Negative electrode and method for manufacturing negative electrode

Abstract

The present invention provides a negative electrode and a method for manufacturing the negative electrode. The negative electrode is capable of securing both excellent productivity and long-term reliability by simultaneously preventing defects in a manufacturing process and deterioration of mechanical properties of a final electrode through a negative electrode dam manufactured from a negative electrode dam composition in which inorganic particles, a cellulose-based compound, a rubber-based binder, and a specific additive are each contained in an optimal content.

Description

Cathode and method for manufacturing the cathode

[0001] The present invention relates to a cathode and a method for manufacturing the cathode.

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0095934, filed July 19, 2024, and Korean Patent Application No. 10-2025-0097289, filed July 18, 2025, the entire contents of which are incorporated herein by reference.

[0003] To reduce dependence on fossil fuels and carbon emissions, demand for rechargeable secondary batteries that can be reused for extended periods of time is rapidly increasing. In particular, lithium secondary batteries, with their superior energy density and lifespan, are being used as a key energy source in various fields, and related technology development is actively underway.

[0004] Lithium secondary battery electrodes are generally formed by applying slurry on a current collector and drying it. During this process, the fluidity of the slurry causes a 'sliding phenomenon' in which the edges become thinner.

[0005] For the positive electrode, some techniques have been applied to prevent slurry spread by forming an insulating layer at the edge of the active material layer. However, for the negative electrode, which lacks a separate insulating layer, a different approach was required. Consequently, a novel technology called a "negative electrode dam" was introduced, forming a support structure at the edge of the active material layer. However, this presented additional technical challenges.

[0006] The construction of a cathode dam is a highly challenging task, requiring consideration not only of the physical properties necessary to prevent slurry spread, but also of the interaction with the cathode active material layer and processability. Conventional technologies have been limited in their ability to simultaneously satisfy these complex requirements.

[0007] For example, there was a clear trade-off between enhancing some properties of the dam composition and creating other problems. Attempting to increase the dam's bearing capacity reduced the tensile strength of the anode active material layer, leading to electrode detachment. Attempting to improve processability resulted in solution clumping or fat-edge defects due to excessive verticalization. Conversely, focusing solely on maintaining the physical shape continued to be problematic, failing to adequately suppress sliding.

[0008] In conclusion, there is a high technological demand for a comprehensively optimized cathode dam composition that can overcome all these trade-offs and simultaneously secure excellent productivity and mechanical reliability of the final electrode.

[0009] The present invention aims to provide a cathode and a method for manufacturing the cathode, which can secure both excellent productivity and long-term reliability by simultaneously preventing defects in the manufacturing process and deterioration of the mechanical properties of the final electrode through an optimized cathode dam composition.

[0010] In order to solve the above problem, according to one embodiment of the present invention, a negative electrode is provided, which includes a negative electrode current collector, a negative electrode active material layer formed on one or both sides of the negative electrode current collector, and a negative electrode dam formed by drying a composition for a negative electrode dam that supports both width-wise edges of the negative electrode active material layer and includes inorganic particles, a cellulose-based compound, a rubber-based binder, and an additive, wherein the contents of each component of the composition for a negative electrode dam satisfy the following (a) to (d):

[0011] (a) 50 to 85 parts by weight of inorganic particles,

[0012] (b) 0.5 to 15 parts by weight of cellulose compound,

[0013] (c) 3 to 20 parts by weight of rubber binder,

[0014] (d) 5 to 12 parts by weight of additive.

[0015] Additionally, in the cathode, the inorganic particles may include at least one selected from the group consisting of AlO(OH), Al2O3, γ-AlOOH, Al(OH)3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, and Mg(OH)2.

[0016] Additionally, in the negative electrode, the cellulose compound may include at least one selected from the group consisting of carboxymethylcellulose, lithium salt of carboxymethylcellulose, and sodium salt of carboxymethylcellulose.

[0017] Additionally, in the above cathode, the weight average molecular weight (Mw) of the cellulose compound may be in the range of 100,000 to 600,000.

[0018] Additionally, in the above cathode, the rubber-based binder may include at least one selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber.

[0019] Additionally, in the above cathode, the additive may include a porous additive and a carbon-based material.

[0020] Additionally, in the cathode, the additive may include 0.1 to 0.6 parts by weight of a porous additive and 5 to 10 parts by weight of a carbon-based material.

[0021] Additionally, in the cathode according to another embodiment, the solid content (%) of the composition for the cathode dam may be in the range of 10 to 40%.

[0022] Additionally, in the above cathode, the tensile strength may exceed 3 kgf.

[0023]

[0024] According to another embodiment of the present invention, a negative electrode is provided, comprising: a negative current collector; a negative active material layer formed on one or both sides of the negative current collector; a negative dam formed along an edge of the negative active material layer; and an overlapping portion including a first component derived from the negative active material layer and a second component derived from the negative dam, wherein the content of the first component is 40 to 70 parts by weight and the content of the second component is 30 to 60 parts by weight.

[0025]

[0026] According to another embodiment of the present invention, a method for manufacturing a negative electrode is provided, comprising the steps of preparing a negative electrode slurry and a negative electrode dam composition, and simultaneously coating the negative electrode slurry and the negative electrode dam composition on one or both sides of a negative electrode current collector, wherein the negative electrode dam composition includes inorganic particles, a cellulose-based compound, a rubber-based binder, and an additive, and the contents of each component of the negative electrode dam composition satisfy the following (a) to (d):

[0027] (a) 50 to 85 parts by weight of inorganic particles,

[0028] (b) 0.5 to 15 parts by weight of cellulose compound,

[0029] (c) 3 to 20 parts by weight of rubber binder,

[0030] (d) 5 to 12 parts by weight of additive.

[0031] Additionally, in the method for manufacturing the above cathode, the simultaneous coating can be performed by a double die coater.

[0032] Additionally, in the method for manufacturing the negative electrode, the additive may include 0.1 to 0.6 parts by weight of a porous additive and 5 to 10 parts by weight of a carbon-based material.

[0033] The method for manufacturing a cathode and anode according to the present invention has the effect of securing both excellent productivity and long-term reliability by simultaneously preventing defects in the manufacturing process and deterioration of the mechanical properties of the final electrode through optimized dam composition.

[0034] Figure 1 is a partial cross-sectional view showing a cathode according to one embodiment of the present invention.

[0035] FIG. 2 is a schematic drawing of an electrode manufacturing device that performs a simultaneous coating process according to one embodiment of the present invention.

[0036] Fig. 3 is a front view showing an example of a double die coater that can be used as a coating device for the electrode manufacturing device of Fig. 2.

[0037] FIG. 4 is a front view showing another example of a dual die coater that can be used as a coating device for the electrode manufacturing device of FIG. 2.

[0038] The present invention relates to a cathode.

[0039] Hereinafter, a cathode according to one embodiment of the present invention will be described in detail with reference to the attached drawings.

[0040] In addition, regardless of the drawing symbol, identical or corresponding components are given identical or similar reference numbers and redundant descriptions thereof are omitted, and for the convenience of explanation, the size and shape of each component depicted may be exaggerated or reduced.

[0041] Fig. 1 is a partial cross-sectional view showing a negative electrode according to one embodiment of the present invention. For reference, Fig. 1 exemplarily shows a cross-section of a negative electrode in which a negative electrode active material layer is provided on one surface of a negative electrode current collector.

[0042] Referring to the drawing, the negative electrode includes a negative electrode current collector (100), a negative electrode active material layer (200) formed on one or both sides of the negative electrode current collector (100), and a negative electrode dam (300) formed by drying a composition for a negative electrode dam that supports both width-wise edges of the negative electrode active material layer (200) and includes inorganic particles, a cellulose-based compound, a binder, and an additive, and the contents of each component of the composition for a negative electrode dam satisfy the following (a) to (d):

[0043] (a) The inorganic particles may be 50 to 85 parts by weight, specifically 55 to 80 parts by weight, 60 to 80 parts by weight, or 70 to 80 parts by weight.

[0044] (b) The cellulose compound may be present in an amount of 0.5 to 15 parts by weight, specifically 1 to 10 parts by weight or 2 to 5 parts by weight.

[0045] (c) The rubber binder may be 3 to 20 parts by weight, specifically 5 to 15 parts by weight or 9 to 14 parts by weight.

[0046] (d) The additive may be present in an amount of 5 to 12 parts by weight, specifically 6 to 10 parts by weight or 7 to 9 parts by weight.

[0047] The present invention controls the content of each component of a composition for a cathode dam within an optimal range, thereby promoting organic interaction and balance of the content of each component, thereby ensuring stability in the manufacturing process and preventing deterioration of the mechanical properties of the cathode active material layer, thereby ultimately providing a highly reliable cathode.

[0048] Below, the role of each component and its corresponding effect are explained in detail.

[0049]

[0050] inorganic particles

[0051] The above-mentioned inorganic particles can form the main skeleton of the negative electrode dam (300) and play a role in maintaining the physical shape. The content can be directly related to the mechanical reliability of the final electrode. If the content is too low and outside the range of the present invention, the structure of the negative electrode dam (300) may be weakened, which may cause the electrode to detach after drying. Conversely, if the content is excessively high, unnecessary interaction with the negative electrode active material layer (200) may be caused, which may cause the tensile strength of the negative electrode active material layer (200) to be lowered. The present invention can prevent these problems and implement a stable structure through an optimal content range.

[0052]

[0053] rubber binder

[0054] The above rubber-based binder can bind the constituent particles of the negative electrode dam (300) to each other and firmly adhere them to the negative electrode current collector (100). The binder content can be controlled within an optimal range considering the trade-off between securing adhesive strength and maintaining processability.

[0055] If the content is too low, the interparticle cohesion and adhesiveness with the current collector (100) may be insufficient, which may cause the negative electrode dam (300) to peel off from the final electrode. Conversely, if the content is excessive, the viscosity and adhesiveness of the composition may become excessively high, which may cause the solution to clump and thus hinder the processability.

[0056] Therefore, the present invention can simultaneously secure strong physical adhesiveness and stable productivity by controlling the content of the rubber-based binder to an optimal range.

[0057]

[0058] Cellulosic compounds

[0059] The above-mentioned cellulose-based compound can play a role in ensuring manufacturing processability by controlling the viscosity and dispersion stability of the composition. If the content exceeds the optimal range and increases excessively, the viscosity of the composition may increase rapidly, preventing the particles from being uniformly dispersed and causing solution agglomeration. This can be a serious defect that interferes with the uniform coating of the cathode dam (300), and therefore, controlling the content within the scope of the present invention may be important.

[0060]

[0061] additives

[0062] The above additives can play a key role in simultaneously resolving the conflicting challenges of ensuring mechanical reliability of the final cathode and maintaining manufacturing processability.

[0063] Specifically, the additive can have a decisive influence on precisely controlling the rheological properties and interfacial stability of the composition, thereby suppressing process defects such as sliding phenomena or fat edges, while also securing the tensile strength of the electrode after drying and imparting structural stability.

[0064] Therefore, the present invention can achieve both excellent processability and high mechanical reliability by controlling the type and content of additives within an optimal range.

[0065]

[0066] In one example, the inorganic particles may include at least one selected from the group consisting of AlO(OH), Al2O3, γ-AlOOH, Al(OH)3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, and Mg(OH)2, and may be at least one selected from the group consisting of AlO(OH), Al2O3, γ-AlOOH, and Al(OH)3. For example, the inorganic particles may include AlO(OH) (hereinafter, also referred to as boehmite).

[0067] The average particle diameter (D50) of these inorganic particles may be an important factor in simultaneously securing the uniform coating property of the composition and the structural stability of the dam formed after drying. The average particle diameter (D50) of the inorganic particles may be 0.1 ㎛ to 100 ㎛, and more specifically, may be in the range of 0.5 ㎛ to 80 ㎛, 1 ㎛ to 50 ㎛, 2 ㎛ to 30 ㎛, 3 ㎛ to 20 ㎛, 5 ㎛ to 10 ㎛, 0.3 ㎛ to 15 ㎛, or 0.3 ㎛ to 10 ㎛. If the particle diameter is too small, the dispersion stability of the composition may be reduced due to agglomeration between particles, and conversely, if it is too large, the uniformity of the coating surface may be impaired and may cause micro-cracks. Therefore, by having a particle diameter in the above range, uniform coating can be enabled and local stress concentration can be prevented, thereby improving the mechanical reliability of the final electrode.

[0068] In this specification, the average particle diameter (D50) can be defined as the particle diameter based on 50% of the particle diameter distribution. The average particle diameter is not particularly limited, but can be measured using, for example, a laser diffraction method or a scanning electron microscope (SEM) photograph. The laser diffraction method can generally measure particle diameters from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0069] Additionally, the cellulose-based compound may include at least one selected from the group consisting of carboxymethyl cellulose, a lithium salt of carboxymethyl cellulose, and a sodium salt of carboxymethyl cellulose. More specifically, the cellulose-based compound may include carboxymethyl cellulose (CMC).

[0070] The above-mentioned cellulose-based compound acts as a thickener that effectively controls the viscosity and rheological properties of the composition even in small amounts, and can play a key role in controlling the conflicting effects of sliding and fat-edge occurrence. Specifically, the cellulose-based compound imparts appropriate viscoelasticity to the composition, thereby preventing the shape from collapsing or spreading after coating, and at the same time, by controlling the surface tension of the composition to a level similar to that of the negative electrode active material slurry, the fat-edge phenomenon occurring due to the tension difference at the interface between the two liquid phases can be effectively suppressed.

[0071] To achieve these precise rheological characteristics, the weight-average molecular weight (Mw) of the cellulose-based compound may be within the range of 100,000 to 600,000. The weight-average molecular weight may be directly related to the thickening efficiency. For example, if the weight-average molecular weight is too low, it may not provide sufficient viscosity to prevent sliding, and conversely, if the weight-average molecular weight is too high, excessive viscosity may result in reduced processability or poor compatibility with other particles. Therefore, the above weight-average molecular weight range may be an optimized range for preventing process defects through effective viscosity and surface tension control.

[0072] In this specification, "weight average molecular weight (Mw)" refers to a conversion value for standard polystyrene measured by gel permeation chromatography (GPC). Specifically, the weight average molecular weight is a value converted from a value measured under the following conditions using GPC, and standard polystyrene of the Agilent system was used to prepare a calibration curve.

[0073] <Measurement conditions>

[0074] Measuring instrument: Agilent GPC (Agulent 1200 series, USA)

[0075] Column: PL Mixed B 2 connections

[0076] Column temperature: 40 ℃

[0077] Eluent: Tetrahydrofuran

[0078] Flow rate: 1.0 mL / min

[0079] Concentration: ~ 1 mg / mL (100 μL injection)

[0080] The above composition for the cathode dam may include a solvent as a medium for uniformly dispersing the components described above.

[0081] The solvent may be an organic solvent such as dimethyl sulfoxide (DMSO) or N-methylpyrrolidone (NMP), or an aqueous solvent such as water, used alone or in combination of two or more. Among these, water may be particularly preferred as a solvent for the cathode dam composition. This may be because the inherent high surface tension of water positively contributes to controlling the surface tension of the entire dam composition, thereby being advantageous in suppressing the fat-edge phenomenon. In addition, the use of an aqueous solvent may have the advantage of enabling an environmentally friendly and cost-effective process.

[0082] In one specific example, the rubber-based binder may include at least one selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber, and specifically, may include styrene-butadiene rubber. In particular, the styrene-butadiene rubber has excellent adhesion to a copper-based negative electrode current collector (100), and thus can effectively suppress the phenomenon of lifting or peeling of the negative electrode dam (300). In addition, the styrene-butadiene rubber has high flexibility and elasticity, and thus can effectively accommodate and buffer the volume change of the negative electrode active material layer (200) that occurs during charge and discharge, thereby preventing cracking or damage to the negative electrode dam (300). Through these characteristics, the styrene-butadiene rubber can make a key contribution to securing the long-term structural stability of the electrode.

[0083] In addition, the additive may include a porous additive and a carbon-based material. For example, the additive may include 0.1 to 0.6 parts by weight or 0.1 to 0.5 parts by weight of the porous additive and 5 to 10 parts by weight or 7 to 10 parts by weight of the carbon-based material.

[0084] The above additive can improve both structural reliability and production stability, which were in a conflicting relationship, by securing the mechanical properties (tensile strength) of the final electrode while suppressing process defects such as sliding or fat edges by including a porous additive and a carbon-based material in a specific content range.

[0085] The above porous additive can play a role in mainly controlling the rheological properties of the composition to suppress the sliding phenomenon and precisely control the shape of the cathode dam (300).

[0086] Specifically, the porous additive may be activated carbon, which has a large specific surface area. While rubber-based binders are essential for ensuring adhesion, excessive use can negatively impact processability, such as by causing sliding. In this case, activated carbon can control and mitigate the excessive effects of the binder by adsorbing some of the binder components through its large surface area and pores.

[0087] These interactions can allow the composition to have viscoelasticity and surface tension optimized for sliding inhibition, which can be crucial in preventing the liquid dam slurry from spreading and maintaining a near-vertical shape.

[0088] To maximize this effect, the porous additive may be activated carbon having a specific surface area (BET) of 700 to 3,000 m² / g. The specific surface area can be measured using the Brunauer-Emmett-Teller (BET) method. For example, the BET 6-point method can be measured using a porosimetry analyzer (Bell Japan Inc., Belsorp-II mini) and a nitrogen gas adsorption flow method.

[0089] The above carbon-based material can play a key role in ensuring the structural stability of the final electrode.

[0090] The above carbon-based material may include at least one selected from carbon black, graphite, carbon nanotubes, and carbon nanofibers, and may specifically include carbon black. For example, the graphite may be artificial graphite, natural graphite, etc., and the carbon black may be acetylene black, Ketjen black, furnace black, channel black, lamp black, thermal black, etc.

[0091] The above carbonaceous material can play a key role in ensuring the interfacial stability of the negative electrode active material layer (200) and the negative electrode dam (300). For example, when the content of inorganic particles (e.g., boehmite) is high, they may mix with the negative electrode active material layer (200) and reduce the structural stability (e.g., tensile strength) of the negative electrode active material layer (200). A carbonaceous material, such as carbon black, can effectively prevent this mixing phenomenon by acting as a physical and electrochemical barrier by being located at the interface between the negative electrode dam (300) and the negative electrode active material layer (200). Consequently, this can contribute to solving the problem of electrode peeling by preserving the tensile strength of the negative electrode active material layer.

[0092] The above composition for the cathode dam can have a precisely controlled viscosity to satisfy both the conflicting goals of maintaining a stable dam shape and excellent production processability. For example, the viscosity measured at 25°C and a shear rate of 1 s¹ can be within the range of 1,000 to 15,000 cP.

[0093] The above viscosity may be a property directly related to the shape retention ability of the cathode dam (300). If the viscosity is too low, less than 1,000 cp, the composition may spread due to its own weight or the lateral pressure of the cathode slurry, making it difficult to suppress the sliding phenomenon. Conversely, if the viscosity is excessively high, exceeding 15,000 cp, it may be difficult to pass through the discharge nozzle of coating equipment such as a double slot die, which may cause a problem of reduced productivity.

[0094] Therefore, the present invention can achieve both stable cathode dam (300) formation and excellent processability by controlling the viscosity within the above range, more specifically, within the range of 2,000 to 9,000 cp.

[0095] The solids content (%) of the above cathode dam composition may be an important factor determining the efficiency of the drying process and the completeness of the final dam structure. The solids content (%) may be within the range of 10 to 40%.

[0096] The above solids content refers to the percentage of the actual active ingredient in the composition, excluding the solvent. If the solids content is too low, such as less than 10%, not only will a lot of energy be required to evaporate the excess solvent, but the cathode dam (300) will also shrink significantly after drying, making it difficult to secure sufficient thickness and a stable structure. On the other hand, if the solids content is too high, such as exceeding 40%, the viscosity will rapidly increase, potentially compromising the stability of the coating process.

[0097] Therefore, the present invention can implement an efficient drying process and ultimately a cathode dam (300) with an excellent structure by controlling the solid content within the above range, more specifically, within the range of 20 to 35%.

[0098] In another example, the tensile strength may exceed 3 kgf. The tensile strength may be a mechanical property that ensures the long-term reliability of the battery. This is because it is an important indicator of whether the negative electrode dam (300) can physically withstand the expansion and contraction stress of the negative electrode active material layer (200) that occurs as a result of repeated charge and discharge. If the tensile strength is insufficient, such as 3 kgf or less, the negative electrode dam (300) may not be able to withstand this mechanical stress and may develop microcracks or be damaged. This may lead to electrode delamination, which may be a fatal cause of reducing the battery life.

[0099] Therefore, the present invention can ensure the structural stability of the electrode and dramatically improve the long-term life characteristics by securing an excellent tensile strength exceeding 3 kgf.

[0100] The above tensile strength can be measured by the following method.

[0101] First, the cathode to be evaluated is cut to a standard size to prepare a rectangular specimen. The specimen is then processed to have a consistent cross-sectional area and any foreign matter on the surface is removed.

[0102] The prepared specimen is mounted on a Universal Testing Machine (UTM), and a tensile load is applied at a constant speed (e.g., 10 ± 1 mm / min) to measure the maximum load (Fmax) until the specimen breaks. The measurement is performed under constant temperature and humidity conditions (e.g., 23 ± 2°C, 50 ± 5% RH).

[0103] Finally, the tensile strength (σ) value is calculated by dividing the measured maximum load (Fmax) by the initial cross-sectional area (A) of the specimen (σ = Fmax / A).

[0104] The present invention can secure long-term structural reliability of the electrode by having a tensile strength measured in this manner exceeding 3 kgf.

[0105]

[0106] Below, each component of the cathode will be described in detail.

[0107]

[0108] negative current collector

[0109] The above negative electrode current collector (100) can serve as a passage for collecting electrons from the negative electrode active material and transmitting them to an external circuit, and as a substrate that physically supports the negative electrode active material layer (200).

[0110] Accordingly, the negative electrode current collector (100) can be made of any material that has high electrical conductivity and is non-reactive within the voltage range of the battery without any particular limitations. Specifically, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. can be used, and stainless steel or an aluminum-cadmium alloy surface-treated with carbon, nickel, titanium, or silver can also be used, if necessary.

[0111] In addition, fine irregularities may be formed on the surface of the negative electrode current collector (100) to strengthen the bonding strength with the negative electrode active material, and the negative electrode current collector (100) may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric. The thickness of the negative electrode current collector (100) may generally be in the range of about 3 ㎛ to about 500 ㎛.

[0112]

[0113] Negative active material layer

[0114] The above negative electrode active material layer (200) is the main electrochemical reaction area where intercalation and de-intercalation of lithium ions occur, and can be formed through a coating process of applying and drying negative electrode slurry on one or both sides of a negative electrode current collector (100).

[0115] The above negative electrode slurry can be manufactured by mixing and stirring a negative electrode active material in a solvent, a binder for bonding between particles and with a current collector, and, if necessary, a conductive material for improving conductivity or a filler for suppressing expansion of the electrode.

[0116] The solvent used at this time may be dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, which may be used alone or in a mixture of two or more. The content of the solvent may be adjusted to have a viscosity suitable for the coating method used, taking into account the applicability and processability of the slurry.

[0117] The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic 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; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more thereof may be used. A metallic lithium thin film may also be used as the negative electrode active material.

[0118] The above carbonaceous material may specifically be both low-crystalline carbon and high-crystalline carbon. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and examples of high-crystalline carbon include calcined carbon such as natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and petroleum or coal tar pitch derived cokes. Specifically, graphite-based negative electrode active materials such as natural graphite or artificial graphite are more preferable because they can reversibly insert and de-insert lithium ions while maintaining structural and electrical properties.

[0119] The above negative active material may be included in an amount of about 80 wt% to 99.5 wt% or 88 wt% to 99 wt% relative to the total weight of the negative active material layer (200), but the content is not limited thereto.

[0120] The above binder is not particularly limited as long as it is a component that assists in the bonding of the negative electrode active material and the conductive material and the bonding to the current collector, and examples thereof include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers.

[0121] When the solvent of the cathode slurry is an aqueous solvent such as water, the above binder is preferably an aqueous binder. In a specific example, the aqueous binder may include at least one selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluoroelastomer, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, hydroxypropylmethylcellulose, hydroxypropylcellulose, and diacetylcellulose.

[0122] In a specific example, the aqueous binder may include at least one selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber. For example, the aqueous binder may be styrene-butadiene rubber.

[0123] The above binder may typically be included in an amount of 1 to 30 wt% based on the total weight of the negative electrode active material layer (200).

[0124] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, and the like; conductive fibers such as carbon fiber or metal fiber; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and 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.

[0125] The above-mentioned conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the negative electrode active material layer (200).

[0126] The above filler is optionally used as a component that suppresses expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery. For example, olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber can be used.

[0127]

[0128] cathode dam

[0129] The negative electrode dam (300) can be formed by applying a negative electrode dam composition to one surface of the negative electrode current collector (100) and drying it. In the present invention, the negative electrode active material layer (200) and the negative electrode dam (300) can be formed integrally through a simultaneous coating (co-coating) process.

[0130] FIG. 2 is a schematic drawing of an electrode manufacturing device that performs a simultaneous coating process according to one embodiment of the present invention, FIG. 3 is a front view showing an example of a double die coater that can be used as a coating device of the electrode manufacturing device of FIG. 2, and FIG. 4 is a front view showing another example of a double die coater that can be used as a coating device of the electrode manufacturing device of FIG. 2.

[0131] In the drawing, the direction in which the electrode runs is indicated as the machine direction (MD), the width direction as the transverse direction (TD), and the thickness direction as the vertical direction (VD).

[0132] Referring to FIG. 2, the electrode manufacturing device (1000') can be implemented as a roll-to-roll process including a first roll (1100) for unwinding a current collector (cc), a second roll (1200) for winding the current collector (cc), a coating device (1600) for simultaneous coating, and a drying device (1500) for evaporating a solvent.

[0133] The above coating device (1600) may be a dual die coater, specific examples of which are illustrated in FIGS. 3 and 4.

[0134] Fig. 3 illustrates a first example of a coating device (1600) in detail. Referring to Fig. 3, the coating device (1600) may be composed of an upper die (1610), a lower die (1620), and a single coating shim (1630) interposed therebetween. In this structure, a first discharge unit (1630H1) for discharging a composition for a cathode dam and a second discharge unit (1630H2) for discharging a slurry for a cathode may be formed together within the single coating shim (1630).

[0135] Meanwhile, Fig. 4 illustrates another example of a coating device (1600'). Unlike the example of Fig. 3, Fig. 4 may use two separate coating shims. Specifically, the coating device (1600') of Fig. 4 may include an upper die (1610'), a middle die (1620'), and a lower die (1630'), and may also include an upper coating shim (1640) interposed between the upper die (1610') and the middle die (1620'), and a lower coating shim (1650) interposed between the middle die (1620') and the lower die (1630').

[0136] A composition discharge unit (1640H) for a cathode dam may be positioned in the upper coating core (1640), and a slurry discharge unit (1650H) for a cathode dam may be positioned in the lower coating core (1650). This multi-core structure may be more advantageous in independently controlling the flow rate or pressure of each composition.

[0137] In this way, the present invention can enable two types of liquid compositions to be precisely and uniformly simultaneously applied onto a current collector (100) in one process through a dual die coater of various shapes.

[0138] This co-coating method can be advantageous in forming a more robust and stable interface than forming the two layers separately, in addition to the advantage of simplifying the process. For example, using equipment such as a dual die coater, the negative electrode slurry and the negative electrode dam composition can be precisely applied simultaneously onto the current collector (100) and dried together. As a result, the negative electrode dam (300) can be formed integrally on the same surface as the negative electrode active material layer (200).

[0139] A detailed description of the components of the composition for the above cathode dam is omitted as it overlaps with the above.

[0140]

[0141] Overlap section

[0142] The overlap portion (400) can be formed by naturally mixing the liquid-state negative electrode slurry and the negative electrode dam composition at the interface where they come into contact during the previously described co-coating process. Therefore, the overlap portion (400) can exist as a region having a composition gradient, where a component derived from the negative electrode active material layer (200) (first component) and a component derived from the negative electrode dam (300) (second component) are physically mixed.

[0143] Such a naturally formed interface can be much more effective in alleviating mechanical stress than an artificially formed, abrupt boundary. In other words, the overlap portion (400) can serve as a buffer layer that gradually changes the physical and electrochemical properties between two regions with different properties, thereby contributing significantly to ensuring the structural stability of the electrode.

[0144] Therefore, the present invention can implement the desired effect by precisely controlling the composition and various physical properties of the composition for the cathode dam, thereby optimizing the structure and characteristics of the overlap portion (400) that is ultimately formed.

[0145]

[0146] In one example, the cathode according to the present invention can satisfy the following equation 1:

[0147] [Formula 1]

[0148] 0.005 < Wa / Wb < 15

[0149] In the above equation 1, Wa is the width of the overlap portion (400), and Wb is the width of the cathode dam (300).

[0150] This ratio may be a key factor in controlling the balance between forming an ideal buffer layer between two dissimilar material regions and maintaining the dam's inherent support function.

[0151] For example, if the Wa / Wb ratio is less than 0.005 and there is almost no overlap (400), two regions with different properties form a sharp boundary. This boundary can cause stress concentration during the repeated expansion and contraction of the electrode during battery charging and discharging. The concentrated stress can eventually cause delamination at the edge of the electrode, which can be a major factor in reducing the lifespan and reliability of the battery. Therefore, the present invention can prevent this problem by securing an overlap (400) of a significant width.

[0152] Meanwhile, the reason why the Wa / Wb ratio must be controlled to be less than 15.0 may be to ensure the structural support role, which is the inherent function of the negative electrode dam (300). If this ratio becomes excessively large, exceeding 15.0, the pure negative electrode dam (300) area (Wb) may become relatively too narrow, making it difficult to fully perform its role as a physical support. This may result in the inability to effectively suppress the sliding of the negative electrode slurry during the manufacturing process, or the inability to firmly support the edge of the active material layer during charge and discharge, which may cause structural collapse or deformation of the electrode.

[0153] In conclusion, the negative electrode of the present invention satisfies the above equation 1, thereby simultaneously preventing the problem of 'interfacial peeling' that lowers the long-term reliability of the electrode and the problem of 'structural collapse' due to the malfunction of the dam, thereby maximizing the performance and durability of the battery.

[0154] In another example, the width (Wa) of the overlap portion (400) may be within the range of 0.01 to 2.0 mm. When Wa is within the above range, the overlap portion (400) can serve as an effective buffer that gradually bridges the physical and chemical property differences between the negative electrode active material layer (200) and the negative electrode dam (300), which are different materials. This can secure interfacial adhesion between the two regions and alleviate mechanical stress generated during charge and discharge, thereby improving structural stability.

[0155] If the above Wa is too narrow, less than 0.01 mm, it may not sufficiently perform its buffering role, causing stress to be concentrated at the interface, which may ultimately cause interface delamination and reduce the lifespan of the battery.

[0156] Conversely, if the above Wa is excessively wide, exceeding 2.0 mm, the overlap portion (400) may encroach on the effective area where the active material is to be coated, resulting in a loss of battery capacity.

[0157] In one specific example, Wb may be in the range of 0.1 to 3.0 mm. When Wb is within the above range, the negative electrode dam (300) can stably perform its role as a structural support that supports the edge of the electrode and maintains the shape of the electrode. When Wb is excessively narrow, less than 0.1 mm, the structural support function of the negative electrode dam (300) may be reduced, making it difficult to effectively suppress the sliding phenomenon. Conversely, when Wb is excessively wide, exceeding 3.0 mm, this may also reduce the effective area of ​​the active material, resulting in a loss of battery capacity.

[0158] In one specific example, the thickness (t) of the cathode dam (300) may be within the range of 5 to 200 um, within the range of 10 to 150 um, within the range of 10 to 100 um, or within the range of 10 to 50 um. The cathode dam (300) satisfying the above thickness (t) can perform a stable function as a support structure. If the thickness of the cathode dam (300) is too thin, the physical support force may be insufficient, and if it is too thick, it may cause a step problem during battery assembly or may cause an increase in material costs.

[0159]

[0160] According to another embodiment, the present invention relates to a cathode that maximizes the reliability of the electrode by optimizing the composition within the overlap portion (400) where the cathode active material layer (200) and the cathode dam (300) meet. Detailed descriptions that overlap with the above-mentioned contents will be omitted below.

[0161] The negative electrode according to the other embodiment includes a negative electrode current collector (100), a negative electrode active material layer (200) formed on one or both sides of the negative electrode current collector (100), a negative electrode dam (300) formed along an edge of the negative electrode active material layer (200), and an overlap portion (400) including a first component derived from the negative electrode active material layer (200) and a second component derived from the negative electrode dam (300), wherein the content of the first component is 40 to 70 parts by weight, and the content of the second component is 30 to 60 parts by weight.

[0162] Specifically, the first component may be 45 to 65 parts by weight, and the second component may be 35 to 55 parts by weight.

[0163] This composition control may be intended to allow the overlap portion (400) to optimally perform two conflicting roles simultaneously: mechanical buffering and smooth ion transfer.

[0164] If the first component in the overlap portion (400) exceeds 70 parts by weight and the second component is relatively too small, the characteristics of the overlap portion (400) may become close to those of the negative electrode active material layer (200), so that the difference in physical properties with the negative electrode dam (300) cannot be effectively mitigated, and the mechanical stress relief effect may be minimal.

[0165] Conversely, if the second component exceeds 60 parts by weight and the first component is too small, the electrical resistance of the overlap portion (400) may increase, resulting in an electrochemically inactive region that impedes the movement of lithium ions. This may cause a decrease in the output and life characteristics of the electrode.

[0166] Accordingly, the present invention can achieve a dual effect of securing structural stability through mechanical stress relief and preventing electrochemical performance degradation by ensuring a smooth ion transfer path by controlling the composition of the overlap portion (400) within the above-mentioned specific range.

[0167] In one example, the first component may include a negative active material, and the second component may include inorganic particles and additives.

[0168] Additionally, the additive may include at least one of a porous additive, a carbon-based material, and a viscoelasticity-imparting agent.

[0169]

[0170] According to another embodiment of the present invention, a method for manufacturing the aforementioned cathode is provided. Detailed descriptions that overlap with those described above will be omitted below.

[0171] A method for manufacturing a negative electrode according to the present invention includes a step of preparing a slurry for a negative electrode and a composition for a negative electrode dam, and a step of simultaneously coating the slurry for a negative electrode and the composition for a negative electrode dam on one or both sides of a negative electrode current collector.

[0172] The above composition for the cathode dam comprises inorganic particles, a cellulose-based compound, a rubber-based binder and an additive, and the content of each component of the composition for the cathode dam satisfies the following (a) to (d):

[0173] (a) 50 to 85 parts by weight of inorganic particles,

[0174] (b) 0.5 to 15 parts by weight of cellulose compound,

[0175] (c) 3 to 20 parts by weight of rubber binder,

[0176] (d) 5 to 12 parts by weight of additive.

[0177] The above preparation step may include a step of preparing a composition for a cathode dam by mixing and stirring each component in a solvent so as to satisfy the contents of (a) to (d).

[0178] In addition, the above preparation step can prepare a slurry for a negative electrode including a negative electrode active material, a binder, etc. in a conventional manner.

[0179] The above-described simultaneous coating step can be performed using equipment such as a dual die coater (1600), as previously described with reference to FIGS. 2 to 4. This allows the negative electrode slurry to be positioned centrally, and the negative electrode dam composition to be applied in parallel to both edges thereof. Thereafter, the simultaneously coated current collector is dried using a drying device (1500) or the like to remove the solvent, thereby manufacturing a final negative electrode in which the negative electrode active material layer (200) and the negative electrode dam (300) are integrally formed.

[0180] In one example, the additive may include 0.1 to 0.6 parts by weight of a porous additive and 5 to 10 parts by weight of a carbonaceous material.

[0181]

[0182] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention solely to these examples.

[0183]

[0184] Example 1

[0185] Preparation of a composition for a cathode dam

[0186] A composition for a cathode dam was prepared by mixing and stirring in water 75.9 parts by weight of boehmite (product name JD3M-A-02) as an inorganic particle, 11.2 parts by weight of styrene-butadiene rubber (SBR, product name M37) as a rubber-based binder, 4.7 parts by weight of CMC (product name BH230) as a cellulose-based compound, and 0.2 parts by weight of activated carbon and 8.0 parts by weight of carbon black as additives.

[0187] At this time, the solid content of the final composition was 20%, and the viscosity (25℃, 1s -1 ) was measured at 4820 cps.

[0188]

[0189] Preparation of slurry for cathode

[0190] A slurry for the negative electrode was prepared by mixing and stirring artificial graphite as a negative active material, styrene butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC) as a thickener, and carbon nanotubes as a conductive material in water at a weight ratio of 95:2:1.5:1.5.

[0191]

[0192] Manufacturing of cathode

[0193] The negative electrode slurry and the negative electrode dam composition prepared above were simultaneously coated (co-coated) on a copper foil current collector having a thickness of 10 μm using a double die coater. At this time, the negative electrode dam composition was applied so as to be positioned at both edges of the area where the negative electrode slurry was applied. Thereafter, the negative electrode of Example 1 was manufactured by drying and rolling at a temperature of 90°C.

[0194]

[0195] Example 2

[0196] Preparation of a composition for a cathode dam

[0197] A composition for a cathode dam was prepared by mixing and stirring in water 74.9 parts by weight of Boehmite (product name JD3M-A-02) as an inorganic particle, 13.0 parts by weight of styrene-butadiene rubber (SBR, product name M37) as a rubber-based binder, 4.0 parts by weight of CMC (product name BH230) as a cellulose-based compound, and 0.1 parts by weight of activated carbon and 8.0 parts by weight of carbon black as additives. At this time, the solid content of the final composition was 20%, and the viscosity (25°C, 1 s -1 ) was measured at 4840 cps.

[0198]

[0199] Preparation of slurry for cathode

[0200] A slurry for the negative electrode was prepared by mixing and stirring artificial graphite as a negative active material, styrene butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC) as a thickener, and carbon nanotubes as a conductive material in water at a weight ratio of 95:2:1.5:1.5.

[0201]

[0202] Manufacturing of cathode

[0203] The negative electrode slurry and the negative electrode dam composition prepared above were simultaneously coated (co-coated) on a copper foil current collector having a thickness of 10 μm using a double die coater. At this time, the negative electrode dam composition was applied so as to be positioned at both edges of the area where the negative electrode slurry was applied. Thereafter, the negative electrode of Example 2 was manufactured by drying and rolling at a temperature of 90°C.

[0204]

[0205] Comparative Example 1

[0206] Preparation of a composition for a cathode dam

[0207] A composition for a cathode dam was prepared using the same method as in Example 1, except that 49.5 parts by weight of boehmite (product name JD3M-A-02) as an inorganic particle, 40 parts by weight of styrene-butadiene rubber (SBR, product name M37) as a rubber-based binder, 10 parts by weight of CMC (product name BH230) as a cellulose-based compound, and 0.5 parts by weight of activated carbon as an additive. (Carbon black not included) At this time, the solids content of the final composition was 11%, and the viscosity was measured to be 5300 cps.

[0208]

[0209] Manufacturing of slurry for cathode and cathode

[0210] The preparation of the slurry for the cathode and the preparation of the cathode using the same were performed in the same manner as in Example 1.

[0211]

[0212] Comparative Example 2

[0213] Preparation of a composition for a cathode dam

[0214] A composition for a cathode dam was prepared using the same method as Example 1, except that 87.5 parts by weight of boehmite (product name JD3M-A-02) as an inorganic particle, 8 parts by weight of styrene-butadiene rubber (SBR, product name M37) as a rubber-based binder, 4 parts by weight of CMC (product name BH230) as a cellulose-based compound, and 0.5 parts by weight of activated carbon as an additive. (Carbon black not included) At this time, the solids content of the final composition was 23%, and the viscosity was measured to be 3050 cps.

[0215]

[0216] Manufacturing of slurry for cathode and cathode

[0217] The preparation of the slurry for the cathode and the preparation of the cathode using the same were performed in the same manner as in Example 1.

[0218]

[0219] Comparative Example 3

[0220] Preparation of a composition for a cathode dam

[0221] A composition for a cathode dam was prepared using the same method as Example 1, but using 82.5 parts by weight of boehmite (product name JD3M-A-02) as an inorganic particle and 17.5 parts by weight of CMC (product name BH230) as a cellulose compound. (Binder and additives not included) At this time, the solids content of the final composition was 25%, and the viscosity was measured to be 4000 cps.

[0222]

[0223] Manufacturing of slurry for cathode and cathode

[0224] The preparation of the slurry for the cathode and the preparation of the cathode using the same were performed in the same manner as in Example 1.

[0225]

[0226] Comparative Example 4

[0227] Preparation of a composition for a cathode dam

[0228] A composition for a cathode dam was prepared using the same method as in Example 1, but using 80.8 parts by weight of boehmite (product name JD3M-A-02) as an inorganic particle, 9.6 parts by weight of styrene-butadiene rubber (SBR, product name M37) as a rubber-based binder, 5.4 parts by weight of CMC (product name BH230) as a cellulose-based compound, and 0.2 parts by weight of activated carbon and 4.0 parts by weight of carbon black as additives. At this time, the solids content of the final composition was 20%, and the viscosity was measured to be 5080 cps.

[0229]

[0230] Manufacturing of slurry for cathode and cathode

[0231] The preparation of the slurry for the cathode and the preparation of the cathode using the same were performed in the same manner as in Example 1.

[0232]

[0233] Comparative Example 5

[0234] Preparation of a composition for a cathode dam

[0235] A composition for a cathode dam was prepared using the same method as in Example 1, except that 70.3 parts by weight of boehmite (product name JD3M-A-02) as an inorganic particle, 13 parts by weight of styrene-butadiene rubber (SBR, product name M37) as a rubber-based binder, 4 parts by weight of CMC (product name BH230) as a cellulose-based compound, and 0.2 parts by weight of activated carbon and 12.5 parts by weight of carbon black as additives. At this time, the solids content of the final composition was 20%, and the viscosity was measured to be 4300 cps.

[0236]

[0237] The production of the slurry for the cathode and the production of the cathode using the slurry for the cathode were carried out in the same manner as in Example 1.

[0238]

[0239] Comparative Example 6

[0240] Preparation of a composition for a cathode dam

[0241] A composition for a cathode dam was prepared using the same method as Example 1, except that 70 parts by weight of boehmite (product name JD3M-A-02) as an inorganic particle, 13 parts by weight of styrene-butadiene rubber (SBR, product name M37) as a rubber-based binder, 4 parts by weight of CMC (product name BH230) as a cellulose-based compound, and 13 parts by weight of carbon black as an additive. (Activated carbon not included) At this time, the solids content of the final composition was 20%, and the viscosity was measured to be 4580 cps.

[0242]

[0243] Manufacturing of slurry for cathode and cathode

[0244] The preparation of the slurry for the cathode and the preparation of the cathode using the same were performed in the same manner as in Example 1.

[0245]

[0246] Experimental Example - Evaluation of Cathode Properties

[0247] In order to confirm the effectiveness of the present invention, the main physical properties of each negative electrode manufactured in Examples 1 and 2 and Comparative Examples 1 to 6 described above were evaluated, and the results are shown in Table 1 below. Tensile strength was measured according to the measurement method described above.

[0248] Wa / Wb tensile strength (kgf) evaluation results Example 10.74 No problem Example 20.73.9 No problem Comparative example 10.72.7 Electrode detachment Comparative example 20.70 Low tensile strength Comparative example 3--Solution lumping Comparative example 46.73 Low tensile strength Comparative example 50.73.3 Excessive verticalization Comparative example 6203.6 Verticalization failure

[0249] As can be seen from the results in Table 1 above, only in the cases of Examples 1 and 2 having the optimal composition according to the claims of the present invention, stable cathodes were manufactured without any special issues.

[0250] Specifically, Examples 1 and 2 exhibited excellent tensile strength values ​​of 4.0 kgf and 3.9 kgf, respectively.

[0251] On the other hand, Comparative Examples 1 and 2 are cases where the content of inorganic particles (boehmite) was outside the optimal range. Comparative Example 1, which had an excessively low content, had a tensile strength of only 2.7 kgf, ultimately resulting in electrode detachment, and Comparative Example 2, which had an excessively high content, had a tensile strength of 0 kgf due to excessive mixing with the active material layer, completely losing structural stability.

[0252] Comparative Example 3 had an excessive content of cellulose compound (CMC), which resulted in solution clumping, making uniform coating impossible.

[0253] Comparative Examples 4 and 5 demonstrate that the carbonaceous material (carbon black) content exceeded the optimal range. Comparative Example 4, with its extremely low content, exhibited poor mechanical properties, with a tensile strength of 3.0 kgf. Conversely, Comparative Example 5, with its excessively high content, exhibited a tensile strength of 3.3 kgf, exceeding the standard. However, despite this, it suffered from a process defect due to excessive verticalization known as "fat edge."

[0254] Lastly, Comparative Example 6 is a case without a porous additive (activated carbon). The tensile strength was high at 3.6 kgf, but the 'vertical failure (sliding)' problem occurred, preventing the dam from performing its original function.

[0255] In conclusion, the present invention has confirmed that it is possible to provide a highly reliable cathode by organically controlling the content of each component of the cathode dam composition within a specific range, thereby simultaneously resolving several conflicting problems such as securing excellent mechanical properties exceeding 3 kgf and suppressing process defects and structural defects.

[0256]

[0257] The preferred embodiments of the present invention described above are disclosed for the purpose of illustration, and those skilled in the art having ordinary knowledge of the present invention will be able to make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions should be considered to fall within the scope of the following claims.

[0258] Description of the symbol

[0259] 100: Negative current collector

[0260] 200: Negative active material layer

[0261] 300: Negative dam

[0262] 400: Overlap section

Claims

negative current collector; A negative electrode active material layer formed on one or both sides of the negative electrode current collector; and A negative electrode dam is formed by drying a composition for a negative electrode dam that supports both edges in the width direction of a negative electrode active material layer and includes inorganic particles, a cellulose-based compound, a rubber-based binder, and an additive. The content of each component of the above cathode dam composition satisfies the following (a) to (d): (a) 50 to 85 parts by weight of inorganic particles, (b) 0.5 to 15 parts by weight of cellulose compound, (c) 3 to 20 parts by weight of rubber binder, (d) 5 to 12 parts by weight of additive. In the first paragraph, the inorganic particles are cathodes comprising at least one selected from the group consisting of AlO(OH), Al2O3, γ-AlOOH, Al(OH)3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, and Mg(OH)2. In the first paragraph, the negative electrode, wherein the cellulose compound comprises at least one selected from the group consisting of carboxymethyl cellulose, lithium salt of carboxymethyl cellulose, and sodium salt of carboxymethyl cellulose. In the first paragraph, the weight average molecular weight (Mw) of the cellulose compound is in the range of 100,000 to 600,000, the negative electrode. In the first paragraph, the rubber-based binder comprises at least one selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber. In the first paragraph, the negative electrode comprises a porous additive and a carbon-based material. In claim 6, the negative electrode comprises 0.1 to 0.6 parts by weight of a porous additive and 5 to 10 parts by weight of a carbon-based material. In claim 6, the carbon-based material is a negative electrode comprising at least one selected from carbon black, graphite, carbon nanotubes, and carbon nanofibers. In the first paragraph, the solid content (%) of the composition for the negative electrode dam is in the range of 10 to 40%. In the first paragraph, a cathode having a tensile strength exceeding 3 kgf. negative current collector; A negative electrode active material layer formed on one or both sides of the negative electrode current collector; A cathode dam formed along the edge of the cathode active material layer; and An overlapping portion comprising a first component derived from the negative active material layer and a second component derived from the negative electrode dam, The content of the first component is 40 to 70 parts by weight, A cathode having a content of the second component of 30 to 60 parts by weight. A step of preparing a slurry for a cathode and a composition for a cathode dam; and A step of simultaneously coating a slurry for a negative electrode and a composition for a negative electrode dam on one or both sides of a negative electrode current collector, The above composition for the cathode dam comprises inorganic particles, a cellulose compound, a rubber binder and an additive, The content of each component of the above cathode dam composition satisfies the following (a) to (d): Method for manufacturing a cathode: (a) 50 to 85 parts by weight of inorganic particles, (b) 0.5 to 15 parts by weight of cellulose compound, (c) 3 to 20 parts by weight of rubber binder, (d) 5 to 12 parts by weight of additive. A method for manufacturing a cathode, wherein the simultaneous coating is performed by a double die coater in the 12th paragraph. A method for manufacturing a negative electrode in claim 12, wherein the additive comprises 0.1 to 0.6 parts by weight of a porous additive and 5 to 10 parts by weight of a carbon-based material.

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