si-Y 합금(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님)로 이루어진 군으로부터 선택된 1종 이상을 포함할 수 있다. 상기 원소 Y로는 Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db (dubnium), Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, 및 이들의 조합으로 이루어진 군에서 선택될 수 있다.

[0061] The above-mentioned cathode active material may be included in an amount of 60% to 99% by weight based on the total weight of the cathode composite layer, preferably in an amount of 70% or more, 80% or more, 85% or more, or 90% or more by weight, and may also be included in an amount of 98% or less, 97% or less, or 95% or less by weight.

[0063] The above-mentioned binder is a component that assists in the bonding of the electrode active material and conductive material, as well as the bonding to the electrode current collector. Any material used as a binder for lithium secondary batteries may be used without any special restrictions.

[0064] Examples of such anode binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers.

[0065] Typically, the anode binder may be included in an amount of 1 to 20 weight%, preferably 1 to 15 weight%, and more preferably 1 to 10 weight% based on the total weight of the anode composite layer.

[0066] Next, specific examples of cathode binders include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0067] The above cathode binder may be included in an amount of 1 to 30 weight%, preferably 1 to 20 weight%, more preferably 1 to 10 weight% based on the total weight of the cathode composite layer.

[0069] The above conductive material is a component for further enhancing the conductivity of the electrode active material, and is not particularly limited as long as it possesses conductivity without causing chemical changes in the battery.

[0070] Examples of cathode conductive materials may be used, such as carbon powders including carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, or carbon nanotubes (CNT); graphite powders including natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powders such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0071] Typically, the anode conductive material may be included in an amount of 1 to 20 weight%, preferably 1 to 15 weight%, and more preferably 1 to 10 weight% based on the total weight of the anode composite layer.

[0072] Examples of cathode conductive materials include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotube; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. Preferably, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube, or a combination thereof may be used as the cathode conductive material, and it is more preferable to use point conductive materials and linear conductive materials together in terms of improving conductivity. At this time, the point-shaped conductive material is a material having a particle shape in which the contact form with the negative electrode active material is in the form of a point, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, etc., and the linear conductive material is a material in which the contact form with the negative electrode active material is in the form of a line, such as carbon fiber, carbon nanotube, etc.

[0073] The above cathode conductive material may typically be included in an amount of 1 to 30 weight%, preferably 1 to 20 weight%, and more preferably 1 to 10 weight% based on the total weight of the cathode composite layer.

[0075] The above-mentioned dispersant is intended to improve the dispersibility of conductive materials, etc., and may include, for example, one or more selected from the group consisting of polyacrylate, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polyvinyl alcohol, polyacrylamide, polyethylene oxide, hydrogenated nitrile copolymer, cellulose-based compound, and diisopropylamine (DIPA). Here, the hydrogenated nitrile copolymer may be hydrogenated acrylonitrile-butadiene rubber, and the cellulose-based compound may be carboxymethyl cellulose (CMC) or hydroxyethyl cellulose (HEC).

[0076] The above-mentioned dispersant may be included in an amount of 2 weight% or less, preferably 0.1 to 2 weight%, and more preferably 0.1 to 0.5 weight%, based on the total weight of the anode active material layer.

[0078] The above solvent may include at least one selected from the group consisting of distilled water, N-methylpyrrolidone, ethanol, methanol, and isopropyl alcohol, preferably N-methylpyrrolidone, in order to facilitate the dispersion of the positive active material, binder, and / or conductive material. For example, distilled water may be used as the solvent.

[0079] The amount of the above solvent used is sufficient to dissolve or disperse the electrode active material, conductive material, binder, and dispersant, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when coated for electrode manufacturing thereafter.

[0081] The electrode composite layer (300) can be formed by applying both ends of the electrode slurry so as to adhere to one surface of the coating layer (200).

[0082] At this time, the contact angle between the coating layer (200) and the electrode slurry may be 80° to 130°, preferably 85° to 130°, and more preferably 90° to 120°. When the contact angle between the coating layer and the electrode composite layer satisfies the above range, the solvent contained in the electrode slurry aggregates due to the polarity difference with the coating layer (200), thereby forming a clear boundary without mixing the solvent contained in the electrode slurry and the coating material. In addition, the electrode slurry is uniformly applied, thereby improving the loading drop phenomenon in the width direction of the electrode composite layer (300).

[0083] The contact angle of the coating layer (200) and the electrode slurry can be measured at 25°C using a contact angle measuring instrument. Specifically, the contact angle of the coating layer (200) and the electrode slurry can be calculated by coating the electrode slurry onto a substrate, dropping a coating material onto the electrode slurry coating surface, and measuring the angle between the electrode slurry coating surface and the coating material.

[0084] In addition, the contact angle between the coating layer (200) and the electrode slurry can be calculated through the end cross-sectional shape of the electrode composite layer (300) formed by drying and rolling the electrode slurry.

[0085] The electrode slurry is dried while in contact with the coating layer (200), and a contact angle is formed at the interface, and the interface angle is substantially maintained and fixed even during the subsequent rolling process.

[0086] Accordingly, by measuring the interface angle formed at the end cross-section of the electrode composite layer (300), the initial contact angle between the coating layer (200) and the electrode slurry can be estimated.

[0088] Meanwhile, the coating layer (200) can be removed during the process of drying and rolling the electrode slurry. Since the coating layer (200) volatilizes during the process of drying the electrode slurry, there is an advantage that an additional process for removing the coating layer (200) does not need to be performed, and the process of manufacturing the battery can be carried out without problems, and side reactions in the electrochemical reaction of the battery can be minimized.

Claims

Claim 1 A method for manufacturing an electrode, comprising: a step of forming a coating layer by applying a coating material onto an electrode current collector; and a step of forming an electrode composite layer by applying an electrode slurry onto the electrode current collector on which the coating layer is formed, wherein the coating layer is formed along the longitudinal direction of the electrode current collector and is formed to be in contact with the end portion of the electrode composite layer, and the coating material is an organic solvent having opposite polarity to the solvent contained in the electrode slurry and having a boiling point difference of 50°C or less with respect to the solvent contained in the electrode slurry. Claim 2 A method for manufacturing an electrode according to claim 1, wherein the boiling point of the coating material is 90 to 150 ℃. Claim 3 A method for manufacturing an electrode according to claim 1, wherein the coating material comprises one or more selected from the group consisting of heptane, isooctane, butanol, butyl acetate, toluene, and xylene. Claim 4 A method for manufacturing an electrode according to claim 1, wherein the width of the coating layer is 1 / 6,000 to 1 / 30 of the width of the electrode composite layer. Claim 5 A method for manufacturing an electrode according to claim 1, wherein the width of the coating layer is 0.1 mm to 5.0 mm. Claim 6 A method for manufacturing an electrode according to claim 1, wherein the height of the coating layer is 50% to 150% of the height of the electrode composite layer. Claim 7 A method for manufacturing an electrode according to claim 1, wherein the height of the coating layer is 50 μm to 1,000 μm. Claim 8 A method for manufacturing an electrode according to claim 1, wherein the electrode slurry is an aqueous electrode slurry. Claim 9 A method for manufacturing an electrode according to claim 1, wherein the coating layer volatilizes during the step of drying the electrode slurry. Claim 10 A method for manufacturing an electrode according to claim 1, wherein the contact angle between the coating layer and the electrode slurry is 80° to 130°.

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