Method for manufacturing bipolar electrode, and bipolar assembly and bipolar battery comprising same

Abstract

The present specification relates to a method for manufacturing a bipolar electrode, the method comprising the steps of: forming a patterned wet negative electrode mixture layer, including a non-coated portion and a coated portion, on one surface of a metal current collector; forming a patterned primer layer, including a non-coated portion and a coated portion, on the other surface of the metal current collector; laminating a dry positive electrode mixture film on the patterned primer layer; and forming a patterned positive electrode mixture layer by removing a portion of the dry positive electrode mixture film laminated on the non-coated portion of the patterned primer layer, wherein the partial removal of the dry positive electrode mixture film is performed through a mechanical cutting method.

Description

Method for manufacturing a bipolar electrode, and a bipolar assembly and a bipolar battery including the same

[0001] Cross-citation with related application(s)

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0180042 filed December 6, 2024; and Korean Patent Application No. 10-2025-0189653 filed December 3, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of the specification.

[0003] The present invention relates to a method for manufacturing a bipolar electrode, and a bipolar assembly and a bipolar battery comprising the same.

[0004] Recently, as the application areas of lithium-ion batteries have rapidly expanded to include not only power supply for electronic devices such as electrical, electronic, telecommunications, and computers, but also power storage for large-area devices such as automobiles and power storage systems, there is a growing demand for high-capacity, high-output, and high-stability secondary batteries.

[0005] The electrodes used in such secondary batteries can be classified into monopolar electrodes, in which an active material with the same polarity is coated on both sides of a current collector, and bipolar electrodes, in which an active material with different polarities is coated on both sides of a current collector.

[0006] Secondary batteries utilizing monopolar electrodes have connections between the electrodes, which can lead to a decrease in output due to the electrical resistance of these connections. Furthermore, temperature rise caused by Joule heating can cause various issues regarding cell safety, and battery components for heat dissipation, thermal monitoring, and wiring occupy a significant amount of space within the battery pack, resulting in poor space efficiency. In contrast, secondary batteries utilizing bipolar electrodes stack electrodes without connections, thereby minimizing electrode connection resistance and providing excellent output performance. Additionally, because the structure and components are simplified, they offer good space efficiency, which can significantly improve energy density and output density per unit volume compared to conventional lithium-ion batteries.

[0007] Meanwhile, in the conventional wet process, electrodes for lithium-ion batteries are manufactured by coating a slurry liquid onto a current collector and then evaporating the solvent in a drying oven, whereas in the dry electrode process, a PTFE binder-based electrode mixture powder is fed between two or more calenders with different rotation ratios to form a free-standing electrode film, which is then calendered at least once to achieve the desired loading and thickness, and laminated onto a current collector coated with a conductive primer to manufacture the electrode.

[0008] Currently, since the dry electrode process is conducted as a roll-to-roll process, electrode films (or electrode layers) are produced that are continuously connected and aligned with the process direction, and unconnected areas are provided on both sides for welding between electrodes and connecting leads. However, due to the lack of a method for manufacturing discontinuously connected dry electrodes, there is a problem of low productivity depending on the product shape or purpose.

[0009] In the embodiments according to the present invention, particularly since a bipolar electrode among dry electrodes uses a patterned electrode in which the edges of all four directions are formed as unpatterned areas, discontinuously connected electrodes are required. However, because there is no conventional method for manufacturing such a dry bipolar electrode, the problem of low productivity is to be solved by first forming a continuously connected electrode film and then manually removing the unpatterned area as much as is required.

[0010] Accordingly, the present invention aims to provide a novel manufacturing method that enables the easy production of a patterned electrode for a bipolar battery by pattern coating of a primer layer.

[0011] In one embodiment according to the present invention, a method for manufacturing a bipolar electrode is provided, comprising: a step of forming a patterned wet cathode composite layer including a non-free portion and a retaining portion on one surface of a metal current collector; a step of forming a patterned primer layer including a non-free portion and a retaining portion on the other surface of a metal current collector; a step of laminating a dry anode composite film on the patterned primer layer; and a step of removing the dry anode composite film portion laminated on the non-free portion of the patterned primer layer to form a patterned anode composite layer, wherein the removal of the dry anode composite film portion is performed through a mechanical cutting method.

[0012] The above-mentioned patterned primer layer formation step may include: a step of applying a primer coating solution onto a gravure roll; and a step of selectively removing the primer coating solution onto the gravure roll to form a pattern, and continuously transferring the patterned primer coating solution from the gravure roll to the metal current collector.

[0013] The patterned primer layer and the patterned anode composite layer may have a plurality of line pattern shapes or grid pattern shapes on a plane.

[0014] The patterned primer layer may be formed such that a blank portion is located on the four-directional edge portions of the retaining portion on at least one surface of the metal current collector.

[0015] The patterned primer layer may include a conductive material and a binder.

[0016] The step of forming the patterned cathode composite layer may include applying and drying a slurry composition comprising a polymer binder, a conductive material, a cathode active material, and an organic solvent onto one surface of a metal current collector to form a cathode composite layer.

[0017] The above dry anode composite film is a dry film that does not contain a solvent and comprises an anode active material, a conductive material, and a binder, wherein the binder may comprise a fibrous polymer.

[0018] The above dry anode composite film lamination step may include: a step of forming a dry anode composite film by calendering an anode powder prepared by mixing and grinding an active material, a conductive material, and a fiberizable binder; and a step of attaching the anode composite film onto the primer layer.

[0019] The dry anode composite film portion laminated on the above-mentioned unladen portion can be removed by die-cutting.

[0020] The patterned anode composite layer above may have a porosity of 25% to 30%.

[0021] In addition, the above-described bipolar electrode manufacturing method may further include the step of laminating electrodes stacked in the order of a patterned cathode composite layer, a metal current collector, a patterned primer layer, and a patterned anode composite layer.

[0022] The above lamination step can be performed after removing the dry anode composite film portion laminated on the unlaminated portion to form a patterned anode composite layer.

[0023] The patterned anode composite layer may have the same pattern as the patterned primer layer.

[0024] In another embodiment of the present invention, a bipolar assembly is provided comprising: an electrode for a bipolar cell manufactured by the method described above; and a separator.

[0025] In addition, in another embodiment of the present invention, a bipolar battery is provided comprising a bipolar assembly according to the above, wherein the bipolar assembly is embedded in a battery case, and a positive terminal and a negative terminal are respectively attached to the outermost electrodes on both sides in the stacking direction of the bipolar assembly.

[0026] The electrode for a bipolar battery and the method for manufacturing the same according to the present invention provide a method for manufacturing a bipolar battery electrode patterned by pattern coating of a primer layer, wherein positive and negative electrode layers are simultaneously provided discontinuously on both sides of a current collector through a dry electrode process.

[0027] Furthermore, according to the present invention, when forming an anode composite layer in a dry manner, a patterned electrode sheet can be manufactured by forming the anode composite layer on a sheet-type current collector on which a primer layer is pattern-coated, and removing the anode composite layer in the portion not coated with the primer layer, thereby providing the effect of a simple process, high efficiency, and easy process development.

[0028] As a result, since dry electrodes that meet various product needs can be manufactured, the scope of platform technology can be expanded.

[0029] FIG. 1 illustrates a method for manufacturing a bipolar electrode according to one embodiment of the present invention, showing a step of forming a patterned primer layer during the manufacturing process.

[0030] FIG. 2 illustrates a dry anode composite film lamination step as a method for manufacturing a bipolar electrode according to one embodiment of the present invention.

[0031] FIGS. 3 and 4 illustrate a method for manufacturing a bipolar electrode according to an embodiment of the present invention, showing a step of removing a dry anode composite film portion of the uncoated portion.

[0032] FIG. 5 is a schematic cross-sectional view of a bipolar electrode according to one embodiment of the present invention.

[0033] FIG. 6 is a schematic diagram of the top surface of a bipolar electrode according to one embodiment of the present invention.

[0034] Hereinafter, terms and words used in this specification and claims shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0035] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0036] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0037] In this specification, when a part is described as including a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0038] Hereinafter, embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described below. Also, in this specification and drawings, like reference numerals indicate like components.

[0039]

[0040] Method for manufacturing a bipolar electrode

[0041] Meanwhile, according to one embodiment of the present invention, a method for manufacturing an electrode for a bipolar battery is provided, comprising: a step of forming a patterned wet negative electrode composite layer including a non-free portion and a retaining portion on one surface of a metal current collector; a step of forming a patterned primer layer including a non-free portion and a retaining portion on at least another surface of a metal current collector; a step of laminating a dry positive electrode composite film on the patterned primer layer; and a step of removing the dry positive electrode composite film portion laminated on the non-free portion of the patterned primer layer to form a patterned positive electrode composite layer; wherein the removal of the dry positive electrode composite film portion is performed through a mechanical cutting method.

[0042] FIGS. 1 to 4 illustrate each step of a method for manufacturing a bipolar electrode according to an embodiment of the present invention, FIG. 1 illustrates a step of forming a patterned primer layer, FIG. 2 illustrates a step of laminating a dry anode composite film, and FIGS. 3 and 4 illustrate a step of removing a portion of the dry anode composite film from an unlined area, respectively.

[0043] First, referring to FIG. 1, in order to manufacture an electrode for a bipolar battery, a patterned primer layer including an unpatterned portion and a retaining portion can be formed on at least one surface of a metal current collector.

[0044] Specifically, a primer layer can be coated on a sheet-type metal current collector by a wet coating method. At this time, the primer layer is pattern-coated so that the coated portions and uncoated portions are alternately arranged on the metal current collector.

[0045] For example, the step of forming a patterned primer layer may include: a step of applying a primer coating solution onto a gravure roll; and a step of selectively removing the primer coating solution onto the gravure roll to form a pattern, and continuously transferring the patterned primer coating solution from the gravure roll to the metal current collector.

[0046] To show this pattern coating in detail, Figure 6 schematically illustrates a top view of part of the electrode manufacturing process.

[0047] Referring to FIGS. 1 and 6, specifically, on one side or the other side of a sheet-type electrode current collector, a retaining portion coated with a primer layer and a non-retaining portion not coated with a primer layer are alternately arranged and patterned. This prepares a primer-coated electrode current collector. For example, the patterned primer layer and the patterned anode composite layer may have a plurality of line pattern shapes or grid pattern shapes on a plane.

[0048] Meanwhile, while the retaining portion and the non-retaining portion are arranged alternately, the primer layer is coated such that non-retaining portions are formed on both sides based on the width direction of the metal current collector. That is, the patterned primer layer may be formed such that non-retaining portions are located on the four-directional edges of the retaining portion on at least one surface of the metal current collector.

[0049] Meanwhile, the patterned primer layer may include a conductive material and a binder. In particular, by including a conductive material, it can maintain an electrical connection with a metal current collector.

[0050] In an exemplary embodiment, the conductive material is not particularly limited as long as it is conductive without causing a chemical change in the battery, and for example, graphite such as natural graphite or 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 or metal fibers; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives may be used.

[0051] The above binder is not limited to those having general binder components and may be, for example, one or more selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butylene rubber, and fluororubber.

[0052] At this time, the content of the conductive material may be 5 to 50 weight%, specifically 5 to 30 weight%, and more specifically 10 to 30 weight%, based on the total weight of the patterned primer layer. If the content of the conductive material is too low outside the aforementioned range, a sufficient conductive path with the metal current collector may not be formed, which may result in increased resistance, and if it is too high, the adhesion may be reduced, which is undesirable.

[0053] In addition, the binder may be included in an amount of 1 to 10 weight percent, specifically 1 to 5 weight percent, based on the total weight of the patterned primer layer. If the content of the binder is too low outside the aforementioned range, the adhesive strength may be too low, resulting in insufficient adhesion with the metal current collector and causing delamination; if it is too high, the resistance may increase.

[0054] For example, when the electrode is the anode, a primer layer is formed on an anode current collector mainly composed of Al, so carbon black may be included as a conductive material and PVDF may be included as a binder. Meanwhile, the respective contents can be controlled within the above range.

[0055] Meanwhile, the patterned primer layer may be formed with a thickness of 0.1 to 10 μm. If formed too thin outside this range, the desired adhesion cannot be sufficiently secured by application, and if formed too thick, the total volume may increase, which may reduce the energy density relative to volume, and the resistance may increase due to the longer conduction path, which is undesirable in terms of secondary battery performance.

[0056] The step of forming the patterned cathode composite layer may include applying and drying a slurry composition comprising a polymer binder, a conductive material, a cathode active material, and an organic solvent onto one surface of a metal current collector to form a cathode composite layer.

[0057] In addition, the above-mentioned cathode composite layer is formed by a wet method. Specifically, a cathode slurry can be pattern-coated onto an electrode current collector by a coating method known in the art, such as a coater, and then dried by passing it through a dryer and rolling it with rolling rolls. That is, the above-mentioned cathode composite layer can be formed through a wet method without forming a separate primer layer, and can be manufactured by performing pattern coating.

[0058] Specifically, the patterned cathode composite layer can be pattern-coated such that, like a dry anode, a retained portion coated with the cathode composite layer and a non-coated portion not coated with the cathode layer are alternately arranged on the other side of the electrode current collector (i.e., the side opposite to the one side on which the patterned primer layer is formed). This patterned cathode composite layer may have a plurality of line pattern shapes or grid pattern shapes on a plane.

[0059] The patterned cathode composite layer may have the same shape as the anode composite layer, but may be laminated with a larger area than the anode composite layer. This is to prevent Li from being plated (precipitated) on the current collector after Li moves from the anode to the cathode. Specifically, the patterned cathode composite layer is formed on the other side of the metal current collector to correspond to the area of ​​the retaining portion of the patterned primer layer and the area of ​​the retaining portion extended by a predetermined length in the direction of the unretaining portion, and may have an area of ​​110 to 120% of the area of ​​the retaining portion of the patterned primer layer.

[0060] Meanwhile, the cathode composite layer is a coating layer in which the solvent has evaporated from a cathode slurry prepared to contain a solvent, and may include a cathode active material, a conductive material, and a binder. However, it does not necessarily include a fibrous polymer as the binder.

[0061] The above-mentioned negative electrode active material is carbon such as non-graphitizable carbon, graphite-based carbon, etc.; Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, and 3 elements of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SiO, SiO / C, SiO x(1 <x<2), SiO2등의 실리콘계 산화물; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료 등을 사용할 수 있다.

[0062] In addition, the above binder may include, for example, polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0063] Typically, the binder may be included in an amount of 0.5 to 20 weight%, more specifically 0.5 to 10 weight%, and more specifically 0.5 to 5 weight% based on the total weight of the cathode layer (124).

[0064] In addition, for example, the metal current collector may include a clad current collector, a SUS current collector, etc., in which Cu and Al foils are attached to each other. For example, in the case of a clad current collector, it may have a structure in which an anode composite layer is formed in the direction of the Al foil and a cathode composite layer is formed in the direction of the Cu foil. For example, the metal current collector may have a thickness range of 10 to 50 μm.

[0065] Next, referring to FIG. 2, a dry anode composite film can be laminated onto the patterned primer layer. The dry anode composite film can be laminated to cover both the unlaid portion and the retained portion of the patterned primer layer, and since the dry anode composite film is laminated in direct contact with the retained portion of the patterned primer layer, an empty space can be formed in the unlaid portion.

[0066] According to this method, since the electrode layer is formed after the primer layer, there is a difference in adhesion between the current collector and the electrode layer and between the primer layer and the electrode layer. This allows for pattern coating of the electrode layer to be performed in a very simple manner, making it the most desirable method.

[0067] Prior to such lamination, a step of manufacturing the dry anode composite film may be performed first. Specifically, the dry anode composite film lamination step may include: a step of forming a dry anode composite film by calendering an anode powder prepared by mixing and grinding an active material, a conductive material, and a fiberizable binder; and a step of attaching the anode composite film onto the primer layer.

[0068] The above dry anode composite film is a dry film that does not contain a solvent and comprises an anode active material, a conductive material, and a binder, wherein the binder may include a fibrous polymer. In particular, to solve the problems of difficulty in processability and difficulty in aligning electrodes when forming an electrode layer using a conventional wet process, a dry anode composite film can be applied as an electrode layer.

[0069] When forming a dry anode composite film using a dry process, it is easy to form an electrode layer with the same area on the part where the patterned primer layer is formed, which not only increases process ease but also prevents adverse effects on the electrode that may occur due to the drying process essential in wet processes, and allows the electrode to be manufactured without color transfer issues.

[0070] In addition, as the dry anode composite film is formed as a dry film distinct from the cathode composite layer, appropriate rolling density and porosity required for the anode composite film and the cathode composite layer can be achieved under equivalent rolling pressure, and the rolling process can be made more efficient.

[0071] In addition, by including a dry film-type anode composite film, it can contain a larger loading amount of anode active material compared to a conventional anode composite layer and can be formed with a greater thickness on a metal current collector. Accordingly, the bipolar electrode can provide a bipolar secondary battery having improved energy density.

[0072] Accordingly, according to the present invention, the positive electrode included in the electrode for the bipolar battery may be a dry positive electrode composite film manufactured in a dry manner without containing a solvent, and as described below, a patterned positive electrode composite layer is formed by removing the portion of the dry positive electrode composite film laminated on the unpatterned portion of the patterned primer layer.

[0073] Here, the dry anode composite film comprises an anode active material, a conductive material, and a binder, and for dry manufacturing, the binder may comprise a fibrous polymer that is fiberized by shear.

[0074] Specifically, the positive electrode active material is not limited to lithium transition metal oxide or lithium metal iron phosphate, provided it is in the form of a metal oxide, and, for example, may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, Ca, Zr, Ti, B, P, W, Si, Na, K, Mo, V, Nb, Ru, or Ga, and x = 0.01 ~ 0.3); chemical formula LiMn2-x M x Lithium manganese complex oxides represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the Li in the chemical formula is substituted with alkaline earth metal ions; lithium metal phosphate LiMPO4 (where M is M = Fe, CO, Ni, or Mn), disulfide compounds; Fe2(MoO4)3, etc., are examples, but are not limited to these.

[0075] The above conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; graphene; activated carbon; activated carbon fiber; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fiber such as carbon fiber or metal fiber; metal powder such as fluorinated carbon, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; conductive materials such as polyphenylene derivatives, etc., may be used, but more specifically, in order to ensure uniform mixing of the conductive material and improve conductivity, it may include one or more selected from the group consisting of activated carbon, graphite, carbon black, graphene, and single-walled or multi-walled carbon nanotubes, and more specifically, it may include carbon black or activated carbon.

[0076] The conductive material may be included in an amount of 0.1 to 20 weight%, specifically 0.5 to 10 weight%, and more specifically 0.5 to 5 weight% based on the total weight of the patterned anode composite layer.

[0077] In addition, the fiberizing polymer as the binder may be polytetrafluoroethylene (PTFE). This fiberizing polymer may be included in an amount of 50% by weight or more based on the total weight of the binder, and may also be 100% by weight.

[0078] Since the above-mentioned fiberizing polymer is fiberized by shearing, a dry film (freestanding film) can be manufactured by mixing an anode active material, a conductive material, and a binder and shearing them without a separate solvent, and a patterned anode composite layer can be formed using the dry film manufactured in this way.

[0079] In addition, the binder may further include, in addition to the polytetrafluoroethylene, PEO (polyethylene oxide), PVdF (polyvinylidene fluoride), PVdF-HFP (polyvinylidene fluoride-co-hexafluoropropylene), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof, and may further include other binders known in the art.

[0080] For example, the anode composite film (30) may further include additional polymer binders in addition to the fiberized polymer binder described above, for example, PEO (polyethylene oxide), PVdF (polyvinylidene fluoride), PVdF-HFP (polyvinylidene fluoride-co-hexafluoropropylene), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, or various copolymers thereof.

[0081] Typically, the binder may be included in an amount of 0.5 to 20 weight%, more specifically 0.5 to 10 weight%, and more specifically 0.5 to 5 weight% based on the total weight of the patterned anode composite layer.

[0082] Meanwhile, in some cases, a filler that inhibits the expansion of the electrode may be additionally introduced into the above-mentioned dry cathode composite film. The filler is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery, and for example, olivine-based polymers such as polyethylene and polypropylene; or fibrous materials such as glass fibers and carbon fibers are used.

[0083] Next, referring to FIGS. 3 and 4, a patterned anode composite layer can be formed by removing the dry anode composite film portion laminated on the unpatterned portion of the patterned primer layer. In particular, in this step, the removal of the dry anode composite film portion can be performed through a mechanical cutting method. Since this mechanical cutting method has no limitations on electrode size, dry electrodes that meet various product needs can be manufactured, thereby enabling the expansion of the platform technology's scope. Furthermore, the unpatterned portion cut through the mechanical cutting method can be cleanly removed, and the remaining retained portion can also have excellent quality without cracks.

[0084] Among these mechanical cutting methods, preferably, the dry anode composite film portion laminated on the unladen portion can be removed by die cutting. Through this, the patterned anode composite layer can have the same pattern as the patterned primer layer.

[0085] Meanwhile, in an exemplary embodiment, the method for manufacturing a bipolar electrode may further include the step of laminating an electrode stacked in the order of a current collector, a patterned primer layer, and a patterned anode composite layer.

[0086] The above lamination step can be performed by a lamination roll, and the patterned primer layer and the patterned anode composite layer are bonded to each other according to the lamination to form a strong bond, thereby preventing peeling of the anode composite layer.

[0087] In addition, the lamination step can be performed after removing the dry anode composite film portion laminated on the unlamination portion to form a patterned anode composite layer. That is, prior to lamination, the dry anode composite film portion laminated on the unlamination portion is removed to pre-shape the electrode and selectively transfer the electrode layer to the current collector; this can improve the quality of the edge portion compared to the conventional method of removing the electrode after lamination.

[0088] In addition, a target porosity can be achieved by forming a wet cathode composite layer on a metal current collector and then forming a dry anode composite layer. For example, the patterned anode composite layer may have a porosity of 25% to 30%.

[0089] Optionally, a cutting process for cutting the laminated electrode sheet into unit electrodes may be further included. For example, the cutting process may be performed by a cutter, and each unit electrode may be cut such that it includes a blank area on the edges in four directions.

[0090] Figure 5 shows a cross-section of an electrode for a bipolar battery manufactured by the method described above.

[0091] First, referring to FIG. 5, the electrode for the bipolar cell is coated such that a patterned primer layer forms an uncoated area on one side of the metal current collector, and referring to FIG. 6, it is coated such that an uncoated area is formed on the four edges, and the patterned positive electrode composite layer formed on the patterned primer layer can also be formed in such a way that it does not cover the uncoated area.

[0092] Meanwhile, the patterned positive composite layer may be coated on one side of a metal current collector, and the patterned negative composite layer may be coated on the other side of the metal current collector (not illustrated). The structure and composition of the negative composite layer are as described above.

[0093] Due to the characteristics of bipolar cells, a non-free zone must be formed at the edges of the current collector; accordingly, the primer layers and electrode layers have a structure coated to have a non-free zone at the edges of the current collector.

[0094] However, since the aforementioned blank portion is formed for the purpose of attaching electrode leads for sealing purposes during subsequent assembly into a bipolar unit cell, it is sufficient to have a width greater than a certain portion.

[0095]

[0096] Bipolar assembly and bipolar cell

[0097] According to another embodiment of the present invention, a bipolar assembly is provided comprising: an electrode for a bipolar battery manufactured by the method described above; and a separator.

[0098] In the structure of the above-described bipolar electrode assembly, a plurality of bipolar electrodes of one embodiment, comprising the cathode composite layer, metal current collector, primer layer, and anode composite film, may be stacked. Furthermore, these plurality of bipolar electrodes are alternately stacked via a separator, an electrolyte layer, or a stack thereof, and the cathode composite layer and anode composite film of adjacent bipolar electrodes face each other with the separator or electrolyte layer, etc., in between.

[0099] In such an electrode assembly, an anode composite film and a cathode composite layer facing each other with a separator, an electrolyte layer, or a stack thereof in between can be defined as a single unit cell.

[0100] Here, the separator may be a composition known in the art as a separator for a lithium secondary battery and may be applied to the present invention.

[0101] At this time, the electrode assembly may include only a polyolefin-based porous separator, but may also include a gel electrolyte layer separately from the separator, or include a gel electrolyte-separator laminate in which a gel electrolyte is impregnated on the separator. By doing so, the sealing structure in the bipolar secondary battery can be simplified while effectively suppressing the leakage of electrolyte from the bipolar secondary battery.

[0102] In a more specific example, the electrolyte layer including the gel electrolyte comprises, for example, a polyurethane-based or polyacrylic-based crosslinked polymer, a lithium salt, and a non-aqueous organic solvent, and may have a form in which the lithium salt and the non-aqueous organic solvent are dispersed or encapsulated within the crosslinked polymer. However, since the types of crosslinked polymers, lithium salts, and organic solvents that may be included in the gel electrolyte are obvious to those skilled in the art, further explanation regarding this is omitted.

[0103] Furthermore, according to another embodiment of the present invention, a bipolar battery comprising the bipolar assembly is provided.

[0104] Specifically, the bipolar battery may have a structure in which the bipolar assembly is embedded in a battery case, and positive and negative terminals are attached to the outermost electrodes on both sides in the stacking direction of the bipolar assembly, respectively, and various bipolar battery structures known in the art may be applied to the present invention, except for each electrode structure.

[0105] Meanwhile, in the above-described bipolar electrode assembly, electrode terminals electrically connected to the respective current collectors (10a, 10b) on both sides in the stacking direction of the unit cells (100) may be directly connected or indirectly connected via a separate current collector plate. Additionally, the above-described bipolar electrode assembly may be housed in a separate case, and the electrode terminals may be connected to the outside of the case to form a bipolar secondary battery.

[0106]

[0107] Hereinafter, the present invention will be described with reference to examples to demonstrate the enhanced effects intended by the present invention.

[0108]

[0109] Example 1: Bipolar electrode (die cutter)

[0110] A cathode slurry was prepared by mixing 96 wt% graphite as the cathode active material, 0.5 wt% Super C-65 as the conductive material, and 3.5 wt% of an SBR binder and thickener. The prepared slurry was pattern-coated and dried on one side of a copper foil current collector, and then rolled to produce a wet cathode layer. At this time, the cathode composite layer was 10.6 × 10.6 cm 2 Coated in size.

[0111] A primer coating solution comprising 2 kg of carbon black (product name: Li-250) as a conductive material, 0.1 kg of carboxymethylcellulose (product name: Dicel) as a binder, and isopropyl alcohol as an organic solvent was coated onto a gravure roll. The coating was performed selectively so as to correspond only to the area where the anode composite film is to be finally formed, excluding the uncoated area. Using this gravure roll, the primer coating solution was transferred to one side of an aluminum foil current collector and dried at a temperature of 100 to 120°C to form a primer layer.

[0112] 96g of LFP (BTR, LFP-S20) as the positive active material, 0.5g of carbon black as the conductive material, and 3.5g of polytetrafluoroethylene (PTFE) as the binder were added to a blender and mixed at 10,000 rpm for 1 minute to prepare a mixture. The temperature of the kneader was stabilized to 150℃, the mixture was placed into the kneader, and then operated at a speed of 50 rpm for 5 minutes under a pressure of 1.1 atmospheres to obtain a lump of the mixture.

[0113] The obtained mixture aggregate was fed into a blender, ground at 10,000 rpm for 40 seconds, and classified using a sieve with 1 mm pores to obtain electrode powder. Subsequently, the prepared electrode powder was fed several times into a lab calender (roll diameter: 88 mm, roll temperature: 100℃) to achieve an electrode layer loading of 600 mg / 25 cm 2 A free-standing anode composite film with a thickness of 100㎛ was manufactured.

[0114] A self-standing electrode film was fed into a continuous calendering machine and calendered once, and the prepared anode composite film was attached to one side of the aluminum foil having the primer layer formed thereon. The anode composite film in the uncoated portion without the primer layer was removed from the calendered electrode film through die cutting to produce the bipolar electrode of Example 1. At this time, the anode composite layer was 10 × 10 cm 2 It was cut to size.

[0115]

[0116] Comparative Example 1: Bipolar electrode (air blower)

[0117] An electrode was manufactured in the same manner as in Example 1, except that an air blower was used instead of a die cutter to remove the electrode layer of the uncoated portion that was not equipped with a primer layer.

[0118]

[0119] Comparative Example 2: Bipolar electrode (air blower & suction)

[0120] An electrode was manufactured in the same manner as in Example 1, except that an air blower and suction equipment were used together instead of a die cutter to remove the electrode layer of the uncoated portion that was not equipped with a primer layer.

[0121]

[0122] Comparative Example 3: Bipolar electrode (suction plate)

[0123] An electrode was manufactured in the same manner as in Example 1, except that a suction plate was used instead of a die cutter to remove the electrode layer of the uncoated portion that was not equipped with a primer layer.

[0124]

[0125] Preparation Example: Bipolar Cell Preparation

[0126] Two bipolar electrodes of Example 1 and Comparative Examples 1-3 were prepared, respectively. One had its cathode composite layer removed and the other had its anode composite layer removed, and an SRS separator was placed between the remaining anode composite layer and the cathode composite layer, and a carbonate-based liquid electrolyte was injected to manufacture a bipolar cell.

[0127]

[0128] Experimental Example

[0129] In the electrodes prepared by the methods of Example 1 and Comparative Examples 1 to 3 above, the electrode loading amount, electrode layer thickness, electrode layer density, process speed, appearance characteristics, presence or absence of edge detachment, presence or absence and length of electrode burr, battery capacity, and adhesion were measured and compared and are shown in Table 1 below.

[0130] Each characteristic was evaluated using the following method.

[0131] - Electrode loading amount: After punching out 5cm x 5cm, the weight of the electrode was measured excluding the weight of the foil.

[0132] - Electrode layer thickness: The thickness of the electrode layer excluding the foil thickness was measured using SEM cross-sectional analysis or a thickness gauge.

[0133] - Electrode layer density: The density of the electrode excluding the foil was measured and calculated using the electrode loading amount and electrode layer thickness.

[0134] - Appearance characteristics: Visually inspect the electrode for cracks or splitting at the ends, and evaluate electrodes without scratches as OK and electrodes with scratches as NG.

[0135] - Presence or absence of edge detachment: Evaluated based on SEM measurement or visual inspection for defects.

[0136] - Electrode burr occurrence and length: The electrode exterior was checked with a magnifying glass and evaluated as OK if it was within 0.1m and NG if it exceeded 0.1m.

[0137] - Battery capacity: Two charge-discharge cycles were performed by applying a current corresponding to 0.33C of the bipolar cell capacity of Preparation Example 1. Through this, the first and second capacities of the cell were confirmed to verify the capacity retention rate and efficiency. The capacity error was within 2%.

[0138] - Adhesion: After cutting the electrode to 2cm x 10cm, double-sided tape was attached to a slide glass, and the surface of the electrode to be measured was attached to the slide glass with the double-sided tape. Then, the slide glass was placed on the UTM equipment, and the electrode layer was peeled off at a speed of 2m / min at a 90-degree angle to measure.

[0139] - Porosity: In calculating the porosity of the electrode (anode or cathode) composite layer or composite film, first, the electrode density was calculated by dividing the loading amount of each electrode composite layer or composite film by its thickness. In addition, the porosity was calculated according to the following Equation 1 from the electrode density and the true density of the electrode active material:

[0140] [Equation 1]

[0141] P = (1-D) / T×100

[0142] In the above Equation 1, P represents the porosity of the electrode composite layer (or composite film), D represents the electrode density, and T represents the true density of the electrode active material excluding the current collector from the electrode. Here, true density refers to the intrinsic density of the electrode active material without pores.

[0143]

[0144] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Electrode loading amount (mAh / cm²) 2 )600600600600 Electrode layer thickness (㎛) 94.494.494.4 Electrode layer density (g / cm³) 3)2.522.522.522.52 Process Speed ​​(m / min) 2-52-52-52-55 Appearance Characteristics OK NG NG NG Presence of Edge Detachment OK NG NG NG Electrode Burr Occurrence & Length (mm) OK < 0.1 NG 1-3 NG 1-3 NG 1-3 Battery Capacity (%) 98-99 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-97 96-4030 96-30

[0145] Referring to Table 1 above, it can be seen that according to the present invention, not only is the electrode adhesion strength superior and the appearance characteristics excellent, but the target porosity is also achieved.

[0146]

[0147] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

1. A step of forming a patterned wet cathode composite layer including an unpatterned portion and a retaining portion on one surface of a metal current collector; A step of forming a patterned primer layer including an unpatterned portion and a retaining portion on the other side of a metal current collector; A step of laminating a dry anode composite film onto the patterned primer layer; and The method includes the step of forming a patterned anode composite layer by removing the dry anode composite film portion laminated on the unpatterned portion of the patterned primer layer. A method for manufacturing a bipolar electrode, wherein the removal of the above dry anode composite film portion is performed through a mechanical cutting method.

2. In Paragraph 1, The above patterned primer layer formation step is, A step of applying a primer coating solution onto a gravure roll; and A method for manufacturing a bipolar electrode, comprising the step of selectively removing a primer coating solution on the gravure roll to form a pattern, and continuously transferring the patterned primer coating solution from the gravure roll to the metal current collector.

3. In Paragraph 1, A method for manufacturing a bipolar electrode, wherein the patterned primer layer and the patterned anode composite layer have a plurality of line pattern shapes or grid pattern shapes on a plane.

4. In Paragraph 1, A method for manufacturing a bipolar electrode, wherein the patterned primer layer is formed such that an unpatterned portion is located at the four-directional edge portions of the retaining portion on at least one surface of the metal current collector.

5. In Paragraph 1, The above patterned cathode composite layer formation step is, A method for manufacturing a bipolar electrode, comprising applying and drying a slurry composition containing a polymer binder, a conductive material, a negative electrode active material, and an organic solvent onto one surface of a metal current collector to form a negative electrode composite layer.

6. In Paragraph 1, A method for manufacturing a bipolar electrode, wherein the patterned cathode composite layer is formed on the other side of a metal current collector to correspond to the area of ​​the retaining portion of the patterned primer layer and the area of ​​the retaining portion extended by a predetermined length in the direction of the unretaining portion, and has an area of ​​110 to 120% relative to the area of ​​the retaining portion of the patterned primer layer.

7. In Paragraph 1, A method for manufacturing a bipolar electrode, wherein the above dry anode composite film is a dry film that does not contain a solvent, and comprises an electrode active material, a conductive material, and a binder, wherein the binder comprises a fiberizing polymer.

8. In Paragraph 1, The above dry anode composite film lamination step is, A step of forming a dry anode composite film by calendering electrode powder prepared by mixing and grinding an active material, a conductive material, and a fiberizable binder; and A method for manufacturing a bipolar electrode comprising the step of attaching the anode composite film above onto the primer layer.

9. In Paragraph 1, A method for manufacturing an electrode for a bipolar battery, wherein a portion of a dry anode composite film laminated on the above-mentioned non-removable portion is removed by die-cutting.

10. In Paragraph 1, The patterned anode composite layer is a bipolar electrode having a porosity of 25% to 30%.

11. In Paragraph 1, A method for manufacturing an electrode for a bipolar battery, further comprising the step of laminating an electrode stacked in the order of a patterned cathode composite layer, a metal current collector, a patterned primer layer, and a patterned anode composite layer.

12. In Paragraph 1, A method for manufacturing an electrode for a bipolar battery, wherein the above lamination step is performed after removing a dry anode composite film portion laminated on the above-described unlaminated portion to form a patterned anode composite layer.

13. In Paragraph 1, A method for manufacturing an electrode for a bipolar battery, wherein the patterned positive electrode composite layer has the same pattern as the patterned primer layer.

14. An electrode for a bipolar battery manufactured by any one of claims 1 to 13; and A bipolar assembly comprising a separator.

15. A bipolar battery comprising a bipolar assembly according to paragraph 14, A bipolar battery in which the above-mentioned bipolar assembly is embedded in a battery case, and positive and negative terminals are respectively attached to the outermost electrodes on both sides in the stacking direction of the bipolar assembly.

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